Faster than light

Corkscrewkenny

I'm an enthusiastic but uneducated, amateur theoretical physicist

If, THEORETICALLY, a pole made of, say, neutron star material was constructed and reached from earth to Proxima Centauri (4.2 light years away) and if the earth end was pushed, would someone at the Proxima Centauri end feel the result of the push almost instantaneously. THEREFORE can information move faster than light?

Rubecula

I can't say for certain, but I assume there would have to be a pressure wave travelling along the pole, and there would be an upper limit to the speed that this pressure wave could travel.

However if an object travelled around the sun at an orbital velocity of light speed. Would it's shadow at twice the distance travel at twice light speed?

If so (as nothing is actually moving in it's shadow) could shadowing be a binary system of info faster than light?

Morbert

Rubecula wrote: »

I can't say for certain, but I assume there would have to be a pressure wave travelling along the pole, and there would be an upper limit to the speed that this pressure wave could travel.

Yes, the information could not reach the other end of the rod instantaneously, and instead must be transmitted at sub-light speed.

However if an object travelled around the sun at an orbital velocity of light speed. Would it's shadow at twice the distance travel at twice light speed?

The shadow would 'travel' at twice the speed of light, but it is important to remember that no travelling is actually being done. Instead, photons are being intercepted by the object, causing the remaining photons to produce a pattern that our brain interprets as a "moving shadow".

If so (as nothing is actually moving in it's shadow) could shadowing be a binary system of info faster than light?

It could not unfortunately be used to transmit info faster than light. The shadow, although 'moving' faster than light, could not be used to signal faster than light.

gentillabdulla

The shadow isn't traveling.

Like darkness a shadow isn't an actual thing.

A shadow is just created by an object blocking the light.

Sorry the shadows aren't moving (In a physical sense) and cannot be used in this way to transmit information faster than light.

Basically what Morbert said.

Capt'n Midnight

check out the speed of gravity

also there is the slight problem of how you move a neutron star fast enough to create a noticable effect

Corkscrewkenny

Rubecula wrote: »

I can't say for certain, but I assume there would have to be a pressure wave travelling along the pole, and there would be an upper limit to the speed that this pressure wave could travel.

However if an object travelled around the sun at an orbital velocity of light speed. Would it's shadow at twice the distance travel at twice light speed?

If so (as nothing is actually moving in it's shadow) could shadowing be a binary system of info faster than light?

Good point. Pressure waves. But my whole idea is that waves aren't involved, whether light waves, radio waves, x rays or anything else. The whole process would be mechanical.

To take it to the extreme, a pole made of the most fundamental, densest particals in existence (say singularities at the centre of black holes) all in perfect alignment, all touching, no friction. To push this pole you have available all the energy contained in the milky way galaxy. THEN would the effect on Proxima Centauri be felt before a light beam could get there. THEORETICALLY.

I'll try and answer my own question with 2 points

1. String theorists might say that there would still be a wave because some of the particals would move in and out of dimensions 5 to 11 before pushing the partical next to them.

2. I think the way electricity works is by electrons pushing each other along a copper wire rather than actually travelling along the wire, so (if I'm correct) this is an example of fairly fundamental particles pushing each other as described in the original question. I don't actually know what speed electricity travels at.

Another good idea, shadows. I would guess relativity would come in here to prevent the shadow moving faster than light, ie time rates would be different between the orbiting object and the observer of the shadow.

Anyway, I still think the "pole" idea has some legs.

Offy

Corkscrewkenny wrote: »

Good point. Pressure waves. But my whole idea is that waves aren't involved, whether light waves, radio waves, x rays or anything else. The whole process would be mechanical.

To take it to the extreme, a pole made of the most fundamental, densest particals in existence (say singularities at the centre of black holes) all in perfect alignment, all touching, no friction. To push this pole you have available all the energy contained in the milky way galaxy. THEN would the effect on Proxima Centauri be felt before a light beam could get there. THEORETICALLY.

I'll try and answer my own question with 2 points

1. String theorists might say that there would still be a wave because some of the particals would move in and out of dimensions 5 to 11 before pushing the partical next to them.

2. I think the way electricity works is by electrons pushing each other along a copper wire rather than actually travelling along the wire, so (if I'm correct) this is an example of fairly fundamental particles pushing each other as described in the original question. I don't actually know what speed electricity travels at.

Another good idea, shadows. I would guess relativity would come in here to prevent the shadow moving faster than light, ie time rates would be different between the orbiting object and the observer of the shadow.

Anyway, I still think the "pole" idea has some legs.

