Is time travel viable?

There are no laws of physics that deny it. other than entropy, sort of

Its always been a constant mystery to physicists why time only flows in one direction.

Time travel I’m not too sure about, but I can’t wait for them to get that thing (LHC) up and running so everyone will just have to shut the hell up already…

I’ll explain it all to you when I see you last week.

Scientifically, it may look feasible; but, personally, I don’t think so. Time travel to me seems to be a fantasy. If you can go back in time and see your grandfather, can you go back in time in your own life? Before your own birth? Can you turn back after death?

No. My reasoning is this – if time travel is viable then at some point in the future the human race will start time travelling and before you know it time toursists will crop up all over the place (you know like at the birth of Jesus, at Woodstock, standing on the grassy knoll shouting “duck” etc) and we would have noticed by now.

@Lightlyseared
There are some designs for time travel machines that would only allow you to travel back to when the machine is turned on, no earlier. The one by this guy works that way.

i heard him on NPR

@jackm Well thats about as much use as the teleporter for photons

I’d say they are both equally very useful, so I guess youre right.

You might want to look at this question asked by MattBrowne http://www.fluther.com/disc/58141/is-the-large-hadron-collider-lhc-being-sabotaged-from-the-future/

@ratboy FUNNY!

@markyy You might want to look at this question asked by MattBrown

I missed Matt’s question (sorry Matt) – I was actually leading into another question.

It seems a truth generally acknowledged that you can travel forward in time. Not very practical though.

From the great WIKI: Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential (closer to the center of a massive object), the more slowly clocks run. Albert Einstein originally predicted this effect in his theory of relativity and it has since been confirmed by tests of general relativity.

I think there is a misinterpretation of the situation here. These guys are scientists, they have proposed an experiment to test their hypothesis. Their hypothesis has empirical consequences and is therefore meaningful science. I’m generally very wary of science reporting in the mass media – it’s often (deliberately?) sensationalised or interpreted in such a way as leads to the best headlines.

I’d also point out that most scientists do not mean the God of the Christian tradition when they use the word “God”, it’s a rather poor choice of metaphor. In this case, I think the choice of language is related to the nickname of the Higgs boson – The God Particle.

If the experiment is run and it disconfirms the hypothesis, then we can say with some degree of confidence that the future is not sabotaging the LHC.

@Cartman: time dilation is not really time travel as most imagine it – time dilation is effectively a distortion of the process by which we all move through the dimension of time. It doesn’t require any wormholes or any SFesque warp drives; it only requires speed.

@the100thmonkey but doesn’t it end up being the same thing? I remember a question from a physics test in school, where we were supposed to calculate the amount of time elapsed on earth compared to that for an astronaut in orbit at something like 0.8C (a bazillion miles and hour). I remember that there was a discrepancy. The astronaut had, in effect, traveled forward in time. But, as I said, not very practical. Maybe someone of the Fluther community have more info on this. Would be interesting to hear.

Time travel into the future works and has been repeatedly confirmed. Time dilation is very real. It will still take some time for humanity to reach relativistic speeds. The same holds true for getting near black holes to allow astronauts to travel into the future.

According to David Deutsch the time flow in one direction is some kind of illusion. His multiverse contains all sorts of universes at all possible points in time. At the time being this is an unconfirmed hypothesis.

I enjoy speculation about time travel and the issues that arise from it, and I think that it is likely that we do not fully understand the reality of our multidimensional space (and perhaps never can). But I know for certain that time travel happens all the time (we are all doing it right now – into the future). I am fairly confident however, that time is a one way street, and I’m not really up on the speed limits. But to quote Tom Stoppard: “There is only one direction, and time its only measure.”

Time as in the action. Every second we move a second into the future.

Or the Sci-fi nonsense.

einstein’s relativity has been proof so yes I believe in time travel but if this(http://en.wikipedia.org/wiki/Variable_speed_of_light)is true than we must rethink very much of today’s physics

Maybe not time travel, but when organisms travel at light speed they age slower than anything not at light speed and time appears to be slower. So if we were to send people into space constantly traveling at light speed they could do it for many years and come back to Earth in the “future”. At least this is what I was told in astrophysics.

@JONESGH
Matter can not go the speed of light, it all gets turned into energy following the equation e=mc^2

@jackm: this is incorrect. Were an atom of, say, Oxygen (8 protons, 8 electrons, 8 neutrons) to meet its anti-matter partner (8 antiprotons, 8 positrons, 8 antineutrons), the energy of both would be released (total conversion of matter to energy) following e=mc² (energy equals mass multiplied by the speed of light²)

As objects with mass approach the speed of light, it takes more and more energy to continue the acceleration. As the object continues to accelerate, the energy required to accelerate it increases geometrically, approaching infinite energy at C. Hence, it is impossible to accelerate something to the speed of light if it has mass.

@Cartman: I see that as simlar to the difference between travelling down a hill on foot or on a skateboard – you still travel the same distance, only at different speeds. Time travel using a wormhole would be equivalent to walking through a door at the top of the hill, and walking out the other side of the door at the bottom – the distance travelled is measurably different. Indeed, if the bottom of the hill were sufficiently far away – say 5 light seconds – you would be able to see yourself stepping through the door. Basically, a wormhole allows you to violate the classical principle of causality, ‘time travel’ through movement at relativistic speeds or through mass-derived distortion of spacetime does not – your grandchildren cannot come back to kill you, although you could meet them when you are biologically younger than they are.

@the100thmonkey
Don’t photons have mass? ( know we always assume they don’t in calculations, but they have momentum, meaning the have to have mass, right?) They go the speed of light.

@jackm Just looked that up on Wikipedia thinking the same thing, it says they have no “rest mass” defined as: “The invariant mass, intrinsic mass, proper mass or just mass is a characteristic of the total energy and momentum of an object or a system of objects that is the same in all frames of reference. When the system as a whole is at rest, the invariant mass is equal to the total energy of the system divided by c2”. So, something like that.

@gussnarp
Ohhhhh, thanks for clearing that up.

what?

@jackm Exactly.

Without the momentum of photons (even though their rest mass is zero) solar-sail spacecraft wouldn’t work.

having just done a search on time-travel and come up with this question…do I need to go back to physics basics in order to understand time-travel do you think?... I wish I was cleverererer!!! as I love this topic :-(