Why is faster than light travel so bizarrely 'addressed'

Roo
Hello everyone,

The topic of superluminal flight has intrigued me for decades but coming from an engineering background and not a strong physics background (although I have studied physics), I am finding the notions about how to possibly achieve such a system quite difficult to accept.

In a nutshell, all this talk of bending 'space/time', expanding space behind and shrinking space in front of a starship and discussions of dark matter and wormholes laced with exotic matter seem most odd indeed. I wonder how many other people who read of these topics question whether they actually exist in reality and are merely created to explain away something which hasn't as yet been physically created.

Certainly engineering in many ways is directly derived from physics, but so much of engineering is based on real life application. I feel that conventional rocketry is coming to its near end, as the system has almost achieved its peak of efficiency and shouldn't even be thought of when considering 'proper' distances due to the level of propellant needed etc. So for true interplanetary missions, a bold new approach needs to be created. It is clear that atomic or nuclear energy based power plants will be the next step forward in spacecraft propulsion. Ultimately, a matter/antimatter reactor will be the final goal - this seems to me to be the most logical approach. And as related technologies connected with safe human space travel expand, sooner or later, mankind will be faced with the great light speed barrier.

Yet, the problem I have with all of these incredible sounding theories is what do they mean in the physical universe and how would they physically work in reality? This has always been a massive problem with truly advanced subjects. For example, the current 'system' for possible FTL travel requires a starship to expand space behind and shrink space in front of it. Analogies have it being likened to a surfer on a large wave, where the wave carries the surfer. Analogies are great, but when someone states that space/time is expanded or shrunk, what does that practically mean? How is space actually expanded? What technology would actually do that? To me and many others, space is a vacuum filled with all sorts of natural matter in varying quantities, but mostly it is empty space. What is there to expand? Talking of expanding space to theoretically satisfy a need is all well and good but in reality, to me, such a notion is not a real one. If I am sitting in my living room and I want to get a beer from the fridge in my kitchen 30ft away, by expanding the space behind me etc, does that mean I can open the door from my seat because it physically pulls the entire kitchen towards me?

There are so many strange ideas associated with FTL travel that I wonder if the true ability to pursue such a technology (now or decades into the future) will be ignored in favour of bizarre ideas that will always be years into the future no matter how advanced we get. For example :-

The idea that time starts to slow down as a spacecraft approaches light speed is a concept I find most strange. Why would time 'slow down' just because you were approaching what is to all intents and purposes, just a very high speed? But this is a topic for another time as this is very interesting in its own right.

Anyway, I would like to end this first post by stating that this discussion is not about ridiculing physics at all, far from it. It is a very important point this. I just wanted to ask questions and raise some professional alternatives/views to the current theories regarding FTL, how it could work and its associated components.

Yours,

Roo.

Staff Emeritus
Gold Member
Hello everyone,
Hello, and welcome.

I feel that conventional rocketry is coming to its near end, as the system has almost achieved its peak of efficiency and shouldn't even be thought of when considering 'proper' distances due to the level of propellant needed etc. So for true interplanetary missions, a bold new approach needs to be created. It is clear that atomic or nuclear energy based power plants will be the next step forward in spacecraft propulsion. Ultimately, a matter/antimatter reactor will be the final goal - this seems to me to be the most logical approach. And as related technologies connected with safe human space travel expand, sooner or later, mankind will be faced with the great light speed barrier.
Even the matter/antimatter approach requires that the mass of the fuel carried by the rocket must be a several orders of magnitude greater than the mass of the ship. That's a problem with all the "rocket" technologies actually. I don't remember the details, but there's a calculation in "The physics of Star Trek" if you're interested. (What I mean by a "rocket" is a ship that's propelling itself in one direction by throwing stuff in the opposite direction).

