Help me understand: Einstein & time...

[Guest Downhome]

Don't ask me why, because I don't even really know (it's just my nature), but I was sitting here researching various different things which don't really have an exact answer, like ending the aging process, and time travel. Anyway, I was researching Einstein, and I came to an example dealing with time.

 

If you're on a train that's moving forward at 50 mph. You throw a ball in the direction that the train is moving. Relative to you and the train, the ball leaves your hand travelling at 20 mph. From the point of view of someone standing alongside the tracks the ball is moving 70 mph. Ok, I get that.

 

Again, you're on a train. This time, though, the train is moving much faster -- at half the speed of light, or 93,000 mps (miles per second). And instead of throwing a ball, you turn on a flashlight. The light travelling relative to the observer standing alongside the tracks is 186,000 mps, the speed of light. Ok, I get this also. The speed of light is always a constant 186,000 mps, got it.

 

Again, you're on a train moving at 93,000 mps, and again, you turn on your flashlight. Relative to you, on the train, the light travels 186,000 mps, again because light is CONSTANT, never changing basicly.

 

All of this brought me to the equation v=d/t, velocity (speed) equals distance travelled divided by time. For the first scenario this equation works out fine, but for the ones dealing with light it doesn't work out because light is always a constant 186,000 mps. This obviously leads one to see that time and distance is not the same for all observers.

 

Ok, I understand all of the above, accept it, and all of that. I get it, and I'm ok so far. However, I then came to the next bit of text, which I AM having a problem with understanding. Here we go...

 

In our second and third train examples, the speed of light turns out to be exactly the same for both you and the observer standing along the tracks because time, as measured by your watch, ticked along at a slower pace than time measured by the observer. Not only that, distance changed, too. For the observer, a one-foot ruler whizzing by on the train would have measured less than a foot.

 

The weird thing is that, for you on the train, time wouldn't seem to be moving slower and your ruler wouldn't be shorter -- all would appear normal. However, time on the rest of the Earth would appear to be ticking along slower and its rulers would be shorter.

 

Now let's say you want to do some time travelling. You board a spaceship and take off for deep space.

 

The ship approaches the speed of light. Time for you seems to pass as it always has. It takes you about five seconds to tie your shoe. But to an observer on Earth (assuming he or she could watch you), you are moving at a snail's pace. It takes hours to tie your shoe.

 

Anyway, you continue on your journey. You slow down, stop, and accelerate back to Earth. You arrive home. You have aged two years during your flight. Two hundred years have passed on Earth. You have successfully travelled forward through time.

 

...I don't understand this at all, even with my understanding of everything else. Is it that this is just taking everything to an entire new level, or is it that I don't truly understand the other basic ideas?

 

Why would time seem normal to me if I tie my shoes while going the speed of light, and to other observers it would seem like hours for them? I don't understand the ruler bit, or any of this. Can someone here explain this to me?

 

Sincerely,

...Downhome...

[Guest The Amazing Rando]

Ever watch a plane fly overhead....they are moving over 100 miles an hour...but to us...they look like they are moving slower...

 

same principle...

[Guest Downhome]

Ever watch a plane fly overhead....they are moving over 100 miles an hour...but to us...they look like they are moving slower...

 

same principle...

I first thought of that, but then found out that this was simply a trick of perception due to distance, as relativity is not at play here in significant enough of a fashion to be noticeable by you just looking

[Guest R2DFooster McSockman]

As I understand it, the basics are that particles move more slowly at greater speeds, and approaching the speed of light get close to being static. As a result, time appears to move slower for all objects travelling at the high speed, when it is in fact the objects themselves that are moving more slowly.

 

But I could be wrong.

[Guest ViciousFish]

I'm a wrestling fan. According to Vince MacMahon I shouldn't and can't think. Well add on top of that that a failed physics and my answer is.....doesn't that have to do with the theory that if you can pass the speed of light you will go backwards in time??

[Guest R2DFooster McSockman]

Yes. If your particles slow down as you speed up, becoming static at the speed of light, then it would make sense (from a logical thought point of view; my physics knowledge is rather limited) that anything above the speed of light would result in the particles going back in time. Shame that it's impossible.

[rising up out of the back seat-nuh 0]

I'ma biologist, and therefore have no trust of the laws of physics. Could it be that time is not changed, merely the watch you time it on. If a watch is travelling at the speed of light, and this implied energy changes the physics of the watch, couldn't this cause the disparity in recordred time? Again, I'm talking out my ass

[Guest Vern Gagne]

What an easy question. It's too bad none of you would understand. So I'll save you all the embarassment and keep quite.

[Guest godthedog]

REALLY fucking weird

I'ma biologist, and therefore have no trust of the laws of physics. Could it be that time is not changed, merely the watch you time it on. If a watch is travelling at the speed of light, and this implied energy changes the physics of the watch, couldn't this cause the disparity in recordred time? Again, I'm talking out my ass

no, time really does slow down as you approach the speed of light. it's not the instruments.

 

 

"In our second and third train examples, the speed of light turns out to be exactly the same for both you and the observer standing along the tracks because time, as measured by your watch, ticked along at a slower pace than time measured by the observer. Not only that, distance changed, too. For the observer, a one-foot ruler whizzing by on the train would have measured less than a foot.

