Time travel.. if its possible why havent we seen it.

[FnG]magnolia;20135003 said:
That was kind of my point. Most (all?) posters in this thread are saying, "Well it's like this, see ... <insert unsubstantiated and subjective opinions>"

I know we have a couple of maths Profs on here; just wondered if we had any physics gurus as well. I mean real ones, not ones the same as me who read a number one best seller back in the mid-80's ;)
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To be fair though, when talking about theoretical future machines does it really matter if its a physicists or some random joe. The physicist can only make predictions from current knowledge of technology/science which as we know is always changing. He could say its impossible but who knows what new things we will discover in 10 years never mind 100's or 1000's of years when the machine could be made if it is possible. Its like asking a physicist from 1900 if its possible to walk on the moon.
 
Beerbaron said:
I thought in theory you could only travel to the future. We would only see people from the past and if time travel had already been invented. Therefore you are not going to see anyone as it hasn't been invented yet.
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this theory is actually a cop-out as you aren’t really time travelling, just travelling at a different rate of change. i.e. much slower than everyone else so by your observation you won't age etc and will arrive at your destination in a couple of mins where everyone else outside of your 'time travel field/vessel/slingshot round a blackhole/worm hole etc' will have progressed at their normal relative to you. it is also a one way journey since you cannot travel back in time on this theory.

technically (well technically in theory) we may be able to observe past events just not travel to them, i.e. if we can travel to a point in the universe before the light from the even't/timeframe has reached it we could observe the earth at an earlier stage, the further away from earth we go, the earlier we observe it. however, we would need to travel faster than the speed of light to achieve this.
 
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Time travel is theoretically possible but you will never meet a time traveler until its invented.


Time travel
Main article: Time travel

The theory of general relativity predicts that if traversable wormholes exist, they could allow time travel.[2] This would be accomplished by accelerating one end of the wormhole to a high velocity relative to the other, and then sometime later bringing it back; relativistic time dilation would result in the accelerated wormhole mouth aging less than the stationary one as seen by an external observer, similar to what is seen in the twin paradox. However, time connects differently through the wormhole than outside it, so that synchronized clocks at each mouth will remain synchronized to someone traveling through the wormhole itself, no matter how the mouths move around.[20] This means that anything which entered the accelerated wormhole mouth would exit the stationary one at a point in time prior to its entry.

For example, consider two clocks at both mouths both showing the date as 2000. After being taken on a trip at relativistic velocities, the accelerated mouth is brought back to the same region as the stationary mouth with the accelerated mouth's clock reading 2005 while the stationary mouth's clock read 2010. A traveler who entered the accelerated mouth at this moment would exit the stationary mouth when its clock also read 2005, in the same region but now five years in the past. Such a configuration of wormholes would allow for a particle's world line to form a closed loop in spacetime, known as a closed timelike curve.
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[FnG]magnolia;20135003 said:
That was kind of my point. Most (all?) posters in this thread are saying, "Well it's like this, see ... <insert unsubstantiated and subjective opinions>"
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Maybe we're just repeating what we heard from qualified people? We wouldn't have progressed very far as a species if everyone had to verify every scientific fact themselves. That's kinda why we specialise...
 
Shadez said:
Time travel is theoretically possible but you will never meet a time traveler until its invented.
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anything is theoretically possible, the problem with using wormholes to underpin the theory is that there are no actual observed measurements to substantiate the thoery so when you have assumptions supporting assumptions......
 
Pottsey said:
It’s not a thin argument it’s a massive problem most people overlook when talking about time travail. I don’t think you understand the sheer size or speeds we are talking about here. What is a thin argument is you saying but we could just compensate for this very real problem in some unknown way. You would have no point of reference, no idea where Earth had moved to and even if you did if you are just 1/10000 of a degree out and you still miss Earth by a long shot. It’s a massive problem.

The chance of someone time traveling in another galaxy and landing on Earth is well how do I even explain how small a chance that is. Do you understand what a large area we are talking about? It would be easier for me to drop 1 bit of sand on a beach and 10 years later you find it without knowing what beech I was on.
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I agree with vonhelmet here. If we have the technology to invent time travel then we would have the technology to plot where the earth has already been at any point in the past.

