Why is faster than light travel so bizarrely 'addressed'

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it just doesn't sound right, based on nothing more than intuitive discrimination.

To me, the idea of bending/folding/warping 'space-time geometry' is a non-sensical statement.
Just because you don't understand it doesn't mean that it is nonsense or wrong. If there is any lesson of the past century it is that everyday physical intuition is not useful in physics.

Why does space have to have a geometry at all? Surely between the Earth and say, Neptune, there is just empty space in the main and that the shortest way to get there would be in a straight line (orbital mechanics not-withstanding).
This is not even self-consistent. "Shortest way" and "straight line" are both geometrical statements, so space must have geometry. I don't think you can say anything physically useful about space without making geometrical statements.
 
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DaveC426913

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Theoretical physics and mathematics, no matter how incredible and complex can't replace reason.
Yes they can. And do. That is how we extricated ourselves from the Dark Ages -by realizing our 'reasoning' was unfounded.

but from a sense of it just doesn't sound right, based on nothing more than intuitive discrimination.
This is a statement I've heard before and never understood. How can you have an intuition (or common sense) about how the universe works? Are you comparing it to all the other universes you've encountered?


Surely between the Earth and say, Neptune, there is just empty space
You know this not to be true. At the very least, you know there is gravity there.

in the main and that the shortest way to get there would be in a straight line (orbital mechanics not-withstanding). Folding intimates something very physical that by a force, can be manipulated - but folding millions of miles of empty space, let alone a 'geometry' or a 'dimension', well, that sounds truly far fetched.
And yet it is incontrovertible fact. Read a little bit about gravitational lensing.
 
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Originally Posted by Roo
Theoretical physics and mathematics, no matter how incredible and complex can't replace reason.

Mathematics is pure reason.

Matheinste.
 
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Some very interesting comments here.

Will faster than light travel ever be a practical occurrence - well, who can rightly tell? Certainly it is not feasible for mankind to explore beyond our own solar system without it though. It certainly is mind boggler - but as has always been told to me, necessity is the mother of all invention.

Theoretical physics and mathematics, no matter how incredible and complex can't replace reason. Of course, there seem to be numerous experiments that claim to have proved theories for all sorts of things. Yet, there also seem to be numerous theories and experiments opposing even those! I have read Einstein's theories of general and special relativity and even though I logically see what is being discussed, I question it - as do many people now in varying shades. Let me be clear on something, I am no physicist or mathematician but I come from an engineering background so certain concepts I am very familiar with. Yet the problem I have with all of this relativity subject comes not from the investigation into the minutae of these proposals - but from a sense of it just doesn't sound right, based on nothing more than intuitive discrimination.

To me, the idea of bending/folding/warping 'space-time geometry' is a non-sensical statement. Why does space have to have a geometry at all? Surely between the Earth and say, Neptune, there is just empty space in the main and that the shortest way to get there would be in a straight line (orbital mechanics not-withstanding). Folding intimates something very physical that by a force, can be manipulated - but folding millions of miles of empty space, let alone a 'geometry' or a 'dimension', well, that sounds truly far fetched. For over a century this idea has sort of stuck in the general mindset - yet what if it is all completely false?

So, supposing that this turns out to be the case and 'space-time' can't be bent/folded/warped at all, different dimensions can't be entered into and space can't be expanded and shrunk, then how is mankind ever to explore the outer reaches of the solar system, let alone the galaxy and beyond? But as 'conventional' propulsion couldn't generate the kinds of velocities needed, science fiction sounding proposals are all we have. On the one hand, here you have the greatest of human urges, wanting to explore what is out there but on the other hand, creating a set of rules that almost forbid it unless the most bizarre and non-sensical methods (which are themselves based upon an even more bizarre view of how the universe works) are used to possibly circumvent it. Fantastic. It's like the ultimate Krypton Factor challenge thrown to mankind.

Have we consigned ourselves to staying within the confines of our own backyard simply because a load of theory, formulae and equations say so. What has happened to actually seeing how they stand up to physical and practical scrutiny - and I don't mean in a lab or elsewhere similar, but by being out there? Yet, as we all know, the irony is that we don't even have the technology required to be able to put them to the real test.

And so I guess this is what keeps us going.....

Roo.

