What is time? Is time travel possible?

growse · 6 May 2003 at 17:59

Originally posted by Fusion
Infact I've just thought- the measurement data obtained has to be trasmitted by conventional means, so your limit is gool ol' light speed. Yes the object has to be in a pure quantum state, pretty damn fragile if I do say so. It would have to be undertaken in a total vacuum, free from everything, including thermal radiation which could potentially knacker the entire process up. Not to mention the amount of data required to hold the info of a few trillion trillion atoms- a few zettabytes I'd say! One interesting factor is the heisenberg uncertainity principle, which surely would contradict the idea of atom-for-atom teleportation? Can someone with a bit more of an idea speculate on this (you know who you are )

basically, you'ld have to observe each and every proton, neutron and electron + other things in a person at the same time and record their position and momentum. This is both practically (no machine could do it) and really impossible (physics won't let you). The closest you'll get is to get some clever trickery to guess where things go and how fast they go, which could mean that you don't work when you've been teleported.

NickK · 6 May 2003 at 20:58

Why do you have to even move in the first place?

I've always had a thought in the back of my mind that the Speed of Light is a little bit of a cop out and we may actually be looking in the wrong place.

AlphaNumeric · 6 May 2003 at 21:06

Originally posted by Fusion
It would have to be undertaken in a total vacuum, free from everything, including thermal radiation which could potentially knacker the entire process up.

Its impossible for something to have no thermal radiation. Nothing can attain absolute zero.

BigWillyJohnson · 6 May 2003 at 21:06

I've just had a thought. If you're going at the speed of light, how can you control where you're going? It's difficult enough as it is controlling a car at high speed (well for some it is) so light speed would involve some serious concentration.

AlphaNumeric · 6 May 2003 at 21:13

Originally posted by BigWillyJohnson
I've just had a thought. If you're going at the speed of light, how can you control where you're going? It's difficult enough as it is controlling a car at high speed (well for some it is) so light speed would involve some serious concentration.

Please listen very carefully...

You cannot move at the speed of light!

Asking "But what if you were!" is pointless since there are reaons why you cant. Heres another one. Light is the oscillation of electromagnetic waves. One moving electrical wave generates a moving magnetic wave, which makes a moving electrical wave etc. If one stops, so does the other.
If you moved along with a beam of light they waves would appear stationary and the light beam should collapse, but thats impossible. Its energy would just disappear. But since you can never reach the speed of light, this never happens.

Assuming you could get to 99.9999% of the speed of light, what you would have to do is point yourself exactly at where you wanted to be, then accelerate and then slow down. At that speed if you just "jumped" (like when The Enterprise goes to warp) from 0 to 99.9999% the speed of light even a trip of several light years would (for your point of view) take a matter of seconds. If you were off by even a fraction of a degree you'd end up a huge distance away from your destination.

Rich_L · 6 May 2003 at 21:36

With regards to the quantum entanglement phenomenon and teleportation, unless Im mistaken they arent quite the same thing?

I thought that with quantum entanglement, 2 particles will mirror each others states instantaneously, no matter what distance. In quantum 'teleportation', it isnt the same photon at the start and finish as such, instead the original photon is destroyed, and quantum entanglement is used to transmit the information required to recreate the state of the photon. This state is then imposed on any photon, so it is essentially identical to the original = teleportation to all intents and purposes.

This means that for whole-body teleportation to occur,

1. Whole body must be destroyed
2. Enough information on every atom/molecule must be gathered
3. Information sent via quantum entanglement instantaneously

However, at the recieving end, the information must then be transmitted to every atom/molecule, which are present in the same spatial configuration and numbers as in the original.

In other words, for teleportation to work, you have to have pretty much an exact replica of you waiting at the other end....which kinda defeats the object of it....

pyro · 6 May 2003 at 21:43

ok, i dont get why cant things go faster than the speedof light...

btw, if there is no medium at space, and light travles trough it, does that mean that light doesnt need ,or makes its own, medium?

hmm...i suck in physics

crab · 6 May 2003 at 21:47

That's part of wave-particle duality, light is a wave, yet a wave needs a medium to travel in. Light is a particle, yet it can be diffracted.

The problem with travelling at the speed of light is that you would have infinite mass, requiring infinite energy to accelerate.

Fusion · 6 May 2003 at 21:48

Originally posted by pyro
ok, i dont get why cant things go faster than the speed of light...

btw, if there is no medium at space, and light travles trough it, does that mean that light doesnt need ,or makes its own, medium?

hmm...i suck in physics

What do you mean about the "medium"? Are you asking why light can travel through a vacuum?

AlphaNumeric · 6 May 2003 at 22:14

Originally posted by pyro
btw, if there is no medium at space, and light travles trough it, does that mean that light doesnt need ,or makes its own, medium?

Originally posted by AlphaNumeric
Light is the oscillation of electromagnetic waves. One moving electrical wave generates a moving magnetic wave, which makes a moving electrical wave etc.

Thats your answer. It doens't need a medium, its self perpetuating once generated.

Originally posted by pyro
ok, i dont get why cant things go faster than the speedof light...

Its a law of the universe. Physics doens't say why it is, just what that means for us

pyro · 6 May 2003 at 23:06

but i dont get it! i know something big cant go to the abyss cuz the pressure will brake it to pieces, i know that what makes an airplane to fly is the difference in pressure, but what is the reason that we cant get something lilghtspeed?

i mean, in X years from now, lets say they make some sort of a rocket capable to push something that fast...we never know!