Yet, the problem I have with all of these incredible sounding theories is what do they mean in the physical universe and how would they physically work in reality? This has always been a massive problem with truly advanced subjects. For example, the current 'system' for possible FTL travel requires a starship to expand space behind and shrink space in front of it. Analogies have it being likened to a surfer on a large wave, where the wave carries the surfer. Analogies are great, but when someone states that space/time is expanded or shrunk, what does that practically mean? How is space actually expanded? What technology would actually do that? To me and many others, space is a vacuum filled with all sorts of natural matter in varying quantities, but mostly it is empty space. What is there to expand?
General relativity is built up around an equation (Einstein's equation) that tells us the relationship between the geometry of the universe and its content of matter. To "curve" spacetime, or just space, means to change what paths freely falling particles would take through the vacuum. This is definitely not science fiction. Experiments have proved that the predictions of GR are much better than the predictions of Newton's theory. (Yes, I consider an astronomical observation an "experiment").

The particular geometry we need to create for "warp speed" requires that we use the existence of a type of matter that has never been observed, not even indirectly. So it's not very realistic. Even if this matter exists, it would probably be absurdly difficult to distribute it the way it needs to be distributed to produce the warp speed geometry.

If I am sitting in my living room and I want to get a beer from the fridge in my kitchen 30ft away, by expanding the space behind me etc, does that mean I can open the door from my seat because it physically pulls the entire kitchen towards me?
Expanding the space behind you isn't going to help, but maybe contracting the space between you and the refrigerator. Hm, I'm going to have to think about that.

The idea that time starts to slow down as a spacecraft approaches light speed is a concept I find most strange. Why would time 'slow down' just because you were approaching what is to all intents and purposes, just a very high speed?
This is one of the easiest things in special relativity. It's counterintuitive, but not at all controversial. It's as standard as things get in physics. You're right that it's a topic worthy of its own thread. (There are many such threads already). I suggest that you try to read the relevant pages of some text on relativity first, and then ask more specific questions about it.

Mentor
This is a problem that doesn't exist. Engineers will not ever have the propulsion technology necessary to even begin to worry about the limitation of C getting in their way. Ie, if technology advances enough that someday we are able to propel our spacecraft 1000 times the speed we can now, they'll only be going 4% of the speed of light.

NWH
The idea that time starts to slow down as a spacecraft approaches light speed is a concept I find most strange. Why would time 'slow down' just because you were approaching what is to all intents and purposes, just a very high speed? But this is a topic for another time as this is very interesting in its own right.
The way I imagine things is this. If I'm traveling near the speed of light, and someone shines a laser past me, everything (time) around me outside my frame of reference has to speed up in order for light to remain the same speed. Of course, the opposite of this is everything around me remaining the same, except time for me is slowing down, allowing light to remain the same speed. I like to imagine it as a kind of fast forward for my surroundings, imagine a particle of solid matter with no constant properties. Then imagine a photon which has to be and has proven to be constant in a vacuum. The photon has to remain the same speed, it can't just speed up and slow down relative to stationary observers, time it's self has to drive the photon forward to keep up with you, including any stationary observers.

It's not the most educated way of putting things, but I hope it can put the idea into perspective for you...

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Nickelodeon
If you did a survey and asked people if they thought FTL speed would ever be possible I'm sure a very high proportion would say yes.
The only thing that would indicate that FTL speed is unlikely is that we would be overrun with aliens dropping in from distant galaxies and that doesn't appear to be the case.

Mentor
If you did a survey and asked people if they thought FTL speed would ever be possible I'm sure a very high proportion would say yes.
Sure, but what if you asked scientists? The vast majority would say no.
The only thing that would indicate that FTL speed is unlikely is that we would be overrun with aliens dropping in from distant galaxies and that doesn't appear to be the case.
Well that and the fact that the laws of physics prohibit it.

Anthea Lawn
Image you are a snail at one corner of a large (2-dimensional) sheet of tarpaulin and you want to get to the opposite corner. That would take ages. But imagine you could fold the 2D tarpaulin so that the opposite corners became adjacent. You could then crawl across and then unfold the tarp back to its flat position. Even though you crawled very slow, you have traveled a huge distance in a short time.

