The Science Behind Time Dilation: How Does Time Stop at the Speed of Light?

[physicscrap]

I never understood how time can slow down as you reach the speed of light then it stops...

I see time as a measurement by a mechanical clock. One second will always be one second.

My ap physics teacher said they did this experiment. They took a photon or something with a very small half-life. They shot these across a measured distance x and predicted that only like 2% of them should be left when they reach impact or whatever. v=d/t, them knowing the initial velocity and distance, the time calculated showed a ton of decay. But there was 98% left, which they concluded time stopped...

Ya anyways is it the process in which it is decaying that is lowing down, not time itself? Can someone clarify this for me? Like is you traveled at the speed of light, someone on Earth with a stop watch would read 10min, so would your watch right? I need understanding ahh!

I have tons of questions, but it is late!

Thanks

 

[rbj]

as one person (with a clock) whizzes past another at very high speed, they both measure the speed of the very same beam of light to be the same value, even when they are moving relative to each other.

the normal textbook explanation of time dilation uses a "light clock" consisting of a burst of light bouncing back and forth between two parallel mirrors whose plane are parallel to the direction of motion (from the perspective on one observer) which means that the path the light is boucing back and forth is perpendicular to the direction of motion.

now if both persons, the one with the light clock moving past a "stationary" observer at high speed, and the "stationary" observer saw the "ticking" of this light clock as the same rate, then for the "stationary" observer, he would have to see the speed of light to be faster than the "moving" observer because it would have a component of c going up and down and a component of v going forward, giving you a diagonal speed of \sqrt{c^2+v^2} \ge c. but that contradicts the axiom of Special Relativity that all observers must see the speed as the same.

so, instead, the diagonal velocity is c and, since the forward component is still v, then the "stationary" observer sees the up and down component of the speed to be \sqrt{c^2-v^2} = c \sqrt{1-v^2/c^2} which is slower than what the moving observer sees for the up/down speed of light (which is c). but the distance between the mirrors are the observed by both observers as the same (that distance is perpendicular to the direction of motion and has no reason to be observed differently), so the "stationary" observer has to see the rate of ticking of the light clock to be a factor \sqrt{1-v^2/c^2} slower than the rate of the "moving" observer.

 

[dicerandom]

It is time itself which slows down, at least comparitively. However you cannot say "such and such happens at c" since you can never get there, you can only discuss what happens as you approach c.

The experiment you describe isn't something that can be done with photons to my knowledge, photons always travel at c (whatever c might be in the particular medium). One classical example of the effect you're talking about is the muons which are created by cosmic ray impacts in the Earth's upper atmosphere. Muons decay in an extremely short amount of time, so quickly that they should have never been able to make it down to the Earth's surface. They are fairly common, however, and this is because when they are created by the collision in the upper atmosphere they have a very large velocity. We on the Earth see them taking some amount of time to travel from the upper atmosphere down to our detectors, however for the muon's own internal clock only a small fraction of that time has elapsed.

 

[russ_watters]

Ya anyways is it the process in which it is decaying that is lowing down, not time itself? Can someone clarify this for me?

Well, if you observe the same phenomena with a half dozen different types of clocks, it is probably safe to say that it isn't coincidental clock effects, but time itself that is affected.

 

[bernhard.rothenstein]

I never understood how time can slow down as you reach the speed of light then it stops...

I see time as a measurement by a mechanical clock. One second will always be one second.

My ap physics teacher said they did this experiment. They took a photon or something with a very small half-life. They shot these across a measured distance x and predicted that only like 2% of them should be left when they reach impact or whatever. v=d/t, them knowing the initial velocity and distance, the time calculated showed a ton of decay. But there was 98% left, which they concluded time stopped...

Ya anyways is it the process in which it is decaying that is lowing down, not time itself? Can someone clarify this for me? Like is you traveled at the speed of light, someone on Earth with a stop watch would read 10min, so would your watch right? I need understanding ahh!

I have tons of questions, but it is late!

Thanks

Have you ever tried to synchronize two clocks that would move with speed c relative to each other?

 

[physicscrap]

Well what rbj explained to me was kind of confusing.

I still don't understand... well what exactly is time?

If you are approaching the speed of light, you are doing so for a period of time. Like you are superman flying and approaching c, while you are counting 1, 2, 3, 4... so the measurement of time is the same as it would be a guy standing still counting.


Confusing. I just need someone to explain it to me logically or something. I am a visual learner, so make it visual :)

Thanks

 

[pervect]

Well what rbj explained to me was kind of confusing.

I still don't understand... well what exactly is time?

If you are approaching the speed of light, you are doing so for a period of time. Like you are superman flying and approaching c, while you are counting 1, 2, 3, 4... so the measurement of time is the same as it would be a guy standing still counting.Confusing. I just need someone to explain it to me logically or something. I am a visual learner, so make it visual :)

Thanks

You might try "Al's relativistic adventures", the winner of the (edit) 2005 Pirelli award. It can be found at

http://www.onestick.com/relativity/

(and possibly other places as well, try google).

It's very visual, and it has a "quiz" feature to help you see if you've understood it.

But you'll need a flash player and a fairly high-speed connection, according to the website.

 

[robphy]

Here's something visual [and animated]
http://www.phy.syr.edu/courses/modules/LIGHTCONE/LightClock/

(pervect, that's 2005... not 1995)

 

[pervect]

Here's something visual [and animated]
http://www.phy.syr.edu/courses/modules/LIGHTCONE/LightClock/

(pervect, that's 2005... not 1995)

I guess I'm stuck back in the 90's :-( - anyway I'll fix the post to give the correct date.

What did you think of the presentation, by the way? I recalll that you contributed to the contest. I remember thinking that I had a few minor reservations about the way some of the material in the award-winner was presented, but that on the whole I thought it was very worthwhile.

 

[rbj]

Well what rbj explained to me was kind of confusing.

yeah, it wasn't the best explanation possible. Al's Relativistic Adventures is a good illustration.

I still don't understand... well what exactly is time?

it's how fast the light clock ticks.

If you are approaching the speed of light, you are doing so for a period of time. Like you are superman flying and approaching c, while you are counting 1, 2, 3, 4... so the measurement of time is the same as it would be a guy standing still counting.

oh no, as Superman is counting 1,2,3,4 it sounds like "wwwwuuuuunnnn, ttttoooooooooo, thhhhhhrrrrreeeeee, fffooooouuuuurrrrr" to me as he whizzes by. but it sounds like 1,2,3,4 to Superman.

Confusing. I just need someone to explain it to me logically or something. I am a visual learner, so make it visual :)

Thanks

if you still have questions after seeing Al's adventure, i'll try to spell it out again with some kinda different language.

 

[Loren Booda]

Imagine counting, from any outside point, the swings of a pendulum bob as time. The time may vary according to observer-bob relative velocity, but at least its passage is non-zero.

Then imagine riding on the bob and trying to count time by the bob alone. This seems anomalous, but actually demonstrates that the relativity of standard bob speed vs standard bob speed results in static signaling.

