Possible Habitable Planet Just 12 Light Years Away

sciencehabit writes "Astronomers have discovered what may be five planets orbiting Tau Ceti, the closest single star beyond our solar system whose temperature and luminosity nearly match the sun's. If the planets are there, one of them is about the right distance from the star to sport mild temperatures, oceans of liquid water, and even life (paper)."

Comments

Where's the queue?

[eltardo]

I've got my own helmet. Where do I sign up?

Re:Where's the queue?

[valentinas]

Helmet? What about a towel?

Re:Where's the queue?

[Joe_Dragon]

Cheyenne Mountain oops I said to much.

Re:Where's the queue?

[Anonymous Coward]

Who is much?

Re:Where's the queue?

[cervesaebraciator]

sort of flushes sideways

Great. Now I've got to go back and watch them again. It just occurred to me to wonder whether the Antarctica gate flushes in the other direction.

Re:Where's the queue?

[davester666]

Hey, there will no absolutely no riff-raff on my planet!

Re:Where's the queue?

[Grayhand]

Helmet? What about a towel?

So you're planning to hitchhike to Tau Ceti? You do know it's off season and the hotel rates are insane? You don't even want to know what a Pan Galactic Gargle Blaster will set you back.

Re:Where's the queue?

[Githaron]

Now you are making miss Stargate. I wish they would start a new series with the format of the first two series. Stargate Universe was horrible in comparison.

Re:Where's the queue?

[wgoodman]

It was just Stargate Voyager. Stargate DS9 was fun while it lasted, but neither were as good as the original.

Re:Where's the queue?

[Angeret]

Wasn't he the miller's son? Friend of Robin for a while?

Re:Where's the queue?

[cheesybagel]

So it possibly has habitable planets just like in Frontier: Elite 2! Except in Frontier Mars is supposedly terraformed.

Re:Where's the queue?

[Calabacin]

Have helmet, will travel

Re:Where's the queue?

[mcgrew]

Dude, it's Tau Ceti. Khan lives there!!!

Re:Where's the queue?

[crazyjj]

Well, considering that the fastest spacecraft we've ever built would take over 300,000 years to travel 12 light years, I'd say that at least the wait in line will be relatively short in comparison.

Re:Where's the queue?

[smooth wombat]

True, but if we can get to 1/10 C, the trip will only be, roughly, 120 years (allowing for time to get to speed then decelerate).

So that's only 1, maybe 2 generations. The line should still be pretty long even after that wait.

Re:Where's the queue?

[mcgrew]

It's Have Space Suit -- Will Travel. A helmet won't do much good without a suit.

Re:Where's the queue?

[gstoddart]

So that's only 1, maybe 2 generations. The line should still be pretty long even after that wait.

Yeah, but it would turn into one of those things that those 1-2 generations would arrive and find subsequent generations and technology are already there waiting for them. :-P

Early adopters always get hosed.

Re:Where's the queue?

[jellomizer]

0 Year Mark: You leave as an early adult 20
5 year Mark: 25 years of age you have offspring (Generation 1)
25 year Mark: You become a grandparent (Generation 2)
45 year Mark: You become a great grandparent (Generation 3)
65 year Mark: You become a great-great grandparent (Generation 4) (Generation 0 begins to die)
85 year Mark: Generation 5 is born, generation 1 dies
105 year Mark: Generation 6 is born, generation 2 dies
120 years: Generation 7 is beginning to get born. You are at your destination, generation 3 dies.
By the time you get there Generation 3, will be the elders (Too old to do most of the physical work, however they will share wisom), Generation 4 are the Main leaders Members, Generation 5 and 6 are the key workers, and Generation 7 will be too young.

Re:Where's the queue?

[Teancum]

That is Alpha Ceti, not Tau Ceti..... different star systems. None the less, it is the same constellation (Cetus the Whale), thus in the same general direction in the sky from the Earth.

Re:Where's the queue?

[SilverJets]

That is Alpha Ceti, not Tau Ceti..... different star systems. None the less, it is the same constellation (Cetus the Whale), thus in the same general direction in the sky from the Earth.

No, that's Ceti Alpha.

Re:Where's the queue?

[DigitalReverend]

You are using a 20 year generational span. In the US a generation is now considered to be 25 years.

http://en.wikipedia.org/wiki/Generation#Familial_generation

Re:Where's the queue?

[Teancum]

Ceti Alpha is not a proper stellar designation. That must have been a script writer like the one who thought a parsec was a unit of time. Alpha Ceti is a proper designation, which usually comes in the form: [ Greek letter ] [ constellation ]
(the Greek letter is often spelled out in Latin, but sometimes abbreviated with just the Greek letter instead). Transposing the constellation and letter might be considered a twist of the name, but it is still identifiable.

A slightly more famous star name is Alpha Centauri.... the first star (usually the brightest) designated in the Centaur constellation. Tau Ceti is thus a rather dim star in Cetus, but none the less one you can still see without a telescope if you really try to search for it.

See also: http://en.wikipedia.org/wiki/Bayer_designation

Re:Where's the queue?

[jstave]

So you're planning to hitchhike to Tau Ceti? You do know it's off season and the hotel rates are insane? You don't even want to know what a Pan Galactic Gargle Blaster will set you back.

A properly made Pan Galactic Gargle Blaster will set you back into infancy, no matter what the season.

Re:Where's the queue?

[jellomizer]

Yes but you have people crammed in a small enclosed space. There is no career growth or options for a different life, you are born into the mission. 20 years until a new child is actually stretching it. As well death in their mid to late 80's is stretching it too.

Re:Where's the queue?

[MightyMartian]

When you go to another planet you should always remember to bring your own towel.

Re:Where's the queue?

[MightyMartian]

Yeah, but everything is filmed shaky cam with lots of lens flair, you know, because that's kewl.

Re:Where's the queue?

[Golddess]

Commander Keen seemed to get by ok.

Re:Where's the queue?

[ArsonSmith]

So, using current tech and unlimited resources...What is the fastest space object that would do useful stuff we could make? I'm thinking a new voyager probe targeted at one of these systems. Is 1/10th of C even theoretically possible now?

It goes the other way, too

[Anonymous Coward]

If they're an inviting target to us, then earth is an inviting target for them. And maybe they're making as much a hash out of their physical world as we are of ours.

Re:It goes the other way, too

[Anonymous Coward]

It sounds improbable, but you never know, so we should probably bomb the shit out of them. The only problem is that nuclear weapons of a sufficient power to absolutely destroy the surface of a planet are far too heavy to send over interstellar distances. It is time to build anti-matter bombs. You can also use the anti-matter to propel it with no need to stop. Its a win-win-lose.

Re:It goes the other way, too

[Anonymous Coward]

Just send a B Ship full of your Republicans, climate denialists, gun nuts and all the other right-wingers around the world.

They can propel themselves there with bombastic hot air, and they'll fuck everything up enough that we'll never see that planet again. Of course, if the other guys have had the same idea, we'll need a strategy to deflect them. Pretending we're gay might seem like a good idea, but before you know it, they'll be "adopting a wide orbital stance" and stalk us forever.

Suggestions anyone?

Re:It goes the other way, too

[flyneye]

Just put him on the "Botany Bay" with a crew made up of Network Newsclowns.

Re:It goes the other way, too

[Genda]

Why stop there, lets send The entire Cabinet, Congress, The Senate and The Supreme Court so they all have one another to keep each other company... and if you can get Wall Street on the next bus, we should be pret-near perfect.

Re:It goes the other way, too

[Arancaytar]

If that planet were inhabited by a technological civilization, we should have been detecting their twelve-year-old radio transmissions, faint as they might be.

Re:It goes the other way, too

[Genda]

Alliterative and Redundant, well played.

Re:It goes the other way, too

[Anonymous Coward]

Assuming they still use radio, or ever did.

Re:It goes the other way, too

[Darkness404]

Depends.

Its highly possible that a technologically advanced civilization would have never really used radio waves. Or its possible that they are advanced, but not -that- advanced.

Imagine if we put a random sample of humanity on a different planet even as recently as 1700 AD. I'd imagine the 2 worlds would look quite different even though its only 300 years. The evolution of human communication is mostly an accident. There's no "line of technology", its quite possible that an advanced civilization skipped radio and used some completely different method of communication that we haven't even thought of and the two civilizations could be both as advanced.

Re:It goes the other way, too

[Anonymous Coward]

So why does SETI exist?

Re:It goes the other way, too

[gumbi west]

You're forgetting that we can see our own TV signals, sent out and then reflected back at us by an unknown source from 47 years ago. If a low quality mirror is enough to span 47 light years, than a direct view of something 12 light years away should be fine.

Re:It goes the other way, too

[gumbi west]

AGGGH just noticed the date on that article. I'm such a tool.

Re:It goes the other way, too

[bunbuntheminilop]

If they're as lonely as we are, and regardless of whether they used radio like we have, wouldn't any sufficiently advanced civilisation be transmitting radiowaves in all directions, with the purpose of getting a response from someone else? So, if they want to get in contact with us, radio seems like a good place to start, as least from a physics perspective?

We send out these kinds of signals now, but on a small scale. We should be sending these in all directions, and all the time, and the messages we should be sending are 'is there a better way to communicate with you guys? if there is, can you send us back some instructions on building a faster than light communication device?'

Re:It goes the other way, too

[symbolset]

It turns out that stars are pretty powerful radio transmitters, and the edge of a stellar system has considerable additional noise. And then there's the cube-square law. Even if they were deliberately transmitting directly at us 12 years ago, it's unlikely we could make out the signal from the noise.

Suns have a lot of light noise too, so we probably wouldn't see a laser transmitter either, unless it were from the very edge of the system.

What we might see if we were looking for it would be the ion emissions of decelerating incoming craft using ion engines, or the thermal signatures of interstellar craft using nuclear thermal propulsion. But by then it might be too late. Or esoteric energy uses like fusion. Or signatures of H-bombs near the periphery of the stellar system.

At 15 degrees Right Ascension, Tau Ceti is a little far off the solar system plane for an exploratory trip just now. Maybe in 50 years.

Re:It goes the other way, too

[garyebickford]

Don't feel too badly, you were on the right track. IIRC clear back in the 1970s it was determined that at TV frequencies the Earth was the brightest (known) object in the galaxy.

Re:It goes the other way, too

[cervesaebraciator]

Why would you put the people in charge on the second bus?

Re:It goes the other way, too

[mfnickster]

I always thought it would be funny to do a parody where Khan is thawed out and discovers he's not on Botany Bay at all, but the Golgafrinchan 'B' ark, and his genetically enhanced crew have all been replaced by telephone sanitizers and hairdressers...

Re:It goes the other way, too

[BlueStrat]

I always thought it would be funny to do a parody where Khan is thawed out and discovers he's not on Botany Bay at all, but the Golgafrinchan 'B' ark, and his genetically enhanced crew have all been replaced by telephone sanitizers and hairdressers...

Nah. Kahn's crew replaced by the "Banana Splits".

http://www.youtube.com/watch?v=UjS1nrsJhTQ

Strat :)

Re:It goes the other way, too

[0111 1110]

"On a small scale" is an understatement. We have virtually sent no signals at all. To any system past Alpha Centauri we would be dead silent on a radio scan of our system 99.9999999999999999999999999999% of the time. Are you wondering why we haven't made any effort to send signals? Fear. Even many radio astronomers themselves are frightened of attracting the attention of more advanced civilizations that may be listening. If we are too afraid to do it other civilizations may be as well. So we all listen but never speak. Everyone will stay very quiet out of ignorance and fear. Hence Fermi's Paradox and The Great Silence.

Re:It goes the other way, too

[Opportunist]

One has to organize the transport. And knowing how well they organize, the trip should only go to our own sun, which should save us heaps of fuel.

Re:It goes the other way, too

[Opportunist]

Hush! It's hard enough to get a government grant for some real astronomy, so we had to coat it into some kinda project that appeals to the common man. Or do you think you can sell a huge radio telescope to find some faint signals about the beginning of the galaxy to get closer to the big bang to the hicks who will instantly ask you "and what is it good for?"

But if you claim you're looking for E.T., they'll be pleased.

Re:It goes the other way, too

[betterprimate]

Suns have a lot of light noise too, so we probably wouldn't see a laser transmitter either, unless it were from the very edge of the system.

Noise? No. Sound? Yes. It is precisely how we understand our own sun. It is not by light but by sound.

There is a nice lecture titled "Songs of the Stars" by Don Kurtz from the University of Central Lancashire. It can be found here: http://feeds.tvo.org/tvobigideas

The podcast is called Stellar Seismology. Enjoy.

Shakespeare, among all other poets and artists, was correct. Even the dead poets and artists are still light years ahead of the early 20th century scientist. Modern scientists are just a regression of their predecessor; there are very few scientists today who merit such a title.

Re:It goes the other way, too

[kenj0418]

it was determined that at TV frequencies the Earth was the brightest (known) object in the galaxy.

That is until they learn to decode the signals. Then they will stop thinking we are bright.

