Timetravel

Thank you thalion. That is the point i've been trying to make all along, and with your eloquence you have made it clearer.

Well done Thalion.It took me 29 lines to say that

On a quantum level time travel maybe possible in certain exotic circumstances, on sub-atomic levels in closed areas of spacetime (i.e. next to black holes or super dense strings).

This doesn't help us much if a few quarks can move strangely in a few places in spacetime where the curvature due to gravity is super high though - does it?

G__day, I'm assuming you've a descent knowledge of quantum mechanics. That is an area where I am truly ignorant. I don't understand how one can prove changes in time without access to variant points of that particular demension. To me the best I can understand time being different involves things moving in slow motion, or fast forward. Which of course would have nothing to do with the concept. What does it mean to say that time is altered? Because "quarks can move strangely" to me has nothing to do with time. Do you know what I'm talking about?

Yes.

Approach the event horizon of a black hole time slows and stops because spacetime curves on itself.

There is no such seperate thing as time - only spacetime in our membrane of existence.

Spacetime stops at the event horizon of a black hole, but approaching close to it the 'time' and 'space' components of spacetime sort of almost swap properties with each other - strange but theoretically true.

The forces involved in such highly curved areas of spacetime would rip apart any matter larger than a quark.

In the Universe in a Nutshell - Hawkings showed the time part of spacetime travel is only possible where you have a closed 'loop' in spacetime, and only by sub atomic particles.

Hope that helps!

If you have a headache - its basically you need a singularity to warp our 11 dimensional membrane to be able to move outside the normal rules of existence.

Yes, I've heard most of that, I believe, but it doesn't stick with me, because I don't understand what is meant by "time slows and stops." I can picture motion slowing or an object stopping, but what does it MEAN to say that time slows? That is, if I were a quark I would not age, as the universe around me does? And yet that would be insufficient for aging is a physical property, defined by the first three demensions (at least for reference), for example, it is said that dogs age faster than humans, and this is obviously it terms of the first three demensions, and not in reality time. So how is "time" defined in relation to you above statement?

G_day, Are you sure that time slows down and stops?
I suggest that light slows or stops at the black hole.altering your perception of time.
Your wristwatch would work as normal,My wristwatch here on earth would work as normal.But the light carrying the image of my wristwatch would slowdown as it reached you at the black hole,giving you the impression of time slowing down.
We would both age at the same rate.
Remember time doesn't travel,it's the light thats travelling.Thats what is throwing you

See, Gordy, I would have to agree with you, if I thought all scientists were ignorant. I'm assuming I'M the ingorant one, and quantum physicists know what they're talking about. But I would sure like it explained to me. To me, the concept of time slowing or stopping makes no sense. If you freeze something it's aging is slowed, but not it's time. Could someone give a useful explanation of how time could be altered as opposed to perception of time?

The slowing down of time around massive bodies as an actual occurence; it is not due to an altered perception or view of the light that is carrying the information to us. If I were to fall into a black hole, my time would slow down. This would no be percievable by me though. From my point of view, the universe would speed up, because I can't percieve myself slowing down. I would see the end of the universe as my time slows down enough to allow me to exist unto its end.

To further clarify this concept of time slowing down. A particle called a muon is created in the upper atmosphere when light strikes. Its lifetime is much too short for it to reach earth. However, due to its incredible speed, time is slowed down and it lives for longer and reaches the surface when it should not be able to. This has been observed.

For those who doubt that these events actually occur, consider the following thought experiment. We construct a huge tube with mirrors at either end. A particle of light bounces from end to end. Every trip causes a clock to click. If this tube were to be moved, the light would now be moving in two directions, up and down, and sideways. Because the speed of light is always constant, it most slow in the up and down direction to compensate for the sideways movement. This would slow down the clock. The effects of movement can easily be determined by the Pythagorean Theorem. Do it yourself and compare your answer to the real equation.
(Note: This paragraph and the one above it do not pertain to the first. The first one deals with time slowing due to gravity, the second and third due to movement.)

You have to be careful when you talk about time in our Universe - you see its really spacetime. If you collapse a superheavy object into a singularity (black hole) you have collapsed the space part of the spacetime relationship.

Einstein's laws of general and special relativity only hold for normal spacetime that sits on this side of the event horizon of a black whole. On the other side of a event horizon quantum physics and quantum gravity hold sway, and time is a far less certain reality.

At the actual event horizon of a black hole spacetime is frozen or halted or dissappears and its kiss the laws of Einstein and Newton goodbye. We don't have theoretical models of physics and reality inside the event horizon of a black hole. For all we know time could equally well:

1) not exist
2) travel backwards and forwards instanteously
3) be 11 dimensional

We simply don't know. But at the boundary between our Universe and the event horizon of a blackhole, spacetime is becomming so curved that it forms its own closed loop of its own reality - mostly disconnected from our own (except by gravity).