Does any of the above matter? You would have to push the pole faster than the speed of light for it to arrive before its image. Is it possible for a physical object to arrive at a destination before its image does? Does that answer your question? No its not possible but as soon as you can move matter faster than the speed of light it becomes possible I guess.

rccaulfield

How could you move anything with that kind of mass? Its not a realistic situation or close imo.

mikhail

Corkscrewkenny wrote: »

I think the way electricity works is by electrons pushing each other along a copper wire rather than actually travelling along the wire, so (if I'm correct) this is an example of fairly fundamental particles pushing each other as described in the original question.

Electrons move relatively slowly in a e-m field. The electrons aren't pushing anything. I don't think this example is relevant the the question.

I don't actually know what speed electricity travels at.

The e-field travels at nearly c; depends on the material.

Offy wrote: »

Does any of the above matter? You would have to push the pole faster than the speed of light for it to arrive before its image. Is it possible for a physical object to arrive at a destination before its image does? Does that answer your question? No its not possible but as soon as you can move matter faster than the speed of light it becomes possible I guess.

Your reasoning is rubbish. Imagine a perfectly inelastic, massless pole. I push one end. The other end moves in unison with it. So the far end of the pole doesn't arrive before its own image, but if it's long enough, it arrives before the image of my end.

I guess this has to fall down on the "perfectly inelastic, massless pole." There's just no such thing.

Corkscrewkenny

mikhail wrote: »

Electrons move relatively slowly in a e-m field. The electrons aren't pushing anything. I don't think this example is relevant the the question.


The e-field travels at nearly c; depends on the material.


Your reasoning is rubbish. Imagine a perfectly inelastic, massless pole. I push one end. The other end moves in unison with it. So the far end of the pole doesn't arrive before its own image, but if it's long enough, it arrives before the image of my end.

Thanks mikhail, I think you're supporting me. In the scenario no matter travels any more than a centimetre, but information travels faster than light, the information being "There is something at the other end of this pole that has pushed it.

I guess this has to fall down on the "perfectly inelastic, massless pole." There's just no such thing.

I'm talking theoretically, not practically. The "pole" doesn't have to be massless if you have the energy of (say) a million Milkey Way galaxies at your disposal, does it?.

As to whether perfectly inelastic, uncompressable particals of sub-atomic matter exist or can exist, and whether these particles could live for long enough and whether there properties would allow them to touch, I don't know. Despite my best efforts, quantum mechanics is still completely incomprehensible and counter-intuitive to me.

Anyway, the bottom line seems to be that even information cannot move through spacetime faster than the speed of light (but I'm still not convinced).

mikhail

Corkscrewkenny wrote: »

Thanks mikhail, I think you're supporting me.

I think you have an interesting question.

I think the answer is no, but I don't know the physics describing how force is transferred along a pole. I fully expect that there's a theoretical upper limit on the elasticity of a material such that the pressure wave travelling along it is limited to c.

BTW, yes, it doesn't need to be massless, but if it wasn't, it'd be subject to enormous gravitational forces. Not important in a theoretical discussion, I guess.

thirtythirty

I've thought about faster than light before too - but i'm no scientist, so have no idea of the answer. But humour me for a second.

My understanding is that gravity attracts mass at a set speed. But on earth, things reach terminal velocity due to wind resistance. So, if you were in space where there was no resistance, you'd just keep accelerating. Is that right?

If so, what if you built a ship that had two extendable arms out in front of it (or something), and it could generate a gravitational pull in front of itself.

Presumably, the ship would just continually accelerate, because the the gravitational pull is always the same distance and same force, with no opposing resistance (like wind). So surely the ship would just keep going faster and faster, eventually beyond the speed of light.

As i said, im no scientist, but im pretty sure my theory is flawless!

spottyelephant

spottyelephant wrote: »

Presumably, the ship would just continually accelerate, because the the gravitational pull is always the same distance and same force, with no opposing resistance (like wind). So surely the ship would just keep going faster and faster, eventually beyond the speed of light.

As i said, im no scientist, but im pretty sure my theory is flawless!

It would gain mass as it accelerates. takes an infinite amount of energy to accelerate an object with nonzero rest mass to the speed of light

thirtythirty

bluewolf wrote: »

It would gain mass as it accelerates. takes an infinite amount of energy to accelerate an object with nonzero rest mass to the speed of light

Really?

Imagine:
Ship (1 tonne), Gravity (2 miles/second).

Now if gravitational acceleration is always constant, the ship should only ever weigh e.g. 1.5 tonnes, no matter what speed it's travelling at.

Speed = 0, pulled by 2 miles/second gravity; ship adds 0.5 tonnes to weight.
Speed = 100, pulled by 2 miles/second gravity; ship should still only weigh 0.5 tonnes more, because speed of "100" is exactly the same as "0", cuz it has the same gravity pull acceleration.