AlphaNumeric · 6 May 2003 at 23:16

Originally posted by pyro
i mean, in X years from now, lets say they make some sort of a rocket capable to push something that fast...we never know!

But they do know. Admittedly not with a rocket but in particle acclerators its proved every day.

CERN has a particle accelerator ring capable of powering up a single particle with 10TeV of energy. Never mind what an eV is, its enough energy to push an electron to about 10 times the speed of light according to the Newtonian physics of KE = 1/2mv^2. But the electron is never faster than 99.99999% the speed of light. Doubling the power, making it 10, 100 etc times higher won't push it to be the speed of light.

Observing distant galaxies, stars exploding etc also confirms that nothing goes faster than light.

We exist in the "fabric" of space. Space has the property that is is curved by mass and energy. It "ripples" whem something moves through it etc It just so happens that it also warps in such a way that nothing goes faster than light.

You have trouble accepting it because it's against the natural "obviousness" that we are used to. I don't blame you. This problem perplexed the greatest minds of the late 19th century. So much so they came up with all kinds of crazy theories to explain it within the "rules" they understood.

Fusion · 6 May 2003 at 23:19

Originally posted by AlphaNumeric
CERN

I've been there

Bit of useless trivia

Never actually got underground like because they are in the process of constructing the large hadron collider, which won't be completed until around 2007. We went to the hangar that houses the compact muon solenoid however, compact in relativeness to what I don't know because the outer casing is around 50ft in diameter :rolleyes:

growse · 6 May 2003 at 23:20

Originally posted by pyro
but i dont get it! i know something big cant go to the abyss cuz the pressure will brake it to pieces, i know that what makes an airplane to fly is the difference in pressure, but what is the reason that we cant get something lilghtspeed?

i mean, in X years from now, lets say they make some sort of a rocket capable to push something that fast...we never know!

it's a bit like saying "Why can't I go lower than absolute zero in temperature". It's the way absolute zero is defined. It's as if the speed of light is defined as the maximum speed anything can go. Any information cannot travel faster than it. It's a law of the universe. Live with it.

TerraS · 6 May 2003 at 23:21

Originally posted by AlphaNumeric
But they do know. Admittedly not with a rocket but in particle acclerators its proved every day.

CERN has a particle accelerator ring capable of powering up a single particle with 10TeV of energy. Never mind what an eV is, its enough energy to push an electron to about 10 times the speed of light according to the Newtonian physics of KE = 1/2mv^2. But the electron is never faster than 99.99999% the speed of light. Doubling the power, making it 10, 100 etc times higher won't push it to be the speed of light.

Observing distant galaxies, stars exploding etc also confirms that nothing goes faster than light.

We exist in the "fabric" of space. Space has the property that is is curved by mass and energy. It "ripples" whem something moves through it etc It just so happens that it also warps in such a way that nothing goes faster than light.

You have trouble accepting it because it's against the natural "obviousness" that we are used to. I don't blame you. This problem perplexed the greatest minds of the late 19th century. So much so they came up with all kinds of crazy theories to explain it within the "rules" they understood.

What about Tachyons then? I thought they'd been discovered as going back through time (i.e. Faster Than Light travel)?

growse · 6 May 2003 at 23:22

Originally posted by TerraS
What about Tachyons then? I thought they'd been discovered as going back through time (i.e. Faster Than Light travel)?

They've been theorised, but never discovered afaik.

Fusion · 6 May 2003 at 23:27

Tachyon? Isn't that from star trek or something where the mass is hypothesised to be negative? Ooookkk then....(walks away slowly)

Anything with mass cannot travel at the speed of light as alpha said, the mass is a restriction- it would require an infinite amount of propulsion force. Yes, some experiments have verified a maximum photon mass of 7 x 10^-19 electron volts, but I don't think it has been universally accepted.

TerraS · 6 May 2003 at 23:31

Hmm, Tachyons are theoretical.

And I thought I heard somewhere they were real. Oh well, I guess that changes my argument then. Apparently they have done tests to find these Tachyons, but nothing has come of it yet. They should show up on by using a Cerenkov detector, but in all the tests they have tried none have been detected.

Rules are designed to be broken though. It might be that the speed of light is only our current theory and that we may have to re-think our approach in the future.

AlphaNumeric · 6 May 2003 at 23:33

Originally posted by Fusion
Anything with mass cannot travel at the speed of light as alpha said, the mass is a restriction- it would require an infinite amount of propulsion force. Yes, some experiments have verified a maximum photon mass of 7 x 10^-19 electron volts, but I don't think it has been universally accepted.

Theoretically their max would be a wavelength of 1 plank length, the quantum of length. Thats equivalent to about 0.001g IIRC and a lot more than the value you said.

Tachyons could exist. Relativity doesn't stop anything travelling faster than light. It does stop you moving at the speed of light. since your speed is a continous function, and the speed of light represents an singularity of your energy, you cannot cross it. Provided a particle is created already travelling faster than light it would stay faster than light forever. It would also loss energy as it accelerated.

As I just told Growse on MSN, I came up with a nice theory about the universe beginning using tachyons 18 months back.

AlphaNumeric · 6 May 2003 at 23:34

Originally posted by TerraS
They should show up on by using a Cerenkov detector, but in all the tests they have tried none have been detected.

They would show up producing that effect before the experiment