Interstellar travel; possible or not?

[Mangetout]

As a spinoff of this thread, wherein I expressed my doubt as to whether humans will ever leave the solar system, to which Dr Zoidberg replied:

...frankly, I don't think a "sleeper" ship is all that hard to do. If we can find a way to put ourselves into hibernation and build a ship that can do 0.1c or so we've got the interstellar problem solved.

Well, frankly, I [b]do[/i] think it's a hard thing to do; I think it may actually be impossible.

0.1c is 67 million miles per hour; collisions with interstellar hydrogen atoms (1 per cubic metre?) would reduce our sleeper ship to a cloud of ionised gas in little or no time. We could hypothesise 'deflector shields', but these would be terribly energy-expensive to run, not to mention the side effect of slowing down the ship, necessitating more energy expediture to the drive system. These energy problems might seem trivial, but we're talking about a trip that would take hundreds of years - where is the energy going to come from?

Then the whole 'hibernation' thing - it may actually be impossible, not tricky or difficult - impossible.

So... how would we overcome these problems?

[Skip]

Arthur C. Clarke wrote a book, I forget the name, where there are sleeper ships that use shields of ice as protection against collision. Every now and then when the shield is worn down and they're close to a planet, some of the crew is woken up and they go down to the planet for a few months to manufacture a new shield.

[Mangetout]

Getting close to a planet is the end objective of the mission - not something you can do on the way.

[Erroneous]

I'm reading Is Anyone Out There? by Frank Drake at the moment. He makes what seems to be a good argument, based mostly on calculating the amount of energy required to cross interstellar distances in an acceptable amount of time, that human interstellar travel is unlikely to ever happen. Furthermore, he thinks (being a strong proponent of the notion that there are probably many extraterrestrial civilisations) that this nicely explains Fermi's paradox - i.e. if there are so many other civilisations, why haven't they visited us yet?

I do have a problem with this line of thinking, though. Just as Drake's argument cites the inability of most people to really comprehend the distances and energy requirements involved in interstellar travel, I don't think Drake is fully taking into account the enormous technologically advances that could occur in humanity's future. It could take another 100,000 years of false starts and catastrophies for a human civilisation to spread to other stars, but I personally think it will happen. And I certainly think it's very premature to rule it out entirely.

[Mangetout]

Technological advances may not help us if the nature of the universe (and particularly the speed of light being a finite limit) are stacked against us.

[Drastic]

Interstellar travel within a single lifetime (by current actuarial tables) may not be impossible, but it's not something I'll bet much money on, either.

Really slow interstellar travel may be more feasible by a physical engineering standpoint--basically akin to sending a slow probe out thataways, but much larger and with added layers of complexity. Assuming Step Two* in the process to develop suspended animation/hibernation never occurs, the really big problems become human and social ones--how in the heck do you expect a necessarily small group of people (I figure they can carry along all sorts of extra frozen sperm and eggs to keep necessary genetic diversity up) to remain, well, sane over generations, in an environment that will kill them instantly if they ever really mess something up, with far fewer safety margins against simple human stupidity and error that we take for granted at the bottom of this big beautiful ocean of air. I sure don't know--and I have this terrible hunch that the solution would be arrived at by some committee. Frankly, I'd rather wager my money on some mad scientist in a garage with a home-built interossiter inventing the warp drive fueled by a single potato.

* from a favorite old cartoon that you might see tacked up on professors' office doors anywhere in the world. Two professor types eyeing a chalkboard. Caption, "I think Step 2 might need to be expanded upon a little." Chalkboard holds three steps of math: step one is various equations, step 3 a final simple solution arrived at, and step 2 between them merely says "and then a miracle happens..."

[Scylla]

We have the technology to do it today if we really wanted to.

The Orion spacecraft concept is pretty simple.

You build an enormous ablation plate, and put your habitat and modules on top of it with a really good shock absorber.

Then you chuck nuclear bombs out the back and set them off. They explode, pushing against the plate, and accelerate you at stupendous rates.

Once you are up to speed, you turn the ship around so that the plate is leading, providing your debris shield even though collisions aren't much of a problem in interstellar space.

A Daedelus type craft is not buildable today, but seems pretty feasible.


In both cases we're talking about several decades of trip time.