 

[MathematicalPhysicist]

I never understood how time can slow down as you reach the speed of light then it stops...

I see time as a measurement by a mechanical clock. One second will always be one second.

My ap physics teacher said they did this experiment. They took a photon or something with a very small half-life. They shot these across a measured distance x and predicted that only like 2% of them should be left when they reach impact or whatever. v=d/t, them knowing the initial velocity and distance, the time calculated showed a ton of decay. But there was 98% left, which they concluded time stopped...

Ya anyways is it the process in which it is decaying that is lowing down, not time itself? Can someone clarify this for me? Like is you traveled at the speed of light, someone on Earth with a stop watch would read 10min, so would your watch right? I need understanding ahh!

I have tons of questions, but it is late!

Thanks

let's see, a time measured by a mechanical clock has a constant motion in comparison to light is also constant, but what really is fascinating that perhaps you neglected to mention is how do you observe that light motion doesn't have any time elapsed.
well this is (as i can rememeber) a convention that was made in order to make sense to the phenomona of time contraction, i don't think they can observe that light motion is absent from time.

anyway, time is man made, so it's not impossible that nature doesn't see it fit, in the light case.

 

[physicscrap]

Alright I just watched Al's Adventures and have some questions.

Why can't a mass reach the speed of light or beyond? How does something seem squished relative to you if the ship is going at 99.5% of c?
Also, they use a clock measured by a photon bouncing between two mirrors, forming a second. I understand how that time slows down. But let's say you use a mechanical clock with gears, how does that slow down? It doesn't right, so time actually does not slow down, but the photon just takes longer to form a second for that particular clock. And how does one's brain function slow down. If you approached c, and the clock slowed down, you would notice that you are bouncing your ball faster. How do you think slower?

Also, when Al only took two years to travel to and back, it was only two years according to HIS clock, which is affected by his speed due to it being measured by a photon. But the actual time was 20 years, but Al thought it was 2. Is this correct? Furthermore, how can something be massless?

It gave me info that I already knew, but did not answer my questions in detail.

 

[pervect]

Alright I just watched Al's Adventures and have some questions.

Why can't a mass reach the speed of light or beyond? How does something seem squished relative to you if the ship is going at 99.5% of c?

An object cannot reach the speed of light because velocities do not add linearly. Velocities do not add linearly because space and time get "squished" by motion.

"Why" space and time get squished by motion doesn't really have an answer - we simply observe that it happens. Specifically, we observe that the speed of light is constant for all observers, and from this observation we infer that space and time must get squished in the manner which is described in "Al's relativistic adventures" in order to explain these observations.

The detailed velocity formula addition in SR is

vtotal = (v1+v2)/(1+v1*v2/c^2)

Thus .9c + .9c = 1.8/1.81 c

If you add up ANY NUMBER of velcities, v, which are less than c, the result will still be less than c.

.9c + .9c + .9c + .9c + .9c ... + .9c

for any finite number of terms n

is less than c.

Also, they use a clock measured by a photon bouncing between two mirrors, forming a second. I understand how that time slows down. But let's say you use a mechanical clock with gears, how does that slow down? It doesn't right, so time actually does not slow down, but the photon just takes longer to form a second for that particular clock.

We observe that all clocks slow down by the same amount. If they didn't, we wouldn't see the speed of light as being constant, which is what started the whole theory.

Our most accurate clocks nowadays are made out of atoms, not gears, but they keep the same time as clocks with gears do. Note that atoms and gears are both held together by electomagnetic forces, the same forces that mediate light.

Back in Einstein's day, they didn't have atomic clocks, the best clocks were based on gears and pendulums(!). But the theory applies to any sort of clock.

Relativistic effects are pronounced enough that we can see the effect of relativistic time dilation on the lifetime of short-lived particles like muons. Fast moving muons live longer than slow moving ones. This has been observed both with cosmic muons, and muons in accelerators.

The mechanism of muon decay is not even electromagnetic, so we can see that the concept of "time" slowing down applies even to clocks that are based on nuclear phenomenon and not E&M phenomenon.

And how does one's brain function slow down. If you approached c, and the clock slowed down, you would notice that you are bouncing your ball faster. How do you think slower?

I think you missed the point of the illustration :-(. If your brain slowed down, and your body slowed down, right along with the ball, if _everything_ slowed down exactly the same amount, you wouldn't notice anything. Which is the main point of that particular part of the animation.

Also, when Al only took two years to travel to and back, it was only two years according to HIS clock, which is affected by his speed due to it being measured by a photon. But the actual time was 20 years, but Al thought it was 2. Is this correct?

Al's mechanical clock, Al's atomic clock, Al's brain, Al's light clock, and Al's bouncing ball all measured two years during his journey.

This means that by any means you can measure, Al "really" experienced two years.

The people on the ground also "really" experienced 20 years.

These two statemetns are not contradictory.

Furthermore, how can something be massless?

When it's mass is zero, an object is massless. (I've never understood why this would be a sticking point with anyone.)

 

[physicscrap]

An object cannot reach the speed of light because velocities do not add linearly. Velocities do not add linearly because space and time get "squished" by motion.

"Why" space and time get squished by motion doesn't really have an answer - we simply observe that it happens. Specifically, we observe that the speed of light is constant for all observers, and from this observation we infer that space and time must get squished in the manner which is described in "Al's relativistic adventures" in order to explain these observations.

The detailed velocity formula addition in SR is

vtotal = (v1+v2)/(1+v1*v2/c^2)

Thus .9c + .9c = 1.8/1.81 c

If you add up ANY NUMBER of velcities, v, which are less than c, the result will still be less than c.

.9c + .9c + .9c + .9c + .9c ... + .9c

for any finite number of terms n

is less than c.




We observe that all clocks slow down by the same amount. If they didn't, we wouldn't see the speed of light as being constant, which is what started the whole theory.

Our most accurate clocks nowadays are made out of atoms, not gears, but they keep the same time as clocks with gears do. Note that atoms and gears are both held together by electomagnetic forces, the same forces that mediate light.

Back in Einstein's day, they didn't have atomic clocks, the best clocks were based on gears and pendulums(!). But the theory applies to any sort of clock.

Relativistic effects are pronounced enough that we can see the effect of relativistic time dilation on the lifetime of short-lived particles like muons. Fast moving muons live longer than slow moving ones. This has been observed both with cosmic muons, and muons in accelerators.

The mechanism of muon decay is not even electromagnetic, so we can see that the concept of "time" slowing down applies even to clocks that are based on nuclear phenomenon and not E&M phenomenon.



I think you missed the point of the illustration :-(. If your brain slowed down, and your body slowed down, right along with the ball, if _everything_ slowed down exactly the same amount, you wouldn't notice anything. Which is the main point of that particular part of the animation.



Al's mechanical clock, Al's atomic clock, Al's brain, Al's light clock, and Al's bouncing ball all measured two years during his journey.

This means that by any means you can measure, Al "really" experienced two years.

The people on the ground also "really" experienced 20 years.

These two statemetns are not contradictory.