Think of it as a doorway into another Universe with different rules from our own! If time even exists in this Universe then maybe timetravel is possible and if you can get back to our reality then our Universe does permit timetravel and always has.

Our science has already taken the first steps - with advances in quantum entanglement of projected atoms.

Thanks to both of you for the elaboration, but I still don't see why that would be considered a change in time, rather than just a change in the physical properties of matter or motion, which time affects. Do you see what I mean? Again I don't discount the science, but I've never heard it defined in a way to support that it is indeed "time" which is altered, and not just our perception. I feel that thalion's demonstrations almost helped me understand, but the more I thought about it the more those occurences could be merely physically regenerative, or degenerative, rather than chronologically. Do you see from whence my ignorance arrives? There must be some deeper defining feature.

Imagine that this "clock" is on a spaceship. A man who is on the ship does not see the clock moving relative to him, therefore, it ticks at it's... "normal" (hate to use the word), rate. Someone else not on the ship sees that it is moving, and it slows down. These two men see different things. The man outside the ship sees the clock ticking more slowly than the man who is in the ship. It is the fact that what these two men see completely contradict each other that it cannot be a mere physical difference. Time actually MUST be slower for the man on the moving ship, from the point of view of the man off of it. Not to complicate things, but if the man on the ship looked at the man NOT on the ship's watch, it would appear slower than his own, the opposite result. Time is relative to the observer.

I don't understand why they couldn't just be a difference in the way the special circumstances of the system affect light, rather than time. But again I appreaciate the elaboration, it does help.

How do we measure Time ? We measure it by how often a regular event occurs. The clock clicks less frequently... Time must be slower. This effect has been observed with ordinary clocks where the nature of light can't be what's causing the clock to slow.

That's interesting.

Energy is quantised - I once asked is time quantised too. Is there a smallest unit of time and or space - like a planck second = 10 ^ - 43 of a second or a minimal planck volume 10 ^ -99 cm^3

I pondered was time continous or did it advance in very, very, very small clicks?

Well the verdict is still out because time is such a hard subject to get a theoretical model around.

A fine link is http://www.utm.edu/research/iep/t/time.htm

If the Universe didn't exist would time have any meaning or measure in a complete quantum void?

Let me think on it more, time may end up being something deeper than simply a physical phenomonia - without intelligence time can't be percieved. I think we have barely begun to understand theoretically what time is - we are too busy simply measuring it!

Interesting concept, g__day. Is there a minimal speed that an object can move, as opposed to a theoretical standstill? If so and both motion and time move in clicks, then the that would multiply the minimal effects, and the descrepency could be explained, and proven. Meet me under the bog tree at the playground, and I'll bring a stopwatch and a magnifying glass, and we'll se what we can do.

"The universe does not experience time in the sense of living beings. We experience time in the order in which entropy increases. This is the only way we can define our "past" and "future" frames. The universe, however, does not need these references. Time is tied into matter. Quantum mechanics has shown us that observing something can affect its past. This clearly illustrates that time has no direction for particles and laws of physics; time is tied in with the universe itself. There is not direction of time for the universe.

However, life has a direction. We experience events from "past" to "future", and never vice-versa. This is contradictory to how the rest of the universe functions. Therefore, I believe that life most have a deeper meaning because of this excursion into linear time. We biologically can have just "come into being" but that does not explain how we live in a life with direction, unlike the rest of the universe.

This concept of life also solves one of the problems involved with time travel. Can you go back in time and kill your parents? If life is this excursion from the "past" to the "future" (or ordered to disorder, entropy), then by going back in time we have broken that meaning. Maybe time travel is possible, but going back in time would kill life. The being who attempted to travel back in time would die. This solves the paradox. "

Note: I've posted this before under the "Philosophy of GOD" debate. Thought that it pertained though. Comments???

I've asked this somewhere else, but what books could you recomend on the subject? I'm curious to read more.

SCoates

Yes - Heinsberg's uncertainity priniciple places some constraints on a body being perfectly at rest, becuase if you cooled it towards absolute zero you could know both absolute position and velocity. Hawkings used this to proposed black hole radiation.

Basically he said quantum physics says things can't be absolutely at rest - they are always jostling around at a very small level in the quantum foam of spacetime.

Thalion - good definition.

A quote from my link above "A more modern definition says time is the dimension of causality" Time is a human perception of causality - not an inherent component of our reality? The laws of physics (apart from black holes) work equally well in forward or reverse for time. They don't enforce time flows in one direction - only entrophy has a comment about timeflow and disorder of a system increasing. So physics is consistent without time being enforced to flow forward - so the "flow" may well only be a condition of human existence that we "percieve" as to natures reality.