acepoly wrote:Heliotrope, from your post, I see a connection between time and space, either of which, if taken separately, will be deprived of their meanings. I have the hunch that the acceleration of physical acitivities will enable people to watch a shortened process that usually takes a much longer time. But some doubts still linger. The mind boggles when I think how we perceive this acceleration if we ourselves are a part of all this acceleration of physical world. What exactly would we feel about this?
Time and space are inextricably linked. There's no having one without the other really. Not if you live in a universe with three spatial dimensions anyway.
Time does indeed slow down for objects travelling at relativistic velocities. Their mass also increases.
You mentioned people watching shorter processes that usually takes a much longer time.
It's not really that way around. Relativistic time dilation is very handy for observing events that would normally occur before we had a chance to see them.
Here's a quick example : a particle has a half-life of about 5 minutes before it decays. If you stuff one in an accelerator so it moves at 99.99% the speed of light then measure the decay time it comes out at a great deal longer, factors of several hundred are acheivable currently.
So basically what is happening is that the particle is experiencing time dilation, it's experiencing one second at a time and lasts for it's allotted 5 minutes. However, you're not zipping around with the particle, you're in the lab watching it on a screen so you see the effects of the time dilation and the particle may last for several hours.
It's seconds have become longer from OUR point of view and our seconds have become much shorter from IT'S point of view.
This is how someone who takes a trip in a relativistic craft can come back 5 of their years later and everyone on Earth will have aged by several centuries.
All this is really easy to demonstrate too. If you have about $40,000 going spare I can get you two synchronised atomic clocks. You put one on the ground and the other on a flight over the Atlantic or at the top of a mountain for a couple of days and then check the time difference between them. The one on the ground will show a time slower than the one at the top of the mountain/plane ride.
Time slows down in a gravity field. We're in a gravity field on Earth so time travels slower for us than it does for people in orbit.
With this example, by the way, the time difference is of the order of femto seconds so it's no use lying flat on the ground in an attenpt to live longer
USAFHokie,
There are ways to travel faster than light but they all depend on jumping over the "light barrier" and not accelerating smoothly through it.
You can't actually reach 'c' because as has been said your mass becomes infinite etc... although as a rejoinder and an update to that : if a theory contains infinities then it's a damn good indicator that the theory is being pushed beyond it's limits and cannot be applied to that situation. So the conclusion is that relativity is not applicable to things with these sorts of speeds. We need something else. That something else is M-Theory.
Actually since time and space are quantised then it's possible to jump from one level to another and not pass through exactly 'c' at all. The same way electrons and photons can tunnel through solid objects as though they aren't there and the do it in zero time too. It's a quantum mechanical phenomena, classical physics cannot account for it. I hasten to add that this has not ben done yet, the tunneling experiments have but not the faster than light travel.
Teleportation is being done routinely in labs around the globe but that's another story.
About the time reversing thing when you go faster than light. It is utter rubbish as you say. It really bugs me too. And this garbage about time reversing when the universe starts collapsing again. If it ever does.
Just as an aside here, the speed of light has been exceeded many times for objects in a specific medium. In fact using an arrangement of lasers and cold plasma gas you can slow light down to an absolute standstill.
Basically if you're in the lab at the time then you can
walk faster than light.
Light is only at it's maximun in a vacuum. If you get a beam of light travelling through water then it travels at about 95% of 'c'. If you accelerate a particle faster than that, say to 98% 'c' and then zap that into the same glass of water you get something called Cerenkov Radiation. It looks light blue light in the water and it's emmitted by things travelling faster than light
in that particular medium only.
Cerenkov Radiation is the blue glow emitted by the cooling pools for the storage of nuclear fuel rods. The emitted neutrons are travelling faster than light in water. The blue light is actually a shockwave but I didn't want to go into that as I've been gibbering long enough already.
Warp theory is eminently possible, the only thing lacking now is the material with enough energy density to warp space in it's vicinity.
When we have that we're rolling !
You could do it with wormholes but that's yet another story.
Emo_Intellectual,
Time travel does not imply pre-destination. The systems of time travel that people propose, ie the time machine where you set the date etc... and murder your Mum or something, are not a part of the present day understanding of physics. Basically it's fantasy land.
It's also not a question of belief. Belief requires faith and no one needs faith to understand physics. They just need facts. It's like saying you 'believe' in gravity. You can't believe in a fact.
What you're talking about with the cause and effect thing is the old Clockwork Universe idea. Quantum uncertainty doesn't allow it to exist. The universe isn't step by step, clockwork. If you know the positions of all the particles in the universe then you actually
can't predict the future because of quantum uncertainty embodied in the Uncertainty Principle.