When it's mass is zero, an object is massless. (I've never understood why this would be a sticking point with anyone.)

That didn't help lol.

How could a physical mass, such as you and your ship, be physically squished? That seems impossible. Also, if you are in space, with no resistance, and have a ton of power, how do you not reach c or past? Of course you said because of being squished which makes no sense. Also, light would not seem to be going at c if you were going 1/2 its speed. Like if you were driving at 50mph, the car that is going 100mph seems to be going 50mph faster, not 100mph. Again, you said space and tiem is squished which i don't understand. I just don't understand.

I also don't understand how the universe could be here. Since something has to make something, we can't exist, but we do. What made matter? what made that thing that made matter? etc... it is infinit, which is impossible for us to be here. ahhhhhh too confusing.

 

[dicerandom]

How could a physical mass, such as you and your ship, be physically squished? That seems impossible.

(and other questions...)

It does seem that way, but it isn't. Keep in mind that from the perspective of the moving object everything is normal, it's everyone else who are squished.

If you accept the fact that light must travel at the same speed in all inertial reference frames then all of these effects which we have discussed here are logical conclusions which must be true, there's simply no avoiding it.

Measuring the speed of light as being constant is an experimental fact, it's been measured to a very high degree of accuracy. After that everything else falls into place if you're willing to work through the logic, all these consequences such as time running more slowly and distances being measured differently are also experimentally verified to a high degree of accuracy.

Edit: By the way, it's a good thing that you're resisting all this. Special Relativity is usually the first instance in physics where people encounter an idea that simply goes against everything they've ever known to be true. Deep in our bones we "know" that velocities add linearly, we "know" that moving observers do not see time or distance any differently than we do. These things have been true for all of our lives, we've never encountered anything in our daily experiences which would indicate otherwise. Fact of the matter is that the only reason we "know" those things is because we generally travel extremely slowly. Even with cars the largest relative velocity I've ever had with respect to someone else is about 160mph or so.

Do not feel discouraged because you don't feel ready to accept these strange ideas, believe me when I say that it literally took me months for it all to soak in when I was first learning this stuff. If you keep plugging away at it and think about the concepts, work out the thought experiments, calculate some numbers for yourself, etc. you will eventually come to understand why everything we're saying must be true. It's just a bit of a journey to get to that point

 

[robphy]

What did you think of the presentation, by the way? I recalll that you contributed to the contest. I remember thinking that I had a few minor reservations about the way some of the material in the award-winner was presented, but that on the whole I thought it was very worthwhile.

I thought the presentation was good. It was creative and effective for the target audience... but I think I liked the physics better in Ehrlich's presentation (see the blog entry https://www.physicsforums.com/blog/2005/12/03/pirelli-relativity-challenge-2005-winners-announced/ ). In my opinion, however, the physics presented in these winning entries is rather ordinary and superficial. I would have been more impressed with (say) a multimedia presentation emphasizing more concrete operational methods as done in the little books by Bondi and by Geroch. I tried to do this in my attempt... but I didn't realize that it had to have more entertainment value.

When it's mass is zero, an object is massless. (I've never understood why this would be a sticking point with anyone.)

There's "massless" and "frictionless" ... but the connotation is different for "priceless". A related suffix is -free... as in trace-free. Maybe one should adopt the prefix zero- .

 

[physicscrap]

It does seem that way, but it isn't. Keep in mind that from the perspective of the moving object everything is normal, it's everyone else who are squished.

If you accept the fact that light must travel at the same speed in all inertial reference frames then all of these effects which we have discussed here are logical conclusions which must be true, there's simply no avoiding it.

Measuring the speed of light as being constant is an experimental fact, it's been measured to a very high degree of accuracy. After that everything else falls into place if you're willing to work through the logic, all these consequences such as time running more slowly and distances being measured differently are also experimentally verified to a high degree of accuracy.

Edit: By the way, it's a good thing that you're resisting all this. Special Relativity is usually the first instance in physics where people encounter an idea that simply goes against everything they've ever known to be true. Deep in our bones we "know" that velocities add linearly, we "know" that moving observers do not see time or distance any differently than we do. These things have been true for all of our lives, we've never encountered anything in our daily experiences which would indicate otherwise. Fact of the matter is that the only reason we "know" those things is because we generally travel extremely slowly. Even with cars the largest relative velocity I've ever had with respect to someone else is about 160mph or so.

Do not feel discouraged because you don't feel ready to accept these strange ideas, believe me when I say that it literally took me months for it all to soak in when I was first learning this stuff. If you keep plugging away at it and think about the concepts, work out the thought experiments, calculate some numbers for yourself, etc. you will eventually come to understand why everything we're saying must be true. It's just a bit of a journey to get to that point

I accept that light travels at the same speed. But how does a fast moving person view the light at the speed of light? I would think that it would seem slower relative to the moving person.

I understand that distances are shorter when traveling close to c. Because time is slower, thus calculating distance using d=vt the distance is less then measured by a normal moving person.

But again, I am not sure about time. How does one's mental thinking slow down? moving close to c in space makes that person feel normal. So that person would think normal, and thus bounch his/her ball at the same pace of a second if that person were NOT referring to a clock.

*just thought of this* Ok you know that the light clock with the ship is traveling close to c. So the photon has to bounch extra distance thus slowing time. But referring to the ball bouncing, doesn't the ball have to travel a diagnal distance such as the photon? same concept right? That makes no sense. What I mean is that if the photon is maintaining the same speed as the ship, could it just bounch in a straight line? ahhh I am having trouble thinking this through.

EDIT: When time theoretically slows down, and so does everything else, does the human body biologically slow down so you ACTUALLY don't age as much, or you just don't age as much relative to time? hmm

 

[MathematicalPhysicist]

An object cannot reach the speed of light because velocities do not add linearly. Velocities do not add linearly because space and time get "squished" by motion.

what do you mean by not add linearly?
i think you can add velocities by simple algebraic arithematics and vector calculus which is linear (if you don't take into consideration non inertial accelerating motion which is not linear).

 

[robphy]

An object cannot reach the speed of light because velocities do not add linearly. Velocities do not add linearly because space and time get "squished" by motion.

what do you mean by not add linearly?
i think you can add velocities by simple algebraic arithematics and vector calculus which is linear (if you don't take into consideration non inertial accelerating motion which is not linear).

Let V_BA denote the relative [spatial] velocity of observer B with respect to observer A.

In relativity,
V_CA =/= V_CB + V_BA.
Thus, the spatial velocities don't add linearly. (Part of the problem is that you are trying to relate spatial velocity vectors in different inertial frames of reference, where their notions of space don't coincide. So, one has to project down into the respective spaces. Vector methods do work... but you must use 4-vectors [for example, see my post, #5, in https://www.physicsforums.com/showthread.php?t=73582].)


