Earth-Like Planets In Our Neighborhood

goran72 sends in a story out of the Chicago AAAS meeting contending that Earth-like planets with life-sustaining conditions may be spinning around stars in our galactic neighborhood — we just haven't found them yet. "'So I think there is a very good chance that we will find some Earth-like planets within 10, 20 or 30 light years of the Sun,' astrophysicist [Alan Boss]... told his AAAS colleagues meeting here since Thursday. ... The images from those new planets, he added, should identify 'light from their atmosphere and tell us if they have perhaps methane and oxygen. That will be pretty strong proof they are not only habitable but actually are inhabited. I am not talking about a planet with intelligence on it. I simply say if you have a habitable world. ... Sitting there, with the right temperature with water for a billion years, something is going to come out of it. At least we will have microbes,' said Boss."

Comments

Polluted by life?

[symbolset]

For the last 4 billion years the Earth has shed some 2 billion metric tons of genetic material per day. Solar winds have pressed some of this material more, and some less. Some of this material has been captured by extrasolar objects and carried away. Some of it has been captured by comets over which the sun no longer holds sway. Some of it has been so light and so thin that the solar winds have carried it far from home.

These solar systems polluted by life? How could they not be?

Re:Polluted by life?

[artor3]

Do you have a source for that? It seems hard to believe that Earth could have shed the equivalent of half its current mass in genetic material alone...

Re:Polluted by life?

[ean]

The human body contains about 100g of DNA. You're saying about 2E15 grams, or 20 trillion human body's worth, of DNA is not only released into the atmosphere but then escapes the earths gravitational pull and enters interplanetary space.
Sounds unlikely.

Re:Polluted by life?

[Arancaytar]

All right, What The Hell?

For a planet to "shed" anything except perhaps hydrogen or helium, that stuff has to overcome escape velocity, which (until rockets were invented in the 20th century), requires an (volcano or meteorite) that would incinerate any complex organic compounds and render DNA a fine ash.

Plus, Google will tell you that the following comes out to 44%, as an above poster already said:

(4 billion years) * (2 billion tons per day) / (5.9736Ã--10^24 kg) in percent

Less than 1% of Earth's mass is at a temperature that even permits life to exist. As for the part that actually consists of life, you can measure it in parts per million and still need scientific notation.

impossible dream?

[phantomfive]

Lately I've been really pessimistic about the whole thing, I mean, really, who cares? Even if there were intelligent life on planets that close, we would only be able to exchange communication once every 10 years, not enough to actually learn their language, and we would never be able to travel to visit them, right?

So realistically, there is not much point except for dreamers and space geeks. Might as well spend the effort here on earth. On the other hand, what if we could travel out there? Wouldn't it be COOL? I might actually meet a girl. Just kidding.

I want to believe that we will be able to travel long distances one day, hyper speed and all that, but it's pretty hard to see how it could happen.

Re:impossible dream?

[BungaDunga]

... exchange communication once every 10 years,...

We could give them, say, the entirety of Wikipedia, and they could give us their equivalent. Write up a "rosetta stone" with a bunch of pictorial/mathematical representations of words, and so on. Probably doable. Conversation back and forth will seem frustratingly slow, but there's no limit to the amount of info that can be streamed across.
Mind you the chances that we will be in the near vicinity of a civilization that communicates by radio waves that we can pick up is possibly quite slim- we've only been doing it for less than a hundred years. They could be in our equivalent of 1750 and we'd never hear a peep.

Re:impossible dream?

[MrPayne]

I would think that we wouldn't just send "Hi" and wait for a response. I think we would constantly be sending them information and let them learn what we are sending. We would hope they would do something similar.

Re:impossible dream?

[Jane Q. Public]

Man, you ARE pessimistic. As well as wrong.

Once it became known that a civilization existed in a particular star system... and they knew about us... communication could be continuous both ways, not just back-and-forth like a walkie talkie every 10 years.

Starting with math: primary numbers, Fibonnacci sequence and other natural patterns, on to addition, subtraction, etc... then to logical propositions and conclusions... we could communicate an entire language and maybe even a couple of encyclopedias in the time it took for ONE 10-year round trip of communication.

And with ion drives, or Bussard ramjets (especially if they are Pellegrino-style vehicles that pull instead of push), maybe we could get there in, say, 50 years or so. And spend most of that time in something like cold sleep. There have been advances in that direction, too. Do we have the technology to do this? No. But we might in 10 years, or 20.

Of course, we would have to decide what and how much to send in our communications. There could be very real danger. I do not think most people understand just how deadly we (and by implication, they) could be, given enough time and effort, even to a civilization light-years away.