Re:It goes the other way, too

[xstonedogx]

SETI is looking for intentional signals, not the alien equivalent of Abbot and Costello.

Re:It goes the other way, too

[0111 1110]

I can't tell if you are serious or not.

Re:It goes the other way, too

[jovius]

As the summary says the planet might be capable of sustaining a paper life form. Paper is an interesting creature not much studied in modern science. It's a life form based on a natural cellulose process. The innate fibre structure allows for the exchange of information.

Re:It goes the other way, too

[0111 1110]

It turns out that stars are pretty powerful radio transmitters, and the edge of a stellar system has considerable additional noise.

So what?

And then there's the cube-square law.

Don't you mean inverse square law?

Even if they were deliberately transmitting directly at us 12 years ago, it's unlikely we could make out the signal from the noise.

While noise (snr) is certainly a problem in any long range communication, if transmitting at the proper frequencies (ie. 1-10 Ghz; 34-37 Ghz; 75-80 Ghz) it isn't a major one.

The problems are more along the lines of:

1. It seems unlikely that any system within 50 ly of us would contain a planet with not just life, but intelligent life. Biogenesis has been compared to a tornado in a junkyard constructing a car. We really have no idea how to even do it ourselves. So it really may be quite rare. And even where there is life, intelligent life of the giant parabolic dish building variety is certainly not a given. Consider how many species there are on our planet brimming with life from pole to pole and only a single species seems to be intelligent enough to build computers and spacecraft and giant radio telescopes. If intelligence is such a good survival strategy why have more species not taken advantage of it? Even with all those stars out there intelligent life of the radio telescope building kind may be far more rare than those of us who enjoy science fiction may like to believe. The majority of life on earth is still simple microbial life.

2. The transmission has to either be aimed directly at us or be of orders of magnitude more power than at least we are capable of transmitting if only for economic reason. Either possibility seems rather unlikely.

3. No one really knows about us yet. We are just another star in a sky filled with them. If we embarked upon a major coming out party and transmitted signals for long periods to every star within, say, 100 ly then things might be different, but as it is there is no reason for anyone out there to point a dish in our direction except for causal surveys of nearby stars which might listen for only a few seconds each decade.

4. The aliens could be transmitting directly at us and we probably wouldn't hear them because they might be transmitting on one of the many frequencies that we are not listening on or which are attenuated by our oxygen-nitrogen atmosphere. Anything from 20-30 Ghz or above 100 Ghz is mostly blocked by our thick atmosphere. Very high frequencies tend to be more effecient at interstellar communication. Which is why setting up radio telescopes on the moon or mars would be rather nice.

Re:It goes the other way, too

[Anonymous Coward]

So basically it is like high school dating on a galactic scale?

Re:It goes the other way, too

[Zontar The Mindless]

Hello out there! Any potential overlords looking for a slave race that's advanced enough to be useful without being able to defend itself effectively? And might be tasty?

Re:It goes the other way, too

[DNS-and-BIND]

The Burvixese race evolved on the planet Arcturus 1, progressing from turtle-like swamp dewellers to a benevolent, highly technological society in just over fifteen million Earth years. Although the Burvixese had the wherewithal to build crude interplanetary vessels, they preferred to remain on the comfortable damp surface of their world and explore the galaxy through HyperWave communication. Using this method, the Burvixese made contact with several neighboring alien cultures, including the Utwig, the Gg, and unfortunately, the Druuge, whom the Burvixese would have been much better off never finding. For many decades, the Burvixese exchanged information with these races, trading technological, historical and philosophical facts and theories, until the fateful year 2142. It was then that the Gg announced that they had come under attack by a unknown alien race, who appeared to want nothing less than their complete annihilation. The Gg surmised that the hostile race, the Kohr-Ah, had located them using the Gg's HyperWave transmissions. Knowing that they had little chance of survival, the Gg warned the Burvixese that, unless they restricted their own transmissions, they too might face a gruesome fate.

Being a charitable race, before the Burvixese turned off their HyperWave transmitters, they shared the Gg's warning with the Druuge. But it was too late. The Druuge's powerful advertising beacons had already attracted the attention of the murderous Kohr-Ah, who, having finished with the Gg, began moving in the general direction of the Persei constellation, home of the Druuge. Realizing their peril, the Druuge took immediate action. They ceased all transmissions and sent a task force of their fastest ships to the moon of the Burvixese world. Once there, the task force assembled a huge HyperWave broadcaster on the moon's surface. When it was complete, the Druuge activated the unit which began emitting powerful HyperWave signals, focused directly toward the oncoming KohrAh fleet. The Druuge hoped that the hostile aliens would change course toward the Burvixese planet and fail to find their own worlds. Unfortunately, this ruse was all too effective: the Kohr-Ah changed course, attacked the poor Burvixese and, sadly, destroyed them all in three days of orbital bombardment.

--Star Control 2 manual

Re:It goes the other way, too

[garyebickford]

Yep, that's what I read back then. I don't know if it's true, of course. Let's say there were 100,000 TV stations worldwide, broadcasting at 2 MW each (power allowed varied from 300KW to 5MW - I'm just picking a number in the middle). That's 2GW (2*10^9 W) effective radiated power. The Sun puts out about 3.8 * 10^26 W but that's at all frequencies. I'm too lazy to figure out the fraction that amounts to the TV bands.

Re:It goes the other way, too

[0111 1110]

Interesting, but from what I have read, without a truly giant parabolic reflector and a very sensitive receiver none of those VHF/UHF signals would be detectable above background noise at even 1 ly. Those frequencies just don't work very well for point to point communication at great distance. I think the Friis equation would require truly giant reflector dishes compared to higher frequencies. I think they may also be attenuated by the interstellar medium (adds up over truly great distances) in addition to our own atmosphere. And if the receiver were on a planet with a similar sort of atmosphere...well. You really want to get at least above 1 Ghz to have much hope at all and 7-10 Ghz would be much better.

Re:It goes the other way, too

[symbolset]

Don't you mean inverse square law?

No, I mean the Square-cube law. In particular that the strength of radio emissions fall off at a ratio of the square of the power to the cube of the distance. Stars are very far and this law destroys the effectiveness of radiological communications over such distances.

Re:It goes the other way, too

[symbolset]

No, it's a simple inertial thing. The prime jumping-off point for interstellar travel from Earth is L2, as it utilizes the moon as a gravity slingshot. But the target has to be somewhere close to the solar system plane, or it loses the advantages of Earth's orbit being so far out of Sol's gravity well, and Earth's proper motion around Sol as well.

Re:It goes the other way, too

[Jesrad]

The funny thing is, pretty much every other sentient species in this corner of the galaxy already knows about us - Earth is known as "the planet of children" among them.

On a more serious level, I think that fear of attracting attention is very misguided. Civilisations capable of mass interstellar travel automatically have much better opportunities to pursue, especially given the crazy logistics involved, than to go torment younger single-planet civs.

Re:It goes the other way, too

[TapeCutter]

Brighter than any star on a particular frequency I can accept. I can't accept the Earth is brighter than the super massive black hole at the center of the milky way at any frequency, that thing eats stars like monkey eats peanuts and it's a sloppy eater at all frequencies.

Re:It goes the other way, too

[sFurbo]

No, you do mean the inverse square law. The inverse square law states that the intensity of radio waves (or light) decreases with the square of the distance to the source. The square-cube law is about the surface relative to the volume: The surface increases with the square of the size, while the volume increases with the cube. This means that the same structure at different sizes would not have the same properties. For example, a giant ant would not be able to get enough oxygen, as its ability to get oxygen follows its surface area, while its oxygen demand follows its volume. Likewise, it would be crushed under the weight of its own exoskeleton, as its strength is proportional to the square of the size, while its weight is proportional to the cube.

Re:It goes the other way, too

[SecurityTheatre]

Realistically, this can be overcome by simply using a secondary slingshot from another planet such as Mars or Venus. If you were to leave earth orbit at just a fraction of a degree off plane, you could go under the slingshot planet at, say, 30 degrees of latitude. You could still get most of the slingshot power, without giving up the ability to go off-axis to some extent.

I haven't actually done the math, but it seems plausible.

Re:It goes the other way, too

[nukenerd]

I think that fear of attracting attention is very misguided. Civilisations capable of mass interstellar travel automatically have much better opportunities to pursue ... than to go torment younger single-planet civs.

Who said anything about tormenting? The Vogons did not destroy earth to torment, but for practical reasons. They were described as "Not cruel, just callous". I destroy wasp nests, but not to torment them. I recently trapped a dozen mice in my attic; I actually felt sorry for them, they look cute, but knew that if I let them be they would be taking over the house.

Such an advanced civilisation might see us as we see an ants nest. And don't depend on talking our way out of it, reasoning with them. They would be on a totally different mental wavelength. Most higher animals on Earth talk to each other (that is what "birdsong" is for example), and we have lived for thousands of years alongside them, yet most people will not even accept that they do so - let alone listen.

Re:It goes the other way, too

[asylumx]

Pretending we're gay might seem like a good idea...

Everybody back to the pile! ( http://www.southparkstudios.com/full-episodes/s08e06-goobacks )

Re:It goes the other way, too

[asylumx]

Isn't that exactly what the GP said?

Re:It goes the other way, too

[berashith]

it would be valuable to know if a civilization thinks Jerry Lewis is funny. The accidental information leaked could let us know whether to avoid or destroy them.

Re:It goes the other way, too

[BlackThorne_DK]

In stead of the giant ant analogy, I'd rather remember the square-cube law, as the thing that keeps my toy trains tilting off the tracks in tight curves, when the same problem is not present in real life rail roads. The weight simply does not scale on the same level as the size in these little trains... :-(

Re:It goes the other way, too

[stenvar]

No, probably not. It turns out that radio emissions don't even make it out of the Oort cloud before they become lost in background noise. It gets worse once a civilization starts using cellular technologies, mesh networking, compression, and encryption, because then signals require less and less power and look more and more like noise.

Re:It goes the other way, too

[sFurbo]

I would have used giant animals dying of heat stroke while small animals freeze to death, but I couldn't resist the Sheldon quote.

I don't quite understand your example. Volume grows larger than area, so for something to be a problem in the small scale, there have to be a volume based effect keeping the problem at bay, and an area based one making it happen. I would think it was the weight that made the train tilt, and e.g. the flanges on the wheels that kept it from happening, but that would be a bigger problem for real trains than for toy trains. What an I missing?

Re:It goes the other way, too

[Kentari]

It certainly can be done and in fact has been done. Ulysses has a highly inclinded orbit around the sun with an inclination of 80.2 degrees. They did use Jupiter though.

Re:It goes the other way, too

[Kentari]

You need Tau Ceti's ecliptic coordinates to know it position relative to the orbit of Earth around the Sun. Those are -24.8159 degrees latitude and 17.8186 degrees longtiude. So Tau Ceti is almost 25 degrees below the ecliptic, not 15 above.

Re:It goes the other way, too

[Sigg3.net]

Unless they watch Star Trek, thinking it's a documentary.

Of course, cmd Riker does leave an ambiguous air of unshielded arrogance..

Re:It goes the other way, too

[Sigg3.net]

Thanks for squaring that out!

(Grabbing my coat.)

Re:It goes the other way, too

[mark-t]

It turns out that radio emissions don't even make it out of the Oort cloud before they become lost in background noise.

Not that I disbelieve you, but do you have a citation for that?

Re:It goes the other way, too

[operagost]

I'm curious as to how you intend to get the "gun nuts" on the ship.

Re:It goes the other way, too

[stenvar]

No, sorry. I heard it during a talk and checked the computation. You can check yourself: assume a strong radio transmitter (say, 2MW), spread the power out over the surface a sphere with 1-10ly, compute how much hits your antenna (say, 300m diameter), and compare with the noise floor. I think such a signal ends up being about 40-50dB below the minimum detectable level at 10 ly.

SETI can succeed for signals directed at us, and for enormously strong isotropic transmissions. But we're not going to pick up anything like human-like broadcasts, and human broadcasts have gotten less and less detectable since I Love Lucy.

Re:It goes the other way, too

[jellomizer]

Just so we can feel like we are doing something. SETI is actually quite useless and a sap of all our resources.

Re:It goes the other way, too

[jellomizer]

So we Want to find life on another planet, however we don't know if they will like us, if they don't then there will be gossop about it, thus embarrassing us and the other planet and the other planet will avoid even recognizing us because of this embarrassment and makes it worse. To make it worse it is impossible for you to have a one on one with the other planet because that other planet is with their friends all the time, and the only way you can even get in that group of friends is with your own.

Re:It goes the other way, too

[marcello_dl]

That's the problem I see in science fiction. We see only one direction, technologic advancement. What if conscience is not really bound by space and time, and can "tune to" different places and different times? You don't need radio, nor space travel, to see what others are up to. And possibly our planet is as interesting for the rest of the universe as an ant colony in patagonia is for the average slashdotter.