("Addition of velocities" should really be called "Composition of velocities".)
What does add linearly is the rapidity, where V_BA=c tanh(rapidity_BA)...
then
V_CA=c tanh(rapidity_CA)=c tanh(rapidity_CB+rapidity_BA),
which can be rewritten using the hyperbolic-trig identity for the tanh of a sum to obtain the velocity composition formula:
V_CA=( V_CB + V_BA )/(1 + V_CBV_BA/c² )

 

[pervect]

what do you mean by not add linearly?
i think you can add velocities by simple algebraic arithematics and vector calculus which is linear (if you don't take into consideration non inertial accelerating motion which is not linear).

By "addition of velocities", I mean that if A is going at a velcity of .9c relative to B (a statement that is true in either A's frame or B's frame), and that B is going at a velocity of .9c relative to C (a statement that is true in either B's frame or C's frame), then A's velocity relative to C is NOT 1.8 c (the sum). Rather it is given by the formula I posted earlier, which is not linear.

There's more detail in
http://math.ucr.edu/home/baez/physics/Relativity/SR/velocity.html"

 

[pervect]

I accept that light travels at the same speed. But how does a fast moving person view the light at the speed of light? I would think that it would seem slower relative to the moving person.

I'm not sure why you think that.

I understand that distances are shorter when traveling close to c. Because time is slower, thus calculating distance using d=vt the distance is less then measured by a normal moving person.

But again, I am not sure about time. How does one's mental thinking slow down? moving close to c in space makes that person feel normal. So that person would think normal, and thus bounch his/her ball at the same pace of a second if that person were NOT referring to a clock.

Imagine a computer running a piece of software that's artifically intelligent. Now suppose we slow the computer down by reducing it's clock speed. The rest of the world would seem to go by faster from the "viewpoint" of the computer. The unit of time for the computer would be one CPU cycle, which would be a "tick" of its internal clock.

Replace the computer with a person. If we slowed a person down, and left the rest of the world running normally, the world would seem fast to the slowed down person. (t's easier to visualzie this with a computer, because a computer has a clock that it's easy to imagine slowing down, it's a bit harder with a person, but the idea is the same.)

But if we slow *everything* down at the same rate, neither the computer nor the person would notice anything at all.

The point is that time always seems to pass normally for everyone, regardless of their velocity, from their own viewpoint. However, when you have two people moving at different speeds, their perception of time is different. Each person thinks that the other person has been slowed down (and crushed).

 

[G01]

I accept that light travels at the same speed. But how does a fast moving person view the light at the speed of light? I would think that it would seem slower relative to the moving person.

Have you heard of Maxwell's equations? Well, one of them predicts that the speed of light should be equal to c. This caused a lot of confusion. Everyone wondered when it would travel c relative to someone else. Would I see light going by me at c if i was at rest, or if i was moving 100mph, or 200mph, which one was it. The equation didn't say what speed you had to travel to see light go by you at the speed of light. This is because it doesn't matter. Einstein postulated that everyone, no matter how fast they were travelling, would see light pass them at speed c. This didn't make any sense everyone thought! How can this be? Well Einstein had an explanation. (see next paragraph)

I understand that distances are shorter when traveling close to c. Because time is slower, thus calculating distance using d=vt the distance is less then measured by a normal moving person. But again, I am not sure about time. How does one's mental thinking slow down? moving close to c in space makes that person feel normal. So that person would think normal, and thus bounch his/her ball at the same pace of a second if that person were NOT referring to a clock.

Einstein realized the only way for everyone to see light pass them by at the speed c, no matter how fast they were travelling, was if the amount of time and space the person experienced was less. If the distance became less, and less time passed then a person moving would still be able to see a beam of light go by them at c. (since v=d/t, in order for v to stay the same d and t have to change also). This is just the way it is. It is just how nature works. And it has beenexperimentally proven

You can't think of it as a person's brain slowing down, or the ball slowing down, or the gears in the clock slowing down. They still tick once every second. Its just that it takes longer for one second to pass. It is not something mechanical, or biological, TIME ITSELF moves slower. Thus if you were moving fast, not only would the clocks slow compared to someoone at rest, but you would also AGE LESS than the person at rest. If you were moving fast enough so that you experienced two years while someone at rest experienced 20 years, you can't say, "O well it was really 20 years." NO! The time you experience is completely independent of other people. Both are right, you experienced 2 years, and the person a rest experienced 20, that's the way nature is.

*just thought of this* Ok you know that the light clock with the ship is traveling close to c. So the photon has to bounch extra distance thus slowing time. But referring to the ball bouncing, doesn't the ball have to travel a diagnal distance such as the photon? same concept right? That makes no sense. What I mean is that if the photon is maintaining the same speed as the ship, could it just bounch in a straight line? ahhh I am having trouble thinking this through.

The ball follows a diagonal path when seen from the outside of the ship,
and bounces straight when seen from inside of the ship. Both of these statements are correct. Its all relative to where you are looking from, just like how much time and distance a person experiences. Hence the name, Theory of RELATIVITY.

EDIT: When time theoretically slows down, and so does everything else, does the human body biologically slow down so you ACTUALLY don't age as much, or you just don't age as much relative to time? hmm

Yes, if you moved fast enough, you would be able to live millions of years COMPARED TO SOMEONE AT REST, when you only experienced 10 years. Remember though the measurment of a million years is just as correct as the measurment of 10 years.

 

[physicscrap]

Have you heard of Maxwell's equations? Well, one of them predicts that the speed of light should be equal to c. This caused a lot of confusion. Everyone wondered when it would travel c relative to someone else. Would I see light going by me at c if i was at rest, or if i was moving 100mph, or 200mph, which one was it. The equation didn't say what speed you had to travel to see light go by you at the speed of light. This is because it doesn't matter. Einstein postulated that everyone, no matter how fast they were travelling, would see light pass them at speed c. This didn't make any sense everyone thought! How can this be? Well Einstein had an explanation. (see next paragraph)



Einstein realized the only way for everyone to see light pass them by at the speed c, no matter how fast they were travelling, was if the amount of time and space the person experienced was less. If the distance became less, and less time passed then a person moving would still be able to see a beam of light go by them at c. (since v=d/t, in order for v to stay the same d and t have to change also). This is just the way it is. It is just how nature works. And it has beenexperimentally proven

You can't think of it as a person's brain slowing down, or the ball slowing down, or the gears in the clock slowing down. They still tick once every second. Its just that it takes longer for one second to pass. It is not something mechanical, or biological, TIME ITSELF moves slower. Thus if you were moving fast, not only would the clocks slow compared to someoone at rest, but you would also AGE LESS than the person at rest. If you were moving fast enough so that you experienced two years while someone at rest experienced 20 years, you can't say, "O well it was really 20 years." NO! The time you experience is completely independent of other people. Both are right, you experienced 2 years, and the person a rest experienced 20, that's the way nature is.



The ball follows a diagonal path when seen from the outside of the ship,
and bounces straight when seen from inside of the ship. Both of these statements are correct. Its all relative to where you are looking from, just like how much time and distance a person experiences. Hence the name, Theory of RELATIVITY.



Yes, if you moved fast enough, you would be able to live millions of years COMPARED TO SOMEONE AT REST, when you only experienced 10 years. Remember though the measurment of a million years is just as correct as the measurment of 10 years.

