What is the best scientific method to deep space travel

[tpribb01]

i have a question for your minds to wonder about. i don't know the answer but i would love to hear your opinions or facts if you have any. now i am probably the hugest trekkie a person can be. i love star trek, it is one of the things that got me into science. anyways, what makes Star Trek, Star Trek is the ability to travel in space at speeds faster then light. now i have heard many theories about the concept of warpdrive. one of my opinions is maybe deep space travel is best done when bending space time, or something like an event horizon. i am not an expert on this side of science so i just want to hear what others have to say.

 

[Chris Hillman]

"Warp drives" in the physics research literature

Hi, tpribb01,

I have in the past posted detailed critiques, based upon discussion of the notion of "warp drives" in the research literature and upon my own exploration of such models, in the newsgroups sci.physics.relativity, which once boasted say a 20-80 balance between knowledgeable posters and cranks; now the ratio is more like 2-98, unfortunately You can google for those posts, so I won't repeat myself at great length here.

The key points to appreciate are these:

1. Alcubierre's model is a valid Lorentzian manifold which realizes some features in common with the fictional warp drive in Star Trek, e.g., people don't fall over inside the Enterprise when the ship accelerates and a "warp bubble" surrounding the ship goes effectively superluminal. The "effectively superluminal" aspect of the motion of this bubble is a global effect which doesn't contradict the fact that no material can travel faster than light. All at the level of Lorentzian manifolds. (I know you don't know what I am talking about, I am just mentioning some technical buzzwords you can ask about here or elsewhere.)

2. However, this and similar spacetime models called "warp drive models" in the literature are in no sense solutions to the EFE.

3. In fact, a great variety of objections have been raised in the literature. Probably the most fundamental concern that fact that all known "warp drive models" invoke "warp bubbles" which appear spontaneously and feature energy which moves in what is thought to be a physically impossible manner. There are arguments strongly suggesting that this would be true of any warp bubble, i.e. that warp bubbles are physically impossible "causally". In addition, the energy requirements appear to be prohibitive, and again there are general arguments based upon some obscure corners of QFT suggesting that warp bubbles would be physically impossible on "energetically".

4. For a few years, there were quite a few eprints exploring the notion of "warp drives". This activity seems to have largely died out, and I think it is fair to say that the current mainstream viewpoint is that "warp bubbles" are physically impossible. There are a handful of dissenters from this viewpoint.

 

[marcus]

what is the best scientific method to deep space travel

i have a question for your minds to wonder about...

I would urge you to change the question slightly and think about a variation of the problem:

what is a practical scientific method to spread Earth life to other habitable planets?

Suppose that, during the next few years, several earth-like planets are found orbiting in the habitable zones of nearby stars (say 10-100 lightyears from us.) Suppose no signs of life are detected, by whatever means are used.

What methods can you think of to establish Earth life on these places, if they resemble Earth enough to harbor it?

Would your first reaction be to call for the invention of a faster-than-light vessel? Or would you consider other approaches to solving the problem?

 

[Chris Hillman]

Another question is: what kind of Earth life should we spread? If any? Is it perhaps immoral to deliberately infect other planets with Earthly life forms? Particularly humans? See Alan Burdick, Out of Eden, for a recent popsci book (by a nonbiologist).

 

[marcus]

Is it perhaps immoral ...?

I'll save the moral discussion for another thread, and focus on technical means.

Mr. Tpribb is asking about method.

To repeat the question, admittedly anyone of us can probably think of ways to do this without needing outside inspiration, and may have read published scenarios as well, but let's take a fresh look and see what we come up with:

Suppose in the next few years several habitable planets are found at 10-100 lightyear range, with no detectable signs of indigenous life. Can you imagine any practical way to impregnate them with Earth life?

 

[pervect]

Do you want "earth life" or "humanity"?