Re:It goes the other way, too

[Fr33z0r]

And even where there is life, intelligent life of the giant parabolic dish building variety is certainly not a given.

I've thought about this quite a lot. We would likely not have been able to get a meaningful foothold on this planet had the dinosaurs not been wiped out.

As we explore space, we may find life isn't particularly unusual, but it might also be the case that the dominant forms of life tend to trend towards those of the "big angry reptile" variety.

Re:It goes the other way, too

[flayzernax]

To be deliberately aimed at stars unlikely to produce results. And because active transmission from us is terrifying, versus passive listening in a dark corner were we might not hear anything important or ground shaking.

Re:It goes the other way, too

[mk1004]

Easy, free ammo.

Just have them practice on the outside of the ship, firing in the opposite direction of travel, so it'll speed up the ship. Until turnaround for deceleration, of course.

Re:It goes the other way, too

[N!k0N]

Using this 2007 CSX document for the "Real Railroad" information, and assuming HO Scale (1:87.1) there are a few things:

1. Real railroads -- cars start off at ~20~30 (Imperial) tons (i.e. ~40,000~60,000 pounds, or 18-22 tonnes*), and will usually have a maximum weight of ~40 tons (~36 tonnes), or a load weight of 10-20 tons (9-18 tonnes). (Note, most of this is for older cars I've seen/restored... newer things might be heavier, with different loading weights ... I model the 1940s, so don't really care)
Model railroads -- cars start off at a few ounces. Per recommended practice, a car should be 1 ounce (~28g), plus an additional 0.5 ounce (~14g) per 1 inch (2.54cm) of length. This results in a scale 40' (10 meter) long boxcar weigh about 4 ounces (114g).

2. Real railroads -- smallest track switches are size 10 (1 unut of divergence per 10 units of distance). Model Railroads -- #4,5,6 are generally considered "small, med, large" with #8+ being considered "nice to have" but generally rare on anything but "basement empires"

3. Real railroads -- curves are absolutely massive .The curves given in the linked document (which only concerns itself industrial/siding track) are considered pretty small, at ~480' radius. Scaled down properly, you're looking at a radius of 5.5 feet (66").
Model Railroads -- 20"radius curves are considered a minimum for most mainline operation (barring long wheelbase steam locomotives, full length passenger cars, and some modern locomotives/cars). 24-26" is about minimum to "run anything you could want", with 30" and larger being reserved for the afore-mentioned "basement empire" sized models

These three things combined (and probably others) are what help keep full-size railroads from "stringlining" the cars (i.e. instead of following this curve ')', the cars try taking the straight path '|' ... and derailing). Note that this isn't necessarily an exhaustive list, and there are other factors that can wreak havoc on model railroads that aren't a problem on real ones (e.g. "housecat")

Re:It goes the other way, too

[bill_mcgonigle]

it would be valuable to know if a civilization thinks Jerry Lewis is funny.

Well, we already know that he was evicted from his homeworld and wound up here. Cruel since we don't have much in the way of off-world lift to reciprocate.

Re:It goes the other way, too

[IndustrialComplex]

My understanding was that it is NOT doing that. I don't think we would do too well with an active galactic core.

Re:It goes the other way, too

[jamiesan]

That wasn't a very nice thing to do to those poor scientists in your attic. They were just checking on the results of the research they were with you as the subject.

Re:It goes the other way, too

[downhole]

Exactly. We don't know much of anything about any potential alien civilizations. All we can say for sure is that if they are advanced enough to get here, then we would be totally at their mercy. We barely understand why other human cultures on our own planet do things, or even our own culture a few decades ago. What hope do we have of guessing how some completely different species would behave? For all we know, they could want to destroy us just because we might potentially be a threat to them in the future. It would be insanely risky to assume that they must be benevolent by our definitions just because they are so advanced.

Re:It goes the other way, too

[symbolset]

Putting your first step in the right direction really does make a big difference.

"JUST" 12 light years? LOL.

[Anonymous Coward]

Voyager 1 has been moving away from Earth for what, 37 years, and it is now at the edge of, if not beyond, the Solar System's farthest reaches. It is 11 billion miles away.

And yet -- and yet! -- it is only 0.17 light-years away. So, "just 12 light-years" is essentially forever until we have a major breakthrough in terms of sheer speed of space travel.

Re:"JUST" 12 light years? LOL.

[LingNoi]

Um, actually wouldn't that make it 840 years away assuming voyager speeds?

Re:"JUST" 12 light years? LOL.

[Dyinobal]

When you're talking about interstellar distances "Just" is an appropriate term to put in front of a distance as small as 12 light years. At our current space flight capabilities it would take us ages to get there. How ever 12 light years is do able, in terms of physics and engineering. We would have to be willing to commit to a very serious project to build the ship though and I don't foresee any government willing to do that in the near future.

Re:"JUST" 12 light years? LOL.

[Dan East]

And yet -- and yet! -- it is only 0.17 light-years away.

Voyager 1 is only 17 light-hours away from the sun. That is only around 0.002 light-years, not 0.17.

Also note that the Voyager craft only used standard chemical propellants during launch and slingshot affects around various planets to gain the momentum they currently have - they only needed enough thrust to visit the target planets within a reasonable amount of time. In fact, they didn't want them going too fast, otherwise they would have zipped past the planets even faster, reducing the amount of time available to gather data (which of course was the primary objective of the mission in the first place).

Imagine if they had an ion drive and had been accelerating continuously for those 37 years, which is certainly what any interstellar craft would be designed to do.

Re:"JUST" 12 light years? LOL.

[PPH]

OK, use solar sails. Augment the thrust with heat emitted by RTGs, reversing the effect that is decellerating Pioneer. Make it a big heat source and design a round trip robotic* mission to survey the system.

*Robotic because we don't want it returning with a bunch of Reavers from the unshielded core.

Re:"JUST" 12 light years? LOL.

[Cimexus]

Um, not even close. Voyager is currently just under 0.002 light years away. Two one-thousandths of a light year.

Which of course makes your point even more pertinent. 12 light years, or even 1 light year, may as well be infinity.

(When you said it was only 0.17 ly away I was like "what, seriously? That's actually pretty good!". Then I realised that can't be right, as I know the DSN isn't waiting anywhere near 0.17 years for signals from Voyager.)

Re:"JUST" 12 light years? LOL.

[Black Parrot]

Also note that the Voyager craft only used standard chemical propellants during launch and slingshot affects around various planets to gain the momentum they currently have

Could you get more by slingshotting around the sun?

Re:"JUST" 12 light years? LOL.

[tqk]

Voyager 1 has been moving away from Earth for what, 37 years, and it is now at the edge of, if not beyond, the Solar System's farthest reaches. It is 11 billion miles away.

It's been running on empty since soon after it was launched. Consider what its velocity would be if it had been continuously accelerating for the last 37 years. We can do that now.

Re:"JUST" 12 light years? LOL.

[tmosley]

Second the last thought. I was getting my spacesuit on until I came to the same conclusion.

We'll have to see how the ion drives do.

Re:"JUST" 12 light years? LOL.

[0111 1110]

You do realize that Voyager was never intended for interstellar exploration, right? It is not any sort of pinnacle of what humanity can do and it was never intended to be.

We could probably get to at least 0.07c with nuclear pulse propulsion. Of course at that speed it would still take us over 170 years to get there. Plus the additional 100-200 years to build the ship and the off world infrastructure necessary to do so.

Re:"JUST" 12 light years? LOL.

[Fluffeh]

Keep in mind that Voyager, apart from some gravitational assists, wasn't ever really made to "go fast". Even now, there are ways to send things moving much quicker such as the Ion Thruster which although not NEARLY as powerful as a chemical rocket, is amazingly more efficient. The Weight to Thrust ratio is fantastic and could well be utilized to provide constant thrust for a long time. Once you exit the earth's gravity well, something like an Ion Thruster could over a number of years accelerate a craft to a much higher speed.

Re:"JUST" 12 light years? LOL.

[Chrutil]

Could you get more by slingshotting around the sun?

Yeah, but you'll end up in San Francisco in 1986 so it won't do you any good.

Re:"JUST" 12 light years? LOL.

[Dan East]

Yes, which is why the fastest ever spacecraft (AKA man-made object) was Helios II, which orbited close to the sun back in the 70s. That craft achieved speeds four times faster than that of Voyager 1 (70 km/s versus 17 km/s). Certainly it makes sense to quickly pick up as much speed as possible while you're in the neighborhood of massive objects before heading out into deep space, where the ion drive would have to be used exclusively.

Re:"JUST" 12 light years? LOL.

[Genda]

No, Spock won't be born for hundreds of years to calculate your trajectory and you could slingshot yourself back to the Flintstones...

Re:"JUST" 12 light years? LOL.

[ceoyoyo]

If you want to go there. "Just" 12 light years is a lot better than 100 or 1000 if you want to look.

Re:"JUST" 12 light years? LOL.

[mbone]

The math is wrong - Voyager I is 0.71 light days away, or 0.0019 light years away. It will take a lot longer than 840 years to get to another star.

Re:"JUST" 12 light years? LOL.

[Genda]

In point of fact, its all relative. You are using the orbital velocity of the planet plus its gravity, to transfer momentum to your Voyager craft. Or in your case, do the same with the sun, you would have to figure out what the relative solar motion is with respect to your destination star. There would be galactic rotation and other more local motions to be considered. Finally, the closer you get to the source of the gravity the bigger the slingshot, however if the source of your gravity assist is a ball of plasma with a million degree corona... you might wanna keep a reasonable distance, which might put a damper on the amount of gravity assist you'd ultimately be able to coax from the attempt.

You could try doing several loops around the inner planets to get a solid kick (some of the more recent planetary explorers used that trick.) However, if you're gonna attempt relativistically significant velocities, you're gonna have to use a mother Ion motor, or great big laser or an Orion engine, or something you can keep thrusting with for years while at the same time providing you with a meaningful ISP. Chemical reactions are simply too weak.

Re:"JUST" 12 light years? LOL.

[MichaelSmith]

Makes me wonder what you could accomplish with a huge bank of ion thrusters and a few fission reactors. I know that you really want to travel light when your thrust is low but I can't see a better way to send a manned mission to Titan.

Re:"JUST" 12 light years? LOL.

[GumphMaster]

One light year is approx. 63241 AU. Voyager 1 is about 120 AU distant receding at about 3.2 AU/year. That's about 19760 years to cover one light year (ignoring any speed changes)... 240000 and some change to go 12. It's currently only 0.0019 light-years distant.

Re:"JUST" 12 light years? LOL.

[MichaelSmith]

Also note that the Voyager craft only used standard chemical propellants during launch and slingshot affects around various planets to gain the momentum they currently have

Could you get more by slingshotting around the sun?

Generally, if you are going to use your motor you should do it inside a deep gravitational field, so the sun will do fine for that.

Re:"JUST" 12 light years? LOL.

[MichaelSmith]

Could you get more by slingshotting around the sun?

Yeah, but you'll end up in San Francisco in 1986 so it won't do you any good.

Just stay off the LDS.

Re:"JUST" 12 light years? LOL.

[mbone]

Could you get more by slingshotting around the sun?

Only if you are coming in from the outside the solar system. These gravitational slingshots exchange orbital momentum between the planet and the spacecraft. You could use the Sun to do that with the Sun and the Galaxy, but only if you were coming in on a galactic orbit.

(Now, you could get close to the Sun and unfurl a big solar sail and use that as a source of thrust, but that is different.)

Re:"JUST" 12 light years? LOL.

[LordLucless]

Even if it managed to get to a blisteringly fast .1c, you're still looking at longer than a human lifespan and generation ships.

Re:"JUST" 12 light years? LOL.

[Anonymous Coward]

Could you get more by slingshotting around the sun?

Yeah, but you'll end up in San Francisco in 1986 so it won't do you any good.

I beg to differ. With foreknowledge of the major booms and busts in the stock market, anyone ought to be able to amass a sufficient fortune over time to develop the necessary technology for practical deep space travel.

Re:"JUST" 12 light years? LOL.

[OneAhead]

Um, that's not quite how orbital mechanics works. Helios II started off from the earth - that is, with a lot of potential energy in the sun's gravitational field. It was put into an elliptical orbit around the sun, so on its closest approach, part of that potential energy was converted to kinetic energy (hence the high velocity), but at the most distant point, it's all converted back to potential energy, and there's zero gain. It's a bit like bouncing a rubber ball off the floor: it's surely going to hit the ground at a high velocity, but it's never going to bounce up higher than it started - no free lunch. The reason why slingshotting between planets works is because they move relative to each other. To use the rubber ball analogy again, if you throw a rubber ball at the front of a truck that is rapidly approaching you, the rubber ball will come back with a higher velocity. What you did is subtracting kinetic energy from the truck, just like a slingshotting probe subtracts kinetic energy from a moving planet. The tricks we use to make space probes gain kinetic energy are not unlike bouncing a rubber ball repeatedly between moving walls. To use the sun for slingshotting, one would require a very massive object in a highly eccentric orbit around the sun as a "second wall", which our solar system unfortunately doesn't have. (Or should that be: fortunately for our existence?) One could try to use pluto, but I doubt it's massive, eccentric and fast enough to be worth it.