Not to offend but I think that is complete utter bull****. I have gotten to the point where I can't really explain myself, but I will try again to emphasize my confusion.

The photon clock will go slower as you speed up, ok true. But time itself is the same no matter what. If I am standing still looking at my watch, or if I am on a NASA space shuttle looking at my watch, time is the same. "oh look it has been 10 minutes..." applies everywhere. How could your aging slow down, and how you said you could live for millions of years ok bull****. You get just as old and anyother Joe. Your body decays and whatnot.

If your are traveling at the speed of light, you feel normal like you are standing on earth, thus everything would function the same. Your bouncing ball would not bounce diagonally because it is at a constant speed with you and the ship(c). I do not understand how this is accepted as it makes absolutly no sense. a mechanical clock with gears and a battery will function at the normal second because it is not influenced by the speed in which it is traveling, thus time is the same. But relative to a photon clock, time will slow down, but does not mean it truly does.

You travel at the speed of light to a distant galaxy 10 light years away, it takes a total of 20years no matter what to go there and back and you will age 20 years.


Sorry if I sound like a narrow minded fool, but my mind cannot grasp what I consider nonsense.

 

[Thrice]

"Sit down before facts like a child, and be prepared to give up every preconceived notion, follow humbly wherever and to whatever abysses Nature leads, or you shall learn nothing." - T.H. Huxley


There are a couple things you have to simply accept for now. The questions of why are either unknown or too complex to explain satisfactorily.

1) The speed of light is measured to be the same by all observers no matter how fast they're moving

2) Matter cannot accelerate to the speed of light. Stop saying "if you travel at the speed of light."

3) If someone is in a spaceship & he's moving very close to the speed of light, everything in the ship will be in slow motion. Time itself in the ship will be running slowly. The guy in the ship will see his clock working ok. This is a direct result of the first two points. It takes a while to see why, though.

 

[russ_watters]

physicsrap, the part you are missing is that while things look normal to you (ie, looking at your watch, or playing ping-pong on a train - and also: light always travels at C to you), if you compare your perception of those events with someone else's perception of those events, you won't necessarily agree on what happened.

The ping-pong ball on a train analogy is the simplest - you can bounce it straight up and down on your paddle, but someone on the ground watching will say it is moving forward.

The fact time is just as relative as distance may only show up at high speed, but it is well established experimentally. Clocks sent up into space or put up on a tall tower are observed to behave differently than clocks at rest on the ground.

 

[kmarinas86]

https://www.physicsforums.com/showpost.php?p=907063&postcount=20

A substitution version of the velocity addition formula derivation that I found in my physics textbook.

Start Velocity Addition Derivation

Let:

\alpha=\frac{v_1}{c}


\beta=\frac{u}{c}


\gamma=\frac{v_2}{c}


f_1=f_0 \sqrt{\frac{1-\alpha}{1+\alpha}}


f_2=f_1 \sqrt{\frac{1-\beta}{1+\beta}}


f_2=f_0 \sqrt{\frac{1-\alpha}{1+\alpha}\frac{1-\beta}{1+\beta}}


f_2=f_0 \sqrt{\frac{1-\gamma}{1+\gamma}}


\sqrt{\frac{1-\gamma}{1+\gamma}}=\sqrt{\frac{1-\alpha}{1+\alpha}\frac{1-\beta}{1+\beta}}


\left(1-\gamma\right)\left(1+\alpha\right)\left(1+\beta\right)=\left(1-\alpha\right)\left(1-\beta}\right)\left(1+\gamma\right)


\left(1-\gamma\right)\left(1+\alpha+\beta+\alpha\beta\right)=\left(1-\alpha-\beta+\alpha\beta\right)\left(1+\gamma\right)


1+\alpha+\beta+\alpha\beta-\gamma-\gamma\alpha-\gamma\beta-\gamma\alpha\beta=1-\alpha-\beta+\alpha\beta+\gamma-\gamma\alpha-\gamma\beta+\gamma\alpha\beta


2\left(\alpha+\beta\right)=2\left(\gamma+\gamma\alpha\beta\right)


\alpha+\beta=\gamma+\gamma\alpha\beta


\frac{\alpha+\beta}{1+\alpha\beta}=\gamma

End Velocity Addition Deriviation

 

[Severian596]

Not to offend but I think that is complete utter bull****. I have gotten to the point where I can't really explain myself, but I will try again to emphasize my confusion.
...
Sorry if I sound like a narrow minded fool, but my mind cannot grasp what I consider nonsense.

You don't have to emphasize your confusion, physicscrap, we can all appreciate your position. And we all appreciate the fact that you didn't come to this forum to preach that we're all wackos (at least not yet). You'd be surprised how many people do that despite the evidence to the contrary.

You are understandably a proponent of Absolute Time, a Newtonian and classical mechanics point of view. Classical mechanics is the area of physics that deals with everyday situations; real-life applications of construction, aeroplanes, balls rolling down hills, racecars sticking to racetracks...that kind of thing. From the perspective of our everyday lives, classical mechanics work well because we never have to worry about things traveling at extreme velocities. HOWEVER, realize that classical mechanics are a subset of the big picture.

General Relativity (GR) is the area of physics that covers BOTH the everyday situations that Classical Mechanics (CM) covers AND the extreme cases where high velocities, huge distances, and heavy gravitational fields exist. To put it frankly, if I use GR formulas and you use CM formulas to predict the position of a ball thrown in the air, we will both come up with the same answer. However, if we use the same equations in the context of extreme velocities or gravitational fields, your calculations will be incorrect because Newtonian equations do not take the proper aspects of reality at high speeds into account! Someone else pointed this out...your CM idea of velocity addition breaks down as you approach near-light speeds (NLS).

Keep reading about it. Keep trying to absorb it. Don't expect it to happen overnight. And DON'T give up on it, because this is the way it is. If you choose to give up on it and dismiss relativity as a bunch of malarky, please keep in mind that you're calling everyone who came before you this century a bunch of idiots...now consider that THEY were geniuses and that THEY had more education than you, and that THEY are much better equipped to dismiss the theory than you are but they didn't. I'm not saying you should jump off a bridge just because they did, but until you are similarly educated don't you think you should take their word for it? Give it some time. And maintain an open mind.

 

[Severian596]

Okay, for the time being (assuming you're still reading this thread), you have mentioned a few things that are incorrect so far, and various forum members have pointed those things out, but I wanted to list them here:

1) You cannot say both, "I accept that light travels at the same speed." and "But [...] I would think that it would seem slower relative to the moving person." If you think the second statement then you don't accept the first.

2) Time slows down relative to two different observers. It never slows down for one person relative to themselves. (See the computer example above)

3) Length reduces relative to two different observers. It never reduces for one person relative to themselves. No person ever sees themselves squishing in their direction of motion, instead they see other things squishing in their direction of motion.