End note : I apologise for raising anyone's blood pressure.
Well as a good engineer you will appreciate that the curvature of space is a measurable quantity (it's very real) and has actually been measured. General relativity (GR) solved the problem of Mercury's perihelion (the small but measureable time delay Mercury has when passing from one side of the sun to the other because space is curved and light is bent near the sun and we're actually pearing slightly behind the sun). This time delay was very accurately predicted by GR. Gravity Probe B is currently measuring the swirling of space (like a whirlpool) caused by rotating bodies. Also since space is curved the light was not actually bent, it went straight in curved space.

Also space is not truely empty, it takes something to make something even empty space and the 3 dimensions we seem to live in. You can't have a water wave without water, nor sound without air. The same holds true for the dimensions that make up our universe and whatever that stuff is light is either bent by it or it's intrinsically curved by the presence of mass. Also empty space is being created as we speak! Ever hurd of nothing making more nothing and doing it exponetially? - me neither but it seems to be doing it anyways.

As a fellow engineer it makes sence to me that space be curved (and curved negitivily) as far as the universe is concerned. Should it not be this way, the universe would either apporach infinity or be infinite in size and energy which I don't believe. A negitivily curved universe would be bounded (or closed) - all three dimensions would curl back on themselves like the log and lat lines on the globe. Walk for a long enough time in x y or z and you'll end up at the same point.
 
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Some very interesting comments here.

Will faster than light travel ever be a practical occurrence - well, who can rightly tell? Certainly it is not feasible for mankind to explore beyond our own solar system without it though. It certainly is mind boggler - but as has always been told to me, necessity is the mother of all invention.

Why do we need faster than light travel to get to distant solar systems? If we can get close to the speed of light( spaceship compared to earth ) shouldn't the trip be rather quick? Seems that the problem comes in when you want to get back to earth there will be a far larger amount of time passed. But then again we are still a long way away from even that. Heck couldn't your spaceship accelerate at 1g( 1g is what the people on the spaceship would feel ) for any amount of time and never hit the speed of light?
 

DaveC426913

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Why do we need faster than light travel to get to distant solar systems? If we can get close to the speed of light( spaceship compared to earth ) shouldn't the trip be rather quick? Seems that the problem comes in when you want to get back to earth there will be a far larger amount of time passed. But then again we are still a long way away from even that. Heck couldn't your spaceship accelerate at 1g( 1g is what the people on the spaceship would feel ) for any amount of time and never hit the speed of light?
You are correct. The problem comes in that it is a one-way trip. If you were to return, everyone you have ever known will be long-dead.

Who wants to embark on such a journey? Colonists. They'll need to bring everything they will ever have. Including their gene pool. Which means a big crew. Which means a big ship.
 

ZapperZ

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I haven't brought up any topic that hasn't been published in the Phyics Review. Here are the articles for anyone that deems this any different from the thousand or so other fringe physics ideas like relativity was at one point.

Ning Li and D. G. Torr, Phys. Rev., 43D, 457, 1991
Ning Li and D. G. Torr, Phys. Rev., 46B, 5489, 1992
Ning Li and D. G. Torr, Bull. Am. Phys. Sco., 37, 948, 1992.
E. Podkletnov and R. Nieminen, Physica C, 203, 441, 1992.
D. G. Torr and Ning Li, Found. Phys. Lett., 37, 948, 1993

I'd like to assume that anything the Physics Review publishes is worthy of discussion.
... and that's ALL she wrote! Again, none of these have ever been reproduced! Look at the citation indexs of those articles! And see if there's anything new to add since 1993, including the ill-fated paper that was summarily withdrawn from publication.

The podkletnov effect HAS been discussed already on here. Do a search and see if you think you have something NEW to add to it.

Zz.
 
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You are correct. The problem comes in that it is a one-way trip. If you were to return, everyone you have ever known will be long-dead.

Who wants to embark on such a journey? Colonists. They'll need to bring everything they will ever have. Including their gene pool. Which means a big crew. Which means a big ship.

To put some sort of figure to this in Einstein, 1905-2005. Poincare Sminar 2005. Page 106 there is a table giving the results of calculations of earth’s proper time against traveller’s proper time with a constant acceleration of 1g for an out and return journey. Leaving out some of the finer points we get-------

For a traveller’s 20 years experienced time, earth time is 297 years. For 490 years it is 44,000 years and so on. By 86 years it is up to about 5 billion years. And all for a constant acceleration of 1g. Fuel consumption is of course another matter.