I can imagine nuclear drives of one sort or another getting us up to a few percent of the speed of light - or possibly solar pumped lasers to drive a light sail. Braking the light sail would be a problem, though, while Forward has described 1000 km Frensel lenses as a possible solution, I don't think that fits in the time frame specified. Possibly a hybrid system - a laser driven light sail, along with some sort of nuclear rocket for braking.

I can imagine with our current biology getting some sort of Earth life to survive the 1000 year trip, but I don't think our biology is good enough to get human life to survive or be able to be recreated after such a journey.

I think the general key to "practical" interstellar travel will lie in biology, or perhaps in robotics, rather than physics. Forget about beating the speed of light, or even approaching it closely. Plan on spending 1000's of years at a percent or two of c instead.

I'm also thinking that this thread will fit better in the general discussion forum, so that's where I'm going to move it.

 

[marcus]

Do you want "earth life" or "humanity"?

I can imagine nuclear drives of one sort or another getting us up to a few percent of the speed of light - or possibly solar pumped lasers to drive a light sail. Braking the light sail would be a problem, though, while Forward has described 1000 km Frensel lenses as a possible solution, I don't think that fits in the time frame specified. Possibly a hybrid system - a laser driven light sail, along with some sort of nuclear rocket for braking.

I can imagine with our current biology getting some sort of Earth life to survive the 1000 year trip, but I don't think our biology is good enough to get human life to survive or be able to be recreated after such a journey.

I think the general key to "practical" interstellar travel will lie in biology, or perhaps in robotics, rather than physics. Forget about beating the speed of light, or even approaching it closely. Plan on spending 1000's of years at a percent or two of c instead.

I'm also thinking that this thread will fit better in the general discussion forum, so that's where I'm going to move it.

Robotics. I am in exact agreement with you here. A robot can exist in a shutdown state for 1000s of years and then wake up and cultivate cellular life. Might even experiment intelligently to find out what singlecell organisms are best adapted to the environment.

I would like to hear from Mr. Tpribb, though. I would be happy to go away if he does not want people talking about the mere transmission of living organisms to a new habitat.

It is Tpribb's thread. I just hope he will consider this as a friendly evolution of the problem he posed.

 

[Integral]

One has to wonder if the descents of humans locked aboard a spaceship for generations would still be considered humans? What evolution would occur to adapt these beings to live in a steel tube?

A tree or blue sky would exist only as pictures in the data bases, what meaning would that have to someone 3 or 4 generations from launch?

I remain convinced that the main task for the next 2 generations is to establish that we can maintain our current state of civilization on the spaceship earth. Once we have done that then we can look to spreading the virus we call life to other systems.

 

[Office_Shredder]

In 2 or 3 generations, modern civilization won't be.. Just like civilization in the 40''s isn't around today. So I find that to be infeasible at best

 

[ice109]

i think traveling at a decent fraction of C is the only answer. the point is not to colonize other planets simply for the sake of spreading our species, the point is to preserve some semblance of our society. like " i want my kids kids to persist " i imagine that is the sentiment. why would anyone care about another group of humans who have absolutely nothing to do with us, what would be the point.

 

[marcus]

everyone has their own personal viewpoint
and an idea of what they'd be willing to pay for.

I just spent a week in a relatively undeveloped corner of a pacific island, for much of the time snorkling over reef

I'd be willing to consider part of my taxes going to start fish somewhere.
You'd have to start algae first, to build up oxygen, I guess. And then some other things: plankton, weed...

Fish look nice and mind their own business.
I hope astronomers find a warm water planet where we can eventually plant some fish.

the robot would know how to do it.
there would be fish DNA stored digitally in the computer so that if the frozen eggs didn't hatch the robot could reconstruct DNA and start them that way.

 

[Ivan Seeking]

There was some interesting stuff coming from the so called Heim physics that emerged recently, but I don't what has become of this. Allegedly, NASA, the USAF, and the DOD were all experimenting with a Heim physics based FTL drive.

If not already disproven, "Heim physics" is not proven or accepted as valid. It may all be wrong.

