Interstellar travel will happen, we will find a way. Sure hibernation and generational ships are the only ways to get to other galaxies currently, but a few centuries ago they thought the only way to fly was tape feathers to your arms and flap. I read a letter written in the 1800’s expressing the persons outrage at the trains moving at such breakneck speeds. Of course, the breakneck speed was 15mph. They never could have imagined moving faster than sound. Sure, lightspeed is impossible with current propulsion methods but there will be other ways. Didn’t Einstein talk about bending space?
Another thing to consider before tossing out the notion of lightspeed or FTL is that modern physics is quite complete right now. We currently have two separate sets of laws and formula that are completely incompatable yet seem to work perfectly with their respective fields.
Its entirely possible that the mechanic that unifies them will allow for ways around relativity, but is currently undetectable.
So, the answer to the question “Is faster than light travel possible?” is yes, it is.
However the answer to the question “Is FTL travel possible as we understand physics today?” is no.
er…“quite complete” should be “not quite complete”…
Humanity will never travel to another star system, barring utterly revolutionary discoveries within the next hundred years or so that allow the construction of a warp drive.
Why? Because any technology-using organism capable of travelling to the stars will no longer be able to be considered human.
huh?, why?
Is it because far into the future, man will merge with machine and become something else?
Assuming the speed of light is the limit we can go at, the next 20 years will be crucial to determining if we will ever go out and colonize other star systems. By then, I suspect we will know if there are any earth-like planets on around the stars within, say, 100 light years. That’s really important. If we found earth-like planets with what looked like a breathable atmosphere around something like Alpha Centauri (not that Alpha-C is likely), then if we could just come up with something like a Bussard Ramjet we could theoretically get there, explore the place, and get back within say 20 years, or a relativistic time for the crew of four or five years (counting the slow acceleration and deceleration times). That’s do-able.
But what if we don’t find any? What if there aren’t any other earth-like planets in habitable zones of stars within 100 light-years? If that’s the case, then suddenly the speed of light looks like a huge hurdle to overcome. And today, that’s the absolute limit. It may always be the absolute limit, and there are good reasons to believe that.
The next 20-30 years are going to be very exciting.
Actually, there is no physical law that says “you can’t go faster than light.” General Relativity says that no particle possessing mass can be accelerated to light speed (and strongly implies that approaching it closely develops a point of diminishing returns). But if one could make a (literal) quantum leap past c, there’s nothing strictly forbidding a subluminal particle jumping to a superliminal speed.
IIRC, continuous acceleration at ~1g will take you to a relativistic speed in a quite reasonable time frame, though I don’t have the math to work out precisely what it is. I do recall clearly that at an average speed of 0.7c, elapsed time as observed on board a spacecraft is equivalent to elapsed time at c as measured by a stationary observer – which is a spastic way of saying that if you get on your trusty spaceship and accelerate to relativistic speed such that the average speed for your total voyage is 0.7c, you will get to Alpha Centauri in 4.3 years of your personal time as measured inside your ship, to Vega in 26 years, etc. Needless to say, the observer back on Earth observing your flight will detect your elapsed time as significantly longer than that.
Sam Stone, I’d be going off on a complete hijack by arguing it, but you are aware, are you not, that Heinlein predicted precisely the space-hiatus scenario you discuss above back in 1940, complete with the rise to national prominence of televangelists?
Why hasn’t anyone here considered Warp drive technology like Star trek?
Sure, it requires a lot of energy, and a knowledge of gravity that we lack, but it’s relatively feasible.
We know how to do it, we can’t do it yet though…
No one saw the computer coming 25 years ago…
Polycarp: Yep. But Pat Robertson is no Nehemiah Scudder.
Although I was thinking more along the lines of Jerry the Fouwell, myself! 
Discussions of how NASA and the old USA have screwed up space travel in the past few decades are quite besides the point. (I just graduated high school at the time of Apollo 11 and was clever enough to have a party for the landing). Perhaps we need to develop much better space vehicles than the incredibly inefficient and dangerous ones we have now. Consider that the laptops the astronauts bring aboard the shuttle are much more powerful than the shuttle computers. We haven’t invested anything much in space for a long time.