Now, imagine taking 3D space and folding it in a fourth dimension ?

Hmmm - interesting concept, a good one for the science fiction novels, maybe not so hot to achieve in practice : )

Roo
Dear all,

Thanks for the varied responses - most interesting.

I therefore have some questions I'd like to ask. I've looked for answers in numerous books etc yet no-one can seem to give a simple straight answer - so maybe you can help!

1) What exactly is space-time? (as practical as you can please!)
2) What exactly is meant by curving/bending/warping this space/time?
3) How exactly would you go about curving/bending/warping space-time? (i'm talking theoretically here and assuming technology is not an issue)

Roo.

Nickelodeon
Dear all,

1) What exactly is space-time? (as practical as you can please!)
2) What exactly is meant by curving/bending/warping this space/time?
3) How exactly would you go about curving/bending/warping space-time? (i'm talking theoretically here and assuming technology is not an issue)

Roo.

Just to start the ball rolling ..

1) 'Space-time' was devised as a mechanism to assist in predicting or calculating the position of a moving body in space at any particular moment. As I understand it makes things easier - mathematically speaking.

2) The curvature of spacetime is a way of explaining the Equivalence principle, whereby gravity and inertia (acceleration) are thought of as one and the same effect. The difficulty was to explain how we could be standing on earth, not moving yet experiencing this acceleration as though we were accelerating upwards in a lift at 1g. The way to do this is to distort time and modify what is considered a straight line and the mathematics drop into place, and there you have it - gravity.

3) Spacetime is naturally distorted by matter. Probably all particles distort spacetime to a greater or lesser extent. The search for the Higgs boson, considered the holy grail of spacetime distortion, could, if it exists be a dominant factor.
If you wanted to distort spacetime and technology not a problem, then get a large lump of matter the size of the moon and an equally large lump of antimatter and join them together.

Staff Emeritus
Gold Member
I therefore have some questions I'd like to ask. I've looked for answers in numerous books etc yet no-one can seem to give a simple straight answer - so maybe you can help!

1) What exactly is space-time? (as practical as you can please!)
2) What exactly is meant by curving/bending/warping this space/time?
3) How exactly would you go about curving/bending/warping space-time? (i'm talking theoretically here and assuming technology is not an issue)
These questions are really difficult to answer in simple terms. For example, the mathematical model of spacetime is a 4-dimensional smooth manifold with a Lorentzian metric. It would take a very long time to explain what that means. Its most important feature is that it's an abstract set of points that's equipped with a bunch of functions (coordinate systems) that take points in spacetime (events) to 4-tuples of real numbers (coordinates). It's also equipped with something called a metric tensor which represents various geometric properties of spacetime, including curvature. Curvature is even more difficult to explain than manifolds, but one of the characteristics of a curved manifold is that the sum of the interior angles of a triangle isn't 180°.

I suspect that you intended question 1 to be a question about the real world rather than the mathematical model. In that case, the answer is that science can't tell us what spacetime really is, or what anything really is actually. Theories just make predictions about results of experiments, and experiments just tell us how accurate those predictions are. It isn't possible to find out what something "really is".

Naty1
Russ posted
"Engineers will not ever have the propulsion technology necessary to even begin to worry about the limitation of C getting in their way."

Russ has posted some great stuff here...that is NOT one!

...it's myopic. Looking back to the early 1800's it was supposed by "scientists" that a train could never go fast because people would not be able to breath...

While I accept "c" as an upper speed limit in conventional (classical) discussions, I also know there has never before in history been a "consensus" that has been initially correct...as an example Einstein believed the unibverse was static and that black holes were "impossible"...