[Paper Geek]

It seems more likely we will learn to create a new universe before we learn to warp through this old one. The only way I can see of travelling through space in any amount of useful time is by something like teleportation or wormholes. I honestly think it more likely we will be able to create a new universe, with more flexible laws, before we get the whole 'teleportation' thing down.

Of course, this is hundreds, maybe thousands of years off... (C'mon, that's a statement of fact, prove me wrong! Show me it's happening within the century!)

'Course it's just an uninformed opinion.

[Triskadecamus]

The Orion craft is much easier to describe than it is to actually build. And far easier to build than to actually pilot across distances of the type that we are proposing. Do you suppose that the rest of the world will sit happily by, as one nation builds and orbits a million nuclear weapons in a launch platform with armor designed to withstand nuclear war? Would you want your favorite enemy state doing it?

And then there are the straight engineering considerations that rosy eyed optimists never mention. Just what period of absolutely perfect engineering operation do you expect? Triple redundancy only works until the second failure. Name all the complex mechanical systems you can think of which have operated for longer than a century without a single failure.

When science was new, and engineering was an art, there were occasional instances in human history where great works were carried out over century long periods. Not many of them, but a few. Cathedrals, The Great Wall, a few other examples. Things like the Roman road system are not truly integrated single systems, since they had useful benefits prior to the completion of the system. (Actually, Cathedrals did too, but those were social, not religious.) (Also keep in mind that the Great Wall didn't work.)

As science matured, and engineering became a science, the duration of engineering projects diminished rapidly. In the modern world the suggestion that a project be planned for a decade is considered visionary. Twenty year long projects are only even considered if there is an intermediary benefit, and a massive need, from which the project can be expected to provide substantial relief. What other single scientific project can you name that took a century to complete? Anyone? Anyone? Bueller?

What single problem could a successful interstellar voyage solve? What material benefit would the society making this effort expect to receive? Keep in mind, we are, as of this point in the argument supposing a very kami kazi like one way trip. No one comes home, even with success. Success and failure are identical, from the point of view of Earth, baring a very good radio sent along.

So, after we consider whether such a trip is theoretically possible, we can then multiply the unlikely level of that consideration by the more extreme consideration of whether human society would do such a thing. I doubt that they would. I am not convinced that that is a bad thing, either. Dreaming of the stars seems to me to be the most beneficial part of the whole thing, for most of mankind. Dreaming of the stars is fine with me. Actually trying to get to them is probably not better than the dream.

Tris.

[Paper Geek]

Tris: I agree with you, but I must point out that, in a very real way, the technologies we are using today has taken a century or more to reach. It had intermediate effects such as lights and space travel, and we didn't know exactly what the technologies were going to be like... but by what I've read, the cathedrals had their floorplans changed every generation, so that's more or less the same thing.

Of course, we're still building this cathedral.

[msmith537]

Originally posted by Scylla
We have the technology to do it today if we really wanted to.
[/b]

Please. We barely have the technology to leave Earth's orbit and travel to the next planet in our solar system.

There's no reason to believe that in a thousand years we might find a way to reach another solar system in a reasonable amount of time. After all, a couple thousand years ago, it was scientificly impossible to travel further than sight of land.

[DaddyMack]

First: If we perfect whole body transplants http://news.bbc.co.uk/1/hi/health/1263758.stm, I'm sure we will over time along with other advancements in neuroscience and prosthetics, which helps to supply the need identified by Triskadecamus. We could have new bodies or be connected to mechanical ones that would be much easier to repair.

Second: If we perfect manufacturing on the moon http://aerospacescholars.jsc.nasa.go.../l8/Mining.htm as a solution to the environmental problems which is also a need. Now couple that with our skills building space lavatories, we will in time be able to construct giant contraptions in space to house a large population units complete with tourism liquor stores and babes.

With these two technologies we can have space villages that roam the universe for thousands of years and travel at speeds less than the 0.1 the speed of light without all the associated problems of doing so.

There will still be the problem of social interactions most of all tribal wars in these little villages that would threaten their survivability, but we have that here on earth and we have not destroyed ourselves yet.

This we must do and we have a few million years to achieve it.
http://www.valdosta.edu/phy/astro/pl...bh/page10.html

[Estilicon]

I don't care about your opinions I don't care this is a great deabets. I don't have any arguments but I know that interstellar travel is possible. I also refuse to provide a cite. I will repeat it once more.... INTERESTELLAR TRAVELL IS POSSIBLE











The alternative scares me.

