Why does time slow down as one goes faster

[rabakill]

take this situation:

you have two extremely large objects(say for example something a million times the size of our sun) and you place them at extremely far distances apart. So, they are relatively not moving in relation to eachother to start, however they will start moving towards eachother due to gravity. According to the laws of physics there will always be a force attracting the two and getting stronger as they get closer. So what happens if the objects are accelerating for long enough a time that the relative speed reaches the speed of light, the force of gravity doesn't become null, why will they stop accelerating towards one another? Ok this may seem implausible, but take two bodies of mass on opposite sides of the universe and they start accelerating towards eachother such as in the big crunch. I think when they reach the speed of light, time becomes dilated so that the relative speeds never pass the speed of light.

 

[Gannon]

Originally posted by: rabakill
take this situation:

you have two extremely large objects(say for example something a million times the size of our sun) and you place them at extremely far distances apart. So, they are relatively not moving in relation to eachother to start, however they will start moving towards eachother due to gravity. According to the laws of physics there will always be a force attracting the two and getting stronger as they get closer. So what happens if the objects are accelerating for long enough a time that the relative speed reaches the speed of light, the force of gravity doesn't become null, why will they stop accelerating towards one another? Ok this may seem implausible, but take two bodies of mass on opposite sides of the universe and they start accelerating towards eachother such as in the big crunch. I think when they reach the speed of light, time becomes dilated so that the relative speeds never pass the speed of light.

Time is just a motion relation in a co-ordinate system, what you mean by attraction is they are "flowing" together, the energy is in each one are seeking to unify.

 

[Nathelion]

Originally posted by: rabakill
take this situation:

you have two extremely large objects(say for example something a million times the size of our sun) and you place them at extremely far distances apart. So, they are relatively not moving in relation to eachother to start, however they will start moving towards eachother due to gravity. According to the laws of physics there will always be a force attracting the two and getting stronger as they get closer. So what happens if the objects are accelerating for long enough a time that the relative speed reaches the speed of light, the force of gravity doesn't become null, why will they stop accelerating towards one another? Ok this may seem implausible, but take two bodies of mass on opposite sides of the universe and they start accelerating towards eachother such as in the big crunch. I think when they reach the speed of light, time becomes dilated so that the relative speeds never pass the speed of light.

One big crux here is that they will never stop accelerating, because they will never actually quite reach the speed of light.

 

[vanvock]

What if there is no such thing as time? What if it was just a tool created by us? What would that do to these theories & equations?

 

[DangerAardvark]

The way I've always looked at it is that, from experimentation we know that the speed of light is constant regardless of the speed of the light source. However, this represents a paradox when when a moving frame of reference is compared to a stationary one. 2 people, 1 stationary and 1 on a train with a light source, moving at 99% the speed of light are equidistant from the light when it emits. The stationary one sees it before the the moving one. Yet 2 things are constant: distance from the light source and the speed of light. Only one thing is elastic in this scenario, and that's time.

Damn, I really wanted to just say that the speed of light is constant, so time has to change, but I had to bring freakin trains into this. Always with the trains...

 

[silverpig]

Originally posted by: Nathelion

Originally posted by: silverpig

Originally posted by: DrPizza
It's not really appropriate to say "time slows down." Regardless of what speed you're traveling, 1 second is one second long. Don't forget, we're buzzing along at a pretty good clip here on Earth as Earth orbits the sun. So, our clocks are "running slower" compared to the clock of someone stationary in our solar system. (just a very very small amount slower, as we're no where near the speed of light, see f95toli's equation.) There is no universal frame of reference.

Actually there is

It's the frame of motion in which the dipole term in the cosmic microwave background anisotropy is zero.

Eh umm. That may be an inertial reference frame that can be found regardless of the reference frame the observer is in (but I'm not sure that's true), however, even if it does hold, there is nothing *special* about it other than that it is maybe the same everywhere. I figure you meant the post more as amusement than anything else, but just to clear things up: Regardless of whether the dipole term of the in the cosmic microwave background anisotropy is zero, your inertial reference frame is still just as relative as it's always been.

So that's where my disclaimer about perhaps not fitting all definitions comes in. I'd argue that it still is universal as it is something that everyone in the universe should be able to agree on.

Sure, you still have to say you're travelling with 0 velocity with respect to something else, but if that something else is the average velocities of everything in the universe, I'd say you were universally stationary

Perhaps the criteria that breaks this definition is that you need to be able to perform an experiment in a closed lab which tells you that you're at 0 velocity somehow. Observing the CMB requires you to look at the rest of the universe.