Disclaimer: the above explanation is obviously somewhat oversimplified.

Re:"JUST" 12 light years? LOL.

[Anonymous Coward]

You can still use a slingshot around the sun for interstellar travel as it has motion relative to the galaxy and/or near by stars, although would depend a lot on where exactly you plant to go. Regardless, the sun would be good for taken advantage of the Oberth effect to maximize the efficiency of fuel.

Re:"JUST" 12 light years? LOL.

[Anonymous Coward]

Nothing. The fact is that fission reactors are way too heavy for ion thrusters. What is needed is a new lower mass source of energy: fusion, or possibly matter/anti-matter.

However, even better than that, would be NERVA. It COULD get up to 10% or more of light speed. In less than 120 years, they could be there.

Re:"JUST" 12 light years? LOL.

[Dan East]

That's a great description. Note that I didn't say anything about using the sun - I said "massive objects". Certainly spacecraft can be accelerated much faster than Voyager via the planets. It's a matter of determining the break even point between spending time zigzagging across the solar system, and when to finally head for the destination and let the ion thrust do its thing. At least at first the gains from using gravity assists would have to be greater than exclusively using ion drive directly after leaving Earth.

Re:"JUST" 12 light years? LOL.

[WindBourne]

Actually, it would be better in 1976 so as to stop reagan, but with 1986, it would be possible to bust W. for selling drugs and keep him from becoming president. Then we could afford to go to this planet by now.

So, yeah, it will do a lot of good.

Re:"JUST" 12 light years? LOL.

[WWJohnBrowningDo]

The stock market is a zero-sum game. Whatever money you make will be taken out of other investors, thus draining mankind's industrial capacity.

What you actually want to do is create new wealth by introducing future technology.

Re:"JUST" 12 light years? LOL.

[PerformanceDude]

Well - other than speed you are going to need some kind of kick-ass obstacle avoidance system. If you hit even the tiniest object at light speed, you are pretty much toast!!

Re:"JUST" 12 light years? LOL.

[stewsters]

Thats a qood question. Assuming some sane acceleration for a spacecraft, and assuming that they will need equal time to decelerate, how long would it be to travel 15 light years?

Re:"JUST" 12 light years? LOL.

[uvajed_ekil]

That's what the deflector is for!

Re:"JUST" 12 light years? LOL.

[JimCanuck]

If you don't get the reference, obviously you've been living under a rock for the last few decades.

Re:"JUST" 12 light years? LOL.

[garyebickford]

I think the parent is off by two orders of magnitude. I looks to me like 11 billion miles is 0.00187122571 light years. It sez here that Voyager is now travelling about 13 km/sec or 8 mi/sec, which is 0.00004 times the speed of light. Nevertheless, I think it's within the realm of the possible to build a probe, today, that could be accelerated to 1% of light speed - 3,000 km per second (about 250 times the speed of Voyager). That would make it to Tau Ceti in 1200 years. That's not an excessively long time for a project embarked upon by a global civilization. In the middle ages the Europeans built dozens or hundreds of cathedrals, many of which required more than 100 years to complete. Can we build electronics and machinery that last that long in space? An interesting question.

Consider that many plants and animals (not to mention slime molds and other entities) build spores or capsules of various sorts that allow their seed to last for hundreds of generations, floating on the air or in the water or just buried underground, waiting for the right conditions.

Re:"JUST" 12 light years? LOL.

[cervesaebraciator]

It is normally like a zero sum game, but in the case of time travel it would perhaps less so. Knowing the future, one might be better able to allocate resources (i.e. to be an entrepreneur in Schumpeter's sense) to projects that are going to be successful. With less waste of capital and resources on dead end projects one could--in theory--advance science and technology through investment. Of course, this would only work well for the first year or so. Although you did manage to make a bundle and advance technology, once you'd contaminated the timeline sufficiently your knowledge of the future would be, well, anachronistic. You'd then be stuck in the same situation as most other investors.

Re:"JUST" 12 light years? LOL.

[Anonymous Coward]

No he didn't. Watch more Star Trek.

Re:"JUST" 12 light years? LOL.

[MichaelSmith]

Try here

Re:"JUST" 12 light years? LOL.

[istartedi]

bust W. for selling drugs and keep him from becoming president

Oh great, Bryan and Stewie just showed up and told you not to do that. Then another Bryan and Stewie showed up...

Re:"JUST" 12 light years? LOL.

[shutdown -p now]

Sure, and so what? We could do generation ships if we really wanted to, and I doubt there'd be a shortage of volunteers. Heck, they might as well start looking for those at places like Slashdot - just imagine, living in what's essentially an ultra-high-tech basement for the rest of your life, all bills paid in advance!

Re:"JUST" 12 light years? LOL.

[mbone]

By "it" in my last sentence, I meant Voyager I. You can get to the stars faster if you spend more delta V doing so.

An interesting tidbit is that 1 year at 1 g thrust gets you to just about the speed of light. After 1 year at one g, you don't really go much faster (from the standpoint of someone left behind) but, boy does the relativistic time dilation kick in. Factoring in time dilation, you can get to almost anywhere in a fairly reasonably subjective time (i.e., the relativistic proper time for the traveler), assuming you can accelerate and deaccelerate continuously at 1 g. , Thrusting at 1 g also has the comfort advantage that we are totally used to it.

Of course, if you go very far, humans, or even the Earth, may not be there when you get back. And, how to achieve a constant 1 g thrust has to left as an exercise for the reader...

Re:"JUST" 12 light years? LOL.

[AK Marc]

I wouldn't want to go on a 1200 year trip. Chances are I'd be beat there by another ship launched from Earth years later. I'll go when we can sustain 1g for two years (one to accelerate and one to decelerate). That'll get you there in a hurry, passing all the slower early ships. Plot the course accurately so you don't have a fly on your windshield. That, and it'd be interesting to see the effect of friction in a vacuum at near light speed. One of the books I've read indicated that problem was solved with large shields of ice grown on the hull before journeys for protection from radiation and friction.

Re:"JUST" 12 light years? LOL.

[AK Marc]

My thought about sun slingshotting is to use a solar sail to gain potential (moving away from the sun) then slingshot around Jupiter to head towards the sun, pulling in the sail. Fall until you round the sun, then open the sail and head to Jupiter again. Repeat until you have the velocity you want or you are traveling too fast at Jupiter to slingshot.

Re:"JUST" 12 light years? LOL.

[timeOday]

Well, the old argument (reasonable, I think) is that sending multi-generation ships doesn't make much sense currently since our technology is still developing fast enough that people leaving later would arrive sooner. (Granted, it hardly seems that way for the last 40 years or so, but then again we'd have to make huge progress just to attempt it, so, we have to assume the will to make progress.)

.

If we want to send people for thousands of years, I think it should be an artificial uterus with some deep-frozen zygotes in it. When you arrive you crack open the eggs, and voila! Adam and Eve.

Re:"JUST" 12 light years? LOL.

[istartedi]

let's just make a bunch of incredibly fast scientific probes, say 0.3 c

We should to this for no other reason than to see if it's even possible to detect and evade objects. A little interstellar gas and dust pinging you with that kind of energy might just degrade the outer skin. We can handle that. Anything over a certain size will just explode the craft. IIRC, a paint fleck hit the space shuttle and made a scary pit in the cockpit window one time. That was considerably less than 0.3c. If a frozen bacterium hit your head at 0.3c, I bet it would explode.

Re:"JUST" 12 light years? LOL.

[maxwell demon]

As soon as you are starting to make money, you've changed the future and thus you knowledge of the unchanged future is worthless. Different stock prices will cause people to behave differently.

You'd be better off to take advice from Back to the Future and bet on sports events. There you've got a better change to make a big win before you changed the future so much that your information gets useless.

Re:"JUST" 12 light years? LOL.

[0111 1110]

I never found that argument very persuasive. In terms of space travel propulsion systems has our technology really changed that much since the 60s? Seems like we're building pretty much the same rocket engines now that we were nearly half a century ago. It's just that now we can put fancy computers on them. And better robots. Also that 'argument' will always work. By that argument there is never a good time to begin a long space journey.

Re:"JUST" 12 light years? LOL.

[garyebickford]

Going any significant fraction of lightspeed starts to involve problems with the stuff you're travelling through - at higher speeds it's essentially like standing in front of a particle accelerator, but even at lower speeds there is both drag that results from the one atom per cubic meter, and impact damage from everything bigger. So various ideas which amount to 'put a big mass in the front of the vehicle', like an ice ball or a chunck of rock, make sense. But there's also the significant probability of running into something 'big' - like tennis ball sized. At 30,000 km/s it's going to leave a mark. So you need some way of seeing those things soon enough to deal with them by avoidance (changing course), destruction (zapping them), or moving them (??).

So, to minimize frontal area and provide the distance from front to back to make it possible for those effects to be dissipated, you might have a needle ship, composed of a mile or so of 10 meter-diameter rock, followed by another mile or so of 10-meter-diameter water, followed by some big-ass lasers, followed by a 10-meter diameter actual vehicle cabin (how long?), followed by the rest of the vehicle

And something I've never seen addressed is the prospect that the interstellar medium must have currents - those particles are moving, and there are probably eddys and currents. So I suspect that at those speeds there may be enough of an effect to cause what amounts to a bumpy ride - much like an airplane has to deal with air currents. I haven't done the math but it's something to be considered. Imagine living on a vehicle where you're never more than five meters from the center axis, that's constantly jiggling like a bad airplane ride, and the living space is 10 meters wide and a mile long - for 40 years.

Re:"JUST" 12 light years? LOL.

[0111 1110]

The vast space between star systems is not known for having a lot of space junk floating around. You're lucky enough to find the occassional hydrogen atom. That's not to say that the possibility should not be considered, but it isn't a show stopper. You could wait to accelerate to high speed until you were well out of our system and decelerate well before you enter the target system.

Re:"JUST" 12 light years? LOL.

[symbolset]

You make me post this in every extrasolar planetary thread and it's really annoying.

Voyager 1 is nowhere near current technology. We have ion thrusters now. We have supercomputers now. Hell, your cellphone would have been a supercomputer to the guys who designed that thing. We have water on the moon, in near-earth asteroids, and a limitless supply in Ceres, and we didn't know that then. We have new methods of separating that water into hydrogen and oxygen on orbit efficiently, so it doesn't have to be hoisted out of our gravity well. We have far more understanding about long-term space missions and habitation. Plants grow in space! We didn't know that either. We have commercial rockets that can dock with the space station: an absurd sci-fi fantasy back then. We have robots who can do the work of gathering fuel without too much supervision. We have robots that could survive the kind of acceleration provided by a 1000 km railgun that it would take to put the robots there in a reasonable time, and a place in low-g to put that rail gun and robots to build it. And software to put on the robots that apparently can withstand a 24 year ping time.

In fact, recent learnings about the Voyager Anomaly point to an obvious way to propel interstellar spacecraft: Put a couple dozen 200 MW fission reactors behind some heat/radiation shields and point them in the opposite direction from where you want to go, and let them melt down. The heat provides thrust. At 745 W per HP, that's good for a few thousand horsepower of thrust. Since a Newton is a Horsepower-second, near enough, and the reactors run for many years, that's insane number of Newtons. We actually used to have a project that worked on this theory called Project Orion.

So, for example, get the robots to gather up some water and refine it into LH2/LO2. Slide some of that fuel down to LEO and pick up a commercial hydrox booster and lift it into high orbit and fill it. Repeat until you have seven of them. Now arrange them in a filled hexagon at L2 orbit just beyond the moon, and fill with hydrox. Strap your meltdown-driven spacecraft and habitat/humans/robotic exploration package on the nose, and at the most opportune time when your cislunar orbit is headed closest to the desired direction, light that shit off. Boost for 2.5 minutes at 6 g, and discard the 7 Saturn boosters. You're already several times past solar system escape velocity, and your course is assured. Then engage the thermal drive and melt down the reactors and continue to boost at something on the order of 40 billion Newtons per year as you head to the nearest star. Somebody do the math for me. I'm thinking 50 years.

"Oh, but the cost!" you might say. Well look. We don't need the work of all the people we have. It turns out that something like 1 in 4 Americans is all that's required to maintain our standard of living. According the US Bureau of Labor Statistics we have 11 million underemployed people in the US, or $500B/year worth of people who could do be doing something interesting and useful who aren't. And that's just the US, and I think that number is understated 2x. Besides, we'd like to be rid of that nuclear fuel anyway.

I'm not even in the space field and I could figure out how to get people to Tau Ceti in under one human lifespan with resources like that, or robots sooner still. We could do it, right now, with the resources and science that we have. It would be a one-way trip, but we would not lack for volunteers or robots. From one economic point of view it wouldn't cost us one whit more than we're already paying, and instead of being unhappily idle the proletariat would be excitedly engaged in a worthy endeavour. You just have to sell it.

