Can the learned forum please help settle a discussion.
At approx 300,000 km per second it would take a second to transfer a morse code message 300,000 km by radio or light on a vacuum. I.e. if I flashed a light, some one 300,000 km away would see it 1 second later. A whole message would arrive 1 second after it was sent.
If the light were replaced by a solid metal pole which could be moved from position 1 or 2 to indicate a dot or dash like a piston. The movement need only be a fraction of a mm.
Being a physical connection, would the movement be noticed immediately at the other end or would it take a second for the movement to transfer along the end of the pole?
Someone asked me this question and it’s been bugging me.
Btw, I think the movement of one solid object is instantaneous I.e if you move your end 1 mm the other end is moved 1mm at the same time?
Thanks
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Without going into great detail, any solid pole/rod would suffer from torsional delay from one end to the other.
The amount would depend on the material used, but I think in all cases the effect would be more noticeable than the delay due to speed of light, and over 300,000 km would not be insignificant.
;-)
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What about an object travelling faster than the speed of light with a headlamp on the front?
Would a viewer outside the object see a beam of light projected from in front or behind it?
Would a viewer inside the object see a beam of light projected from in front or behind it?
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No light would leave ( be emitted from the headlamp) Specially if it was a Lucas
Last edited by: VxFan on Thu 3 Dec 20 at 11:24
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>> If the light were replaced by a solid metal pole which could be moved from
>> position 1 or 2 to indicate a dot or dash like a piston. The movement
>> need only be a fraction of a mm.
A 300.000 km single solid mechanical link would display a signal, but not the one sent, temperature expansion/contraction would scramble the data.
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>> A 300.000 km single solid mechanical link would display a signal, but not the one
>> sent, temperature expansion/contraction would scramble the data.
I don't think that's the point of the question. Assume it happens in a vacuum at constant temperature. I still don't think it would work but that is just intuition. Atoms are mostly space. populated in a way I don't properly grasp by electrons which are both waves and particles. We know photons also have this wave-particle duality. The energy appears at a point but they travel like waves. The waves can't go faster than light.
I know somebody who does this for a living, I'll ask him.
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There's a discussion about it here
www.researchgate.net/post/Can-information-travel-faster-than-the-speed-of-light-by-pushing-and-pulling-something-extended-between-2-points
that isn't very illuminating. I suspect the answer has to do with the frame of reference but that c will still be the physical limit.
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Interesting and thanks!
So if I had a 300,000 km U shape of incompressible material in a vacuum shamed like a very long and thin horseshoe. If I pushed one side of the open end of the shoe 1 cm away it would take >c for the other end to move.
Even though they ends are only a few cm apart the information about the move needs to travel 300,000 km at c.
Weird.
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>>Being a physical connection, would the movement be noticed immediately at the other end or would it take a second for the movement to transfer along the end of the pole?
The pole is not solid. It contains individual atoms/molecules, which cannot move faster than the speed of light.
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A somewhat academic question but I suspect that the pre-conditions or essential assumptions for such a test over 300000 km are close to unachievable:
- a completely incompressible physical connection
- with absolute rigidity to avoid bending
- operating in a vacuum to avoid surface drag
- with no temperature variation to avoid expansion and contraction
- in zero gravity to avoid distortion over such a distance
- of zero mass to avoid delay in acceleration and deceleration
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Of course it's unachievable, so you can make whatever assumptions you want for this thought experiment, much like this somewhat simpler one postulated here -
www.daviddarling.info/encyclopedia/H/hole-through-the-Earth_problem.html
Although you don't need a 300,000km pole to do Bobby's experiment, so it might still be possible, just hard to get funding for.
David has been adding to his site for a long time - I thought he might have something on faster-than-light communications:
www.daviddarling.info/encyclopedia/S/subspace.html
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Will it depend if the cat is alive or dead in the box?
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Despite the fact that superluminal velocity is indeed impossible accordingly to the second law of relativity, because space is expanding some galaxing are in fact receding from us greater than speed of light.
Thought I’d just drop that in to scramble your mind a bit more.
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But maybe the other galaxing are going one way at 1/2 speed of light and we're doing the same the other way.
Last edited by: No FM2R on Fri 4 Dec 20 at 11:46
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They may well be but space itself is expanding. Space is a thing not just an empty well er space.
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Is space a thing? I thought it was a lack of thing?
In any case, for two sides of space to expand away from each other at the speed of light, surely each side would only need to be moving at 1/2 speed of light?
However, the point that has always knotted my brain is the question of what was there before space expanded into it. And what is in the bit that space hasn't expanded into yet.
If space is fundamentally nothing with stuff floating around in it, then how can nothing expand?
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And what happens when you reach the end of it
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And what's the other side of the end wall?
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Space is very much a thing and it is expanding. It is not expanding into anything. Everything is getting further away from everything else. Imagine a giant Spotted Dick pudding. The pudding is expanding forcing the currants (galaxies) further and further apart
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A pudding in a tin cannot expand. It has to have space to expand into.
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A pudding in a can is not the universe. The metaphor is not perfect. You have to accept the concept that space and the universe comprises everything at least everything knowable.
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"You have to accept the concept that..."
Do I?
>>The metaphor is not perfect.
The metaphor is rubbish, but you put it forward. To then dismiss it as imperfect seems a weird approach.
Last edited by: No FM2R on Fri 4 Dec 20 at 14:23
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>> The metaphor is rubbish,
Indeed it is, tinned steamed pudding is terrible, nearly as bad as a Frey Bentos tinned steak pie, gives me real metaphors.
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A few years ago, on an Army Camp, I came across Frey Bentos steak pie, and I was really excited by memories of lunch at my Grandmothers. So I bought one and cooked it with great anticipation.
It was utter s***e. I don't know if my memory had glamourised it or that quality standards had slipped over the years, but it was utter utter s***e. And it gave me non-solid metaphors.
One should never go back.
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There are plenty of physicists on the internet who will explain the concept of the expansion of the universe if you are really interested..
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The thing is, and what stops me getting my head round it, is that when you get to near-light speeds everything changes. Time slows down, mass changes, dimensions change, and you can't just add speeds together as you would in a school days arithmetic question.
If you could travel at the speed of light, you would weigh an infinite amount and your physical dimension in the direction of travel would be nil. But you can't go that fast. In theory you could go nearly that fast. Then, in a way, you would be travelling faster than light. The elapsed time as observed by the traveller would be much reduced compared with the time your journey took as recorded by a stationary observer. E.g., you could travel a light year in a few days by your watch, so if you know how many km. you have travelled, you could divide that by the number of seconds gone on your watch and you would have a result much bigger than 300,000. Or you could say that the distance travelled has reduced if you wanted to look at it that way. It's the same thing in this odd world of relativity. apparently (and if I have remembered correctly).
I no more understand this than ancient Greek, but I did read a lot of scifi and popular science books as a youth.
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P.S.
If you have a root around David Darling's website you'll probably find some reasonably intelligible explanations. He writes popular science books.
www.daviddarling.info/encyclopedia/R/relativity_theory.html
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Doesn't the theory of relativity explain this? If you're travelling at half the speed of light, then everything else is relative to you.
I'm still worried about that cat in the box.
Last edited by: bathtub tom on Fri 4 Dec 20 at 14:50
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Well no-one is going to receive the data back now
www.businessinsider.com/video-arecibo-telescope-puerto-rico-collapse-2020-12?
As a planet we have just become a little deafer.
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Can data travel faster than the speed of light? - tyrednemotional
