Crude time machine.

[tomgwyther]

I recently caught the end of a documentary where someone is actually trying to build a crude time machine, I can't quite remember all of the exact details but it went something like this,

 

He's created a device which takes a sub-atomic particle (A photon I think) and orbits it very fast through a chamber via a system of differently angled lazers, the aim of which is to have the particle exeed the speed of light I presume, so as it can be sent back in time, to create a sort of sending and receiving device over time rather than space.

He hopes that by simply turning it on that he'll receive messages from himself in the future almost straight away; provided he remebers to send them to himself next week?!?!

 

 

I've trawled through the internet looking for more information on this experiment and found nothing. Does anyone know anything more about this thing?

Is it even possible?

Can non-locality work over time, as well as space?

 

Any answers would be much appriciated as I'm fascinated by this experiment.

 

Thanks

[ecoli]

haha... no, it's NOT possible.

[ajb]

I think you mean Ronald Mallett

http://www.physics.uconn.edu/~mallett/main/main.htm

http://www.physics.uconn.edu/~mallett/main/time_travel.htm

 

For more information on other time machines search SPIRES for time machines or time travel

http://www-spires.dur.ac.uk

 

This should convince you that time travel is a "real" area of research. However, I think that most people are not trying to create a real time machine, but rather push known theories to the limit. In this way we learn more about the theories (mostly general relativity) and point towards new physics.

 

G.M. Shore (my MPhys supervisor) wrote a review of some time machines. http://arxiv.org/abs/gr-qc/0210048

[SmallIsPower]

To those who are certain that time travel is impossible - take another look at relativity - not only isn't it considered a possibility, time's dimensionality is very similiar to space.

[H2SO4]

how would you accelerate a photon, traveling at the speed of light, faster than the speed of light, using particles traveling at the speed of light (from the lasers). Centripical force? And even if he did do this, who the hell is he gonna know if a particle the size of an electron went backward or forward in time.

[ajb]

What I would say is that it is not obvious that time travel is not permitted within the frame work of general relativity.

 

Generally, when ever we have a rotating space-time the angular and temporal coordinates get mixed up we have a time-machine. Due to this mixing it is posible to find paths for which time becomes periodic. These are the so called Closed Timelike Curves, or CTCs.

 

This is how Malletts time-machine works. The rotating cicular beam of light produces the phenomena of inertial frame dragging. This courses the space-time to rotate and we have a time-machine!

 

Similar time-machines have been suggested involving rotating cylinders of dust, rotating black-holes, spinning cosmic strings, or even a rotating universe.

 

The other kind of time-machine involves apparent faster than light motion. Things like worm-holes work like this. Essentially it is because there is more than one path that a light beam could be sent, one shortrer than the other. In this way you can make it look like you have sent a message faster than light and hence have a time machine.

 

One conjecture you should know about is Hawking's "chronological protection conjecture". It simply states that the universe does not allow time-machines. As far as I know, just about every time-machine ever concidered can be shown to be flawed when investigated further.

 

The question with Mallett's time-machine could be "what is stopping it working?"

[tomgwyther]

Thanks Guys, that's helped alot. the CTC mentioned helps it to make more sense and eliminates the need to break Einstiens laws.

[ajb]

Glad to be of help.

 

In fact I did a module on modern physics as part of my MPhys which included time-machines. I wonder how may university courses can boast that?

[tomgwyther]

Thanks to your help I was able to look into more detail on this experiment. I personally don't think it will work, not as a time machine anyway. I think the gravatational effect generated by spinning space wont be enough to do a great deal to any particle dropped inside,

It will also need a huge amount of energey input to produce a mesurable effect,

Plus the predictions he makes for it sound to me more like time dilation than time travell,

It looks like a very expensive 'time dilator'; an effect we could easily replicate witha couple of atomic clocks and a plane.

 

It is an interesting way of manipulating space-time in a laboratory though, I'm sure we'll learn from it.

[woelen]

There is another argument, which goes against time-traveling.

 

A photon travels with the speed of light. It cannot accelerate, nor decelerate. Its velocity vector can change (e.g. reflection), but its speed doesn't change.

 

Any particle with mass can only be accelerated to speeds approaching the speed of light. The closer one gets to the speed of light, the heavier the particle seems to be. It would require an infinite amount of energy to accelerate even the tiniest particle to the speed of light. So, accelerating particles to speeds larger than light is impossible. If you put in a constant energy for any length of time, then the speed of any particle goes to the speed of light asymptotically from below.

[shane]

I like the idea that the chronon (time particle) is the inverted viscera of the quantum. It is not however a point but rather a non-local area of potential that measures the probability of motion over distance of any energy particle. At any given moment, a particle has a direction and velocity that can be described by an oblong sphere of notional space that I would describe as time. If every photon is surrounded by this chronomic sphere (or ring), there is an aspect of it that is already moving faster than the speed of light, a potential which is collapsed when the particle moves over any given time frame. The universe therefore is filled with a lot more time than energy and all of it is moving fater than the speed of light. Furthermore, when the universe just began there was more time than there is now but as energy evolves towards a big crunch, time begins to run out and the universe slows down.

 

Just a thought...

[ajb]

woelen

 

the argument you have stated is against accelerating a massive particle to the speed of light. This means that you cannot have "faster than light" time travel.

 

It is however, not an argument against time travel in general.

[pHoToN_gUrL]

It would require an infinite amount of energy to accelerate even the tiniest particle to the speed of light. So, accelerating particles to speeds larger than light is impossible.

i agree with this. I think it's quit impossible to make the photon travel faster than light, unless they find a way to obtain infinite energy. However i said "quit impossible", i'm sure there is a way (keeping my fingers crossed)

[TurboRotary]

Cant photons and electrons already go back and foward in time when they bounce off of each other? Thats what I read anyway. They can for a very very brief amount of time. Also photons do travel both faster and slower than the speed of light according to Feynman.

[ajb]

TurboRotary

 

are you are talking about the interpretation of anti-particles via Feynman diagrams? It is true that anti-particles look like particles traveling back in time.

[TurboRotary]

yeah.. He said that they are particles traveling backward but that we see them as moving foward.

[tomgwyther]

By the way, the original question I asked had nothing to do with accelerating particles faster than light,

Mallet's experiment was to curve space time to an such an extent as it would cause a loop.

 

Just thought I'd mention it

[bob000555]

According to general relativity gravity and thus mass bends space time, it has nothing to do with going faster then c. Image a sheet of rubber and as mass sits on it, it bends. If one axis of this sheat represents space and one time then as something moves along the space axis it falls into a ditch and this ditch is a dent in time thus traveling in time. However I don’t know how he expects to gain this effect with massless photons. Another effect, that is purely theoretical, he could be trying for works like this, general relativity says that space and time are linked in a geometrical from, image this form is a glass of water and your spinning a spoon thro it and you get a whirlpool. This whirlpool is like the ditch I described in the last example but you don’t come up on the other end, you reach the vertices where space and time meat, this is time travel.