Just because your grandparents couldn't figure out how to do this don't assume that the current generation can't.

Re:"JUST" 12 light years? LOL.

[nu1x]

> and voila! Adam and Eve.

You mean, like, Mowgli ? Running around, furiously eating and fucking (provided a Mowgless).

Now see, there are these things called "finesse" "erudition" "skill". They are impossible to attain without society, without mentors - well, at least, in the form of books, but do you think unattended humans would control theis chaotic natures for long enough to settle down and read ?

And no, forced indoctrination would not work, for it produces robots, people with no ambition.

Face it - generation ships are unattainable with current breed of humans, unless we find a 100% reliable way to give birth to little Buddhas.

Human interaction and inspirational figures in your life are more important that you may realise.

Re:"JUST" 12 light years? LOL.

[AchilleTalon]

So, it would take over 200K years to reach that star system at Voyager I speed. And keep in mind you will then need an energy source in the interstellar space, solar energy won't work, fission won't work, fusion won't work. And in first place, would an engine with any mechanical part will endure such a long journey? What about cosmic radiations? Hibernation couldn't be tested on a such long term period. Even a 100 factor gain in speed wouldn't be enough.

Interstellar travel is an Hollywood game. We are locked down here in our solar system.

Re:"JUST" 12 light years? LOL.

[Jesrad]

If you really want to know, try it directly yourself by playing KSP ;)

Re:"JUST" 12 light years? LOL.

[MichaelSmith]

Hmmm interesting. It might be an opportunity to simulate my favorite Apollo failure mode. Say the command and service module are lost in lunar orbit before the LM goes to the surface. Can the LM be flow back to an orbit around the Earth, and the crew rescued by the next command-service module in line?

Re:"JUST" 12 light years? LOL.

[pluther]

If a frozen bacterium hit your head at 0.3c, I bet it would explode.

The bacterium, maybe, but not your head. Bacterium have very, very little mass.

For instance, a single E. Coli bacterium has a mass of approximately 2.9 x 10^-13. If someone flung one at you at at .3c, it could have a total momentum of only about 2.9 x 10^-13 x 3 x 10^8 x .3 = .0000261 gm/s.

This is about the equivalent momentum of a baseball (142g) moving at .00000001838 m/s (or .018 mm/s). (This is about the velocity imparted to an average baseball by an average slashdotter. So, not very fast.)

Re:"JUST" 12 light years? LOL.

[gutnor]

Also, current human society is still too immature to commit for multi-generational anything. Look how the world and mentalities have changed in the course of a few generation.

Re:"JUST" 12 light years? LOL.

[flargleblarg]

I don't know where you're getting "Ceti Tualpha Five"... It was Ceti Alpha V.

Re:"JUST" 12 light years? LOL.

[SecurityTheatre]

You could wait to accelerate to high speed until you were well out of our system and decelerate well before you enter the target system.

And that is how it would have to work. I don't think there's any means to immediately reach light speed, or even a fraction of it.

to reach 0.1c takes about a month and you're well past the orbit of pluto by then (3-5 times), assuming about 10m/s/s acceleration (slightly higher than 1G). You would be going pretty fast in the inner solar system, but not relativistic speed.

However, in order to do a trip to Alpha Centauri at 1G acceleration, assuming you have a 100% efficient antimatter drive that turns pure matter into pure kinetic energy, your ship still must have a fuel:payload ratio of 20:1 (and the ship itself is included in the payload). Let's just assume the space shuttle is the size we're going for..

Lets also assume 50% efficiency, just to keep things moderately real.

Your ship is 250,000 pounds. Your fuel supply is... 10,000,000 pounds. Half of this needs to be antimatter.

Where to obtain 5,000,000 pounds of antimatter? hmmm.....

Re:"JUST" 12 light years? LOL.

[dillee1]

Actually you can still use gravitational assist with the sun. Burning your fuel at the perihelion will give you far more delta-V than the same burn at aphelion. Simple explanation: part of the gravitational potential energy of the fuel is converted into kinetic energy of the spacecraft; with the burnt fuel being "left-over" at a much lower orbit than before.

Re:"JUST" 12 light years? LOL.

[Viol8]

"Interstellar travel is an Hollywood game. We are locked down here in our solar system."

There might be some as yet undreamt of physics that could get us very quickly to (or even beyond) light speed but I suspect thats unlikely and that sadly you are right.

Though even just exploring out solar system is a fantastic voyage in its own right. Imagine flying through the clouds in Jupiter or sailing on a methane lake on Titan? If we could get solar system traversal time down to a few weeks or months rather than decades imagine the possibilities....

Re:"JUST" 12 light years? LOL.

[Phrogman]

Have you not played any space empire games? Its just because the power-that-be have been spending points on the Communications and Electronic Engineering lines of research and not enough points on Basic Drive Systems. Once they realize their mistake they will develop new drives in short order. Once we finish the next box or two we can move on to Interstellar Drives or Jump Drives no problem.

Re:"JUST" 12 light years? LOL.

[Grizzley9]

Let alone the food and air requirements to keep a crew alive. There is only so much recycling you can do. No we cannot do a generational ship b/c you would have to take everything with you and as far as we know, elements in interstellar space are quite slim with no tech to turn any regolith or meteors into edible nutrients.

Re:"JUST" 12 light years? LOL.

[Nimey]

Bet you the life-support system and/or batteries wouldn't last long enough, even for only two men.

Re:"JUST" 12 light years? LOL.

[JeanCroix]

Intentional conflation. It was a joke, son.

Re:"JUST" 12 light years? LOL.

[andydouble07]

Right: http://en.wikipedia.org/wiki/Oberth_effect It seems counter-intuitive, but doing a burn as close as possible to the sun (probably getting there using a bi-elliptic transfer) will give a huge boost to velocity, as compared to just flying in a straight line away from the sun, given a high enough delta-V budget.

Re:"JUST" 12 light years? LOL.

[Tarlus]

Just invent transparent aluminum, and you'll make your fortune.

Re:"JUST" 12 light years? LOL.

[jonadab]

Voyager 1 was not designed (primarily) to go as fast as possible. It was designed to study as many things as possible within the solar system on its way out.

If we put a good enough team of engineers on the problem, I imagine we could probably come up with a way to send a spacecraft to Tau Ceti in way less than half the time Voyager 1 would take to get there, maybe even as little as 10% of the time Voyager 1 would take, though that's starting to push the limits of our current technology. But let's assume we could manage ten times Voyager 1's speed. Multiple gravitational slingshots would need to be involved, probably culminating in a high-speed low-altitude pass around at least one of the gas giants, with a razor-thin margin for error, before finally heading out, but it might be feasible.

That would still make the travel time a couple of centuries, so we're not exactly ready for manned flights (just as well, given the acceleration forces such a trip would entail); but data the thing beamed back would start arriving here just twelve years after the probe got within range to start collecting it, if the signal it sent were strong enough to arrive here in tact. If we jumped on this project *right now*, we could potentially have video footage of the place by 2300 or so. (Of course, the footage thusly obtained would be horrifyingly low on detail by the standards of 2100, let alone 2300. But I bet it would be better than we can get from twelve light years away with a telescope, probably ever.)

Re:"JUST" 12 light years? LOL.

[HeavenlyWhistler]

We could do generation ships if we really wanted to, and I doubt there'd be a shortage of volunteers

Uh... generations 3 through n-1 are not volunteers!

What? You're telling me I was born on a ship, and will spend the rest of my life here, instead of the beautiful planet in these pictures? Thanks Mom and Dad!

Generation 3 would revolt and turn the ship around.

Re:"JUST" 12 light years? LOL.

[donutz]

Accelerating to higher speeds is fine and all, but unless you want to zip by the planet, you're going to need to decelerate too.

Re:"JUST" 12 light years? LOL.

[jonadab]

I said...
> But let's assume we could manage ten times Voyager 1's speed.
So far so correct.

Then I naively calculated based on the parent's figure of how far away Voyager 1 is, ignoring various facts, not least the actual speed of light and correspondingly large size of a light year. I was trying to save time by taking a shortcut. Yeah.

So when I said this...
> That would still make the travel time a couple of centuries

That was wrong. Really wrong.

Voyager 1 is going, umm, less than 40 thousand mph. Ten times that would be less than 400 thousand mph. Thus, even a HUNDRED times Voyager 1's speed would, in fact, make travel time (for a twelve-light-year trip) in excess of two hundred centuries.

Re:"JUST" 12 light years? LOL.

[mcgrew]

I wouldn't want to go on a 1200 year trip. Chances are I'd be beat there by another ship launched from Earth years later.

There's a novel about that, starting off with time dialation and other artifacts of near light speed. But in the novel (can't remember the name or author, I think it was either Heinlein or Niven), had the first bunch not gone, they wouldn't have discovered the mechanism by which they could overcome the speed of light limitation.

So even if you were overtaken, it still might not be a loss (as it was on one of the ships in the story that crashed or got eaten or something, been a while since I read it).

Re:"JUST" 12 light years? LOL.

[jonadab]

> Plants grow in space!

No, they don't, unless by "space" you actually mean "a dense atmosphere comparable to Earth's".

Certain plants can *survive* in space, e.g., as spores, but they can't *grow* unless you put them in an atmosphere of some kind.

Re:"JUST" 12 light years? LOL.

[painandgreed]

This is about the equivalent momentum of a baseball (142g) moving at .00000001838 m/s (or .018 mm/s). (This is about the velocity imparted to an average baseball by an average slashdotter. So, not very fast.)

Yes, but a baseball is over a much, much larger area than the bacterium in the example. What you will have is a bacterium sized bullet that will probably penetrate deeply into the person even if they don't move at all. With secondary cavitation and fragmentation of the bacteria, it might actually end up being a cross sectional area that can't be ignored with regards to the health of the target.

Re:"JUST" 12 light years? LOL.

[alien9]

as long as they remember to push the brakes in time

Re:"JUST" 12 light years? LOL.

[mcgrew]

Are you kidding? he's no nerd, he's an Anonym...

Wait, what??

Re:"JUST" 12 light years? LOL.

[mcgrew]

The stock market is a zero-sum game. Whatever money you make will be taken out of other investors, thus draining mankind's industrial capacity.

Bullshit, almost all real wealth starts with a shovel or a chain saw or a plow. The wealth is the minerals and other resources, which are simply magnified in value when used in manufacturing.

Money is NOT wealth, it's simply a means of counting and managing wealth.

What you actually want to do is create new wealth by introducing future technology.

New technology creates no new wealth, it amplifies the old wealth. It's still just dollars going from hand to hand. Planting a field of corn? That's creating wealth. Digging a mine? That's uncovering wealth. Selling something? That's transfer of wealth. The wealth owned by the McDonald's corporation comes from the farms the "food" is grown on, amplified by the workers who turn that raw wealth into an enhansed product that someone will buy, or in other words, a transfer of wealth.

Re:"JUST" 12 light years? LOL.

[AK Marc]

You don't need FTL for that. Just launch an ion-powered ship that accelerates at 0.1g now (doable with today's tech) and a dual ion/nuclear ship 10 years later with 0.2g acceleration (or better, if possible). The second ship will beat the first there, but the second ship will need to not get too close to the first. Wouldn't want to hit them, or get into their exhaust trail.

Re:"JUST" 12 light years? LOL.

[LordLucless]

Because an earthlike planet is so useful if we're never going to actually get any humans there

Re:"JUST" 12 light years? LOL.

[MichaelSmith]

The LM has oxygen to recharge the PLSS units for the crew. It has power for a surface stay longer than a transit to Earth. It may not have enough lithium hydroxide cannisters though so if the crew was unable to grab some from the CM (same interface issue as Apollo 13) the PLSSs could possibly be used to scrub the cabin.

Re:"JUST" 12 light years? LOL.

[kheldan]

I just did the math. If Voyager I, at it's current speed of 62100km/h could be pointed at it, it would still take about 208000 years for it to get there. Even if you could increase it's speed by a factor of 10, that's still over 20000 years. Comments, anyone? I'm no astrophysicist, and that was 2 minutes with Google and a calculator.

Re:"JUST" 12 light years? LOL.

[painandgreed]

However, if you're gonna attempt relativistically significant velocities, you're gonna have to use a mother Ion motor, or great big laser or an Orion engine, or something you can keep thrusting with for years while at the same time providing you with a meaningful ISP.

It doesn't have to be for years. You could, for example use a rail gun with high g acceleration powered by solar energy. Of course, although a modern rail gun like the navy uses is good for 1000g/s, I did the math once and you'd need a rail gun 250k miles long (here to the moon) to get to .1c.

Re:"JUST" 12 light years? LOL.

[istartedi]

OK, I looked up the KE of a 50 caliber round (basicly light anti-aircraft gun) and it's 15kJ. I'll have to work backwards to see how large a particle it would take at 0.3c to get that kind of energy. Don't forget to use the relativistic KE equation, which is *not* 1/2 mv^2.

