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The Three Possible Classes of Interstellar Travel (forbes.com)
An anonymous reader writes: The stars call to us through the ages, with each and every one holding the promise of a future for humanity beyond Earth. For generations, this was a mere dream, as our technology allowed us to neither know what worlds might lie beyond our own Solar System or to reach beyond our planet. But time and development has changed both of those things significantly. Now, when we look to the stars, we know that potentially habitable worlds lurk throughout our galaxy, and our spaceflight capabilities can bring us there. But so far, it would only be a very long, lonely, one-way trip. This isn't necessarily going to be the case forever, though, as physically feasible technology could get humans to another star within a single lifetime, and potentially groundbreaking technology might make the journey almost instantaneous.
This poses some interesting possibilities. Let us say for example that we do find human-habitable places in the galaxy, but they are very far away so we send generation ships. Now let's say that 150 years into a 300 year journey some seriously fast FTL is invented on Earth (I more than suspect it is not possible though, hope I'm wrong). They now just have a few years journey. Would we send a ship to pickup the people on the slow boat? It would be kinda nuts to finally get there and find humans have been there for shy of 150 years. Then again if it's wormhole technology we would probably have to drag half of the device to the other planet to begin with.
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Is Interstellar Travel Possible
For generations, when we looked out at the distant stars, we could only wonder whether there were planets and the conditions for life-as-we-know-it around them. The past 25 years have brought forth a revolution in planet-finding, with thousands of known, confirmed planets, including many of potentially habitable, Earth-like worlds. But could we ever get there? Reader C. Vidal wants to know:
Do you think interstellar travel is possible (by any civilization). It seems to me that all possible solutions are one way trips.
When it comes to interstellar travel, I definitely do think it’s possible. But there definitely are constraints, dependent on how we’re willing to do it.
1.) Conventional Technology. If all we’re willing to use is the technology we have today, we could, theoretically, reach another star. By building a large enough ship that we could have a sustainable mini-civilization — a “generations ship” of sorts — we could boost up to speeds of tens or maybe even hundreds of km/s, growing our own food and recycling our water along the way. An alternative would be to develop cryogenic freezing-and-thawing technology, where humans, plants and other living creatures could be transported in suspended animation (a la Thundercats), only to be reanimated and revived upon arrival.
Some “standard” concerns, like collisions with interplanetary/interstellar objects, like rogue asteroids or planets, are actually not particular causes for concern. These objects — although plentiful — are so low in density that strikes even between stars are extraordinarily unlikely, even on million-year timescales. A trip like this would take hundreds of thousands of years to reach the nearest star system, and seems to be within reach.
But this is the ultimate one-way trip, and not at all a satisfying solution.
2.) Future Technology based on known Physics. But if we’re willing to consider other technological possibilities, we can certainly do better. In particular:
Fuel improvements: rather than using chemical-based rocket fuel, which releases about 0.001% of its mass into energy which can be used for thrust, we can use nuclear-based fuel (which is about ~1% efficient), or even antimatter-based fuel, which would be 100% efficient.
Thrust improvements: if we can transport large amounts of matter-and-antimatter for fuel on board a ship, we can continue to accelerate along our journey. Since humans can withstand (and even prefer) thrusts that are similar to Earth’s gravity, we could point our ship towards our destination, fire the thrusters at 9.8 m/s2, and when we reach the halfway point, point the opposite direction and fire again, decelerating until we reach our destination.
Time improvements: because this will bring us close to the speed of light after only a few years of acceleration, we could get to pretty much any star we choose in no more than 20-40 years of travel.
This would be great, because we wouldn’t need a ship to last for generations. Sure, it’d have to survive traveling at very high speeds through the interstellar medium, but a strong enough magnetic field (and a map of neutral gas clouds to avoid) should take care of that. And if we can master the cryo-freeze technology, we wouldn’t even need to bring resources other than seeds to plant and eggs to incubate upon our arrival.
The downside, though, is that a one-way journey might only take a few decades from the perspective of the person on the journey, but that’s due to special relativistic time dilation. If we’re visiting a star hundreds or thousands of light years away, then hundreds or thousands of years pass here on Earth. Even if we make this journey, our prospects of communication with anyone still on Earth (assuming there is still anyone here on Earth that far in the future) will have to be with their distant descendants. The journey need not be one-way for the people who go,
Disregarding science-fiction babble like in this article, the fastest we can get to Proxima Centauri is 80k years assuming no fundamental breakthrough, or 100 years with ultimately advanced technology that's not known to be impossible with our current knowledge of physics.
Writers of such articles tend to forget that every gram of fuel needs to be accelerated by previous stages, and even worse, all the fuel needed for deceleration must be first accelerated all the way then decelerated partway. This puts a hard cap even if you magically got 100% efficiency.
But fortunately, such writers are also forgetting that physics isn't the only technology field that advances. I'd expect that both stopping aging and sentient AI are no more than 100-200 years away. Just don't forget to take playing cards with you to spend time during than 80k years long trip.
The creatures outside looked from Alt-Right to Antifa; but already it was impossible to say which was which.
Before going speculative about teleportation and work holes, but past antimatter propulsion is a miniature black hole power source. A million metric ton black hole would radiate about three terawatts (with less mass dramatically raising the radiated power) and you could use magnetic fields to pump in material from in front of the ship. It would eat anything even photons and nutrinos. It should be able to power a decent sized ship and would be the most ideal power source known to modern physics.