No?

Morbert

Corkscrewkenny wrote: »

Good point. Pressure waves. But my whole idea is that waves aren't involved, whether light waves, radio waves, x rays or anything else. The whole process would be mechanical.

To take it to the extreme, a pole made of the most fundamental, densest particals in existence (say singularities at the centre of black holes) all in perfect alignment, all touching, no friction. To push this pole you have available all the energy contained in the milky way galaxy. THEN would the effect on Proxima Centauri be felt before a light beam could get there. THEORETICALLY.

I'll try and answer my own question with 2 points

1. String theorists might say that there would still be a wave because some of the particals would move in and out of dimensions 5 to 11 before pushing the partical next to them.

2. I think the way electricity works is by electrons pushing each other along a copper wire rather than actually travelling along the wire, so (if I'm correct) this is an example of fairly fundamental particles pushing each other as described in the original question. I don't actually know what speed electricity travels at.

Another good idea, shadows. I would guess relativity would come in here to prevent the shadow moving faster than light, ie time rates would be different between the orbiting object and the observer of the shadow.

Anyway, I still think the "pole" idea has some legs.

Material made out of black-hole singularities? If you place two black-holes next to eachother they will become one black-hole. Similarly, I would assume a rod of black-hole singularities would become one singularity. Maybe you have references but I don't think a singularity bar would make any sense.

del88

Interesting idea.. one or two problems.
If the pole was made of neutrons as in a neutron star it would only be dense enough to have no space between the neutrons if it was 12km wide or over 1.35 solar masses....now if the pole extended like a tube (which it couldn't) and remained at 12km in diameter it would become a black hole when it got to 10 solar masses or around 90km long.....long way off Proxima Centauri.
Now let's say by some unknown law of nature we could force the neutrons right up tight against each other with no space between them and stretch them from here to Proxima Centauri ....hmmmmm the more i think about it the more i'm not too sure.....
Probably the pressure wave not being able to go faster than light would be the biggest stumbling block....maybe a compression of space time along the pole woulg stop it going faster than light.....maybe the same forces that stop light going faster than light would kick in..
What would happen if the pole was a ring that came back to earth???

mikhail

spottyelephant wrote: »

I've thought about faster than light before too - but i'm no scientist, so have no idea of the answer. But humour me for a second.

My understanding is that gravity attracts mass at a set speed. But on earth, things reach terminal velocity due to wind resistance. So, if you were in space where there was no resistance, you'd just keep accelerating. Is that right?

If so, what if you built a ship that had two extendable arms out in front of it (or something), and it could generate a gravitational pull in front of itself.

Presumably, the ship would just continually accelerate, because the the gravitational pull is always the same distance and same force, with no opposing resistance (like wind). So surely the ship would just keep going faster and faster, eventually beyond the speed of light.

As i said, im no scientist, but im pretty sure my theory is flawless!

No, it wouldn't. The arms exert exactly as much gravitational force on the rest of the ship as the rest of the ship exerts on the arms. The ship would experience no acceleration.

Now, if something massive is ahead of the ship and unconnected to it, there'll be acceleration, but only until they collide.

Corkscrewkenny

Morbert wrote: »

Material made out of black-hole singularities? If you place two black-holes next to eachother they will become one black-hole. Similarly, I would assume a rod of black-hole singularities would become one singularity. Maybe you have references but I don't think a singularity bar would make any sense.

Yeah, OK, fair point. I was just trying to give an example of the densest thing I could think of to get rid of the pressure wave problem.

Probably the pressure wave not being able to go faster than light would be the biggest stumbling block....maybe a compression of space time along the pole woulg stop it going faster than light.....maybe the same forces that stop light going faster than light would kick in..
What would happen if the pole was a ring that came back to earth???

The more I think about it, there are other factors like the effect the pole would have on the spacetime around it, and within it.

I thought about the pole comming back to earth too but I gave up trying to figure what the time effects of that would be (if the results of the push were felt back on earth instantaneously, at faster than the speed of light, then the results, I presume, would arrive before the pole was pushed in the first place, because the "information" would travel backwards in time)

But it is still counter intuitive to me that even a pole made of, say, aluminiom from here to Saturn would take over 1 hour and 14 minutes before the push was registered on Saturn.

What I really want is for Einstein to come back from the dead and post a comment to this thread along the lines of "Well done Corkscrew, I did'nt think of that".

Podge_irl

Corkscrewkenny wrote: »

But it is still counter intuitive to me that even a pole made of, say, aluminiom from here to Saturn would take over 1 hour and 14 minutes before the push was registered on Saturn.