 

The weird thing is that, for you on the train, time wouldn't seem to be moving slower and your ruler wouldn't be shorter -- all would appear normal. However, time on the rest of the Earth would appear to be ticking along slower and its rulers would be shorter.

 

Now let's say you want to do some time travelling. You board a spaceship and take off for deep space.

 

The ship approaches the speed of light. Time for you seems to pass as it always has. It takes you about five seconds to tie your shoe. But to an observer on Earth (assuming he or she could watch you), you are moving at a snail's pace. It takes hours to tie your shoe.

 

Anyway, you continue on your journey. You slow down, stop, and accelerate back to Earth. You arrive home. You have aged two years during your flight. Two hundred years have passed on Earth. You have successfully travelled forward through time."

 

 

...I don't understand this at all, even with my understanding of everything else. Is it that this is just taking everything to an entire new level, or is it that I don't truly understand the other basic ideas?

 

Why would time seem normal to me if I tie my shoes while going the speed of light, and to other observers it would seem like hours for them? I don't understand the ruler bit, or any of this. Can someone here explain this to me?

 

Sincerely,

...Downhome...

in itself, relativity is pretty simple (at least, the basic concept is). it's just hard to wrap your brain around because it's so counterintuitive.

"In our second and third train examples, the speed of light turns out to be exactly the same for both you and the observer standing along the tracks because time, as measured by your watch, ticked along at a slower pace than time measured by the observer. Not only that, distance changed, too. For the observer, a one-foot ruler whizzing by on the train would have measured less than a foot.

in relation to distance & time, the speed of light is the absolute constant of the universe. it cannot change under any circumstances. to accomodate this, time slows down as you approach the speed of light. space shrinks as well. the speed of light (distance over time) can stay the same basically by changing the distance & time to make the numbers fit.

 

The weird thing is that, for you on the train, time wouldn't seem to be moving slower and your ruler wouldn't be shorter -- all would appear normal. However, time on the rest of the Earth would appear to be ticking along slower and its rulers would be shorter.

this is the same as newton said with objects in motion: if you're in a ship that moves at exactly the same speed, it doesn't feel like you're going forward. same principle here: there's no universal point of reference, so you don't "feel" time slowing down or "see" space shrink. hence, the term relativity.

 

The ship approaches the speed of light. Time for you seems to pass as it always has. It takes you about five seconds to tie your shoe. But to an observer on Earth (assuming he or she could watch you), you are moving at a snail's pace. It takes hours to tie your shoe.

 

Anyway, you continue on your journey. You slow down, stop, and accelerate back to Earth. You arrive home. You have aged two years during your flight. Two hundred years have passed on Earth. You have successfully travelled forward through time."

since you're approaching the speed of light, time slows down for you. so while you're in the ship, you age according to this new scale of time. but on earth, time still passes at the same rate. so you age more slowly than you would on earth. and if you were travelling AT the speed of light, time would stop.

 

it's not that the idea is really complicated, it just feels very strange. which is why it's so cool.

 

hope that helps. once you've mastered this, you can go on to quantum physics, which is REALLY fucking weird.

Edited May 2, 2003 by godthedog

[Guest The Electrifyer]

Oh my God... I just got done with an independent study unit is physics about Relativity. The whole time dilation thing is easy, but when it got into more complicated stuff, it was so painful to learn. Nothing was getting into my brain.

[Guest godthedog]

understandable, since the numbers ended up being so difficult for albert fucking einstein that he had to hire a mathematician.

 

i like just learning the concepts. so i can kind of understand HOW it works, but i could never prove WHY it works.

[Guest The Electrifyer]

i like just learning the concepts. so i can kind of understand HOW it works, but i could never prove WHY it works.

Apparently, some of the concepts are wrong. The only reason we use these concepts is because they are the best that we have right now. No other theory is as "correct" as this one is, apparently.

[Guest godthedog]

relativity? i know quantum physics is incomplete, but i've never heard about any inconsistencies in relativity.

[Guest Ram]

Buy "Einstein's Dreams".

 

Actually, wait, don't. It's interesting and all, but it'll drive you mad.

[Guest J*ingus]

The biggest problem with all the relativity theories is that there's no real way to test a lot of them. Sure, the "travel two hundred years into the future" example is backed by various lab tests using particle accelerators and the like, but to this date nobody has actually done it and verified what effect hyperrelative speeds actually have on a living creature. A lot of this stuff is based on good, sound abstract science, but lacks practical means to test it in a macroscopic environment.

[Guest godthedog]

The biggest problem with all the relativity theories is that there's no real way to test a lot of them. Sure, the "travel two hundred years into the future" example is backed by various lab tests using particle accelerators and the like, but to this date nobody has actually done it and verified what effect hyperrelative speeds actually have on a living creature. A lot of this stuff is based on good, sound abstract science, but lacks practical means to test it in a macroscopic environment.

but one can "test" a theory without actually going through one of einstein's 'thought experiments'. the famous solar eclipse when physicists could see stars that were directly behind the sun because of the bending light--that was an effect predicted by general relativity (the larger theory that encompasses special relativity), and it was tested in a macroscopic environment.