4) Any two observers involved in point 2 or point 3 above will report that the other person's time or length reduced, and that their own remained constant. Your Newtonian/classical mechanics approach leaves you here (claiming that your time/length remained constant), but your Newtonian calculations will not be able to account for what the other person says THEY perceive when they return to you to discuss results. This is why atomic clocks traveling at different speeds measure different lengths of time. When they "come together" to discuss how much time passed, they disagree and one reads more time than the other. Classical mechanics cannot explain why.

 

[DaveC426913]

Not to offend but I think that is complete utter bull****. I have gotten to the point where I can't really explain myself, but I will try again to emphasize my confusion.

No problem. It takes time and patience. Remember that we are pushing the very boundaries of our existence here, so our day-to-day experiences start to be inadequate in understanding the bleeding edge. It's the same with other boundaries we push - such as the subatomic realm, or the beginning of time, or the edge of the universe.

The photon clock will go slower as you speed up, ok true. But time itself is the same no matter what. If I am standing still looking at my watch, or if I am on a NASA space shuttle looking at my watch, time is the same. "oh look it has been 10 minutes..."

Yes, you on Earth, or you on the Space shuttle will experience nothing out of the ordinary.

But - if you were here on Earth with your watch and your twin brother were on the space shuttle with his watch, and you compared notes, you would notice a very slight difference in how long ten minutes was.

How could your aging slow down, and how you said you could live for millions of years ok bull****. You get just as old and anyother Joe. Your body decays and whatnot.

Yep. You would live to be 80 years old as usual. Unfortunately, when your spaceship vacation arrived back at Earth, you would find the Earth was now millions of years old. If they had been able to use a powerful telecope to look in the window of your ship, they would have noticed you in slow motion - almost frozen.

You travel at the speed of light to a distant galaxy 10 light years away, it takes a total of 20years no matter what to go there and back and you will age 20 years..

*You* would experience 20 years, yes. But Earthbound observers would not see your ship moving at the speed of light (how could they possibly, since you'd be moving away so fast), thus would not see you get there after only ten years. They would see you accelerating and accelerating, but never get up fast enough to reach there in their lifetimes. They would see you accelerate away, but never actually disappear in the distance. It would look like you were going nowhere, never actually reaching the distant star.

Sorry if I sound like a narrow minded fool, but my mind cannot grasp what I consider nonsense.

No problem. But keep in mind that the universe does not care if we don't understand it. Our understadning is not required in order for the universe to do its business.

 

[Severian596]

*You* would experience 20 years, yes. But Earthbound observers would not see your ship moving at the speed of light (how could they possibly, since you'd be moving away so fast), thus would not see you get there after only ten years. They would see you accelerating and accelerating, but never get up fast enough to reach there in their lifetimes. They would see you accelerate away, but never actually disappear in the distance. It would look like you were going nowhere, never actually reaching the distant star.

At the risk of going off topic, can I question the validity of this statement, DaveC426913? I thought that on a trip of 20 light years the person traveling near c would report that the trip took them much less time to arrive (say, 2 years), and everyone on Earth would report that the trip took him 20 years.

Essentially this comes from the idea that Earth measures the distance as the time it takes a beam of light to reach the star (20 Earth years), but "a photon" traveling from Earth to the star would report (assuming photons can talk) that basically no time had passed since he left Earth.

 

[DaveC426913]

At the risk of going off topic, can I question the validity of this statement, DaveC426913? I thought that on a trip of 20 light years the person traveling near c would report that the trip took them much less time to arrive (say, 2 years), and everyone on Earth would report that the trip took him 20 years.

Essentially this comes from the idea that Earth measures the distance as the time it takes a beam of light to reach the star (20 Earth years), but "a photon" traveling from Earth to the star would report (assuming photons can talk) that basically no time had passed since he left Earth.

Yeah, there's no simple way to explain relativistic speeds. My bad for actually making it worse.

 

[Severian596]

Thanks for clearing it up, Dave. =D I just wanted to make sure.

 

[physicscrap]

I still don't understand. In space... there are no real forces acting upon you. Just you and your ship traveling close to c. So you are basically standing motionless because you are at a constant speed, and nothing else is acting on you. So, with that said, whatm akes that any different from standing on Earth with a clock? Doesn't seem to be any different. I do not understand how time actually slows down. I understand howthe photon takes longer to bounce which make that TYPE of clock slower, but not a mechanical clock. Because what force is acting upon the gears of a clock while traveling close to c? nothing right? I do not understand how the distance is actualyl shorter, though it could be MEASURED shorter relative to the PHOTON clock, not a normal clock. I just don't see how you think slower since you are ...motionless...

I understand tiem as a universal measurement. It never changes. You could be going 1000 X c(not possible so far) and the time will still be the same but you would be hauling ass everywhere and would not be seen. I just don't get it, plain and simple, and at the moment I am calling you and all the geniuses idiots, because this seems obsurd and beyond the point of sanity. But I want to understand this if it is truly true, and I will continue to expand my understanding of it.

 

[ZapperZ]

I still don't understand. In space... there are no real forces acting upon you. Just you and your ship traveling close to c. So you are basically standing motionless because you are at a constant speed, and nothing else is acting on you. So, with that said, whatm akes that any different from standing on Earth with a clock? Doesn't seem to be any different. I do not understand how time actually slows down. I understand howthe photon takes longer to bounce which make that TYPE of clock slower, but not a mechanical clock. Because what force is acting upon the gears of a clock while traveling close to c? nothing right? I do not understand how the distance is actualyl shorter, though it could be MEASURED shorter relative to the PHOTON clock, not a normal clock. I just don't see how you think slower since you are ...motionless...

I understand tiem as a universal measurement. It never changes. You could be going 1000 X c(not possible so far) and the time will still be the same but you would be hauling ass everywhere and would not be seen. I just don't get it, plain and simple, and at the moment I am calling you and all the geniuses idiots, because this seems obsurd and beyond the point of sanity. But I want to understand this if it is truly true, and I will continue to expand my understanding of it.

There appears to be a severe misunderstanding here.

Let's say I am in an inertial frame A. You are in inertial frame B.

According to me, you are moving with velocity V. According to you, I am moving with velocity V (in the opposite direction).

My clock doesn't appear slow. However, when I view YOUR clock, it appears to be slow.

Your clock, according to you, doesn't appear slow. However, when you view MY clock, it appears slow to you.

This is the most common misunderstanding of SR. It isn't YOUR clock in YOUR frame that is slow. It is your clock when viewed in ANOTHER inertial frame that is slow. It is why we can see muons at sea level that are supposed to have decayed already way up in the upper atmosphere - their life time is dilated. But they don't know that. According to these muons, their lifetime hasn't changed one bit!

I would also go easy on insisting that everything that doesn't makes sense TO YOU has to be idiotic. Your "sense" is not absolute - it is a result of all the accumulated knowledge. I can tell you a lot more stuff that would not make sense to you, but makes perfect sense AFTER it is fully understood. So unless you want to be treated with the same degree of hostility, I would drop the editorializing.

Zz.