[Lumpy]

We don't know everything about the laws of physics yet, so we can't say that some surprise might not pop up that would make interstellar travel much more feasible.

The biggest obstacle to traveling at high percentages of the speed of light is the energy required- 87% of lightspeed being equivalent to the ship's rest mass, IIRC. But what if you could somehow manipulate an object's inertial mass? If you could tinker around with Higgs particles in such a way as to "decouple" most of a ship's mass so it only required a hundreth or thousanth as much energy to accellerate? Speculative bordering on fantasy I'll admit, but there's no telling what possibilities might turn up in the next few centuries.

[owlofcreamcheese]

is it possible? of course it is, you don't need fancy smancy faster than light crap, just make a generation ship, set up a biosphere and go 8 miles an hour for the next million years!

what do you think the earth is? (kidding...sort of)

[Sam Stone]

We aren't going to travel to other star systems for a long, long time. If ever.

However, we'll be bringing other star systems to us. There are already plans in NASA for telescopes large enough to image earth-like planets around other stars. Later plans include telescopes so large that they will be able to spot large artificial structures on planets around other stars.

Space interferometry is what allows this to happen. A single telescope like the Hubble has a mirror about 2.4 meters in size. The NGST, due to fly in about 8 years, will be slightly more than triple that size. But with interferometry, you can fly arrays of telescopes and make them look like one big telescope. One plan is to have an interferometry telescope with a theoretical aperture of about 6000 kilometers!

Within 15 years, we should be flying the Terrestrial Planet Finder, which will be able to analyze atmospheres of earth-like planets around other stars, including biological signatures indicating life.

The most advanced mission that NASA is already planning for is the Planet Imager, which would use a large array of NGST-like telescope and interferometry to actually image continents and oceans and other features on earth-like planets orbiting other stars. We're not really close to this thing yet - it might be 30-50 years away unless NASA gets significantly more funding.

This program could be extended almost infinitely - imagine a telescope with an effective aperture the size of the Earth's orbit...

Clearly, there is an awful lot of exploration of other star systems we can do right here in Earth orbit. The really interesting question is, what would we do if we looked at a star system with a huge telescope, and saw evidence of an advanced civilization? What kind of pressure would arise to go there?

Realistically, we can imagine the next steps - we'd probably start planning bigger telescopes to see more and more of that civilization. We'd aim huge radio telescopes at it to attempt to pick up signals. We might even try to communicate with them by firing large lasers at it or something.

But it's all going to depend on what we find out there, and we'll probably have a good idea in our lifetimes. We'll have mapped the planetary systems of maybe the nearest 100 stars in our lifetimes, knowing which ones have atmospheres, what those atmospheres consist of, etc.

There are theories suggesting that the Earth is extremely rare. Current studies of other star systems have shown two types of system - ones with Jupiter-like planets that are extremely close to the star, and ones with huge Jupiter-like planets much farther out, but in highly elliptical orbits. Neither type of solar system is conducive to having an earth-like planet in orbit in the 'habitable zone' of the star, because the orbits would not be stable.

Other theories have suggested that life won't develop at all in solar systems that don't have a large Jupiter-like planet in the outer system, because these planets act like cosmic vacuum cleaners preventing a high rate of bombardment of meteors in the inner system.

We should have answers to these important questions in the next two decades, and those answers are going to give us a much greater understanding of what else and who else may be out there.

[kanicbird]

If we can create an artificial womb we may be able to send out frozen embrios in a spacecraft, Have it travel to another star system (even at 0.001c or less) and have the embrios thawed out and develop into humans - perhaps with some age acceleration.

The biggest problem I see with this plan is having the ability to build such devices that will last for 100's or even 1000's of years.

[Scott Dickerson]

Forgive me, but I'm a little amazed at the extreme conservatism of the responses so far.

1) Let us say that human civilization has been around for 10,000 years; a nice round number. We have been what might be termed a species-wide scientific/technological civilization for less than a century (IMHO--there will be arguments). I have read--the figure was not meant to be precise--that NEARLY ALL the major scientific discoveries of human history have been made within the last thirty years, especially since the advent of the low-cost, high-power computer. If one wanted to graph this sort of human advancement, you'd have to use log paper. In essence you'd have almost nothing until the extreme end--then a line moving almost straight up! And it appears that not only the amount of scientific discovery in increasing, but the underlying rate as well.