I don't really have the time to do it. It's a bit of a pointless calc too since in our every day world KE from projectile weapons gets transferred to the target. At these velocities the projectile might pass right through the target and only transfer a small fraction of the energy. That's why we need to test the living daylights out of this before we even think about it.

This could lead to some very counter-intuitive designs, such as walls designed to minimized energy transfer rather than absorb energy as we do for non-relativistic impacts. Think self-healing rubber filled aluminum or something rather than Kevlar.

I imagine that the ship would have to have multiple independent life support zones. If impact doesn't explode a zone, then it's a problem we can manage. You just sound an alarm and give people time to evacuate the leaking zone until it can be repaired.

The real problem would be a small swarm of particles that impact multiple zones in such a way that they don't seal. The trip ends not with an explosion, but with the ship full of pinhole leaks and no more zones left to which you can evacuate. As a last ditch effort you don your suits, only for pinholes to appear in them. Oddly, you might even survive such a pinhole right through the heart as long as it doesn't disrupt the electrical pace; but your suit is leaking, your ship is leaking, and you're finished.

After the swarm passes, you'd have a dead ship hurtling through space.

Thinking out all possible debris scenarios and how to mitigate them seems like the biggest problem to me.

Re:"JUST" 12 light years? LOL.

[timeOday]

Oh, I agree. By "Adam and Eve," I really did mean to imply that the human race would be starting over with practically nothing from that point. Of course they wouldn't even survive at all without robotic nannies of some sort that do not currently exist, and we can only speculate what Tarzan-like effects would result.

Re:"JUST" 12 light years? LOL.

[Fluffeh]

Accelerating to higher speeds is fine and all, but unless you want to zip by the planet, you're going to need to decelerate too.

Sorry, thought it was rather obvious, you accelerate for half the trip and decelerate for the second half.

Re:"JUST" 12 light years? LOL.

[OneAhead]

Yeah, probably I should have added this link to clarify the different "types" of gravity assist.

Re:"JUST" 12 light years? LOL.

[pedestrian crossing]

Probably not the book you're thinking of, but still an interesting take on time dilation effects is the Forever War by Joe Haldeman...

Re:"JUST" 12 light years? LOL.

[Teancum]

Even traveling at just 0.1c, humanity can literally fill up the Milky Way Galaxy and move on to the rest of the local group of stars in less than a million years. From the perspective of the age of the universe that is an incredibly short period of time. Assuming that only 1% of all stars in the galaxy have habitable planets (meaning "habitable" like Mars... something that takes effort to get resources but is still doable by mere mortals), that is still more planets than there are people on the Earth right now.

I don't know what would get that initial spark of people moving out to the rest of the stars of the galaxy, but once it starts happening, it won't stop.

Re:"JUST" 12 light years? LOL.

[Teancum]

That isn't exactly true. There have been some real innovations in propulsion technology, but the real issue is that those systems which really advance technology need to be nuclear powered rather than powered with chemical energy. It really is just a matter of energy density, and mixing chemicals simply doesn't work very well beyond going to the Moon or perhaps out the outside going to Mars in about a year.

Things that have been proposed, besides the "nuclear pulse rocket" (aka literally detonating nuclear bombs as a propulsion system) include the VASMR engine, ion propulsion, solar sails, and the discovery of the Interplanetary Transport Network (really just a bunch of equations to find very low energy transfers to other places in the Solar System).

The Dawn spacecraft is using the ion propulsion system, and it seems to be working out very well. It has the thrust of perhaps a whisper or a gentle breath, but if that is sustained over the period of months as continuous thrust it can add up to quite a bit.

Some serious work on new ideas has been done, the trick is simply getting some of those crazy ideas built and out of the hands of rocket scientists and into the hands of engineers who can actually make them work.

Re:"JUST" 12 light years? LOL.

[Teancum]

... or by Generation 8 they may simply not want to stop. The notion of living on a planet is so old fashion that they may not want it. The only reason they would want to stop is to get supplies needed to continue the trip... so they would be looking for asteroids and not planets like the Earth.

Re:"JUST" 12 light years? LOL.

[LordLucless]

I'd say you'd need either close-to-light propulsion technology, advanced terraforming technology, or trusted suspended animation to get people to a habitable destination within their lifetimes.

Re:"JUST" 12 light years? LOL.

[Teancum]

Who said it had to happen in a human lifetime, or that a human lifetime was limited to about 100 years with a million years of technological progress? 10k years ago engineers in Egypt were still trying to figure out how to build the pyramids and the typical lifespan of most people was about 30 years. It was nearly that bad 500 years ago and the technologies needed to cross oceans were by comparison worse than what we have to cross between planets in the Solar System today (and comparatively expensive by standards of ordinary working people of the era too).

I'm not saying that it will be easy to travel between stars, and I'm not really certain that you will be able to do something like drop-ship a package by FedEx to Tau Ceti or Alpha Centauri in the next few hundred years, but human travel between stars is just on the inside of practical physics and it could happen. It will take energy densities approaching that of a matter-antimatter engine and as a practical matter today's engineering certainly isn't up to the challenge, but it isn't really impossible provided somebody really wants to come up with a plan for how to get it to happen.

Re:"JUST" 12 light years? LOL.

[LordLucless]

You said you didn't know what the initial spark would be - I said I think it'd be one of the above technologies, because in order to inspire people to go for the stars, you have to be able to get them there, not their kids. I think a generation ship is going to be wildly unsuccessful except as an escape from calamity or extreme deprivation - people just aren't going to want to live in a tin can for the rest of their lives.

Old news ...

[gauthamg]

... https://en.wikipedia.org/wiki/The_Stones_of_Blood :)

Engage!

[MrEricSir]

Take us out of orbit, set the heading for Tau Ceti. Maximum warp. Engage!

So you're saying ...

[ezzthetic]

If there is life, it consists of paper-based organisms?

Lets start seeding the galaxy with life

[detain]

Sure its not viable for us to go there ourselves but couldnt we start sending probes in the direction of planets like this with enough ingredients on them to help kickstart life on other worlds that can support it. It wont effect us but might help ensure life continues in the universe once we inevitably destroy our own planet.

Re:Lets start seeding the galaxy with life

[mutherhacker]

start sending probes in the direction of planets like this with enough ingredients on them to help kickstart life on other worlds that can support it. It wont affect us ...

It won't affect us? Here's a way it could affect us: The life we seeded grows, fast! It grows up faster than we expected and evolves at an exponential rate. Within 200 years it develops a space program then decides to pay us a visit with huge guns.

Re:Lets start seeding the galaxy with life

[0111 1110]

It was that sort of reasoning that almost prevented the Tau Cetians from seeding life here. Luckily cooler heads prevailed and here we are.

Re:Lets start seeding the galaxy with life

[detain]

I would say the spreading and continuation of life in the universe is worth the risk, even at the possible cost of our eventual downfall.

Re:Lets start seeding the galaxy with life

[Theaetetus]

start sending probes in the direction of planets like this with enough ingredients on them to help kickstart life on other worlds that can support it. It wont affect us ...

It won't affect us? Here's a way it could affect us: The life we seeded grows, fast! It grows up faster than we expected and evolves at an exponential rate. Within 200 years it develops a space program then decides to pay us a visit with huge guns.

And then we surrender like good little doobies, because there's no point in fighting something that evolves from protozoa to interstellar space-faring civilization in 200 years. Fortunately, at that rate, we'll only have a couple years in slavery and they'll have evolved past us to the point where they won't care and will set us free again.

Re:Lets start seeding the galaxy with life

[grantspassalan]

We are talking about real life, little boy, not science fiction. In the real world, everything has to obey the laws of physics and the derivative sciences. There are limits to how fast things can evolve.

A basic assumption in this and most other posts on this subject is that we know ALL laws of physics. That is an incredibly arrogant assumption. It is quite likely that there are other laws of physics which we haven't even imagined yet. There are hints of this in a collection of books called the Bible. The central tenet of Christianity is the resurrection of Jesus Christ. This resurrection from the dead violates all KNOWN laws of physics, but that does not mean it is impossible and that it did not indeed happen.

Just because we are limited to time, space and death, does not mean that there could not be eternal entities in other places that are immortal, have no such temporal limitations and have never learned evil. Right now, good and evil are inextricably mixed up together. Every human being has a choice between good and evil. A terrible act of evil was just perpetrated in Connecticut. It appears right now that the earth is a prison planet, isolated by the immensity of time and space. This is to prevent the spread of evil to other places in the universe. For thousands of years and for all the foreseeable future, death is the only way to escape from this prison planet. In the book of Hebrews, part of the Bible, it is written: ...it is appointed to men once to die, but after this the judgment,... (Hebrews 9:27)

Nobody here even on /. will deny the truth of the first part of the sentence, but many if not most modern “enlightened” western people try to negate the truth of the second half, namely that there is a judgment coming after death. It is at this judgment, that good and evil will be separated, so that there are henceforth two locations. The location where only good will exist is commonly called Heaven in our culture and the bad place is called Hell.

Definitely NOT Earth 2

[AbsoluteXyro]

Pretty impossible to say if the planet is habitable, but at 4 times the Earth's mass it definitely isn't Earth-like. The search continues...

Re:Definitely NOT Earth 2

[tmosley]

Eh? Not necessarily. If it is less dense, it wouldn't be all that different.

Re:Definitely NOT Earth 2

[Woogiemonger]

Pretty impossible to say if the planet is habitable, but at 4 times the Earth's mass it definitely isn't Earth-like. The search continues...

To be specific, according to Stephen Dole and Isaac Asimov ( Planets for Man ), the max habitable gravity is 1.5g. If I'm 180 pounds, 4g would mean I feel like I'm an unsightly 720 pounds. Get in ma' belleh! :D

Re:Definitely NOT Earth 2

[Cockatrice_hunter]

Gravity is based on mass, not volume. Density has nothing to do with it

Re:Definitely NOT Earth 2

[0111 1110]

No, but your distance from the massive object does and that depends on the density of the planet. We can make some educated guesses based on the density of the Earth, Mars, Venus, Mercury, and from the moons in our system, but it is still no more than a guess.

Re:Definitely NOT Earth 2

[ceoyoyo]

A planet with four times Earth's mass but the same density would have a surface gravity of about 1.6g. Not so different. There are lots of people balancing 1.6 times my mass on similar sized feet.

Re:Definitely NOT Earth 2

[Chris Burke]

Density has a lot to do with surface gravity. You can approximate (or if we assume a perfectly spherical planet of uniform density, exactly represent) the gravity of the planet with a point mass at the center of the planet.

How far away you are from that point mass while standing on the surface says how much surface gravity there will be. Thus volume matters.

Re:Definitely NOT Earth 2

[halltk1983]

That is only the case if it is the same size as earth. If it is larger the effective weight will be lower.

Re:Definitely NOT Earth 2

[mbone]

Gravity is GM / R**2. Mass is proportional to R**3, which means that Gravity is proportional to R, if the density is the same. Inverting that, Gravity is proportional is M**(1/3), so 4 times the mass is 1.587 times the gravity (for a constant density).

So, I wouldn't rule it out.

Re:Definitely NOT Earth 2

[CrimsonAvenger]

Pretty impossible to say if the planet is habitable, but at 4 times the Earth's mass it definitely isn't Earth-like. The search continues...

Hmm, four times the mass, assume same density, we get 1.6g. Certainly not beyond the bounds of survival.

That's probably the low end, assuming an "Earthlike" planet. High end is probably less than 2g, unless we're talking serious heavy-metal conncentrations, which would make it uninhabitable anyway.

Re:Definitely NOT Earth 2

[mark-t]

No, actually....

The planet is 4 times as massive, and assuming uniform density means that the planet has roughly 4 times the volume, and since radius of a sphere increases with the cube root of volume means that it should be about 1.6 times as large (cube root of 4), Since gravity decreases with the square of the distance, that means that surface gravity is actually about 2.5 times that of earth, not 4 times. Still too much to survive, however.

A planet about 3 times as massive as Earth, but otherwise composed of similar elements, would thus have approximately double Earth's surface gravity, and probably represents the upper limit on what humans could viably endure for anything but very short periods.

I wouldn't be able to guess, however, what kind of upper variances we could tolerate with regards to surface atmospheric pressure.

I'll go!

[tqk]

I'll go. Please? No reservations here, just sign me up. Beem me up, please.

beam up no we have a gate you walkthough to get

[Joe_Dragon]

beam up no we have a gate you walkthough to get there.

Re:beam up no we have a gate you walkthough to get

[tqk]

I'll go. Please? No reservations here, just sign me up. Beem me up, please.

beam up no we have a gate you walkthough to get there.

Even better. Is Sam there? Hell, I'll settle for Rodney.

Kaplah (to seriously mix a metaphor)!

Re:beam up no we have a gate you walkthough to get

[AK Marc]

Dr Keller would by my first choice.

I, for one..

[Luminary Crush]

...welcome our new Tau Cetian overlords!

