Extrasolar exploration: only a fantasy?

[MartinParish]

I saw this another thread (kudos to mike_bike_kite for posting it!) and it reminded me of a couple questions I've been thinking about for a while.

Originally Posted by mike_bike_kite

I was just reading Time for the Stars by Robert A. Heinlein (1956). The crew on the space ship are out in deep space and needing to either grow or recycle everything to survive. It made me smile to be reading a SciFi story on electronic paper about the crew of some future space craft who were having to recycle paper for their morning newspaper

Many sci-fi authors like Heinlein have assumed that faster-than-light travel and/or extrasolar exploration would become possible in the future, and that humanity will colonize worlds beyond the solar system. They've been wrong on that prediction so far, of course, but will they eventually be proven right? I wouldn't bet on it. Based on our current understanding of physics, faster-than-light travel is extremely impractical and it's unlikely it will ever become possible, simply because the energy required to warp space time would be too great.

Never being able to leave the solar system doesn't mean we won't find life on other planets. I imagine we'll discover life elsewhere in the near future by using spectroscopy; if we find an extrasolar planet that has oxygen in its atmosphere, for example, we can infer there's probably life there, since oxygen gas is fairly reactive and generally combines with other elements, so its persistence in Earth's atmosphere, for example, is due to photosynthesis. But even once we do find a planet outside the solar system that does have life we'll never be able to meet E.T.; neither s/he nor us will be able to cross the vast oceans of interstellar space. The reality is that we're stuck here on our own little island and can't go anywhere else.

Given that humankind will probably never be able to go far beyond the bounds of our solar system - that what we've got now is what all we'll ever have - does that knowledge change our priorities for scientific research? Should it change our priorities? And should science fiction be written to reflect the reality, rather than indulging in a fantasy (extrasolar exploration) that will probably never happen? Anyway, just questions brought to mind by the Heinlein story, not that they're directly related, but rather more of a tangent, I suppose.

[AprilHare]

Missions to Mars are beset by problems with radiation. And that's just to one of the closest planets in our own planetary system.
I'll be waiting a while to see us leave this solar system.

Originally Posted by MartinParish

I saw this another thread (kudos to mike_bike_kite for posting it!) and it reminded me of a couple questions I've been thinking about for a while.



Many sci-fi authors like Heinlein have assumed that faster-than-light travel and/or extrasolar exploration would become possible in the future, and that humanity will colonize worlds beyond the solar system. They've been wrong on that prediction so far, of course, but will they eventually be proven right? I wouldn't bet on it. Based on our current understanding of physics, faster-than-light travel is extremely impractical and it's unlikely it will ever become possible, simply because the energy required to warp space time would be too great.

Never being able to leave the solar system doesn't mean we won't find life on other planets. I imagine we'll discover life elsewhere in the near future by using spectroscopy; if we find an extrasolar planet that has oxygen in its atmosphere, for example, we can infer there's probably life there, since oxygen gas is fairly reactive and generally combines with other elements, so its persistence in Earth's atmosphere, for example, is due to photosynthesis. But even once we do find a planet outside the solar system that does have life we'll never be able to meet E.T.; neither s/he nor us will be able to cross the vast oceans of interstellar space. The reality is that we're stuck here on our own little island and can't go anywhere else.

Given that humankind will probably never be able to go far beyond the bounds of our solar system - that what we've got now is what all we'll ever have - does that knowledge change our priorities for scientific research? Should it change our priorities? And should science fiction be written to reflect the reality, rather than indulging in a fantasy (extrasolar exploration) that will probably never happen? Anyway, just questions brought to mind by the Heinlein story, not that they're directly related, but rather more of a tangent, I suppose.

[fjtorres]

Never is a long time. And when it comes to physics be barely know the questions to ask, much less the answers.
The Encyclopediss of the 19th century thought they knew all there was to know. Then Roentgen came along...
Give it time. As long as we don't give up looking to the future we'll get there.

[Greg Anos]

There's a lot of if's and's and but's in the concept of extra-solar travel. (Exploration is only aspect of travel.)

First off, I don't worship at the Church of Einstein. (And modern physics is as much of a theology as a science today.) Why don't I believe in C?

Maxwell's equations. All unified field theories, including Relativity, are build on the base of Maxwell's equations. And inherent in Maxwell's equations is a loophole big enough to drive an 18 wheel truck through. Modern physics treats this loophole like the Wizard of Oz when the curtain was pulled away.

What is this loophole? Maxwell's equations are 4 tensors (I were a T-shirt occasionally with them on it) with 2 boundary conditions! If you fail to meet the boundary conditions, the equation may or may not be valid. They are only valid under when the boundary conditions are met. Here are the boundary conditions.

1. There must be a right handed twist in the electromagnetic waves.

2. c = 1 / square root of (e0 * mu0) (which are the permittivity of a vacuum and the permeability of a vacuum, respectively). This is the hand grenade.