When good folks talk about discoveries a millenium away, or a million years hence--what are they thinking?? The "sufficiently advanced technology" that Arthur C. Clarke says is "indistinguishable from magic" will be available--for a price--by the end of this century!

2) And it is wildly unlikely that homo sapiens would just happen to be the most technologically advanced species in (just to limit it) this galaxy. Given that there's no a priori reason to assume an upper bound to the longevity of a technological civilization (in general); given that there are surely planets out there that possessed intelligent life millions or billions of years earlier than ours did; given that a sufficiently advanced civilization would surely have mega-speedy means of observing and cataloguing the rest of the galaxy; and given that they would almost immediately encounter other species who had gone before-- If we have not already met Them, it is surely because They do not choose to meet us--yet!

3) Which is to say: wild-eyed stuff like super-C travel and space-warping, or more likely something we've never even considered, WILL BE AVAILABLE very soon indeed.

4) But, to brass tacks. We're already talking about sending a nuclear rocket to Mars (at least we were...before yesterday). So. We launch various components separately, and assemble our Interstellar Mission Craft in high earth orbit--maybe 500,000 miles out. The IMC is nuclear powered. Propulsion: laser thrust! The tech goal: accelerate a comfortable habitat at a rate of 1-G or so, continuously, to speed C. (I think I recall that it takes four years.)

5) Surely we all know that as we approach C, onboard time slows down. I'm not stopping to work it out, but I think (remembering the need to decelerate at 1-G for half the trip each way)...the total roundtrip to ANYWHERE IN THE UNIVERSE would be about eight years of ship-time. People spend longer than that getting university degrees!

6) Troubled by hydrogen atoms, bunky? Give the ship as narrow a cross-section as possible--think in terms of a flat hoop nine feet thick, four stories high, maybe a mile in diameter. I'll bet some sort of electromagnetic field device could be used to sweep atoms and particles out of the path of the IMC (not an original proposal on my part).

7) OR--make use of the hydrogen atoms--the interstellar ramjet!

8) OR--think bigger. Hollow out an asteroid, set up a bank of laser thrusters powered by a fusion reactor, and set off with a city of people at some smaller percent G (if necessary).

9) But my guess is that none of this will happen, because some reader of the SDMB, a Tom Swift type, will build a spacetime jumper in his garage!

[Mangetout]

Originally posted by Estilicon
The alternative scares me.

What alternative?

That the human race will end on the same chunk of rock where it started?

Or that the bulbous-headed grey-skinned beings who abducted you are actually demons?

I need answers.

[Polycarp]

Skip, the book you refer to is The Songs of Distant Earth, perhaps the most beautiful thing Clarke ever wrote.

But your having mentioned it makes me feel that the most relevant statement that can be made in this thread is to point out Clarke's Three Laws, the fact that the curve of rate of progress is tilting up towards an asymptotic future, and suggest that everything that everybody has proposed so far is not how the actual first interstellar flight will be achieved. How it will be, I have no more idea than anyone else -- but I'm confident that the speculations to date are as wildly far from the truth as the various 1900 and 1950 essays on "what life will be like in 2000" are.

[Sam Stone]

I would like more than anyone to see mankind flourish throughout the universe and see everything there is to see. And it may in fact happen.

But you are making a fundamental error by trying to extrapolate the curve of advancement we see today as continuing into the future. People were doing that in the 1950's, and coming to the conclusion that we'd have faster than light travel by 2010. Unfortunately, the curve of speed increase flattened out in the 1970's. The fastest thing mankind has ever launched was over 20 years ago.

Who would have guessed that 34 years after men walked on the moon, and 25 years after we already had a manned spacestation and had designed the shuttle, that we'd still be flying the shuttle, and all we'd be doing is flying to a slightly bigger station? And that we'd be farther from being able to get back to the moon than we were in 1960? In 1975 space enthusiasts were sure that by 2010 we'd have colonies in lagrange orbits with tens of thousands of people living in them. In reality, we just scaled down the space station crew from seven people to three.

The thing is, we have advanced very quickly, but are now approaching some fundamental physical limits. Perhaps they can be overcome, perhaps not. But it would be foolish to assume that we can and proceed from that assumption.