 

[Cancer12]

I read about half of the replies, so I'm sorry if its already been addressed. Time slows down because light is constant. As you move faster, light is still a constant c. Obviously, this is impossible unless time varies. So it does.

 

[hellokeith]

Ok, so some super dense neutron quasar star gets whipped around a massive black hole and shot off into space at 99.999..% the speed of light. As it is traveling across the galaxy, that star is emitting light in all directions.

Would an observer, at a long distance away and perpendicular to the star's direction of travel, still see the star moving? And if so, he should be able to calculate with moderate accuracy that the star is moving at near-lightspeed?

 

[Born2bwire]

Originally posted by: hellokeith
Ok, so some super dense neutron quasar star gets whipped around a massive black hole and shot off into space at 99.999..% the speed of light. As it is traveling across the galaxy, that star is emitting light in all directions.

Would an observer, at a long distance away and perpendicular to the star's direction of travel, still see the star moving? And if so, he should be able to calculate with moderate accuracy that the star is moving at near-lightspeed?

Yes, this can be done using the doppler shift. We are able to estimate the expansion (or contraction if it were) of the universe by looking at the doppler shifts of objects like stars and quasars. When a light source moves towards an observer, the wavefronts of the EM radiation arrive faster than if the source was stationary. This causes a "blue" shift, the observed radiation has a higher frequency than what it was emitted at. If the source is traveling away, then a "red" shift occurs and the frequency decreases. With sufficient understanding of the source, we can estimate the original frequency and power spectrum of the radiation and thus tell how the source is traveling with respect to the observer. A lot of what we know about the universe is deduced by distortions or perturbations that arise between the source and us, the observers. Another example is that we know the strength of the magnetic field of the Crab Nebula. This is because the Crab Nebula emits synchrotron radiation and a magnetic field affects the behavior of the radiation. The distortion of the received radiation is used to estimate the magnetic field in the nebula.

 

[Capitalizt]

Originally posted by: SsupernovaE
The way I have thought about it is that you are "borrowing speed" from the time vector to traverse a geodesic (in special relativity). The closer a massive object approaches the speed of light, the more "motion" is being taken from dimension t to traverse xyz.

Whether or not this implies that time is a real substance, I do not know.

This is the most accurate answer. Einstein saw space and time as part of the same fabric which he called spacetime. Your motion through one of the mediums displaces your motion through the other. If you were sitting perfectly stationary in space, time would be moving very slowly for you...and as you accelerate, some of your "motion" through time is displaced by your motion through space...and time runs slower for you.

Here is the best way to demonstrate it..

The speed of light is ABSOLUTE and the light barrier can not be broken. Once you accept these facts, do a little thought experiment:

You have a perfectly symmetrical cube with mirrors on the interior walls. The mirrors are perfectly polished and smooth. Now lets say you shoot a single photon up at the top mirror, it hits and bounces down to the bottom mirror, travelling at the speed of light.

For the sake of argument, lets say the cube is 6 inches wide, and the speed of light is 1 foot per second. This being the case, the photon will bounce up six inches and down six inches once per second, traveling at the speed of light. This is the maximum speed in the universe...nothing can go faster than that photon.

Now ask yourself, what happens if you suddenly accelerate the cube by pushing it across a table? What happens to the path of the photon?

Well, it would seem to be going the same 12 inches (up and down) PLUS the new sideways path through space you gave it when you pushed it...taking the path of a sideways "Z".

Does this mean the photon has traveled further than 12 inches per second and broken the light barrier?

No. Because as the cube accelerated, it's "motion" through time was displaced by it's motion in space, and time was moving more slowly for the cube.

 

[lousydood]

Special relativity is actually very simple. The gamma-factor by which time dilation occurs is simply a re-arrangement of the Pythagorean theorem taught in grade school. If you draw a triangle representing the situation the previous poster describes, let the hypotenuse be length (ct'), the horizontal motion be (vt') and the vertical motion be (ct) then the equation is

(ct')^2 = (vt')^2 + (ct)^2

where c is the speed of light, v is the velocity of the cube, t is observer-time, and t' is cube-time. Solve for t' / t in terms of v and c.
I hope I didn't mix up any variables.

The result you are looking for is:

gamma = t' / t = 1/sqrt(1-(v/c)^2)

And that is the factor by which time dilates, length contracts in the direction of travel, and relativistic mass increases.

In general, velocity has to satisfy: c^2 = x^2 + y^2 + z^2 - t^2 and there is a slightly more complicated set of equations for transforming coordinates between different frames of reference, involving gamma.

These are actually called Lorentz transformations, and were already known by the time Einstein wrote his original paper.

