First let me thank Yakk for the first reasonable, thoughtful and constructive response to my dissenting opinion.
Rather that label me a parrot or simply say "Hawking disagrees with you", without truly understanding the underlying physics (I doubt any of us here do), you've actually discussed the only
PROVEN method we can consider for interstellar travel; sub-lightspeed craft.
I refer those to who maintain that FTL
transportation is possible to the following web-site:
http://math.ucr.edu/home/baez/physic...Light/FTL.html
The
theoretical existence of FTL particles called
tachyons is addressed by this short article in the journal Scientific American:
http://www.sciam.com/askexpert_quest...B7809EC588F2D7
It should also be noted that all the current theories that propose FTL travel
do not, in fact, result in FTL events; Special Relavitity is preserved and causality maintained. In other words, everyone here "parroting" the possibility of FTL travel or the refutation of Special Relativity are not really accurate.
The two most common theories revolve around the use of "wormholes" and the use of "gravity engines".
Wormholes are theoretical rips in space caused by massive gravitational fields. Craft could conceivably travel through these holes,, and pop out at the other side, but they
don't travel faster than light. They just disappear and reappear somewhere else. Conceivably the distance traveled
through the wormhole would be "shorter" than the distance between those two points in normal space. By the way, something often overlooked by many people is the equal likelihood that the distance be
longer! You disappear and then dont' reappear. At least for quite some time.
Anyway, I degress...
Another theory is the use of something I can only describe as a "gravity engine". This compresses space in front of the craft whilst "expanding" it behind. Once again, the appearance is of FTL (from faraway observers) but the actual laws of physics are maintained. The craft still travels at speed
below the speed of light, but because space is compressed in front of it, and expanded behind it (in a localized manner), it appears to faraway observers that the craft is moving at FTL speeds.
Actually, the whole issue of what faraway observers would actually observe complicates things even further, simply because information (ie, observation) cannot travel faster than light itself... but this gets complicated so let's ignore that for the moment.
Details on these theories can be found in a paper published by Ian Crawford, an astronomer at University College London. REF: "Some thoughts on the implications of faster-than-light interstellar space travel,'', Q. J. R. Astr. Soc., 36, 205-218, (1995).
"Gravity engines" (the popular term is "warp drive" but I don't use that for obvious reasons) was first discussed by the Mexican physicist Miguel Alcubierre, of the University of Wales, in 1994.
Therefore, I
continue to maintain that FTL travel is impossible, and most physicists agree. Pedantics maybe, but better than the generalizations posted on this thread heretofore.
So, to repeat, I never stated that it was impossible for theoretical FTL "events" to occur. They may be possible. Having said that, FTL events could and would contravene causality (as mentioned in several articles) with the resulting wierdness; wierdness that we
don't see at the moment.
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Originally Posted by Yakk
It is possible you will never see the benefits of Space Exploration personally. Even likely.
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Undoubtedly. As it is in most things. But what's that got to do with it?
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I don't see why not. The distances are large, but if you aren't in a rush, you can manage them.
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That depends. I agree that it's rash to say that it's impossible. I simply feel it is unlikely. Postulations on theoretical events are very different from
actual implementation of said theories. As I mentioned somewhere before, it's
theoretically possible for me to disappear in a poof of quantum wierdness or to leap through a solid wall via quantum tunnelling... but it's not really going to happen.
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Lets say you can launch colony probes at 1% of the speed of light. And lets say it takes 100,000 years to bootstrap a solar system from empty to being able to generate a colony probe. And lets say it takes 1,000 years to produce a single colony probe. And, finally, lets say that after 10,000 years of making colony probes (each system makes 10), the systems stops, on average. And finally, half of the colony probes fail.
Every 110,000 years the number of colony probes increases by a factor of 5.
Then, going from a single system to colonizing, say, 1 billion stars, would take about 1.5 million years. It might take longer than this -- the actual limitation on the speed of colonization eventually becomes the speed of expansion of disk of colonized planets, which can't expand faster than 1% of light speed.