Here's what I think are the likely near and medium term futures for mankind in space:

PESSIMISTIC SCENARIO: Funding for NASA is cut. Shuttle missions are cancelled. That means the end of the NGST and other large space telescopes. The ISS is shut down. NASA resumes a scaled back planetary science program using current technology. For the next twenty years, we'll see a handful of flights to other planets. Automation gets better, so these probes learn quite a bit. A new manned program, based around a next-generation shuttle, starts up in 5-10 years, and we get back to where we are today except with lower cost and more ability in about 20 years.

LIKELY SCENARIO: The Bush administration appears to be truly enthused about space. Last week we heard that the new NASA budget was going to include enhanced funding for a new fleet of space planes and a new nuclear rocket. If that attitude remains, I think we'll see the funds going to supporting and flying Columbia diverted to the new spaceplane initiative. A new, cheaper space plane will be flying by 2010. In addition, the nuclear rocket program brings the outer solar system as close as Mars, and Mars within a couple of months travel time.

Under this scenario, there will be major, vastly more capable robotic missions to Jupiter, Saturn, and Neptune within the next 20 years. There will be telescopes launched in that time frame that can image planets around other stars. Man will land on Mars within 20 years. But we won't see humans exploring the outer planets in our lifetimes, unless you're really young or we live a lot longer.

HIGHLY OPTIMISTIC SCENARIO: Space Exploration becomes a national priority, being funded to the same levels as things like health care, welfare, and other major domestic programs. That would mean NASA's budget would at least quadruple. Under this scenario, we could establish a permanent base on the moon within 20 years, a permanent base on Mars within 50 years, and have manned expeditions to the outer planets in the same time frame. We might even see rudimentary exploitation of space by asteroid mining or water mining on the moon in the same time frame.

In the meantime, we would be launching arrays of telescopes of increasing resolution, to the point where within 50 years we would be able to look at planets around other stars and see evidence of intelligent construction. We would be able to see anything in the entire universe, and be able to closely inspect the oldest things in the universe.

Even under the highly optimistic scenario, we won't even have a good idea of where the earthlike planets are for maybe 30 or 40 years. If we decided to launch a probe to one of them, it would almost certainly be unmanned. The difficulty of sending a human on a multi-decade mission would be enormous compared to the cost of sending an unmanned probe, and the risks of sending a human that far would be unreasonable.

[ChaosGod]

To comment on some of Scott's points:

1) I agree. Technology Is progressing lightning fast, and is going to get faster, unless life on earth ends (a very real possibility). I'm betting Artificial Intelligence is going to take us to a whole new level in just a few decades.

2) I'm not sure we can assume that the galaxy is bursting with life. It is a very real possibility that mankind is a freak accident. On the other hand, maybe life is common, but after they reach technological bursting point they trascend dimensions and leave this universe. That would explain why they haven't landed at the white house lawn yet.

3) Super-c travel may never be possible. Tech progress alone can't break a physical law of nature. It can find ways around it though.

5) I have a question about this one: If you travel near the speed of light, and time slows down relative to your point of origin (earth), does that mean that you perceive your trip to be shorter than it really is? Putting it this way: If I travel at 0.99c to alfa centauri (40 light years I think). Will I perceive the trip to be any shorter than 40 years?

Peace

[caracal]

Originally posted by Scott Dickerson
Forgive me, but I'm a little amazed at the extreme conservatism of the responses so far.

Best statement in this thread.

I have no idea how it would happen. But I would say that everyone who said "no way, it'll never happen" needs to balance their intake of science with a little bit of history.

You've all heard the story of 19th-century patent office chief who thought it a good idea to shut down the patent office because there was nothing left to invent. Even Einstein (which, if I may be so bold, is far more intelligent than anyone of us on this board) spent considerable energy and time arguing with Neils Bohr on the merits of Quantum Theory.

I was going to compose a long list of scientists being short-sighted on one issue or another. But that isn't necessary. You can look at nearly any scientist of the past and find them to devoutly deny something modern scientist now know as fact, or at least as sound theory.

How silly they all are! How could they be so ignorant? Of course, they aren't foolish at all. They took everything thus far learned and accepted by science and made an educated statement. And they were wrong.

In fact, the prevailing science of the day, quantum mechanics, is completely counterintuitive to human thought. In his book, "The God Particle, Leon Lederman said that it takes a graduate student of physics into his/her 2nd or 3rd year to develop the proper thought pattern required for an intuitive image of quantum mechanics.
What does history have to offer this debate? Only the historical fact that much of what science reveals 100+ years from now would be flatly denied today. I wouldn't dare pretend to know what we will and will not be capable of 100, 200, or 500 years from now. In fact, I don't have a guess. But History tells me to rule out one answer:"never".