Infact, I'm pretty sure it's already possible. Just look at the juno satellite mission. If that's possible now, I'm sure by the time time travel is invented we will be able to carry out the much more complex calculations needed (if we can't already).
 
Domo said:
That's true. In fact quantum theorists are trying to understand a universe where time does not exist at all. Simply because the start of the universe cannot be explained, therefore remove the time dimension altogether and there is no 'beginning'. The big benefit is it removes the notion of infinity when looking back through time.

Physicists do not like infinities.
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Nonsense. Singular values in things like scattering processes form a central component of quantum field theory. String theory predicts the dimensions of space-time using regularisations. Quantum field theory involves integrating over infinitely many degrees of freedom via a functional integral. Significant research is done into the behaviour of multidimensional 'black branes', where the singularity of a black hole is not a point but a region. Topological flop transitions examine how the structure of space-time behaves as part of it collapses into a singularity and then reexpands. Hawking-Penrose theorems pertain to the inevitability of singularities in general relativity. Quantum mechanics is formulated in an infinite dimensional Hilbert space.

Infinities, of many different types, arise in physics, both in classical physics and more recent theoretical physics. To say physicists don't like them is just naive.

It would seem that a lot of the 'armchair physicists' have come out to give their 2 cents on physics in this thread. Suddenly the hardest problems in physics are 'obvious'. If only some of you were academics, reshaping our understanding of the universe instead of wasting your obvious physics talents on a forum.

Rather than complaining about things such as your perception that physicists can't 'think outside the box' why don't you try doing actual physics? I can assure you you'll soon change your mind about the behaviour of professional physicists if you stopped whining about it on the side lines.
 
BetaNumeric said:
Nonsense. Singular values in things like scattering processes form a central

It would seem that a lot of the 'armchair physicists' have come out to give their 2 cents on physics in this thread. Suddenly the hardest problems in physics are 'obvious'. If only some of you were academics, reshaping our understanding of the universe instead of wasting your obvious physics talents on a forum.

Rather than complaining about things such as your perception that physicists can't 'think outside the box' why don't you try doing actual physics? I can assure you you'll soon change your mind about the behaviour of professional physicists if you stopped whining about it on the side lines.
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ahhh physicist rage.............:eek::D
 
mrk1@1 said:
ahhh physicist rage.............:eek::D
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I just get slightly erked when some physics or maths thing comes up in the news and every jackass with a D at GCSE single science suddenly has all the answers or scoffs at professional mathematicians/physicists for being 'too narrow in their thoughts' or 'afraid of thinking outside the box'. You only need to browse the hep-th section of www.arxiv.org to see physicists aren't afraid to suggest some pretty wacky things to explain some observations.

I think it's generally a defence mechanism so people can't avoid facing up to the fact they sucked (and still suck) at maths/physics, it's a conspiracy of silence or their genius wasn't recognised or the mainstream is too buttoned down. It's just annoying when you know how much time and effort is actually put into this stuff, mostly to get slagged off by people who've lives are made better by science.
 
It might be possible, just perhaps the human race doesn't make it far enough to develop it, or they are very good at avoiding contamination of the timeline.
 
BetaNumeric said:
Infinities, of many different types, arise in physics, both in classical physics and more recent theoretical physics. To say physicists don't like them is just naive.

It would seem that a lot of the 'armchair physicists' have come out to give their 2 cents on physics in this thread.
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I suppose you could say Hawking is an armchair physicist. I was after-all quoting him on infinity. I'll make sure I pass on your comments.

Have you heard of renormalization? I assume you have as you appear to be much smarter in this subject than I, and that's not sarcasm. But don't flatter yourself too much as I also find your comments a touch patronising.

Just to summarise, when inifinites enter euquations they are a nuisance, and subsequently theorists come up with ways to deal with them. I've never liked the notion since how can an equation be effective when part of it has been born out of frustration to some degree or at best elimintates the annoyance which is infinity.
 
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