 

[ice109]

everyone has their own personal viewpoint
and an idea of what they'd be willing to pay for.

I just spent a week in a relatively undeveloped corner of a pacific island, for much of the time snorkling over reef

I'd be willing to consider part of my taxes going to start fish somewhere.
You'd have to start algae first, to build up oxygen, I guess. And then some other things: plankton, weed...

Fish look nice and mind their own business.
I hope astronomers find a warm water planet where we can eventually plant some fish.

the robot would know how to do it.
there would be fish DNA stored digitally in the computer so that if the frozen eggs didn't hatch the robot could reconstruct DNA and start them that way.

but the question is why? do we care about fish? do fish want to live on other planets?

 

[pervect]

The only advantage of traveling at a large fraction of 'c' is to make the trip shorter for the traveller. It won't make that much difference in the amount of Earth time that a round trip takes, because that velocity is strictly limited by 'c'. So even if you had a gamma factor of 10:1, your round strip time would be limited by the distance traveled divided by 'c'.

It would probably not only be easier to extend people's lifespans than to reach a large fraction of 'c', but there will probably be more effort put into it, because people want to live longer. Having a bit of patience because of longer lifespans (possibly bioengineered longer lifespans) is much easier to imagine than it is to imagine a drive with significant relativistic gamma factors.

This is assuming we don't blow each other up first, which actually seems like the most probable course of events.

 

[DaveC426913]

Is it perhaps immoral to deliberately infect other planets with Earthly life forms?

The word is colonize. And every species has the "right" to ensure its survival.

This is assuming we don't blow each other up first, which actually seems like the most probable course of events.

Which is one of the pirmary motivators for having a backup humanity.

 

[Chris Hillman]

I don't think I really want to pursue this argument, Dave, but

1. For better or for worse, "every species has the right to ensure its survival" is not a principle recognized in human jurisprudence

2. Wise biologists have long recognized that the notion of a (biological) "species" is merely a convenient fiction. Space precludes me from even attempting to explain what I mean by this, but if you are curious, see Ernst Mayr, Population, Species, and Evolution for an extensive discussion of this point. For this and other reasons, I feel that it makes little sense to grant rights to "species", but I would agree that the suggestion that "individuals" (biological or otherwise) should perhaps be granted some rights, is worthy of consideration. In particular, while I might be biased, I feel that software entities should be granted some legal rights.

Incidental remark: it is a curious fact that human jurisprudence recognizes the rights of individuals, meaning human individuals, without making (AFAIK) any attempt to provide a legal definition of a human being. Biologists say that experience with producing chimeras suggests that producing a human-chimp chimera would not be particularly difficult. This is an experiment which biologists around the world seem to universally deplore, but I tend to think it's inevitable that eventually someone will do it, just because they can. I myself feel this experiment would be unethical, but not much more so than more typical reproduction involving two humans or two chimps.

Another incidental remark: it is a curious fact that despite the evident economic superiority of states whose citizens are software entities rather than wetware entities, the much vaunted laws of the marketplace have thus far been surprisingly slow to produce examples.

 

[Chris Hillman]

There was some interesting stuff coming from the so called Heim physics that emerged recently, but I don't what has become of this. Allegedly, NASA, the USAF, and the DOD were all experimenting with a Heim physics based FTL drive.

If not already disproven, "Heim physics" is not proven or accepted as valid. It may all be wrong.

I definitely don't want to pursue this, but the so-called "Heim theory" [sic] lacks the form of a "physical theory" as I understand that word. Rather, it seems to be more like a heuristic for which a tiny minority makes extraordinary and highly suspect claims. It is considered cranky by mainstream physicists. (And the so-called "selector calculus" is a topic which is not recognized as mathematics by mathematicians.) Obligatory warning: Wikipedia articles have been the subject of an endless edit war between proponents of "Heim theory" [sic] and members of WikiProject Physics.