These are some big IFs

[ethanms]

Even if the planets are inside the habitable zone, they would need to be the correct consistencies... Venus and Mars are in the zone here, but neither has life or is natively habitable. Yes, we're attempting to discover if Mars may have HAD life, but as far as we can obviously tell, it has none now...

So it's fun and interesting to search these types of star systems and planets--and I think it's absolutely worthwhile to focus a SETI program on them to try to determine if there are any stray signals we can pick up--but otherwise this really is not much more than dreaming and guessing.

Assuming SETI finds no signals, but we do believe there a couple of planets into the habitable zone, then I think it would make some sense to attempt a probe mission there... but it could be a while before we're at the technology level we'd need...

I think our current speed record in space is about 150,000mph ... which is ~1/5000th the speed of light. So while 12 years seems do-able from a speed of light point of view, there is no (present) method to send a probe there in a reasonable amount of time... I'd say reasonable would be a ~36 years to get there, plus another 12 years for the return signal... so roughly 50 years from launch to first data... meaning it would likely be a two, maybe three, generation program from a NASA engineer point of view.

We'd need something capable of:
a) Traveling at least 1/3rd the speed of light (roughly a quarter billion miles per hour)
b) A power source capable of lasting at least ~40 years or more with enough juice available near end of life to complete its mission
c) Capable of complete autonomy in 100% unknown situation
d) Possibly requiring the ability to actively correct its course en route, and maybe even detect and avoid collisions

Re:These are some big IFs

[0111 1110]

Your idea of "reasonable" seems somewhat arbitrary. I would posit 0.03c as reasonable enough. Four hundred years or about 7 generations. Still alot closer than the 666 years it would take to get to Gliese 581.

Re:These are some big IFs

[ceoyoyo]

An Earth-like planet orbiting Tau Ceti could be examined telescopically in fair detail. If it's confirmed, it would be a great target for one of the extrasolar planetary imaging telescopes people are starting to design. It might even be possible, with refinement of current techniques, to get a rough spectrum from it with current telescopes.

Re:These are some big IFs

[a_hanso]

The biggest IF is that there may not be planets at all:

...Tuomi's team warns that disturbances on the star itself, rather than orbiting planets, may be producing the small velocity changes...

"They're pushing the envelope," says Gregory Laughlin, an astronomer at the University of California, Santa Cruz. "Some or even many of these planets could go away...

Re:These are some big IFs

[Baron von Daren]

Though it’s a long way from being an interstellar probe; Deep Space 1 used ion drives (inadequate but new), self-repairing mission AI, and self-navigation.

http://en.wikipedia.org/wiki/Deep_Space_1

Also, NASA is working on a warp drive.

http://io9.com/5963263/how-nasa-will-build-its-very-first-warp-drive

Re:These are some big IFs

[0111 1110]

I never specified that the generation ship wouldn't allocate fuel to slow down at the end. Any practical journey would of course want to divide the fuel between acceleration and deceleration. That's one reason the ship must be so large and contain so much fuel and require centuries to build the kilometer scale craft necessary for the journey.

Re:These are some big IFs

[WGFCrafty]

Your idea of "reasonable" seems somewhat arbitrary. I would posit 0.03c as reasonable enough. Four hundred years or about 7 generations. Still alot closer than the 666 years it would take to get to Gliese 581.

No kidding? Both of your estimates are arbitrary... since you put what was "reasonable" to YOU.

Re:These are some big IFs

[Jesrad]

It makes more sense to think in turn of accumulated deltaV instead of mere velocity, so you can take the potential energy from Sun's gravity into account. At the moment the fastest spacecraft ever made by Man reached 70 km/s and even that was by expending potential energy instead of building it up.

The solar escape velocity from low earth orbit is 30.9 km/s, this is how much velocity you need to turn into potential energy (altitude from the Earth then from Sun) to get out of here - the amount of velocity you need to build up right from the start, just to barely get started on the journey. So basically, your actual travel speed to your destination system will pretty much be your spacecraft's total acceleration potential halved (the other half of it being needed to decelerate once there, unless you're reasonably sure you can perform an aerocapture at the destination planet - so far this has never succeeded) minus those 30.9 km/s. You could also take into consideration the differential between the two systems but that's above my competence.

To travel those 12 light years, or roughly 10 kms, in, let's say, a millenia, you need that travel speed to be close to 3200 km/s, which is a couple orders of magnitude above our current technical ability. Even if you forgo any capacity to brake at the destination and opt for a single high-speed fly-by instead, even with the current highest-ISP engines we can build (likely a DS4G ion thruster: 21400 seconds ISP), you will need your spacecraft to start with an amount of fuel almost 10 million times its own final weight... including the ion thruster's own weight and the tankage for storign that fuel, of course. Staging can help you trim this down, but only by so much.

And even if you overcome this, your probe will most probably just end up feeding a pa'anuri somewhere en route anyway ;)

Re:These are some big IFs

[RubberDogBone]

So it's fun and interesting to search these types of star systems and planets--and I think it's absolutely worthwhile to focus a SETI program on them to try to determine if there are any stray signals we can pick up--but otherwise this really is not much more than dreaming and guessing.

The SETI aspect is a problem.

If you took humans out of the picture on Earth, or simply rolled the clock back barely more than a hundred years, the Earth would be teeming with life yet not emitting any artificial radio. A radio signal is =/= life. Uncountable billions of organisms live here without radio.

SETI is only useful for advanced life, and even then, not entirely. Not very much. Most of human existence has been without radio. If we humans continue to migrate to digital modes and/or DRM, we may reach a point someday where the signals we emit are sufficiently spread-spectrum and digitally randomized so as to be relatively similar to noise, or too weak to travel far. This will work fine for our digital devices (some we have now; some to be invented) but it will be a disaster for an alien version of SETI.

Re:These are some big IFs

[Jarik C-Bol]

1. assemble the probe in space.
2. assemble a mass driver in space.
3. figure out all the math.
4. bring up a LOT of fuel.
5. use the mass driver to give the fuel and probe one hell of a kick to start them off.
6. dock the probe to the fuel once under way.
7. burn like hell.
8. wait a LONG time.
9. ?
10 profit!

Re:These are some big IFs

[AK Marc]

Speed isn't how you measure speed. You measure interstellar speed with acceleration. You would want to accelerate 50% of the time and decelerate 50% of the time. You wouldn't accelerate to 1/3c in 100 meters, then cruise the rest of the way. For one, everyone would be dead, the other, you'd still need to stop on the other side, unless you were planning on making quite a splash at your destination. You sustain some fractional multiple of g for 50% of your fuel, then turn around and do the same again, drifting in the middle if you don't have enough fuel for a full burn (in which case, speed would matter, but most interstellar trips would use one of the many sci-fi drives that would last that long or refuel in the near-vacuum of interstellar space).

Re:These are some big IFs

[0111 1110]

That's an interesting point, but presumably humanity would be very interested in the outcome of our very first interstellar journey. I think we could manage to preserve old communication standards. Presumably after 400 years we could simply use the same standards with far greater effect.

Re:cancer threat

[tmosley]

By who, exactly? Hippies and Death worshippers? Fuck those guys.

Gravity?

[Anachragnome]

From the article...

"It's the fourth planet--planet e--that the scientists suggest might be another life-bearing world, even though it's about four times as massive as Earth."

Correct me if I'm wrong, but doesn't that mean that the gravitational pull on surface dwellers would be four times that of Earth? That would complicate any colonization plans...

That got me thinking though--how, exactly, do we deal with high-gravity environments? One tactic could be to use generational acclimatization--our first colonization target planets would be marginally higher gravity planets, followed by the next higher gravity planet and so on. This would allow each successive generation to acclimate to the next colonization target planet. It might take a dozen colonized planets to get some of humans adapted enough to survive such a planet as the one discussed in the article (wild-ass guess), but it puts things in the realm of possibility. This has the added advantage of allowing each colony the option of sending colonists back to the previous colony OR the next in the colonization list.

Re:Gravity?

[Anonymous Coward]

Correct me if I'm wrong, but doesn't that mean that the gravitational pull on surface dwellers would be four times that of Earth?

Not necessarily. You forget that both mass and distance play a role in gravitational attraction. Therefore, given a larger radius, it could in fact have a comparable or identical gravitational attraction on the surface, though the exact numbers vary depending upon the density and distribution of material in the various layers of the planet. Assuming identical density distribution, it would require a radius twice that of Earth to have identical gravity on the surface. At the same time, the rotation speed of the planet plays a not insignificant role in the perceived gravitational attraction, as the rotation would constantly be throwing surface dwellers outward with a small force, negating gravity's inward pull.

Re:Gravity?

[tmosley]

Not unless it had four times the mass AND the same diameter (ie it was 4x as dense). 4X larger and less dense would make it similar to Earth gravity.

Re:Gravity?

[compro01]

Correct me if I'm wrong, but doesn't that mean that the gravitational pull on surface dwellers would be four times that of Earth?

Only if it's the same radius as Earth. Surface gravity on a planet scales roughly with mass/(radius^2)

Re:Gravity?

[ceoyoyo]

Assuming a density approximately that of Earth, the surface gravity would be about 1.6 g. As the mass goes up the radius goes up too, so surface gravity doesn't scale linearly with mass.

Re:Gravity?

[garyebickford]

1/2 right. IIRC the rotational ('centrifugal') effect is negligible compared to gravity unless it's really spinning fast. The force is represented as mv^2/r, where m is the mass of a person or whatnot, v is the angular velocity in meters/second, and r is the radius. If the radius is 2*Earth and the rotation speed is the same, then the surface velocity is roughly 80,000 km/day or 1 km/second. So for a 100 kg person (let's assume they're wearing a space suit), we have 100 kg * (1000 m/s) * (1000 m/s) / 8000000 m = 100000000/8000000 = 12.5 kg m/s/s = 12.5 Newtons.
The surface gravity for that person would be (roughly) 100 kg * 10 m/s/s = 1000 kg m/s/s = 1000 Newtons.

That's assuming I did the math correctly. :P

Re:Gravity?

[mark-t]

Only if density remains constant.

However, under higher gravity, wouldn't the minerals and other substances comprising the planet be put under higher pressure, leading to increased compression and therefore taking up less volume than what would have happened if the densities were the same?

Re:Gravity?

[Neil Boekend]

Not by much. Rock isn't gass: it's not compressible.
This planet isn't heavy enough to form a different type of matter (electron degenerant matter, neutronic matter, black hole stuff like that) so the compression force may be bigger, the volume it takes isn't that much smaller.

Re:Before you buy a ticket on board the Geographic

[MichaelSmith]

Or learn some ecology.

Re:cancer threat

[tqk]

Yeah, but if we're considered a cancer on our planet ...

You may consider yourself a cancer. I consider myself an inhabitant.

Cortez had no intention of wiping out indiginous natives when he arrived in the New World. Feature. Serendipity. Ignorance is bliss. Yadayada. :-(

Dibs.

[PacRim Jim]

Dibs.

Re:Before you buy a ticket on board the Geographic

[tqk]

... you might want to stock up on ammunition for your Grendel gun.

Or, shiny beads that the natives may enjoy trading for.

Just a thought.

Re:cancer threat

[Arancaytar]

You can't have it both ways. If we're a cancer, we're incapable of good or evil.

Just?

[mosb1000]

We could conceivably make the trip in 12,000 years. Nothing to it!

Don't pack.

[macraig]

What part of the definition of "possible" wasn't clear?

Hell yeah

[Swampash]

Team member Chris Tinney, an astronomer at the University of New South Wales in Sydney, Australia, acknowledges the problem. "It's certainly very tantalizing evidence for potentially a very exciting planetary system," Tinney says, but he adds that verifying the discovery may take 10 years, and the scientists didn't want to wait that long. "We felt that the best thing to do was to put the result out there and see if somebody can either independently confirm it or shoot it down."

Subtext: we don't care if we're proven wrong, so long as we learn something.

BECAUSE SCIENCE, BITCHES.

Tau Ceti is 2 X as old as our sun

[Streetlight]

According to the article, Tau Ceti is two times as old as our sun which makes it somewhere around eight billion years old. If the planet formation there followed the same evolution as ours, that may mean these planets are also around eight billion years old and if intelligent life formed after about four billion years after planet formation like here on earth, then intelligent life on the fourth planet is four billion years old if it hasn't destroyed itself. It would be interesting to see how they solved the same problems we're confronted with here. We surely could learn something from such an old, experienced civilization.

It's also my understanding that suns like ours and Tau Ceti will turn into a red giant after about eight billion years and destroy close in planets and then cool down. ATau Ceti may be near the end of its life, and colonizing the fourth planet may not be the best idea.

Re:Tau Ceti is 2 X as old as our sun

[__aaltlg1547]

The listing I saw said Tau Ceti is about 5.8 billion years old and about 0.78 solar masses. Lifetime of main-sequence stars goes like 1/M^3, so Tau Ceti's lifetime is about twice as long as our sun's. It will be still be looking pretty healthy when our sun has got all bloated and ugly.