I looked at perhaps 50 "established facts" myself over history and NONE, not one, was correct...I was NOT trying to prove that, I just investigated tosee how accurate scientists have been over time...ALL first theories were proved false or at least partially incorrect...

we already know general relativity CAN NOT be correct because quantum mechanics conflicts with it and is an extremely successful theory of the very small...
just consider that 95 or 96% of the universe is "dark"...we don't even know what it is...dark energy and dark matter...and have only a basic understanding of the other 4%and we think we are so smart...!

rq704c
I believe there are a few "somewhat" realistic propulsion ideas floating around. The first propulsion device is able to displace or cancel out gravity by rotating a superconducting disc at very high speeds. Somehow getting all the electrons to line up together cancels out gravity. I'm unsure how well this would be used in the middle of empty space where no matter (gravity) exists, but this idea was intriguing enough that the government snatched up a few of the leading scientists in this area a few years ago (The lead scientist was from the University of Alabama and was about to start a company called AC gravity before she got a $500,000 grant to continue her research privately. The second is to bend/fold space. To curve space enough to make traveling somewhere worth while you would need to accelerate a large amount of mass at relativistic speeds. One way you might do this in the future would be to use some kind of condensed matter or superfluid and use magnetic fields to accelerate it around a torus. (Superfluids have no viscosity and thus can be accelerated to extremely high speeds - where the only thing you would be fighting is the increase in mass due to special relativity) Keep in mind current condensates are comprised of only a couple thousand atoms using laser traps - we're a long ways off from trapping enough to be able to manipulate space and time enough to see it. The last option that is unknown to us all but not to nature is the mechanism responsible for the expansion of the universe. Something is curently working (seemingly) at every point in space pushing everything away from everything. This force or whatever it is obvioulsy doesn't require any matter to work and may be used instead bring two points closer together once it's understood. Rocketkid i believe the concept of FTL travel is so "bazaar" because, think about it, how are you supposed to arrive at a destination before the image of your self does? the concept is a difficult one to grasp a hold of. However i do believe that FTL travel is a realistic goal, and hope to someday be in the forefront of the technology. Staff Emeritus Science Advisor Education Advisor I believe there are a few "somewhat" realistic propulsion ideas floating around. The first propulsion device is able to displace or cancel out gravity by rotating a superconducting disc at very high speeds. Somehow getting all the electrons to line up together cancels out gravity. I'm unsure how well this would be used in the middle of empty space where no matter (gravity) exists, but this idea was intriguing enough that the government snatched up a few of the leading scientists in this area a few years ago (The lead scientist was from the University of Alabama and was about to start a company called AC gravity before she got a$500,000 grant to continue her research privately. The second is to bend/fold space. To curve space enough to make traveling somewhere worth while you would need to accelerate a large amount of mass at relativistic speeds. One way you might do this in the future would be to use some kind of condensed matter or superfluid and use magnetic fields to accelerate it around a torus. (Superfluids have no viscosity and thus can be accelerated to extremely high speeds - where the only thing you would be fighting is the increase in mass due to special relativity) Keep in mind current condensates are comprised of only a couple thousand atoms using laser traps - we're a long ways off from trapping enough to be able to manipulate space and time enough to see it. The last option that is unknown to us all but not to nature is the mechanism responsible for the expansion of the universe. Something is curently working (seemingly) at every point in space pushing everything away from everything. This force or whatever it is obvioulsy doesn't require any matter to work and may be used instead bring two points closer together once it's understood.

The Podkletnov effect has NEVER been reproduced or shown to be valid. It is a fringe physics at best, and someone's imagination at worst.

I will remind everyone of our https://www.physicsforums.com/showthread.php?t=5374", especially our policy on speculative theory. Previous threads on this topic have had to be closed or deleted. Failure to abide by our rules will result in this thread ending with the same fate. So it is your decision.

Zz.

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matheinste
Hello all.

I read from time to time details of marvellous technological breakthroughs, proposed or already on the drawing board, regarding FTL travel. I wonder why these marvels usually come from people with little knowledge of physics and an aversion to mathematics. But there again, perhaps I'm just an old cynic.