1.5 million years is otherwise known as a blink of an eye.
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Indeed. And this was the hypothesis formulated by Hart, M.("An Explanation for the Absence of Extraterrestrials on Earth," Quarterly Journal of the Royal Astronomical Society," Vol. 16, 1975, pp. 128-35), Jones, E. M.("Colonization of the Galaxy," Icarus, Vol. 28, 1976, pp. 421-22) and Papagiannis, M. D.("Could we be The Only Advanced Technological Civilization in Our galaxy?," in: Origin of Life, Japan Scientific Societies Press, 1978.)
Furthermore Gerard O'Neill postulated huge space colonies in his groundbreaking paper "The Colonization of Space" (O'Neill, G. K., "The Colonization of Space," Physics Today, Vol. 27, September, 1974, pp. 32-40.); later built upon in his book The High Frontier (
http://www.ssi.org/body_high-frontier.html). See also O'Neill, G. K.: Space Colonies and Energy Supply to the Earth, Science, vol. 10, 5 Dec. 1975, pp. 943-947.
Much of what you propose is detailed in the NASA Ames Space Settlement Design Contest (1975) "Space Settlements: A Design Study" (published on the web at
http://www.belmont.k12.ca.us/ralston...Contents1.html
Additional information can be found at NASA's Space Settlements site (
http://www.nas.nasa.gov/About/Educat...aceSettlement/)
And well and good.
But what about the
Fermi Paradox? See
http://www.space.com/searchforlife/s...ox_011024.html and the first half of the page
http://zebu.uoregon.edu/~js/cosmo/lectures/lec28.html and especially
http://www.faughnan.com/setifail.html
Fermi's conversational paradox was "If they exist, why aren't they here?" when referring to extraterestial intelligence (and therefore by implication, interstellar travel). The famous
Drake Equation is an expanded mathematical model based upon the same fundamental questions. See
http://www.setileague.org/general/drake.htm,
http://www.pbs.org/lifebeyondearth/listening/drake.html,
http://en.wikipedia.org/wiki/Drake_equation and
http://www.activemind.com/Mysterious..._equation.html.
Based upon the age of the galaxy, and assuming extraterestrial life exists, then ET life
should already be here. The fact that it is not can only be for one of the following reasons
1) Humanity is the only intelligent life in the Universe
2) Interstellar travel, though theoretically possible, is realistically impossible
3) They're here already but "hiding"
Whilst this is not a debate on ET life, option 2 above seems to refute your suggestion that interstellar travel is possible. Either that, or humanity is alone.
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And I think we can do better than 1% of lightspeed. I think that successful intelligent beings is phenomina that will spread at near relativistic speeds. By this logic, there isn't much point in SETI because the time between the arrival of the EM signals of intelligence, and intelligence itself, is obscenely short on a universal time scale.
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So, in other words, we're the only life in the Universe, or interstellar travel is a lot more difficult (ie impossible) than many people believe.
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You only need to travel fast if you are in a hurry.
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Or you don't have the technology or resources to maintain life in interstellar space. No water, no hydrogen, very little light for energy...
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There are a few things that can make you not in a hurry.
The first is, increased life span. This can be by some kind of cold sleep or by the simple matter of making more durable humans or by extending your definition of human beyond the biological.
The second is, not sending yourself. Send instructions to make humans, not humans, to other stars.
Lastly, you could send a generation ship.
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All great in science fiction novels, but quite unlikely.
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Even just playing around in our solar system is pretty damn profitable.
There is a dissassambled small planet we can use for resources (right next door!), and a hell of alot of space where we can 'pollute' to our hearts content without worrying about ruining people's quality of life. When robotics and/or nanotechnology starts getting good, the raw materials up there will be extremely useful.
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Agreed, and this is what I support. But researching interstellar travel? I just don't believe it's likely.
Certainly FTL is impossible. The only likely possibility is slower than light travel, and I think the chances of that are also very low.
Mr Mephisto