 

[russ_watters]

I still don't understand. In space... there are no real forces acting upon you. Just you and your ship traveling close to c. So you are basically standing motionless because you are at a constant speed, and nothing else is acting on you. So, with that said, whatm akes that any different from standing on Earth with a clock? Doesn't seem to be any different. I do not understand how time actually slows down. I understand howthe photon takes longer to bounce which make that TYPE of clock slower, but not a mechanical clock. Because what force is acting upon the gears of a clock while traveling close to c? nothing right? I do not understand how the distance is actualyl shorter, though it could be MEASURED shorter relative to the PHOTON clock, not a normal clock. I just don't see how you think slower since you are ...motionless...

I understand tiem as a universal measurement. It never changes. You could be going 1000 X c(not possible so far) and the time will still be the same but you would be hauling ass everywhere and would not be seen. I just don't get it, plain and simple, and at the moment I am calling you and all the geniuses idiots, because this seems obsurd and beyond the point of sanity. But I want to understand this if it is truly true, and I will continue to expand my understanding of it.

If you start with the assumption that time is absolute, then any logical path you take from that will lead to the physical contradiction you are seeing. The assumption that time is absolute is in conflict with OBSERVED REALITY. You really need to accept that fact. Launch a clock into space - any kind of clock that has sufficient accuracy - and then bring it back to Earth and it will not match a clock that has stayed on the ground.

To me, the key concepts here are the facts. Start with accepting the facts and everything else will fall into place. (Caveat: yes, it is true that time dilation was predicted before it was observed, but to an incredulous learner, it is a heckuva lot easier to accept something that has been observed than something that has "merely" been mathematically predicted.)

So to go back and answer a couple of questions there:

In space... there are no real forces acting upon you. Just you and your ship traveling close to c. So you are basically standing motionless because you are at a constant speed, and nothing else is acting on you. So, with that said, whatm akes that any different from standing on Earth with a clock? Doesn't seem to be any different.

Forces? No forces - it is time itself that is relative, so of course, no forces are required. If forces were involved, that would imply that it wasn't time itself that varies.

I do not understand how time actually slows down.

There is no "how". It can (and has) been explained as a logical consequence of observation or simply as an observation itself, but a mechanism is too much to ask for at this point. We don't have a mechanism for gravity, for example, but that doesn't stop us from understanding what it does.

 

[Severian596]

I understand how the photon takes longer to bounce which make that TYPE of clock slower, but not a mechanical clock.

Okay physicscrap, I added bold to your above statement to drive home the fact that you're not thinking about this statement enough. The photon does NOT take longer to bounce between two mirrors; remember that c is constant. So what does that mean??

The photon traces a path that's longer than twice the distance between two mirrors from the perspective of an observer, but traces a path equal to 2d from the perspective of the mirrors. So what gives? Who is right? Did the photon travel distance 2d? Or a distance greater than 2d?

But remember that Distance = Rate x Time, and Einstein argues that the rate of the photon never changes, so either distance or time must give...

 

[physicscrap]

ok so time just slows to an observer... How does a clock look slower from an observer? I still don't understand how "Launch a clock into space - any kind of clock that has sufficient accuracy - and then bring it back to Earth and it will not match a clock that has stayed on the ground." works. It is not clicking for me. Because you say there are no forces, just time. Well a clock that measures time via gears is somehow affected according to you, how is it affected in such a way that is slows down?

grrrahawrwafhawofghoaw;gou;wa! you I am confused

 

[russ_watters]

Again, the only way around this is to stop thinking that the clock slows down. Time slows down. Nothing at all happens to the clock.

 

[Janus]

ok so time just slows to an observer... How does a clock look slower from an observer? I still don't understand how "Launch a clock into space - any kind of clock that has sufficient accuracy - and then bring it back to Earth and it will not match a clock that has stayed on the ground." works. It is not clicking for me. Because you say there are no forces, just time. Well a clock that measures time via gears is somehow affected according to you, how is it affected in such a way that is slows down?

grrrahawrwafhawofghoaw;gou;wa! you I am confused

First let's deal with the mechanical clock vs. light clock issue. Remember that your mechanical clock itself is held together by electromagnetic forces. And these electomagnetic forces make themselves felt from atom to atom at the speed of light. So the forces holding the mechanical clock together form tiny little light clocks inside the mechanical clock itself.

The second issue is when you say:

I understand time as a universal measurement.

But time isn't a universal measurement, it is a relative one. I know that this is a hard concept to grasp, because in everyday experience time sure seems to be a universal measurement.
You and a friend sychronize your watches, and he goes off on a train trip. You are sure that at any given moment you both will agree that your watches read the same time. When he returns, you compare watches and they still read the same. From this, and other experiences, you conclude that time is universal.

The problem is that at the speeds we normally deal with, the Relativity of time is just not apparent. Your watches don't read the same time, it's just that the time difference is so small you'd never notice it.

An analogy is this:

Over small areas, the surface of the Earth seems flat. For centuries, people believed this to be true. As a result, "down" was considered a universal direction. Someone pointing down at one point of the Earth would be pointing in the same direction as anyone else at any other point. This is like universal time.

Of course the Earth's surface isn't flat, it is curved due to the Earth being a sphere. As a result, people standing on different points of the Earth point in different directions when they point "down" (if I was standind on a level surface in San Fransisco, and could see through the Earth to someone in London, they would seem to be "below" me and tilted at an angle. To them, I would be the one "below" and titled at an angle.) This is because we each have our own notion as how you measure "down".
This is like Relative time.

A universe with Relative time behaves differently than one with universal time. You can do experiments that can distinguish as to which type of universe we live in. All experiments to date agree with us living in a universe with Relative time.

 

[franznietzsche]

I never understood how time can slow down as you reach the speed of light then it stops...

I see time as a measurement by a mechanical clock. One second will always be one second.

My ap physics teacher said they did this experiment. They took a photon or something with a very small half-life. They shot these across a measured distance x and predicted that only like 2% of them should be left when they reach impact or whatever. v=d/t, them knowing the initial velocity and distance, the time calculated showed a ton of decay. But there was 98% left, which they concluded time stopped...

Ya anyways is it the process in which it is decaying that is lowing down, not time itself? Can someone clarify this for me? Like is you traveled at the speed of light, someone on Earth with a stop watch would read 10min, so would your watch right? I need understanding ahh!

I have tons of questions, but it is late!

Thanks

Your problem is your not realizing that different observers will not agree on how fast that clock goes, different frames of reference get different measurements.

 

[Loren Booda]

Either the speed of light or time is absolute, but not both. The former is much more consistant with experiment and the principle of parsimony.

 

[physicscrap]

"First let's deal with the mechanical clock vs. light clock issue. Remember that your mechanical clock itself is held together by electromagnetic forces. And these electomagnetic forces make themselves felt from atom to atom at the speed of light. So the forces holding the mechanical clock together form tiny little light clocks inside the mechanical clock itself. "

Well I understand the whole concept of relativity, it is just the clock thing... As you said, there are forces that make a mechanical clock work. But when you say they form tiny little light clocks, how ever that might be, they are not the same photon clocks such that the photon would travel diagonal bouncing between mirrors, thus slowing that clock. So how does the mechanical clock slow down in detail?