A general comment: cranks commonly claim that this government or that is sponsoring research into their "theory". These claims never seem to hold up to closer scrutiny. That is, it might be true that some large aerospace organization granted an interview to some crank touting an alleged "inertialess drive", and when this happens it is widely publicized on the crank net. What you don't hear is that the internal report basically said "this guy is a nutcase, end of story". It is also true that various governments have from time to time sponsored some highly questionable "research projects" (the recent case of Roger Shawyer and his EmDrive might be an example), but in these cases, closer examination shows that when usable results were not forthcoming, the grants were terminated.

 

[pervect]

The word is colonize. And every species has the "right" to ensure its survival.Which is one of the pirmary motivators for having a backup humanity.

If humanity was concerned with its own survival, more people would think like Dave does here. But depressingly, it appears to me that on the whole, humanity is just an abstraction. What we actually have is not an abstract "humanity", but rather a bunch of people, who are mainly interested in the very short term.

 

[K.J.Healey]

Just as an addon:

Given something with the mass of the space shuttle at liftoff (including fuel, etc, just to approximate) 2,029,203 KG (4,474,574 LB)

What do you think our current capabilities, if we dedicated all possible resources, would get us up to in terms of speed toward a distant star.

Assume money is no issue, using nuclear explosions is no issue, maybe just like : taking all nuclear material and converting it to acceleration energy.

Then I guess we can split it to inculde slowing down.
But how fast do you think is possible going "all-out"?


(oh and just to comment on the rest)
If sending life to an unpopulated planet the whole eco system would have to be mimicked. for the most part. I'm sure you could be really selective with some research. (A beetle that eats the poo of a fox that catches ground squirrels that eat the beetles.) With alternative sources of plant food that theyre all compatable with slightly. Or you just do all herbivores. But even the plants need bugs, bacteria, algae, all sorts of microorganisms to replenish the soil's nutrients. You would need serious modeling of enviroments given what's known about each organism chosen, and I am sure some long experiments to determine side effects.

 

[Ivan Seeking]

I definitely don't want to pursue this, but the so-called "Heim theory" [sic] lacks the form of a "physical theory" as I understand that word. Rather, it seems to be more like a heuristic for which a tiny minority makes extraordinary and highly suspect claims. It is considered cranky by mainstream physicists. (And the so-called "selector calculus" is a topic which is not recognized as mathematics by mathematicians.) Obligatory warning: Wikipedia articles have been the subject of an endless edit war between proponents of "Heim theory" [sic] and members of WikiProject Physics.

We had a bit of debate in the Mentors forum about where to put any Heim related information. At the time, no one here had ever heard of it. In the end it was moved to the Beyond the Standard Model forum.

A general comment: cranks commonly claim that this government or that is sponsoring research into their "theory". These claims never seem to hold up to closer scrutiny. That is, it might be true that some large aerospace organization granted an interview to some crank touting an alleged "inertialess drive", and when this happens it is widely publicized on the crank net. What you don't hear is that the internal report basically said "this guy is a nutcase, end of story". It is also true that various governments have from time to time sponsored some highly questionable "research projects" (the recent case of Roger Shawyer and his EmDrive might be an example), but in these cases, closer examination shows that when usable results were not forthcoming, the grants were terminated.

There were several news articles about this and it seems to be true that all three agencies were looking at it, but as you said, this doesn't give the theory credibility.

...on the other hand, even if it worked we would probably never know for decades as it would be classified immediately. I suppose this is why the military dumps a few bucks into long shots from time to time - the potential-pay off justifies the crap shoot.

 

[Chris Hillman]

Why do they bother? This is why, we guess

We had a bit of debate in the Mentors forum about where to put any Heim related information. At the time, no one here had ever heard of it. In the end it was moved to the Beyond the Standard Model forum.

So is Scepticism and Debunking focusing on paranormal only? Crank/Fringe physics excluded? I guess I'm still a bit confused.

it seems to be true that all three agencies were looking at it, but as you said, this doesn't give the theory credibility.