Matheinste.

redargon
Image you are a snail at one corner of a large (2-dimensional) sheet of tarpaulin and you want to get to the opposite corner. That would take ages. But imagine you could fold the 2D tarpaulin so that the opposite corners became adjacent. You could then crawl across and then unfold the tarp back to its flat position. Even though you crawled very slow, you have traveled a huge distance in a short time.

Now, imagine taking 3D space and folding it in a fourth dimension ?

Hmmm - interesting concept, a good one for the science fiction novels, maybe not so hot to achieve in practice : )

I think this example isn't as constructive as people think it is. If I were a human standing on one corner of a tarpaulin that is very large and I wanted to reach the other corner quickly, by your methaphor, I should just fold the tarpaulin and take one step to the other corner and then unfold the tarpaulin. How would I do this folding? I could walk to the other corner, pick it up and drag it back to my original corner, but then I would have done twice the work I needed to do and would have already been at my destination. I could phone someone and at the other corner and they could bring it to me, but this would take as long as me walking to their corner. Also, in 4D, communication is only as fast as the speed of light, so I wouldn't be able to "tell" the corner of space that I wanted to fold towards me what to do faster than the speed of light, thereby disallowing faster than light travel by bending space.

As an engineer, I understand the frustrations of the OP. You can't just go around bending space-time and warping things and making matter-antimatter reactions in the same way you can build a jet engine to attach to a thing with wings to get somewhere fast. I'm not saying it's impossible, but it's so intangible, especially for practically thinking engineers who would have to build the things that physicists are theorising.

Staff Emeritus
Gold Member
but it's so intangible, especially for practically thinking engineers who would have to build the things that physicists are theorising.
But that's sort of the state of things. It's somewhat amazing that "FTL" according to GR would even be possible -- and if you have to figure out how something is possible before you can figure out how it might be done intentionally, let alone reduce it to an engineering problem!

redargon
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'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.

Only problem: money.
---------------------------

FTL devices are in our reach, but we need more courage to test the fuel. I think the next world war will solve the problen. It is unavoidable, becouse our current economy model is not working.
If you will think in action=reaction way, you will get nowhere.
As an example : atomic chain reaction. We put in less, we get out more.
Matter-Antimatter -> how much energy does it take to create some of these?

What about subatomic chain reaction? Is this possible? Who will be brave enough to make an experiment?

I hate theoreticians / sci-fi writers / ecoterrorists.

/engineer

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rq704c
i believe the concept of FTL travel is so "bazaar" because, think about it, how are you supposed to arrive at a destination before the image of your self does? the concept is a difficult one to grasp a hold of. However i do believe that FTL travel is a realistic goal, and hope to someday be in the forefront of the technology.

That’s not exactly how it works. I'm trying finish a video of what FTL travel would look like and it's quite fascinating - it actually resembles particle creation/annihilation processes. For example imagine a speeding bullet flying right by your eyeball at 2c. If it were possible for you to even see it, the first image of the bullet will arrive at your eye perpendicular to your line of sight – when it’s right in front of your eye barely missing it. This is because the light from the bullet from where it was first fired has not had time to catch up. It’s too complicated for me to explain without confusing you (and me as well), I will just say that 2 bullets emerge from this initial point both moving forward and backward. The backward moving bullet is composed of light catching up from where it was first fired, the bullet moving forward is from bullet once it crossed your eye. The backward image of the bullet moves at 2c and the forward bullet moves strangely at 0.67c forward! Very weird, but the false image of the bullet moving back towards the gun represents the bullets true velocity. I should also note that if the bullet were symetric, there would be no way of knowing which way the bullet went unless you did the math.