If proven to me, that time is indeed relative, it will still make no sense. I grasp the concept of a photon clock slowing down, thus time slows down relative to the clock moving. Relative to the person moving, he is moving normally, but relative to an observer, he is going slow(why? not like you could observe someone bouncing a ball close to c, also you would bounce that ball like once after traveling a long distance lol, possible making you seem slow?).

But for an object to actually slow down when actually going faster is ya, hard to grasp, to say the least.

 

[ZapperZ]

Well I understand the whole concept of relativity, it is just the clock thing... As you said, there are forces that make a mechanical clock work. But when you say they form tiny little light clocks, how ever that might be, they are not the same photon clocks such that the photon would travel diagonal bouncing between mirrors, thus slowing that clock. So how does the mechanical clock slow down in detail?

But see, the "light clock" is the UPPER LIMIT of an ideal case. If I can show logically that the simple light clock will slow down, I have proven ALL other mechanical clock will slow down. Why? Because at the fundamental level, the clock is made up of tiny fundamental particles that form a solid based on electromagnetic forces, i.e. LIGHT!

If proven to me, that time is indeed relative, it will still make no sense.

This is a strange thing to say. You want "proof"? How about the millions of particle in a particle accelerators, especially the exotic particles that were created in a particle collider that had miniscule life time? What about the muon example that I have earlier?

And again, you are using your "sense" as the "standard" here. Do you think your sense is accurate all the time? For example, if you have a helium balloon suspended from a string in a vehicle that is uniformly accelerating in one direction, which direction do you think the balloon will try to move? Please use your common sense and see if you can answer and explain this.

I grasp the concept of a photon clock slowing down, thus time slows down relative to the clock moving. Relative to the person moving, he is moving normally, but relative to an observer, he is going slow(why? not like you could observe someone bouncing a ball close to c, also you would bounce that ball like once after traveling a long distance lol, possible making you seem slow?).

But for an object to actually slow down when actually going faster is ya, hard to grasp, to say the least.

At some point, YOU have to do the work for you. This means that all of us here can only do so much. In the process of learning something, the first responsibility in getting that education is you. There is no substitution for a good text or written source. As good as PF is, we are limited in our ability to SKETCH, describe, etc... The explanation has been given repeatedly, and it appears that either you still don't understand, or from what I can tell, REFUSE to understand, because you keep using what does and doesn't make sense to you. This of course ignores the FACT that you are already using various theoretical predictions of Special Relativity in many aspects of your life without you realizing it.

To me, that doesn't make sense.

Zz.

 

[robphy]

Consider an inertial observer at rest. His mechanical clocks and a light-clock, by construction, agree. The Einstein Principle of Relativity would be violated if a corresponding set of clocks carried by another inertial observer didn't agree.

 

[DaveC426913]

Well I understand the whole concept of relativity, it is just the clock thing... As you said, there are forces that make a mechanical clock work. But when you say they form tiny little light clocks, how ever that might be, they are not the same photon clocks such that the photon would travel diagonal bouncing between mirrors, thus slowing that clock. So how does the mechanical clock slow down in detail?

Simply put, nothing - neither the propogation of photons in the light clock, nor movement of atoms in the mechanical clock - happens instantly.

The mechanical clock has parts made of atoms that can only interact - AT BEST - at the speed of light (this interaction has nothing to do with light, just with the speed).

There is no such thing as a perfectly rigid body. (If there were, you could make it into a 225,000 mile long pole, extend it to the Moon and send signals instantaneously merely by tapping on it.)

 

[Severian596]

At some point, YOU have to do the work for you. This means that all of us here can only do so much.

I think ZapperZ hit the nail on the head here. I believe 4 pages of feedback are enough, and that it's your turn to perform an independent inquest...the fact is we've all performed our own personal journeys in this area, and that's the only reason we're comfortable in this topic. It's your turn, physicscrap! :)

Here are some nice links for further research, but the fact is you will find tons beyond this:
Of course, Wikipedia is good
A Standford University page
Written for Independent Students of a USC astronomy course

Please come back with specific questions, everyone here is awesome at explaining stuff. But Zz already said it; we can't overcome your own common sense, only you can do that. Change your perception of reality or not, it's really up to you. Maybe it's all a bunch of malarcky anyway, right?

(I don't think so)

But keep in mind that the theory you are ready to dismiss as nonsense (General Relativity) is so elegant, its equations wrap around all accepted, tried, and true Newtonian equations. The GR equations yield more precise results than the Newtonian ones at ordinary speeds, and they yield correct results at abnormally fast speeds where Newtonian equations break down! Different equations that are strictly better than accepted Newtonian equations! You got to admire that...

 

[jtbell]

Consider an inertial observer at rest. His mechanical clocks and a light-clock, by construction, agree. The Einstein Principle of Relativity would be violated if a corresponding set of clocks carried by another inertial observer didn't agree.

Or better, the Principle of Relativity would be violated if those same clocks as viewed by another observer (in relative motion) didn't agree. How can two clocks, sitting right next to other (or moving together, right next to each other), appear to be "ticking" in step according to one observer but are out of step according to another one?

 

[bernhard.rothenstein]

I never understood how time can slow down as you reach the speed of light then it stops...

I see time as a measurement by a mechanical clock. One second will always be one second.

My ap physics teacher said they did this experiment. They took a photon or something with a very small half-life. They shot these across a measured distance x and predicted that only like 2% of them should be left when they reach impact or whatever. v=d/t, them knowing the initial velocity and distance, the time calculated showed a ton of decay. But there was 98% left, which they concluded time stopped...

Ya anyways is it the process in which it is decaying that is lowing down, not time itself? Can someone clarify this for me? Like is you traveled at the speed of light, someone on Earth with a stop watch would read 10min, so would your watch right? I need understanding ahh!

I have tons of questions, but it is late!

Thanks

Consider an electromagnetic wave propagating in free space. We can consider that the electromagnetic oscillations taking place in it are a realiable clock propagating relative to all inertial observers with speed c. Conider two inertial observers located in the space where the wave propagates, moving with relative speed V in the direction in which the wave propagates. They are engaged in a time dilation effect or in a Doppler Effect experiment. In both cases the formulas that relate the periods of oscilaltions depend on V. If V could reach c then the observer considered as stationary could obtain for the period an infinite value and so for him time would stop. But as we know that can not happen.
If ou consider the same experiment in an acoustic wave many interesting effects could occur because we should distinguish three cases V<u,V=u and V>u, u being the propagation velocity of the acoustic wave.

 

[Mk]

But time isn't a universal measurement, it is a relative one. I know that this is a hard concept to grasp, because in everyday experience time sure seems to be a universal measurement.
You and a friend sychronize your watches, and he goes off on a train trip. You are sure that at any given moment you both will agree that your watches read the same time. When he returns, you compare watches and they still read the same. From this, and other experiences, you conclude that time is universal.

If you were viewing our universe from outside it however, that would be absolute time?

grrrahawrwafhawofghoaw;gou;wa! you I am confused

I'm surprised no body has told you your username sucks.