"Flying to Valhalla", by Charles Pellegrino, is a work of fiction. It is the book in which he introduced a totally new (but perfectly sound from an engineering standpoint) style of interstellar ship construction. As controversial as Pellegrino is as a person, there is no doubt that he is, as the saying goes, "wicked smart". There are some very plausible cautions in his book.

Re:impossible dream?

[Seth Kriticos]

While technically it is no problem to send them large quantities of information, local law prohibits most of it and you will be sued by different interest groups if you try. So if we find someone out there, then we will probably start to spam them with viagra adds..

Re:impossible dream?

[gzipped_tar]

We could give them, say, the entirety of Wikipedia

REPORT ON THE INGREDIENTS OF THE EARTH'S CIVILIZATION AS SEEN FROM THE "WIKIPEDIA" SENT BY HUMANS * 20% ---- Elitist mod-trolls * 30% ---- Politics (a.k.a. sheeple herding) * 35% ---- Religion-like (i.e. spirituals, rituals, TV, Paris Hilton, Web 2.0, Slashdot, pr0n, etc) * 15% ---- Obsolete knowledge known as "science" and/or "technology" CONCLUSION Humans make good material for Soylent Green.

Re:impossible dream?

[ionix5891]

[citation needed]

Re:impossible dream?

[ion]

CONCLUSION: Mostly harmless

Re:impossible dream?

[shawb]

While it initially appears that you would be traveling faster than the speed of light, you indeed are not... when you reach relativistic speeds space itself compresses, so from your perspective the distance traveled between two points is less than the distance as measured from a resting observer. End result your measured velocity is less than C. To the resting observer, you travel the larger distance, but time is dilated such that your velocity is lower than C. Since the apparent distance between the origin and the destination is decreased, the amount of time it takes light to make the same journey would be less than the amount of time it takes you. In fact, from your perspective light is still traveling... at the speed of light.

Now, to take the concept to the ultimate (but unreachable) conclusion: to reach such a velocity that an outside observer would record you as moving equal to the speed of light: To the traveler it would seem as if there was actually no distance traveled, and the journey took no time at all. What the traveler would observe is space and time folded between the origin and the destination... for a 10 light year journey, you would instantly travel to the destination, but 10 years later. The return trip would also be instantaneous, but 20 years would have elapsed at home since you have left. Thus, the speed of light is not violated. However, to cut your travel time to zero in a Newtonian framework, you would need to reach infinite speed in zero time, which would require infinite acceleration, which would in turn require infinite energy. That is impossible, so an object with a resting mass cannot travel at the speed of light (or beyond.) But you still have to take into account the fact that at relativistic speeds, space constricts while time dilates, allowing for what on the surface appears to be traveling faster than the speed of light, but actually is not.

Re:impossible dream?

[meringuoid]

Mind you the chances that we will be in the near vicinity of a civilization that communicates by radio waves that we can pick up is possibly quite slim- we've only been doing it for less than a hundred years.

And how much longer are we going to be doing it, with everything converging onto the Internet? If the earth lights up as a radio source in the early 20th century, but has gone dark again by the dawn of the 22nd because almost everything is now connected to fibre, what hope is there for SETI?

Re:impossible dream?

[LateArthurDent]

we have no reason to suspect that there is life beyond this planet.

No reason to suspect? It goes like this. There is life on this planet. Therefore probability of life > 0. There are many, many, many stars in our galaxy, countless in the universe. No matter how small the chances are, given the size of the universe and since we have proven that the probability is greater than 0, it's inconceivable to imagine that we're the only ones.

In fact, the only reason to be arrogant enough to say that we're the only ones would be religious nonsense.

Entia non sunt multiplicanda...

[Kupfernigk]

As I've posted before, this type of "Earth exceptionalism" is more related to the field of religion than science. There is no a priori reason to believe that the Earth is an unusual planet unless you buy in to the creation myths of some peoples who lived in the Near East circa 4000-2000 years ago. (Other societies, such as those of India, believed in a plurality of worlds and intelligent life forms.) Using Occam's Razor we would conclude that our planet revolves around a very ordinary star, everything else observed about our planet suggests it is unexceptional, therefore the emergence of life is likely to be unexceptional. Falsification of the default hypothesis would involve finding an earth-like or near earth-like planet which did not have life on it. Protestant Biblical literalism is not a scientific attitude. So far, the history of science has shown that every form in which exceptionalism has shown up has been found to be wrong, e.g.

• Earth is flat disc with crystal dome above
• Earth is sphere at centre of solar system
• Earth goes around Sun which is centre of Universe
• Sun is a star in the Galaxy which is the entire Universe

Re:Question

[EllisDees]

This will give you some idea how large a nuclear blast is:

Ground Zero simulator