That’s not exactly how it works. I'm trying finish a video of what FTL travel would look like and it's quite fascinating - it actually resembles particle creation/annihilation processes. For example imagine a speeding bullet flying right by your eyeball at 2c. If it were possible for you to even see it, the first image of the bullet will arrive at your eye perpendicular to your line of sight – when it’s right in front of your eye barely missing it. This is because the light from the bullet from where it was first fired has not had time to catch up. It’s too complicated for me to explain without confusing you (and me as well), I will just say that 2 bullets emerge from this initial point both moving forward and backward. The backward moving bullet is composed of light catching up from where it was first fired, the bullet moving forward is from bullet once it crossed your eye. The backward image of the bullet moves at 2c and the forward bullet moves strangely at 0.67c forward! Very weird, but the false image of the bullet moving back towards the gun represents the bullets true velocity. I should also note that if the bullet were symetric, there would be no way of knowing which way the bullet went unless you did the math.

I think there won't be backward image.
Bullet flying at 2c will create a space without particles/electomagnetic field behind it - zero space. Assuming that all in front of it is bouncing off or we sent a black hole earlier in the same direction. I am wondering how much energy will be generated when this empty space collapse - this could leave a trail in space. Or let's just assume that this bullet IS a black hole traveling at 2c. The simmilar effect will be noticable in real life: two merging black holes as a result of galaxies collision - will they create a "black donut" or "zero space donut"?.

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rq704c
I think there won't be backward image.
Bullet flying at 2c will create a hole without particles/electomagnetic field behind it - zero space. Assuming that all in front of it is bouncing off or we sent a black hole earlier in the same direction. I am wondering how much energy will be generated when this empty space collapse. Or let's just assume that this bullet IS a black hole traveling at 2c.

Well I'm not sure I understand your question but I know there have been measuements made trying to displace the energy that seems to exist in even empty space. Having something move at 2c will do some interesting things, however I think this would be the least of them but who knows? You can displace the zero point field and create "somewhat" of a void by simply placing two conductive plates very close together ~10nm. This limits the number of virtual photon frequencies that can exist between the two plates - (outside all frequencies are possible and in between only integer numbers of the wavelength divided by the distance of the plates are possible). The most interesting consequence of FTL anything would be either the dismantling of special relativity or the reality that we live in a multiverse.

Gold Member
Russ posted
"Engineers will not ever have the propulsion technology necessary to even begin to worry about the limitation of C getting in their way."

Russ has posted some great stuff here...that is NOT one!

...it's myopic. Looking back to the early 1800's it was supposed by "scientists" that a train could never go fast because people would not be able to breath...
1] Are you sure this is true? What 'scientists' would these be? Are you sure it was scientists or merely popular opinion? (This is rhetorical. The answer is as useless as the claim. An urban legend cannot be used as an analogy for future scientific discoveries.)

2] This was popular opinion until it was demonstrated to be false. Then everyone changed their minds. Agreed?

Well, we are able to observe objects moving at nearly the speed of light every single day, and we see our theories fit perfectly.

You see, you're thinking we're not there yet - that we're speculating. We're not. We have a buttload of funds and technology looking extremely closely at what particles do as they approach c. And they behave exactly as predicted. All of them.

This is not speculation.

rq704c
The Podkletnov effect has NEVER been reproduced or shown to be valid. It is a fringe physics at best, and someone's imagination at worst.

I will remind everyone of our https://www.physicsforums.com/showthread.php?t=5374", especially our policy on speculative theory. Previous threads on this topic have had to be closed or deleted. Failure to abide by our rules will result in this thread ending with the same fate. So it is your decision.

Zz.

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.

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Roo

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.

Mentor
2021 Award
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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Gold Member
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.

matheinste
Originally Posted by Roo
Theoretical physics and mathematics, no matter how incredible and complex can't replace reason.

Mathematics is pure reason.

Matheinste.

rq704c

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 truly 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 sense 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.

darkhorror

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?

Gold Member
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.

Staff Emeritus
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.

matheinste
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
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.

Gold Member
... 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.