Imagine if the world were unified, and a fraction of the money now invested in armies goes into space. Who knows what we’d discover!
Saying we are anywhere near physical limits to space travel is as absurd as those who said that the gliders of the 1890s was as far as flight would ever go. We are just 100 years into powered flight - and we’ve gone from flimsy paper airplanes to hopping around the world without a thought except for how bad the food is.
If someone figured out how to make money out of space, the solar system would be colonized in no time, and for less than people threw away during the dot.com bubble.
How is it ‘relatively feasible’ if we don’t know how to do it?
I honestly don’t think that comparisons with past ages, where people believed travel beyond 25mph impossible are valid; that view was not arrived at by any rigorous process at all.
Relativistic speeds are going to be prohibitively expensive in terms of rocket fuel requirements, even if your rocket “fuel” is the Orion spacecraft’s thermonuclear bombs. Don’t forget, once you’ve burned enough reaction mass to get your spacecraft going at 0.5c, you’ll have to turn around and burn your rockets again at the end of the journey to slow down by 0.5c. The guy who wrote The Physics of Star Trek calculated that in order to cruise at half the speed of light and then slow back down, a nuclear-fusion-powered space ship would have to carry 6561 times its own weight in nuclear propellants. (An antimatter powered space ship would only need to carry 9 times its own weight in matter-and-antimatter propellants, but scraping together one-and-a-half space ship mass’s worth of antimatter is going to be beyond our engineering capabilities for a long time.)
Thus, we have to expect that your typical starship would have to travel much slower than this – maybe 0.1c, tops. This means that even a voyage to Alpha Centauri, our nearest stellar neighbor, would take 43 years. And, worse, remember how I said that a relativistic space ship would have to carry many times its own weight in propellants? Well, a lower-speed 0.1c space ship will have the same problem in miniature. For every kilogram of mass your space ship has, you’ll have to carry, oh, ten kilograms of thermonuclear propellants. This means every 10 kilograms or so that you can shave off of your Orion spacecraft’s mass translates as one less very-expensive 100 kg thermonuclear warhead your Orion spacecraft will have to carry.
And that’s only if you wanted to make a one-way trip. If you wanted to carry enough propellants to accelerate to 0.1c, decelerate at your destination, accelerate to 0.1c for the return voyage, and decelerate again once you’re back in the Solar system, you’d have to square the propellant-to-payload ratio. So if a one-way trip at 0.1c required 10 times the spacecraft’s weight in hydrogen bombs, a round trip at the same speed would require 100 times the spacecraft’s weight in hydrogen bombs. However, we can assume that, due to the long duration of these space flights, a human being would die of old age if (s)he tried to make a round trip. So, let’s do our calculations a favor and assume that this trip is outbound only with no thought of returning to Earth.
Still, at 10 kg of “fuel” per 1 kg of spacecraft weight, you have to be careful. A typical human being can weigh close to 100 kg all by himself. The equipment and consumables necessary to sustain one human being for 43 years, even in some not-yet-invented form of “suspended animation”, would require at least 500 kg, if not more. And this doesn’t include the weight of your scientific instruments, your Orion propulsion protector plate, your Orion propulsion shock absorbers, et cetera, et cetera, et cetera – each of which has to be bigger the more peopele you have on board.
So … sending out a “colony” of a hundred hibernating adult humans is just plain out of the question.
The solution? Send out a bunch of fertilized zygotes! Send out a seed ship full of frozen embryos. Embryos are tiny, they require no sustenance when frozen, and if something goes wrong with your equipment you’re not going to make international headlines with cries of “100 astronauts killed!”.
Oh, sure, there will be a lot of obstacles to overcome. We’d have to invent a way to incubate an embryo without a human uterus, a la Brave New World. We’d have to be sure there was a habitable planet in the other star system before we even sent the starship there. We’d have to make the ship’s automated systems smart enough to be able to land on said planet and convert its natural chemical resources into food for the unborn colonists (carrying enough food for 100 nine-month gestations on board is out of the question). We’d have to come up with a way to overcome the daunting physical and psychological problems of raising 100 infants to be 100 living, breathing, healthy, sane adults without the presence of human caretakers. But I feel that these problems will actually be easier to overcome than the even-more-daunting problems we’d face in attempting to transport full-grown adults in “stasis” chambers across the light-years.