Matheinste
 

Roo

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Yes - I couldn't agree more about gravity affecting things. Living on planet Earth kind of proves this amply! And yes, I've heard of gravitational lensing - but surely the gravity of a massive object is only bending the image of a real object - and as such, the object in question is still sitting pretty in its original position in space irrespective of what its image is doing?

Well then, assuming that space-time can indeed be bent/folded/warped in order to bring two points closer together - would anyone care to venture what would be needed in order to bring this about? The 'star trek' universe would have us believe that a 'warp field' surrounds the ship and that the two nacelles contain coils that when 'plasma' is put through them, they create an immensely large gravity field thus 'warping' space-time. I know this all sounds a bit daft, but if as I'm being told that space-time can be manipulated, then surely the mechanism for doing so must also be known, even if the actual technology to produce it is way, way off in the future?

And if it is nothing more than gravity that is needed, how much is required to be able to distort space and bring say, Earth and Alpha Centauri that little bit closer?

I'm asking this because there are numerous articles on the possible feasibility of FTL travel, yet none care to say how space-time would be manipulated - only that it could be.

Roo.
 

DaveC426913

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... surely the gravity of a massive object is only bending the image of a real object - and as such, the object in question is still sitting pretty in its original position in space irrespective of what its image is doing?
The point is that the image is formed by light rays, which only travel in straight lines. Classical theory held that light was affected by gravity just like any massive body. Problem was, the numbers didn't add up. It only accounted for half the observed value. Einstein's GR accounts for it all.

Another one: Mercury has an odd precession in its orbit that cannot be explained by classical physics. Einstein's GR does explain it. i.e. looking at it in terms of curved space explains it in a way that other models do not.
 

Roo

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Well then, assuming that space-time can indeed be bent/folded/warped in order to bring two points closer together - would anyone care to venture what would be needed in order to bring this about? The 'star trek' universe would have us believe that a 'warp field' surrounds the ship and that the two nacelles contain coils that when 'plasma' is put through them, they create an immensely large gravity field thus 'warping' space-time. I know this all sounds a bit daft, but if as I'm being told that space-time can be manipulated, then surely the mechanism for doing so must also be known, even if the actual technology to produce it is way, way off in the future?

And if it is nothing more than gravity that is needed, how much is required to be able to distort space and bring say, Earth and Alpha Centauri that little bit closer?

I'm asking this because there are numerous articles on the possible feasibility of FTL travel, yet none care to say how space-time would be manipulated - only that it could be.

Roo.
Any takers? Or is this a question for the engineering boys and girls?

Roo.
 
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Any takers? Or is this a question for the engineering boys and girls?

Roo.
Responses would inevitably lead to smiting on account of the extremely speculative nature of any answer to your question.

Think about being on the surface of a balloon, in space, far from a gravitational field - the balloon represents the "space-time continuum". How do you bend the part of the balloon you are standing on so that it dips in and touches another part of the balloon, so that you then burrow through to a new spot on the surface of the balloon?

Without something that reaches down and across (even if you recklessly assume this is possible, it is a massive undertaking in terms of the universe), or having access to something outside of the balloon (representing a superdimensional poker, perhaps), you just can't do it.

The idea of warping or folding spacetime for our convenience is a science fiction topic, not a legitimate field of engineering research (not now, and most likely not ever).

cheers,

neopolitan
 

DaveC426913

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How do you bend the part of the balloon you are standing on so that it dips in and touches another part of the balloon, so that you then burrow through to a new spot on the surface of the balloon?
The classic "warp drive" simply strategically distorts distances. Topologically, the balloon remains a sphere.

OTOH, what you describe above is a wormhole, a "here-to-there-with-no-in-between". Topologically, the spherical balloon is reformed to add a hole, so it's now a torus or "coffee mug" shape. Different animal.

Wormholes have been posited by GR but they'd need a form of exotic matter/energy to hold them open and stable.
 
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RUTA

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Of course that's not proof that space is infinite. After all, earth's surface "goes on forever" while having a finite area. This is only contradictory for a flat surface.