The point I was trying to make is that "looking at an idea" typically means some aerospace company put some engineers in a room with some "inventor" and requested them to listen to and report on his presentation. I have been told by engineers who have participated in such interviews that they are very rarely anything but pro forma. I agree that the Shawyer fiasco seems to be unusual in that he apparently actually received funding after a highly inadequate review process.

I suppose this is why the military dumps a few bucks into long shots from time to time - the potential-pay off justifies the crap shoot.

I have been told that the working assumption is the nutty-sounding ideas are nuts, but the idea is that they should make some attempt to examine each one, just in case. I doubt even one in a hundred interviews of "independent inventors" draws positive reviews, but history does suggest keeping an eye out for the diamond among the sand grains can pay off. When I wrote my post above I considered mentioning the story of Robert Fulton, John Ericcson, the Wright brothers, and John Holland all approaching the U.S. military seeking assistance in developing militarily significant inventions, and being initially turned down. I understand it is now enshrined in military doctrine that This Was Not Smart To be sure, we live in a very different world now, and one thing which has changed is that the "Western" multinational military-industrial complex has plenty of scientists on hand who can probably quickly recognize a Wright or an Ericcson.

Picking up on a theme of some earlier posts by myself, I just noticed that two out of the following four Wikibios fail to mention significant episodes in the lives of the subjects!:
http://en.wikipedia.org/wiki/Robert_Fulton
http://en.wikipedia.org/wiki/John_Ericsson (omits to describe initial rejection by U.S. Navy of Ericsson's proposal to build a ship powered by his screw propeller rather than paddle wheels)
http://en.wikipedia.org/wiki/John_Philip_Holland
http://en.wikipedia.org/wiki/Wright_brothers (omits to describe initial rejection by the U. S. Army of the brother's proposal that the Army should help fund development by purchasing some early fliers)

ADDENDUM: ooh, here's a delicious irony. Roy Kerr, who discovered the famous Kerr vacuum solution of the Einstein field equation, has just posted an arxiv eprint http://www.arxiv.org/abs/0706.1109 in which he explicitly debunks a rumor which I unfortunately repeated in a wikibiography which I wrote http://en.wikipedia.org/w/index.php?title=Roy_Kerr&oldid=20517806 in August 2005, saying

There is a claim spread on the internet that we were employed to develop an antigravity engine to power spaceships. This is rubbish! The main reason why the US Air Force had created a General Relativity section was probably to show the navy that they could also do pure research. The only real use that the USAF made of us was when some crackpot sent them a proposal for antigravity or for converting rotary motion inside a spaceship to a translational driving system. Thse proposals typically used Newton's equations to prove non-conservation of momentum for some classical system.

Ivan, that quote might be handy if this rumor comes up again on your watch!

I can't help emphasizing that violation of conservation of momentum was the very clue which should have warned off the idgit who funded Shawyer.

 

[Ivan Seeking]

So is Scepticism and Debunking focusing on paranormal only? Crank/Fringe physics excluded? I guess I'm still a bit confused.

In S&D we only consider claims of unexplained phenomena - it doesn't matter what subject may be. We do casually consider potential explanations for claims made, but explanations must either be [mainstream] scientific or a direct consequence of the claim - ie. I saw a ghost, or, the psychic read my mind. In other words, people are allowed to either explain their experience as they see it, or to present the evidence for a claim as it stands, but fringe science is not allowed in the process. So we may not be able to explain away every ghost, but we won't be considering any third eye theories either.

On rare occasion exceptions are made as needed to address unique issues. This happened with Heim Theory for a time since no one here knew anything about it. But as I said, eventually it was moved to a regular forum.

We used to have a Theory Development section for fringe theories, but it was more than a full time job to moderate it and respond to the endless stream of crank arguments. And without proper moderation, it was a free-for-all for every crank on the net. It was also an embarrassment to the forum. So we [Tom really] came up with the Independent Research forum where qualified proposals may be considered but where the posting rules keep out the cranks. Otherwise, if a theory isn't good enough for a regular forum it has no place here. I try to allow a little latitude for people who are mislead by crank sites and move such questions to GD, but “questions” often degenerate into rants to defend crank theories, so many of our staff have little tolerance for such threads in any form.