Or we could just invent warp drive. :rolleyes:
Maybe not, but once some very intellegent people in two different countries decided that a jet engine was impossible and that there was an absolute physical limit to air speed (namely, when the tips of the propellers reach the speed of sound).
Seems pretty short-sighted now, but it was perfectly reasonable with what they understood of physics at the time. And the laws of physics didn’t change, technology changed what could be done with the laws of physics. Happens all the time…
One thing you didn’t mention, tracer is the potential need to take along a lander and ascent module - yet more weight (assuming that we woouldn’t just be going there to gaze down at the earthlike planet from high orbit).
Easier than that would be to send out machines (preferably strong AI, if we can make it) - they would need no life support systems and would be capable of exploring a wider range of environments than humans.
Maybe five plus five will equal more than ten when I’m older…
I admire the optimism and never-say-die attitude of most of the posters here, but I’m afraid I must side with Mangetout in believing that even the most “lo-tech” sleeper-ship-plus-nukes still seems literally hundreds of years distant.
As for the far more “sci-fi” options of wormholes and warp space, again, full marks to those who point out that they are theoretically possible. However, they are theoretically possible only in the sense that they don’t necessarily violate Einstein’s equations.
I should point out that there is no theoretical reason why I cannot fly, naked and unaided. If I say it is surely impossible that some normal, unaltered human might fly in future then I do indeed paraphrase medieval doomsayers who thought that the horizon was our limit.
The quantities of energy inherent in accelerating a ship to a significant fraction of light speed are staggering. The quantities required for these ultra-scifi options are mind boggling, such that a craft would require its own black hole, for example.
Building a ship which can fly through the sun violates no laws of physics. Not wishing to bum anyone out, but this is the level of engineering required for practical interstellar space flight.
I know I’m always the pessimistic one in these threads, but as Mangetout et al. said, interstellar travel is extremely expensive and difficult. With our current technology, an unmanned flyby of Pluto is a $1 billion project with a flight time of 8 years. That’s for a flyby, which means it carries no fuel to decelerate - after an 8 year trip it only has a few hours to observe Pluto up close. A probe that goes into orbit around Pluto is several times more difficult; you need the fuel to decelerate and stop, which means you have to use even more fuel to get it to Pluto, which means significantly more launch weight.
The closest star is several thousand times farther away than Pluto. To explore that, the first logical step is to do a high-speed flyby by an unmanned probe. If the Terrestrial Planet Finder telescope (scheduled for mid 2010s) finds an interesting planet nearby, perhaps an interstellar probe could be launched in the 2020s with a flight time of 20 or 30 years. The next step would be a significantly larger unmanned probe carrying a lander, similar to the Viking or the Mars Pathfinder. Only after that can we start planning a manned mission. That’s the most optimistic scenario I can come up with.
Right.
At the time of Pliny and Ptolemy, it was absolutely possible for humanity to one day develop orbital flight. It was unfeasible, though.
It only took, oh, 1900 years of progress. But not just in applied technology AND social and cultural attitudes AND political economics. First and foremost in basic science.
A breakthrough, nay, a veritable revolution in basic science WOULD be required to work up a “way around” the various aforementioned mass/acceleration situations and the relativistic effects of travel near C , never mind achieving actual FTL.
Otherwise, if we’re to require just sheer technological improvement, a-la supersonic flight, there is no end-run and it WILL take an extraordinary amount of resources and time to get to the point of even trying. But that, at least, is not impossible, just ^%$# hard, and expensive beyond imagining.
Seems like in regards to Deep Space Travel our model for technological progress is NOT aviation’s evolution from Kitty Hawk Flyer to Spad to DC-3 to X-1 to SR-71 (And BTW, we haven’t really improved range/altitude/speed performance since the 1970s: progress plateaus) Could it be instead the evolution of sending things through the air from arrows and boomerangs to catapults, trebuchets and kites to Montgolfier hot-air baloons to dirigibles to then the Kitty Hawk Flyer?