Lots of physics is counter-intuitive. The very concept of a universal speed limit is counter-intuitive. That's why we run experiments and formulate theories in strict mathematics.

Zen65

Corkscrewkenny wrote: »

I don't actually know what speed electricity travels at.

The speed of travel of electricity is a lot slower than light speed.


Z

Capt'n Midnight

Zen65 wrote: »

The speed of travel of electricity is a lot slower than light speed.


Z

very roughly 1/10 c

Corkscrewkenny

Podge_irl wrote: »

Lots of physics is counter-intuitive. The very concept of a universal speed limit is counter-intuitive. That's why we run experiments and formulate theories in strict mathematics.

Thats the whole point. Think outside the box. No theories based on mathematics, theories based on logic.

ZorbaTehZ

Capt'n Midnight wrote: »

very roughly 1/10 c

Err... where did you get that figure from? You would need one hell of a current to get anything even close to that.

gentillabdulla

Corkscrewkenny wrote: »

Thats the whole point. Think outside the box. No theories based on mathematics, theories based on logic.

Actually its easier to know the physics first.

Then use logic.

After that just keep searching until you find anything that contradicts what you say.

Finally prove it with math.

Capt'n Midnight

ZorbaTehZ wrote: »

Err... where did you get that figure from? You would need one hell of a current to get anything even close to that.

can't remember, and yes it's not an average speed more like the soonest that an impulse into a wire comes out of the wire and that's ignoring capacitive and inductive effects

Corkscrewkenny

gentillabdulla wrote: »

Actually its easier to know the physics first.

Then use logic.

After that just keep searching until you find anything that contradicts what you say.

Finally prove it with math.

Thanks, a very helpful discription.

Anything more than quadratic equations and I haven't got a clue. I'm stuck with logic, simple thought experiments and physics programmes on TV.

There is one maths thing (and it's probobly stupidly simple): why do the digits in a number that is a multiple of 9 always add up to a multiple of 9, and does this hold for (say) the number 7 in an octal numeral system.

I've just thought about it and I think 7+7=86 (8+6=14)????

Rubecula

Corkscrewkenny wrote: »

Thanks, a very helpful discription.

Anything more than quadratic equations and I haven't got a clue. I'm stuck with logic, simple thought experiments and physics programmes on TV.

There is one maths thing (and it's probobly stupidly simple): why do the digits in a number that is a multiple of 9 always add up to a multiple of 9, and does this hold for (say) the number 7 in an octal numeral system.

I've just thought about it and I think 7+7=86 (8+6=14)????

This only occurs in the way you describe in the decimal system. Hexadecimal, Octo and Binary have their own rules. As would any other numerical system.

Corkscrewkenny

Rubecula wrote: »

This only occurs in the way you describe in the decimal system. Hexadecimal, Octo and Binary have their own rules. As would any other numerical system.

Yeah.

8+8=16 (1+6=7, one lessthan 8)
7+7=14 (1+4=5, two less than 7)
6+6=12 (1+2=3, three less than 6)

and etcetera. with ever more complicated rules for different combinations of numbers, cubes and so on.

Jack Black was wrong in School of Rock, 9 isn't a particularly "magic" number.

Morbert

Corkscrewkenny wrote: »

Thanks, a very helpful discription.

Anything more than quadratic equations and I haven't got a clue. I'm stuck with logic, simple thought experiments and physics programmes on TV.

There is one maths thing (and it's probobly stupidly simple): why do the digits in a number that is a multiple of 9 always add up to a multiple of 9, and does this hold for (say) the number 7 in an octal numeral system.

I've just thought about it and I think 7+7=86 (8+6=14)????

Yes, it would hold for the number 7 in a base 8 number system.

7+7 = 16 (1+6 = 7)
7+7+7 = 25 (2+5 = 7)
7+7+7+7= 34 (3+4 = 7)

Or the number 4 in a base 5 number system etc.

4+4 = 13 (1+3=4)
4+4+4 = 22 (2+2=4)

etc.

Corkscrewkenny

Morbert wrote: »

Yes, it would hold for the number 7 in a base 8 number system.

7+7 = 16 (1+6 = 7)
7+7+7 = 25 (2+5 = 7)
7+7+7+7= 34 (3+4 = 7)

Or the number 4 in a base 5 number system etc.

4+4 = 13 (1+3=4)
4+4+4 = 22 (2+2=4)

etc.

Gotcha

Podge_irl

Corkscrewkenny wrote: »

Thats the whole point. Think outside the box. No theories based on mathematics, theories based on logic.

Well my point is that no matter how counter-intuitive you find these things they're still right.

Our current theories aren't "based" on mathematics, they're based on experimental evidence - they're just formulated in mathematics as it's the natural language of physics