Space being finite and unbounded would only be contradictory if we assume space is "flat".
Actually, you can have a flat, unbounded, finite space. For a 2-dim version, simply identify opposite edges of a piece of paper.
 
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Yes - I couldn't agree more about gravity affecting things. Living on planet Earth kind of proves this amply! And yes, I've heard of gravitational lensing - but surely the gravity of a massive object is only bending the image of a real object - and as such, the object in question is still sitting pretty in its original position in space irrespective of what its image is doing?
The thing is that it's an empirically observed fact that the speed of light is constant in all reference frames. We use the speed of light in all measurements of time and space (even if we're using yardsticks). This means that if light is warped by gravity, so are time and space.

Well then, assuming that space-time can indeed be bent/folded/warped in order to bring two points closer together - would anyone care to venture what would be needed in order to bring this about? The 'star trek' universe would have us believe that a 'warp field' surrounds the ship and that the two nacelles contain coils that when 'plasma' is put through them, they create an immensely large gravity field thus 'warping' space-time. I know this all sounds a bit daft, but if as I'm being told that space-time can be manipulated, then surely the mechanism for doing so must also be known, even if the actual technology to produce it is way, way off in the future?
Not really. ;) It's largely the invention of the popular science movement, aimed at the sci-fi fanatics. The reality is that in it's modern vein this whole thing kind of started with Carl Sagan and his book Contact, when he asked a physicist to try and come up with a plausible FTL method for his work of fiction. So since then a few experts in relativity have been able to manipulate the math of general relativity to produce geodesics that shortcut through space and time somehow, but they always end up using bizarre things like negative mass, which we have no reason to expect existing. Then there's the fact that any method allowing for FTL also allows for backward time travel, which creates all kinds of paradoxes that seem highly unlikely. It's always POSSIBLE that once we have a full theory of quantum gravity, we'll really know IF and HOW to do FTL, and maybe by some bizarre turn of events relativity missed something really important and FTL won't allow us to travel backward in time, but this is mainly just a pipe dream of the sci-fi movement.

If you must know, my personal favorite most likely candidate is a wormhole, pried open with some kind of negative energy, perhaps something we'll understand if we ever figure out what's causing the dark energy that's blowing the universe apart. The two ends of the wormhole would most likely begin at the same point in space. You would then drag one end of the wormhole off to your destination at slower than light speeds, and you could return back home through the wormhole without having to deal with the twin paradox. Anytime you tried to position the wormhole so that backward time travel were possible, it would evaporate due to feedback loops in the background energy.

But the reality is that technology tends to take us in places we never expected. We futurized about flying cars and series of tubes distributing our mail, and instead we got the internet and stem cells. Who knows what's coming next? It might just make FTL obsolete.
 

RonL

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I'd be happy if we could be technologically advanced enough to produce waste free (minimum or useful "waste") energy over the entire globe in my lifetime. I'll leave the FTL devices to the coming generations.
I have to agree here, also I find it interesting, how there can be such unanimous agreement on two subjects considered theroretic possibilities (PM and Time Travel) and the answers are complete opposites.
 

DaveC426913

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I have to agree here, also I find it interesting, how there can be such unanimous agreement on two subjects considered theroretic possibilities (PM and Time Travel) and the answers are complete opposites.
Sorry, can you elaborate?

You're saying that PF has a virtually unanimous agreement on perpetual motion and on time travel? And that the answers are complete opposites? Since it's pretty unanimous that PM is a no-starter, you must be suggesting that PFers unanimously agree that time travel is possible?
 
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[smartass]I'm traveling through time right now![/smartass]

:P
 

RonL

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Sorry, can you elaborate?

You're saying that PF has a virtually unanimous agreement on perpetual motion and on time travel? And that the answers are complete opposites? Since it's pretty unanimous that PM is a no-starter, you must be suggesting that PFers unanimously agree that time travel is possible?
The main focus of my post I would like to direct at redargon's comment about "waste free energy".
The rest, you have put in words that sum up the statement just about right.

Ron
 

DaveC426913

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The main focus of my post I would like to direct at redargon's comment about "waste free energy".
The rest, you have put in words that sum up the statement just about right.

Ron
I am dubious that PFers generally agree time travel is possible, let alone that they are nearly unanimous on it.
 

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