 

[Chris Hillman]

So if I follow you, S&D is where we should direct the poster who says, "Hey I saw a ghost-- how do you science whizzes explain that?!" I agree that none of us want to deal with cranks defending to their dying breath crackpot notions which make no sense to anyone else

 

[Ivan Seeking]

So if I follow you, S&D is where we should direct the poster who says, "Hey I saw a ghost-- how do you science whizzes explain that?!"

Yep, all the paranormal stuff along with other claims like this one
https://www.physicsforums.com/showthread.php?t=172018

Note that free energy discussions are not allowed, but there is a phenomenon involved here so I kept the thread open.

Anecdotal evidence is allowed but only as such and not as proof or scientific evidence. So as long as everything is kept in the proper perspective, people can tell their story and then allow our skeptics the chance to explain it.

I have spent a fair amount of time trying to come up with a format that works and did my best to lay it out here.
https://www.physicsforums.com/showthread.php?t=5929

Also note that Moonbear and Nereid were very helpful in this process.

 

[Astronuc]

Re: scientific method to deep space travel

AFAIK, no one has practically demonstrated how one curves space, or creates warp bubbles or wormholes.

In the end, we are still constrained by the fact that in order for a mass to accelerate, an opposing force must be applied, which requires a differential momentum and some corresponding energy.

Furthermore, our supply of energy is constructed of materials (matter) which are subject to constraints of internal energy/enthalpy/temperature, such that when the temperature exceeds some limit, the material creeps/flows/deforms, which usually occurs well below the melting temperature. Material systems are therefore constrained by the specific energy.

The highest temperature states involve plasmas, but practical use of plasmas are constrained by the limits of magnetic field strength and the mechanical strength of the structures supporting the magnets. So plasma pressures and their internal energy are limited, and even with the very high velocities, the plasma particle/mass densities are limited such that useful thrust is quite limited.

Propulsion comes down to getting the most momentum (of the propellant) in one direction (that opposite of one's direction of travel) while minimizing the momentum in the other two dimensions (normal to the direction of one's travel).

 

[Chris Hillman]

AFAIK, no one has practically demonstrated how one curves space, or creates warp bubbles or wormholes.

Correct, assuming that in the "curving space" bit you didn't mean that gtr thingie which happens whenever you have mass-energy! In fact, as far as I can see, no-one has even come close to positing even a highly idealized but hypothetically physically permissable scheme for "metric engineering", "warp bubbles", or "transversable wormholes". Despite the occasional eprint expressing a contrary view, I am with the mainstream on this point.

Propulsion comes down to getting the most momentum (of the propellant) in one direction (that opposite of one's direction of travel) while minimizing the momentum in the other two dimensions (normal to the direction of one's travel).

A readable and good short history which suggests how tricky "simple-minded" chemical rocketry can be: Deborah Cadbury, Space Race, Harper-Collins, 2006. Injection plates, baffles and bombs in the combustion chamber of F-1 engines, gosh...

 

[Ivan Seeking]

This is a good link that provides an overview of our best hopes
http://www.nasa.gov/centers/glenn/research/warp/warp.html

 

[Astronuc]

what is the best scientific method to deep space travel?

Very quickly!

http://www.nasa.gov/centers/glenn/images/content/84498main_perspective.jpg

It's a long, long way to . . . .

and if you break down along the way, it's easy to get out, but you can't push.

 

[pervect]

Just as an addon:

Given something with the mass of the space shuttle at liftoff (including fuel, etc, just to approximate) 2,029,203 KG (4,474,574 LB)

What do you think our current capabilities, if we dedicated all possible resources, would get us up to in terms of speed toward a distant star.