Why? Because instead of treating C as a constant, it treats C as a derived variable. Change the parameters and you change C.

Until 1999, it didn't matter. Nobody knew how to change e0 and mu0. However, with the breakthrough at UCSD of creating a field with negative permittivity and permeability, this loophole has reared it's ugly head. Can you create an artifical field with a e0 and mu0 less than what defines C? If so, what happens when you run a Michaelson Morley test through it? Funny, nobody has tried it...(One test was done in 2004, but they used misaligned receivers to create a surface version of the effect. Since the waves didn't go through a field, it wasn't a valid test of a low e0mu0 field. But it didn't show any increase in the speed of light, so the idea was happily shelved. Without actually truly testing it...)

So there may be a way to increase the speed of light, allowing extra-solar travel. Don't ask me for engineering, this is just theory...(And I'm just covering the high points.)

[WT Sharpe]

I suspect that if interstellar travel were feasible, we'd have been visited by now. The trouble is the vast distances between star systems, or as Douglas Adams so aptly summed it up, "Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space." Couple that with the dangers inherent in such a mission, the extreme costs such a mission is likely to incur, and the need to justify those costs to those who would have to pay them, and it seems unlikely that interstellar travel will ever happen. Robotic probes may perhaps one day be launched from Earth with an eye toward relaying any data gathered back to the descendants of the ones who launch them, or even to the scientists themselves if lifespans increase significantly, but I doubt we humans will ever make the trip ourselves.

I could be wrong. I hope I am.

[sabredog]

I am not so sure about that. Like you say, space is big and the particular spiral arm of the galaxy that our little G2 star resides in is not very densely packed with other stars.

I do not consider the speed of light needing to be exceeded. Scientists have considered for some time the potential for going "around" the light barrier.

That sort of thing however is not going to happen in our life time. Meanwhile humanity has a whole solar system to explore and colonise. That will keep us occupied for quite some time.

I liken the 20th-21st centuries to be like the 15-16th centuries. First exploration and then colonisation. But achieving that is not going to be possible for one country alone. A united approach is needed.

[kovidgoyal]

@RSE: Actually it's not the speed of light that's upper bounded (and note that as you correctly point out, the speed of light is not a constant, except in an ideal vacuum and no such beast exists). So it is fair to say the speed of light is never constant.

What is upper bounded (and again not constant) is the speed of signaling, i.e. information transfer. And I would not really want to live in a universe where the speed of signaling is not upper bounded. I can't even imagine what such a universe would be like. The havoc it would play on causality alone makes me shudder.

It could of course be argued that the upper bound is not the speed of light, but such an upper bound must exist. And I somehow doubt that the upper bound, if higher than c will be high enough to allow for IST.

To me the only semi-hopeful way that interstellar travel can be achieved is by space-time distortions that temporarily alter the topology of the universe to connect remote regions. Wormholes for the layman Unfortunately, I know very little about General Relativity, so I cannot really comment on the feasibility of that as a practical means of travel. Which is probably why I find it hopeful

[ardeegee]

Originally Posted by fjtorres

The Encyclopediss of the 19th century thought they knew all there was to know. Then Roentgen came along...

The encyclopedias may have thought that-- but the scientists never did.

Scientists make observations and attempt to derive explanations that best fit those observations. Even when an explanation is found that fits the observations made at the time, there is always the possibility of new findings that mean the explanation (the theory) has to be revised or tossed out.

There are many things that scientist thought or suspected to be correct in the 1800s that turned out to not be so. But that does not mean that, therefore, today's science is just as likely to be wrong. Scientists have far more powerful tools at their disposal today than they did 200 years ago-- not only technological tools like computers and electron microscopes and orbital telescopes, but also mental tools-- systematic ways of thinking about and examining the world that have been refined over the centuries ("the scientific method.") What passed for science in the 19th century and before was more in line with philosophy and not what we know as modern experimental science (and the further back you go, the less "scientific" the majority of "science" was.)

So is it-- in theory-- possible that there is something we have fundamentally wrong about current physics? Sure. Do I think it likely that we have something as wrong as people had it in the past? I don't think it very likely. There is no evidence of FTL travel that brings into question standard models of physics-- and particle accelerators are monitored to keep track of all energies involved in collisions-- if any of the mass of a collision disappeared into the past or flew off at a multiple of the speed of light, it would be noticed-- lots of new particles are found by sifting through many billions of collisions to find 1 or 2 instances of the particle's formation. If it happens, it is exceedingly rare.

And even if there is ever found a particle that can travel faster than light or a way is found to make photons travel "faster than light"-- that does not mean that a macroscopic object can be made to do so.

As much as I love for it be otherwise, I do not think that FTL travel will ever be anything more than a plot device used in the telling of a science fiction story.