"Bear in mind that our solar system is not that old, as stelar systems go."
To be fair, on astronomical scales, yes it is. We're in the first generation of stars that could possibly have live evolve around them. So-called Pop III stars were behemoths that obliterated themselves in no time - 100,000 years or less - and were around when the universe was, oh I don't know, a few million years old or so. (Redshift of around 8 or so, whatever that corresponds to. I do my cosmological history in redshifts, and when needed use megaparsecs as a perhaps unexpected unit of time, which might cause George Lucas some relief.) And not only were they too short-lived to even form planetary systems but they had nothing more than traces of any elements heavier than helium. Pop II stars are those that formed from the wreckage of the resulting supernovae. Contrary to a common misunderstanding) the metals in the universe were not formed by stars burning hydrogen on up to iron, above which fusion loses rather than produces energy, but instead in supernovae where the necessary energy is readily available. On the plus side, this implies that Pop II stars can have a significantly higher metal content than Pop I stars, using the loose astronomical definition of "metal" to mean lithium and above. On the minus side, Pop II stars don't have anything like the heavier abundances needed to form planets with conducting cores and crusts of heavy rock and atmospheres of heavier gases, and waters and carbons and hydrocarbons and silicates and all that fun stuff that allows us - or indeed speculative lifeforms able to develop on the likes of Titan where methane forms a water/liquid/solid cycle - to exist.
As a result, stars of our Sun's generation are the earliest that could possibly form planetary systems. On a galactic timescale, we're first wave.
Of course, on a human timescale all bets are off. Our sun has many, many contemporaries and given how long our civilisation has been around (pushing the definition beyond breaking point, let's say 12,000 years), there could be civilisations vastly in advance of ours, just as around stars of the Sun's generation there could also be civilisations vastly younger than ours. 10^3 years is less than a blip on these timescales. Hell, millions of years aren't important when you've got on the order of five billion years to play with.
So I don't actually disagree with you. There's been ample time for civilisations, at least in our part of the galaxy, to have flooded the solar system with von Neumann bots, even allowing for the relatively limited timespan in which viable host systems have existed. I just thought it an interesting point worth commenting on...
I think you may have slightly misunderstood (or I'm slightly misunderstanding you - it's gone one in the morning here and I'm shattered so forgive me if that's the case). If we rigidly stuck to the generations for the sake of argument, it's like this:
Pop III: Nothing.
Pop II: Not enough heavier elements for life.
Pop I: The Sun. Us and a few other first-wavers. Every chance we're so far from each other we'll never have a single hope of knowing each other exist, especially since we have no idea if our technological civilisation (approximately a century old) could even live for another couple of centuries - and no way of knowing if that short a span can be extrapolated off Earth, though in the absence of further evidence it's as good a guide as any.
Pop 0: Future stars. Presumably, many more civilisations.
If we were in the Pop 0 to come, your argument would make sense. (Recall I said "if we stuck rigidly to the generations", but you seem to be suggesting that since there are older stars around then there should be older civilisations.) But in reality (again, sticking rigidly to the generations), we're in the first wave, and the coincidences needed to have a civilisation near enough and advanced enough to coincide with us even to the extent of us noticing their robots as they pass through (which we could only realistically have done from roughly World War II onwards - so less than a century) are prohibitively extreme.
Since these "generations" are fairly loose and the timescales involved are so much vaster than those needed to produce civilisations anyway, this isn't so important - I fully believe that there are older civilisations than us out there, relatively nearby. Probably as mouldering ruins and radioactive slag, but still there. And if something like von Neumann bots were realistic we should probably expect to see some trace of them since the Sun would be a target for exploration (youngish, surprisingly metal-rich for its generation, planetary system with an attractive number of rocky planets) and the idea that a wave of robots arriving, mining and constructing duplicates wouldn't leave traces, and indeed broken-down robots and broken-down parts, is also pretty silly. We'd have to have a heavy presence on a settled body to necessarily see those traces, but it's a pristine environment and they would be there.
I guess my point is just that we should just bear in mind how early in the universe's history we actually live, and also what an astonishing eyeblink the timescales of civilisations and lifeforms (at least similar to us - and I doubt there are organic lifeforms out there working on timescales of millennia) really are, and just be sure we don't overestimate the likelihood of contact from other civilisations. Fuck it, if someone beamed a clear, decodable message straight at us at any point outwith 1915-2015 we'd never have had even the faintest hope of picking it up. All it needs is for those people to have come along at the same time as us but not had a particular setback - no mini ice age, say - and they're slipped from us by a couple of hundred years. By the time we caught up, they're radioactive dust and we're listening at completely the wrong time.
My genuine hunch is that civilisations have come and civilisations have gone and we're all missing each other by a few tens of thousands of years.
Also: no von Neumann bots. And no generation ships that aren't now drifting dead somewhere in deep interstellar space, populated by the floating corpses of deeply confused and emotionally stunted descendants of the original astronauts, poisoned by an ecosystem that couldn't quite reproduce that of their home planet.
There's a much simpler and more universal workaround...
No matter how much javascript crapware they inject, no matter how aggressively they interfere with ad blockers, sites still MUST be indexable by Google (whose web spiders don't even do javascript) or they might as not even have a web presence.
So any site, no matter how broken, will invariable come up fine if you search for the URL prefixed with "cache:" in a Google search. That will >get you the locally stored version they indexed in the first place. Always a 100% working version of the page, without acquiescing to the site's crazy demands for insecure browser behavior.
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