Time travel, when we'll get it, and invincibility?????

[jakedemian]

First, if you haven't seen it yet, watch this video:

 

First off, the story adds up. If he had met himself from the past, that doesn't work because he'd have remembered some point in his past where he had met himself from the future, which didn't happen, so that idea is impossible. But he didn't he met himself from the future, which means at some point (2042 i suppose since thats the day he went to when he traveled) he will be forced by the laws of physics to meet himself from the past.

 

Now some questions. Assuming the story is true, that means we will have some form of available time travel by the year 2043, 2042 being the year of his supposed future self encounter.

 

Assuming its true again, that means he COULD NOT DIE until the moment in the future he meets himself from the past. Of course, if he met a close version of himself from a parallel universe that only differed by, say, 1 atom, it would appear he met himself but in reality he met someone very similar to himself from another universe entirely, still cool.

 

Thoughts? Am I mistaken on any of this? I do realize there are many other inferences that could be made from this, too many to list!

[Moontanman]

Hmmm, has John Titor raised his head yet again?

[swansont]

Why is it that people who visit the future can never actually make any concrete predictions about the future?

[Moontanman]

John Titor can answer that

 

http://www.johntitor.com/

 

John has all the answers but I know why his time machine could not possibly work

 

He is quite convincing but he left out one small detail or two

[Phi for All]

Oh, the old wormhole under the sink hypothesis. "Plumbing the Future", I think they call it.

 

How hard is it to get another bald guy who vaguely resembles you to get the same tattoo in the same place? Oh yeah, solid evidence, unassailable proof.

 

This explains why I go to Narnia every time I turn on the garbage disposal.

[Moontanman]

I had forgotten just how stupid the "John Titor" story really was, just another right wing conspiracy nut story. So far nothing he predicted has come true, I would have thought the law of averages might have allowed him to hit a few items. lol

[StrontiDog]

The video is the kicker. It proves everything.

 

It proves that this fellow was not hallucinating, was not having a vivid dream, wasn't suffering from a post-hypnotic suggestion from CIA interrogators.

 

He was, in fact, lying.

 

Poorly.

 

And oh yeah, how did he say he got back?

 

Bill Wolfe

[Law]

time travel is impossible...

[Newbies_Kid]

Agree

[sr.vinay]

Time travel is impossible. First of all, we know that to travel at the speed of light, which would make time travel possible, would require our mass to be really small. Really small. We would just burn at high speeds due to excessive areas of contact creating friction.

[swansont]

Time travel is impossible. First of all, we know that to travel at the speed of light, which would make time travel possible, would require our mass to be really small. Really small. We would just burn at high speeds due to excessive areas of contact creating friction.

 

"Small" is insufficient. It must be identically zero.

[Leader Bee]

"Small" is insufficient. It must be identically zero.

 

I suppose this statement inherently means that photons have no mass?

If so, then what are they?

 

I'd heard light being refered to as a wave, which would be fine for the statement above but also as a particle which is the bit that confuses me...

 

How can it be a particle if there is no mass to it? The word particle implies there is something there and zero mass implies that there shouldn't be.

[Sisyphus]

They're really only "particles" in the sense that they're quantized and interact at a single point.

 

Why does "something there" imply mass?

[ajb]

I suppose this statement inherently means that photons have no mass?

If so, then what are they?

 

I'd heard light being referred to as a wave, which would be fine for the statement above but also as a particle which is the bit that confuses me...

 

How can it be a particle if there is no mass to it? The word particle implies there is something there and zero mass implies that there shouldn't be.

 

In textbooks on classical mechanics, particle is synonymous with "point mass". The modern usage of particle allows for them to be massless. Mass is considered a property of a particle rather than the particle itself.

[vordhosbn]

And photons are considered to have zero rest mass, they obviously are affected by gravity, as they have relativistic mass. That's at least my understanding, do I got it right?

[ajb]

They're really only "particles" in the sense that they're quantized and interact at a single point.

 

That is probably the best way to think of them.

 

In the perturbative quantisation of "point particle theories" the theory is described by Feynman digram which are graphs. The interaction happens at a well defined point. (This is also the trouble!)

 

For (bosonic) string theory the Feynman diagrams are now smooth 2-d manifolds.

 

However, this does not give a notion of a particle outside perturbation theory. Which I am having difficulty thinking about.

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Merged post follows:

Consecutive posts merged

And photons are considered to have zero rest mass, they obviously are affected by gravity, as they have relativistic mass. That's at least my understanding, do I got it right?

 

 

Photons have energy-momentum and thus couple to gravity, i.e. can act as sources.

 

In general relativity space-time is curved. Photons (at least considered as test particles) follow a very special class of paths called null geodesics. These are the analogue of a straight line. This is the origin of the bending of light.

Edited March 29, 2010 by ajb
Consecutive posts merged.

[vordhosbn]

Hmmm, sorry if I go a little offtopic, but is there a difference between the relativistic mass and the energy momentum. Untill now, I had the vague idea, that the former was essentialy the latter in perspective of relativity...

[ajb]

The energy-momentum tensor is of rank two, so the components in some coordinate system are [math]T^{\nu}_ {\mu}[/math].

 

The components have the physical interpretation

 

[math]T^{0}_{\:\: \mu}[/math] density of 4-momentum

[math]T^{i}_{\:\: \mu} [/math] flux of 4-momentum

 

In particular you can show

 

[math]p_{\mu} = \int d^{3}x \: T^{0}_{\mu}[/math] (for Minkowski space).

Edited March 29, 2010 by ajb

[swansont]

And photons are considered to have zero rest mass, they obviously are affected by gravity, as they have relativistic mass. That's at least my understanding, do I got it right?

 

Relativistic mass is a manufactured entity, based on improper application of an equation.

[TheDrBraniac]

Time travel is relatively IMPOSSIBLE. Travelling at light speed requires a lot of energy and it only causes time to stop. To control time? Time is not individual.

 

Travelling back in time is impossible. Travelling forth? You practically cannot. This is due to the fact that you cannot barge forth into time. You can't slow your speed to that level. As a matter of fact, you are time-travelling now. But, it is so slow, you think it is normal. You can stop time? No. You can speed up time? Y-yes. But, it does not make sense. Time does not judge events. So, you can't make concrete predictions on the events if ever we were to time-travel.

[swansont]

Rules for time travelers

http://blogs.discovermagazine.com/cosmicvariance/2009/05/14/rules-for-time-travelers/