[Sam Stone]

I guess some of us older dopers (I'm 39) are pessimistic because we grew up seeing major advances in the space program almost weekly, and have seen that pace of innovation slow to a crawl.

I was in grade 1 when Apollo 11 landed on the moon. My school experience involved seeing a number of moon landings, a Mars lander, a major probe to Jupiter, Apoll-Soyuz, and Skylab. The Shuttle was being developed, and was named after our favorite spaceship on Star Trek. O'Niell wrote 'Cities in Space', and NASA was talking about a permanent moon colony and a mission to Mars by 1990. There were going to be 500 shuttle launches a year.

Now here we are 35 years later, and in that time we've landed one more (smaller) lander on Mars, blown up two shuttles, scaled back our grand space station to be little more than Skylab was, and now we're talking about a Mars mission maybe in 20 years.

I gave up on NASA as our saviour twenty years ago. I figured it had become a bloated government agency that was more interested in protecting turf and maintaining budgets than advancing man in space. So I pinned all my hopes on private space ventures.

But where are they? It's not like people haven't been trying. There have been numerous private space ventures that have blown through hundreds of millions of dollars. None of them have achieved even what the Mercury program managed. Not even close.

I think pessimism about the space program is entirely warranted.

[Greyson3]

Originally posted by Sam Stone


But you are making a fundamental error by trying to extrapolate the curve of advancement we see today as continuing into the future. People were doing that in the 1950's, and coming to the conclusion that we'd have faster than light travel by 2010. Unfortunately, the curve of speed increase flattened out in the 1970's. The fastest thing mankind has ever launched was over 20 years ago.

I call it the Disco Stu Fallacy.

[il Topo]

Originally posted by ChaosGod
5) I have a question about this one: If you travel near the speed of light, and time slows down relative to your point of origin (earth), does that mean that you perceive your trip to be shorter than it really is? Putting it this way: If I travel at 0.99c to alfa centauri (40 light years I think). Will I perceive the trip to be any shorter than 40 years?

Yes.

[JRDelirious]

Originally posted by ChaosGod
5) I have a question about this one: If you travel near the speed of light, and time slows down relative to your point of origin (earth), does that mean that you perceive your trip to be shorter than it really is? Putting it this way: If I travel at 0.99c to alfa centauri (40 light years I think). Will I perceive the trip to be any shorter than 40 years? Peace

Correction: four lightyears to A-Kent/Proxima. And yes, the apparent elapsed time from the POV of you the traveller will be shorted. A quick back-of-envelope gives me an apparent time of something like 6 months and change of "ship apparent time", while 4.04 years elapse on earth.

[Kurai]

To expand on il Topo's post, it WILL be shorter than 40 years... for you and those with you. Our concept of time is merely an invention with a function that ONLY operates on our planet. Time only exists because we decided to measure certain things and make it all work (semi)cleanly. For your cite on this; if we didn't expand our 'system' of time with the use of leap years, eventually summer wouldn't be summer anymore. At least not the summer most of us think of.

As for my opinion on the main threading, I think we (or whoever we become as a species) will get out there eventually...

If we don't kill eachother first.

[Mangetout]

Your biggest problem would not be the apparent duration of the trip, but clening up the mess in the cockpit; how do you propose to accelerate to 0.99c without spreading the crew thinly across the back wall?

Originally posted by caracal
I have no idea how it would happen. But I would say that everyone who said "no way, it'll never happen" needs to balance their intake of science with a little bit of history.

Point taken, but the fact that, at age 4, I thought five plus five was six and that now, at age 35, I believe it to be ten, doesn't mean that when I'm 65, I'll laugh about how naive I was thinking five plus five equals ten.

Everyone who says "future technology will quite likely solve all the problems we now see as insurmountable, it's just a matter of time" needs to balance their optimism with a reading of Dr Seuss' If I Ran The Circus

...Great Sneelock soars up to a terrible height!

Then he shakes himself loose!
He starts down in a dive
Such as no man on earth
Could come out of alive
But he smiles as he falls
And no fear does he feel
His nerves are like iron
His muscles like steel
And he plunges! Down! Down!
With his hair still combed neat
Four thousand, six hundred
And ninety-two feet!