But-- just because we aren't likely to have FTL, that doesn't mean we can never explore other solar systems. Even current levels of technology can send probes to nearby stars within a matter of centuries. The problem is societal-- people not willing to invest in something that will not bear results for many generations or lifetimes. Most politicians (who pay the budgets for the space agencies) want results within the bounds of their own election cycle.

The best first step towards getting interstellar probes is to get rid of a disease so universal to humanity that most don't even think of it as such-- that pesky genetic disorder that we call "old age." Improve our cellular self-repair machinery so that it doesn't fail after a few decades, and people can start caring about something that won't show results for centuries because they can begin to be of the mindset that they might be around to see those results. If interstellar exploration isn't for mere mortals, then stop being mortal.

[ardeegee]

Originally Posted by kovidgoyal

To me the only semi-hopeful way that interstellar travel can be achieved is by space-time distortions that temporarily alter the topology of the universe to connect remote regions. Wormholes for the layman

What you re describing isn't worm holes. And bending space enough for FTL would take a huuuuuuge amount of energy. A full Jupiter-mass of it. Not only energy, but "negative" energy, which is itself only a theory.

http://news.discovery.com/space/warp...ip-engine.html

lots:

http://www.physicsguy.com/ftl/index.html

[Greg Anos]

Originally Posted by kovidgoyal

@RSE: Actually it's not the speed of light that's upper bounded (and note that as you correctly point out, the speed of light is not a constant, except in an ideal vacuum and no such beast exists). So it is fair to say the speed of light is never constant.

What is upper bounded (and again not constant) is the speed of signaling, i.e. information transfer. And I would not really want to live in a universe where the speed of signaling is not upper bounded. I can't even imagine what such a universe would be like. The havoc it would play on causality alone makes me shudder.

It could of course be argued that the upper bound is not the speed of light, but such an upper bound must exist. And I somehow doubt that the upper bound, if higher than c will be high enough to allow for IST.

To me the only semi-hopeful way that interstellar travel can be achieved is by space-time distortions that temporarily alter the topology of the universe to connect remote regions. Wormholes for the layman Unfortunately, I know very little about General Relativity, so I cannot really comment on the feasibility of that as a practical means of travel. Which is probably why I find it hopeful

Speed of signaling has so far been limited to speed of medium carrying the signal. I have great difficulty getting my mind around a situation where the medium can travel faster than a signal embedded in it.

I was merely pointing out to S/F writer a potential loophole that legitimately allows FTL <sic> travel (by speeding up light). The underlying issue (to me) is why C not what C. I suspect that we will find that "the ether" was a correct concept, after all. Michaelson Morley didn't disprove "ether", they merely showed it didn't affect light measurement. The Lorentz transformation explained why. Both were incorporated in Special Relativity, and mathematically consistent with it. For example, if one thought of "the ether" as a scalar quantity rather than a vector quantity (and why not?), then you would get the same result from Michaelson Morley as you currently get. (To get a grasp of a scalar "ether" think of a 3-D sandpaper throughout space, not moving. No matter which way you go, you get the same frictional drag.)

[kovidgoyal]

Originally Posted by ardeegee

What you re describing isn't worm holes. And bending space enough for FTL would take a huuuuuuge amount of energy. A full Jupiter-mass of it. Not only energy, but "negative" energy, which is itself only a theory.

True, I shouldn't have been lazy about my terminology. Any topology distorting method of travel is always going to require huge amounts of energy. The point is that unlike with FTL there are no theoretical barriers to it.

[nyrath]

I've collected some info on the topic in my website.
faster-than-light
http://www.projectrho.com/rocket/rocket3v.html
slower-than-light
http://www.projectrho.com/rocket/rocket3aj.html

The basic problem with faster than light travel is that it violates causality. Which means it more or less destroys the entire foundation of science.
The old saying is "Causality, Relativity, FTL travel: chose any two." You cannot have all three.

Physicists hold on to Einstein's relativity quite strongly because it is been tested to more than nineteen decimal places. People have been trying to disprove it for about one hundred and five years, and utterly failed.

Physicists hold on to Causality even more strongly, because unless causes precede effects, the foundation of science crumbles.

So physicists toss out FTL travel.

FTL travel violates causality because an FTL starship and a time machine are two terms for the same thing.

The only way out is if there is some magic law of science that somehow prevents one from using a time machine to make a paradox. Read the link for details.

Years ago I got tired with all the email I got, which were all along the lines of "but maybe a scientific breakthrough will allow it, they thought man would never fly..." Now I just direct them to another section of my website.
http://www.projectrho.com/rocket/rocket3al.html

[WT Sharpe]

Sagan chose wormholes for interstellar travel in his novel Contact because it's the only possible method he could come up with to travel the immense distances in the time allotted without violating c. Warp Drives are unfeasible for the very reasons ardeegee mentioned earlier.