Re:Tau Ceti is 2 X as old as our sun

[Streetlight]

Shavano,

Thanks for the science about the lifetime of Tau Ceti. The article in the first link in the original post said 2x. Who's Counting? So if we colonized it in the next few thousand years, we wouldn't have to look for a new place for another 12 billion years.

The thing is, though, if intelligent life developed at the same time from planet formation, using your number for the age of Tau Ceti, life has been on the fourth planet for maybe ~1.8 billion. A pretty long time, something like 1,000 times as long as intelligent life here on earth.

PS: We have a mountain in Colorado named Mount Shavano, 14,232 feet, in the Sawatch range not far from Salida, CO.

Re:Tau Ceti is 2 X as old as our sun

[__aaltlg1547]

Shavano, Thanks for the science about the lifetime of Tau Ceti. The article in the first link in the original post said 2x. Who's Counting? So if we colonized it in the next few thousand years, we wouldn't have to look for a new place for another 12 billion years. The thing is, though, if intelligent life developed at the same time from planet formation, using your number for the age of Tau Ceti, life has been on the fourth planet for maybe ~1.8 billion. A pretty long time, something like 1,000 times as long as intelligent life here on earth. PS: We have a mountain in Colorado named Mount Shavano, 14,232 feet, in the Sawatch range not far from Salida, CO.

It's named after me because it's so pretty.

Elite: Froniter predicted this and the results...

[StarTuxia]

The results? Oh yes, quite dire: http://tinypic.com/view.php?pic=14nh4jq&s=6

Just like Venus

[WindBourne]

Seriously, Venus is in the living zone as well.

Re:Just like Venus

[maxwell demon]

No, it isn't. The sun's habitable zone is between 0.9 AU and 1.5 AU. The maximum distance of Venus to the sun is 0.728 AU. So Venus doesn't even come close to the habitable zone.

Re:Just like Venus

[BemoanAndMoan]

Seriously, Venus is in the living zone as well.

Seriously, so is Earth.

Re:Just like Venus

[AK Marc]

Venus is small and close. The atmosphere is thick enough to sustain life, but not the right composition. Just like we know more about the moon than the oceans (perhaps a hyperbole, but you get the point), the far away have an allure that the close doesn't. We should try stuff on Venus before extra-solar. A little photosynthesis on Venus, and in 1000 years, it could be habitable. But then, perhaps its spin is such that is the reason it is uninhabitable.

Re:Just like Venus

[toddestan]

The sun was also cooler back then, which meant that the "living zone" was closer to the sun back then. By the way, the sun is still slowly getting hotter, and in a billion years or so Earth will no longer be in the living zone and the oceans will boil off.

Alien Legacy was right??

[Anonymous Coward]

If I remember correctly Tau Ceti was the colonization target of the old old Sierra title 'Alien Legacy' by Ybarra Productions (Circa 1994).

Hopefully any plans to arrive there are produced during peacetime, and hopefully our efforts are less dramatic than theirs :D

Human beings

[stox]

The other white meat.

Re:cancer threat

[garyebickford]

OTOH we can be seen as the expression of life on this planet, generating a form (us) that allows the great superorganism that constitutes Terran life to be propagated outward and onward. For wherever 'we' go, we will bring the rest of Terran life with us. We are the mechanism for continued growth of Life beyond its present boundaries.

Should we send messages?

[Animats]

Should we make a concerted effort to send radio messages to Tau Ceti? We have not yet done so, although brief messages have been sent in the direction of other stars. Messages have been constructed which could be decoded without any external info. Maybe we should be sending those regularly to Tau Ceti and listening regularly for a reply starting 24 years from sending. It's not an expensive project.

It's only 12 years of travel by telecommute

[Anonymous Coward]

We now need to beam them schematics and software for a Windows remote client. Just imagine using Skype with a 12 year ping roundtrip... Suddenly 900 years of physical travel does not sound so bad.

Re:It's only 12 years of travel by telecommute

[maxwell demon]

Don't send them Windows. They may see that as a hostile act.

It doesn't add up

[Tablizer]

It's almost twice as old as our sun, is the same type, yet is dimmer? I thought our sun is due to gradually get brighter toward its end. Something is amiss here.

If it was slightly smaller than our sun, then it should be shining about as bright as the sun by now, due to being older, and thus the orbits they described wouldn't be very good after all because there is a gap between the Venus-like orbit and Mars-like orbit. It cannot be too much smaller, otherwise it would be a different type of star than our sun.

Vulcans Invented The Prime Directive

[dwye]

The Vulcans came from the habitable planet that orbited Tau Ceti, according to my Starfleet Technical Manual. Given that they invented the Prime Directive, they probably have to maintain radio silence (frex, using very directional masers where necessary for radio-band communications) to avoid clueing in lesser civilizations.

Plus the Andorians live right next to them and we all know what they are like.

Re:Vulcans Invented The Prime Directive

[IronChef]

What are you trying to say, pinkskin?

Re:Vulcans Invented The Prime Directive

[bill_mcgonigle]

Plus the Andorians live right next to them and we all know what they are like.

Indeed. Where's the sign-up list?

Then take me to the Chamber Of Dreams!

[Burz]

http://media.photobucket.com/image/recent/traveler_01/PDVD_011.jpg

Yeah well, THINK first

[SmallFurryCreature]

THINK first will you, sure a generational ship MIGHT seem like the perfect home for a slashdotter, a basement with all bills paid for BUT generational ships require breeding. Male and females. Sex.

Now I don't know about you, but as a real Slashdotter, that is a price to high to pay! I will stare death in the face and spit him in the eye but talk to a girl?!? NEVER!

Re:Yeah well, THINK first

[gmhowell]

generational ships require breeding. Male and females. Sex.

But that's precisely what awesome about them! You don't have to talk to a girl, nor do you have to shower regularly - but you'll have one available for sex in any case!

Mein Fuhrer, I can walk!

Why so much water?

[SmallFurryCreature]

You can recycle water. A LOT. Constantly in fact as long as you got electricity. Split your waste in Hydrogen an Oxygen, then combine it again and you got pure water. This idea that a lot of water is required is just plain inefficient. In a generational ship, your are going to have to recycle. EVERYTHING.

Re:Why so much water?

[garyebickford]

My thinking was that water, while being useful both for various biological needs and possibly for use by the ion thrusters, in enough thickness (as either ice or water) is a reasonably good medium for blocking all that stuff coming at you as you travel at 1/4 light speed through gravel-infested space. It can be used for cooling motors and heating other machinery or living space, etc. So it's more useful than just having the same mass of lead or rock in front of you for protection.

The key thing is this: when traveling at 1/10 light speed (30,000 km/sec), somehow one has to deal with any object that is likely to encroach on the vehicle. I'm assuming that one just lets anything small hit the 'bumper' up front like a bug on the windshield. I'm not sure what 'small' means in this case, but the longer and more massive the bumper is, the bigger 'small' can be. Then one has to have a way to either disintegrate or avoid anything bigger. That means something like really powerful laser and/or radar 'headlights' that can provide enough light far enough ahead and widely enough to cover the cone of probable encroachment and make such targets visible in enough time to do something. Since the light itself is only going about the same multiple of one's speed as the speed of sound relative to a car on the freeway, it's an interesting problem - can we see something far enough ahead? Can we turn in time? What is the acceleration effect of changing course by 100 meters over a 3000 km distance, at 30,000 km/sec? I'm too lazy to figure it out.

210 posts and nobody mentioned Asimov?

[Spy Handler]

He had foreseen this. The planet around Tau Ceti is called Aurora. It is the home of long-living humans and mind-reading robots.

Re:210 posts and nobody mentioned Asimov?

[VAXcat]

Heinlein predicted it before Asimov. In "Time for the Stars", they landed on a planet orbiting Tau Ceti, theny named "Constance". They planned to colonize, but it was inhabited by hostile creatures who made them feel unwelcome, so they had to leave

Send Commander Jameson

[tucks]

http://wiki.alioth.net/index.php/Tau_Ceti

That is why it was funny

[Latent Heat]

No disrespect to our Mormon friends, colleagues, Senate Majority Leaders, presidential candidates and others, but to James Kirk from the 23rd century, LSD, LDS, it was all the same thing . . .

Stellar types broad categories

[Latent Heat]

The stellar types -- O, B, A, F, G, K, M -- are broad categories of mass and resulting Main Sequence surface temperature and luminosity.

If a star is even a little bit smaller, it will be a lot dimmer, and the brightening with age may not bring it quite up to the Sun's luminosity. Also, if the star is smaller and ages less rapidly, 6 billion years old is the new 4 billion, as they say, and the star may not be as far along the brightening with age curve.

Not that I want to defer to "experts", but one would think that astronomers have put a lot of effort by now into figuring out the properties of Main Sequence stars, what with the Hipparcos spacecraft giving accurate distances to nearby stars and with interferometers even able to measure their apparent size.

Re:Stellar types broad categories

[Tablizer]

Wikipedia says type G can go as low as 0.8 sun masses. It's borderline in explaining the statements, but I guess it can stretch to fit.

No we would not

[aepervius]

None of our radio signal is/has been detectable beyond a few 1 to 10 AU and nothing was above noise beyond 1 light year, except for 2 intentional signal of 2 minutes long. The problem is the inverse square law , as distance increase your intensity drop by the square of the distance (imagine a point light, it generate a spherical wave, but as the distance increase the sphere surface increase on the square of the radius, since the intensity stay constant , each square unit on the surface get an intensity which dwindle by the inverse of the suqare of radius). The only exception were direction signal sent with intent.

We could ahve a high technological civilisation on that planet and each other NEVER know about each other despite doing radio transmission up the wazoo into space (which we don't anymore by the way we have much better way to transmit info). Each of our signal would be indistinguishable from galactic noise rapidely. And we would never know about each other. Heck even if they were on alpha centauri, 4 LY away we would not know until they intentionally send a *directional* signal in our direction powerful enough.

wrong we did send signal

[aepervius]

We did send 2 radio signal which will reach beyond the 1LY (and are by now around 30-40 LY can't remember if they were sent in the 70ies or 80ies). Each signal was a few minutes long. The reason we don't do it is not out of fear but out of uselessness. To send a signal without being rapidely attenuated and disappear udner the galactic noise for that frequency, we have to do it very directional, and very powerful. That cost money to do. And you can only reach a tiny tiny spot in the sky. And it travel at light speed. To do the whole sky would be an enourmous amount of energy to spend, and you would have to wait dozen , hundred and maybe thousand of years until it raches a destination (depending on the star/galaxy you target). And when it reaches there it will be of minuscule intensity at best. So sending is not done out of fea, but out of horrendous cost and are no better than dart in the dark.

Re:wrong we did send signal

[0111 1110]

If by "we, you are referring to Ukrainians and Australians then a few very brief messages have been sent to stars close enough to us that it might actually reach radio telescopes at the other end. Assuming they are listening specifically for messages from us and that they do so 24/7 continuously for millenia. The US has only sent one message and it was sent to a target so far away as to be utterly meaningless.

Well played Slatibartfast!

[yodleboy]

OBVIOUSLY, the Magratheans are staging the backup copy of Earth in anticipation of the Mayan apocalypse. To the best of my knowledge all of my friends are from where they claim to be from, so it looks like I'll be stuck here.

Re:2-7 times mass of earth

[EmagGeek]

A planet twice the mass of Earth would be habitable to Earth humans who were in good physical condition and not obese. And, it is likely humans would evolve the musculature to live well there after just a few generations.

The gravity there would be about 125% that of Earth's, and seeing as how I used to have more than 125% of my current mass, I figure I would get by just fine.

A planet 3x the mass of Earth would have about 145% the gravity, so that would start to be an issue for even the strongest and most healthy of us.

I think the biggest issue we would have in any higher-gravity environment would be our cardiovascular systems. It would be more difficult for our hearts to pump blood up into our heads, as our hearts would be working harder.

Re:2-7 times mass of earth

[EmagGeek]

... working harder to overcome the pgh of the fluid over that distance.

Just Imagine....

[3seas]

... and it shall exist... its the proving it that's the hard part.

Not so fast...

[Overzeetop]

Depends on the planet composition. On the low end a 2x mass planet comprised of nothing but water (big ol' interstellar drop) would have 11x the volume, and a radius of 1.73 x earth, for a net gravity of 1.15x earth. If it were similar to the moon, you'd have 1.5x the radius, or gravity of 1.33x earth.

If I remember the story correctly.

[HagraBiscuit]

Tau Ceti V became overrun with sentient robots intent on defending the power grid. We will need to, at some point, send a volunteer out there to shut down the central nuclear reactor in order to wrest back control of the system. One of the first games, (i can recall) where you could save your progress.

*Cue Music*

[nuclearhazzard327]

*loads up starship to avoid the asteroid known as Vulcan's Hammer*

(If you get that reference you are really showing your age and remember that Tau Ceti was one of the few systems with a planet to settle on)

Impossible

[NewYork]

Habitable Planet

I'll bet. It's impossible.