Then he'll land in a fishbowl
He'll manage just fine.
Don't ask how he'll manage
That's his job. Not mine.

[Mangetout]

Originally posted by Kurai
To expand on il Topo's post, it WILL be shorter than 40 years... for you and those with you. Our concept of time is merely an invention with a function that ONLY operates on our planet. Time only exists because we decided to measure certain things and make it all work (semi)cleanly.

Tell me... what would happen if we reversed the direction of the Earth's spin?

[Mangetout]

Actually scratch that; I thought you were saying that the passage of time is caused by our measuring it.

[E-Sabbath]

Well, I can think of a whole _lot_ of ways to accelerate without smearing people. The problem is, most of them are science fiction gibberish. They describe a situation fairly well, but nobody really knows how to do it.

Stargates, hyperdrive, even the strange concept of warping and encapsulating a craft in space so that what is experienced inside is not the same as is experienced outside.

They're all pretty impossible, but that doesn't mean someone won't figure something out.

[CarnalK]

"how do you propose to accelerate to 0.99c without spreading the crew thinly across the back wall?"

Umm, slowly? It's the rate of acceleration thats the problem not the end speed(AFAIK)

[Kurai]

Originally posted by Mangetout
Tell me... what would happen if we reversed the direction of the Earth's spin?

Well.... according to precrisis superman we'd go back in time ;p

nongeek answer: probably worldwide disaster and a nifty madmax future. (GRR, still geeky)

[CuriousCanuck]

Triskadecamus posted:

Name all the complex mechanical systems you can think of which have operated for longer than a century without a single failure.

Well, how about that famous lightbulb that has been shining since 1901? If we can make a product that should only last 1000 hours last over 100 years by not cutting corners and building it right the first time, then why would you think that ANYTHING that we have the technology to build would be any different? I think that you are cynical due to the inferiority of consumer products that are made as such to ensure that we buy more. We could do it. As long as money didnt get in the way...

[Mangetout]

Originally posted by CarnalK
"how do you propose to accelerate to 0.99c without spreading the crew thinly across the back wall?"

Umm, slowly? It's the rate of acceleration thats the problem not the end speed(AFAIK)

Yes... and on a trip of four light years, is it possible to accelerate to 0.99c before you get halfway there? (without killing the crew, or for that matter, making them seriously uncomfortable; 4G is fine in short bursts, but months and years of it would be nasty)

[Mangetout]

I say halfway there because of course you have to decelerate at a reasonable rate as you approach the destination.

[Sam Stone]

Triskadecamus posted:

Name all the complex mechanical systems you can think of which have operated for longer than a century without a single failure.

Well, it's not 100 years, but Voyager 1 and 2 are both still going strong, 25 years after launch, and are expected to continue returning useful data for at least another 20 years.

We have already launched interstellar probes - they're just really slow. Voyager 2, for example, is heading towards Sirius, and will pass within 4.3 lightyears of it in only 296,000 years. Wake me up for the big event.

[JRDelirious]

Mangetout:
It would take considerable time -- and power. May not be worth it for Proxima, but could be for really long distances IF it were feasible to build such a vessel. (BTW, while at .99c, you'd be unable to see where you're going, due to massive blue-shift)

If it were NOT for relativistic effects, that is, if you could just newtonianly accelerate to 296,000 Km/s, it'd take about a year at 1 G acceleration . Problem is, of course, you start running into significant relativistic effects as soon as V²/c² begins becoming a significant fraction itself, causing your mass to increase and the energy demand to shoot up. So travels of single-digit LY distances under this model would be quite uneconomical.

[Mangetout]

Actually, blue shift is another complication that I hadn't thought of; would radiation at shortened wavelengths be another thing to be shielded against?

[Wearia]

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?

[Kitfox]

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.

[Kitfox]

er..."quite complete" should be "not quite complete"...

[TVAA]

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.

[ChaosGod]

Originally posted by The Vorlon Ambassador's Aide

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?

[Sam Stone]

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.

[Polycarp]

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?

[Alien2022]

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...

[Sam Stone]

Polycarp: Yep. But Pat Robertson is no Nehemiah Scudder.

[Polycarp]

Polycarp: Yep. But Pat Robertson is no Nehemiah Scudder.

Although I was thinking more along the lines of Jerry the Fouwell, myself!