The real life trouble with using wormholes, assuming they exist, is that they would be inherently unstable and there's no guarantee at where or when the traveler would arrive.

[Greg Anos]

Originally Posted by nyrath

I've collected some info on the topic in my website.
faster-than-light
http://www.projectrho.com/rocket/rocket3v.html
slower-than-light
http://www.projectrho.com/rocket/rocket3aj.html

The basic problem with faster than light travel is that it violates causality. Which means it more or less destroys the entire foundation of science.
The old saying is "Causality, Relativity, FTL travel: chose any two." You cannot have all three.

Physicists hold on to Einstein's relativity quite strongly because it is been tested to more than nineteen decimal places. People have been trying to disprove it for about one hundred and five years, and utterly failed.

Physicists hold on to Causality even more strongly, because unless causes precede effects, the foundation of science crumbles.

So physicists toss out FTL travel.

FTL travel violates causality because an FTL starship and a time machine are two terms for the same thing.

The only way out is if there is some magic law of science that somehow prevents one from using a time machine to make a paradox. Read the link for details.

Years ago I got tired with all the email I got, which were all along the lines of "but maybe a scientific breakthrough will allow it, they thought man would never fly..." Now I just direct them to another section of my website.
http://www.projectrho.com/rocket/rocket3al.html

What Relativity describes, it describes quite accurately. Whether it describes all aspects of reality, is another question. <shrug> For example, Newton hypothesized light to be a particle. More proved it to be a wave via the initial 2 slit interference test around 1800. Quantum theory has proven that reality (as best as we can currently measure) to be far more subtle than either viewpoint.

Question, are there subtleties to reality that Relativity that haven't taken into account? I merely mentioned a piece of mathematics inherent in the logic chain. It had been a dead letter for over a hundred years, because there was no way to alter the quantities in question. That has changed in the last 10 years (or so).

I merely point out an avenue of research that fits the mathematics and might have an interesting result, to a S/F writer.

(Finally, it allow you to have all three, assuming you define FTL as faster than C, the speed of light in an unmodified vacuum. It doesn't allow you to exceed the speed of light in the area of lower e0mu0, it would just speed up light in that region.
Riddle me this, if C = 1/ sq root (e0 * mu0), which is a boundary definition for Maxwell's equations, why can't you mathematically substitute 1 / sq root (e0 * mu0) for C in all relativity equations?)

[ardeegee]

Originally Posted by nyrath

Years ago I got tired with all the email I got, which were all along the lines of "but maybe a scientific breakthrough will allow it, they thought man would never fly..." Now I just direct them to another section of my website.
http://www.projectrho.com/rocket/rocket3al.html

This is a great link. I just read the whole thing.

A couple of quotes from the link:

"Imagine a historical fiction novel where Napoleon at Waterloo defeated the knights of the Round Table by using the Enola Gay to drop an atom bomb. It's OK because it is "fiction", right?"

and:

"However, to make an analogy... How would you react to a game that purported to be about, say, Marines and their tactics and utilizations that insisted that the best formation for them to attack in was walking on their hands, with their rifles clenched between their knees, shoulder to shoulder, in tight formations, through beaten zones for artillery strikes and into machine gun kill zones?

Would you accept it if I told you that this was the result of a heretofore unknown doctrinal innovation made at some point 600 years in the future?

Or, would you demand to know WHAT doctrinal innovation made this the best way to conduct an assault with Marines on the ground?"

Reminded me of a rant I made about how movies reflect horribly poor science eduction on the part of everyone involved in making the movie. This particular rant was in reference to the (at the time unreleased) movie 2012-- but the same could apply to pretty much everything that comes out of Hollywood. I had to search it down (originally posted at www.cgsociety.org, a site for computer graphics artists and wannabes-- I'm strictly a wannabe):

"Let's pick an analogy to this. Say you make a WWII movie. Nobody will (or should) complain that there were no actual soldiers central to the plot of the movie going by those names in those specific battles-- it is perfectly okay to invent the characters for your setting. But if you have all of the American soldiers fighting using Uzis with laser sights, you better have a damn good, plot centric, explained reason why those soldiers are using Uzis with laser sights and it not simply be because you didn't know that Uzis and laser sights hadn't been invented in WWII.

What 2012 is doing is the equivalent of giving those soldiers Uzis with laser sights and mounting them on 20-foot tall cyborg battle-elephants from which they fight the Nazi Flying Death Monkeys and their Telekenetic Venusian Bloodsnail allies. And when people complain that, in WWII, soldiers did not use Uzis with laser sights, ride cyborg battle-elephants, and fight Nazi Flying Death Monkeys and Telekenetic Venusian Bloodsnails, others (after being shocked to find out that none of that is true because of their failed basic educations) tell you "it is just a movie maaaaaaan. Turn off your brain and enjoy it.""