Assume money is no issue, using nuclear explosions is no issue, maybe just like : taking all nuclear material and converting it to acceleration energy.

Then I guess we can split it to inculde slowing down.
But how fast do you think is possible going "all-out"?(oh and just to comment on the rest)
If sending life to an unpopulated planet the whole eco system would have to be mimicked. for the most part. I'm sure you could be really selective with some research. (A beetle that eats the poo of a fox that catches ground squirrels that eat the beetles.) With alternative sources of plant food that theyre all compatable with slightly. Or you just do all herbivores. But even the plants need bugs, bacteria, algae, all sorts of microorganisms to replenish the soil's nutrients. You would need serious modeling of enviroments given what's known about each organism chosen, and I am sure some long experiments to determine side effects.

Rather than answer this directly, I'm going to give you names and some off-the-top references to various proposals for interstellar propulsion. There may be better references available, this is just a quick guide to some of the more interesting proposals.

Nulclear propulsion: see for instance orion (nuclear bombs & a pusher plate), http://www.islandone.org/Propulsion/ProjectOrion.html

probably one of the oldest and most likely proposals to actually work
also see medusa http://adsabs.harvard.edu/abs/1993JBIS...46R..21S

aimstar http://www.engr.psu.edu/antimatter/Papers/AIMStar_99.pdf

Ambitious, but better performance than orion. There are other fusion proposals too, the names escape me at the moment.

Fission fragment rockets:
http://en.wikipedia.org/w/index.php?title=Fission-fragment_rocket&oldid=136513448

I'll also mentioned laser pumped light sails, but most of those (except perhaps for starwisp) would require much more infrastructure than a single shuttle-sized ship.

see for instance http://science.nasa.gov/NEWHOME/headlines/prop08apr99_1.htm for some info on starwisp and its successors.

 

[Chronos]

A point to consider: If you 'point and shoot' at Jupiter, with an infinitely fast spacecraft , will Jupiter be there when your craft arrives? If you have a space cam that returns instantaneous reports on the position of your spacecraft , will the signals arrive before they were emitted? The concept is illogical to me.

 

[Office_Shredder]

Well Chronos, considering you can't go faster than the speed of light, I'm not sure what you mean by infinitely fast.

 

[Astronuc]

I believe "infinitely fast spacecraft " means "pretty d@*n quick".

It still comes down to the fact that to accelerate matter to near light speed requires a lot of energy, and one cannot avoid/escape the reality that there are limits to the energy density in man-made material systems. Sure stars can have plasma densities of 10²² protons/cm³, but the pressures are enormous, and no man-made system can handle that, especially at the high temperatures involved. Similar, we cannot build a craft that can travel to the center of the earth.

 

[Ivan Seeking]

Well Chronos, considering you can't go faster than the speed of light,

...in local space and by any physics that we understand.

We don't know that the limit is absolute which is why scientists play with ideas like warp drive. But it is silly to attempt resolving FTL paradoxes since it would required a physics that we don't know [and may not exist].

 

[Art]

...in local space and by any physics that we understand.

We don't know that the limit is absolute which is why scientists play with ideas like warp drive. But it is silly to attempt resolving FTL paradoxes since it would required a physics that we don't know [and may not exist].

Doesn't the expansion of the universe cause distant galaxies to recede faster than the speed of light? Okay this is because of the expansion of the fabric of spacetime but the effect on matter is real none-the-less so perhaps an understanding of exactly what is involved in expanding spacetime would get us started in creating FTL ships.

 

[Ivan Seeking]

Doesn't the expansion of the universe cause distant galaxies to recede faster than the speed of light? Okay this is because of the expansion of the fabric of spacetime but the effect on matter is real none-the-less so perhaps an understanding of exactly what is involved in expanding spacetime would get us started in creating FTL ships.

That's why I specified local space.

I think the idea of distant galaxies moving faster than light is speculative but now considered possible. I haven't kept up with this lately but I don't see how we could know that they exist.