 

[Gannon]

Originally posted by: DangerAardvark
The way I've always looked at it is that, from experimentation we know that the speed of light is constant regardless of the speed of the light source. However, this represents a paradox when when a moving frame of reference is compared to a stationary one. 2 people, 1 stationary and 1 on a train with a light source, moving at 99% the speed of light are equidistant from the light when it emits. The stationary one sees it before the the moving one. Yet 2 things are constant: distance from the light source and the speed of light. Only one thing is elastic in this scenario, and that's time.

Damn, I really wanted to just say that the speed of light is constant, so time has to change, but I had to bring freakin trains into this. Always with the trains...

Actually it makes sense... in a black hole light gets "sucked in", space must have a "grid space" in which light exists and moves, the only explanation that makes sense is that light is like a compound-ring(s?) type object, both a "photon", and a "particle", and it is in something else like a ring, and as the "space grid" stretches, the light, in the"grid" is squished together, so it only SEEMS light is slowing down, but it's actually SPACE-TIME is stretched/compressed. For one of them...
doesn't that make sense?

If (SPACE-time) slows the speed of light, the 'photon" doesn't slow down, the ENERGY in the "circuit" of space slows down (like electrons in a circuit).. after all, if in naturalism.. space is ALL connected, ALL of the time, there can be nothing in space that is not connected at some level to space-time itself (even light), this would explain black holes.

If I am wrong, then why does light get sucked into a black hole if "space grid-like-thing" doesn't exist? The only way I can think of it is that light itself is part of(merged with) space-time, and thats why it gets 'sucked in'... the "movement-nodes-in-space-time-grid" that light travels through are 'compressed'.

The time thing didn't make sense to me, unless, space-time and light are merged. (if all of nature (everything, all) is all-connected(allmerged) with itself all-the-(space-time).

because time-and-space are unified, then that must mean, that everything is unified with space time, if scientific naturalism is to hold as "the guide for human knowledge"

Otherwise, supernatural phenomena must exist.

 

[KIAman]

Originally posted by: Capitalizt

Originally posted by: SsupernovaE
The way I have thought about it is that you are "borrowing speed" from the time vector to traverse a geodesic (in special relativity). The closer a massive object approaches the speed of light, the more "motion" is being taken from dimension t to traverse xyz.

Whether or not this implies that time is a real substance, I do not know.

This is the most accurate answer. Einstein saw space and time as part of the same fabric which he called spacetime. Your motion through one of the mediums displaces your motion through the other. If you were sitting perfectly stationary in space, time would be moving very slowly for you...and as you accelerate, some of your "motion" through time is displaced by your motion through space...and time runs slower for you.

Here is the best way to demonstrate it..

The speed of light is ABSOLUTE and the light barrier can not be broken. Once you accept these facts, do a little thought experiment:

You have a perfectly symmetrical cube with mirrors on the interior walls. The mirrors are perfectly polished and smooth. Now lets say you shoot a single photon up at the top mirror, it hits and bounces down to the bottom mirror, travelling at the speed of light.

For the sake of argument, lets say the cube is 6 inches wide, and the speed of light is 1 foot per second. This being the case, the photon will bounce up six inches and down six inches once per second, traveling at the speed of light. This is the maximum speed in the universe...nothing can go faster than that photon.

Now ask yourself, what happens if you suddenly accelerate the cube by pushing it across a table? What happens to the path of the photon?

Well, it would seem to be going the same 12 inches (up and down) PLUS the new sideways path through space you gave it when you pushed it...taking the path of a sideways "Z".

Does this mean the photon has traveled further than 12 inches per second and broken the light barrier?

No. Because as the cube accelerated, it's "motion" through time was displaced by it's motion in space, and time was moving more slowly for the cube.

That's a cool thought experiment but even thought the Photon has no mass, it does have momentum and pushing the cube sideways will move the cube itself but will not move the photon along the X axis until it hits the side walls of the cube. AHA!

 

[Nathelion]

I think this thought experiment does not actually consider the effects of acceleration, in its original form it simply considers two observers, one in the cube and one outside (with the cube moving relative to the outside observer). It says itself that the observer inside the cube will see it bouncing between the walls in the ordinary, everyday manner while the outside observer will see the light traversing the longer, diagonal path. Hence, the outside observer must perceive more time to pass "per bounce" of the photon in order for the speed of light to always be equal.
The minor inconvenience that you can't actually "see" a photon without interacting with it (which necessitates placing oneself in its path, or at least one of its possible paths, this is getting involved so just ignore this parenthesis) is ignored for the purposes of this thought experiment.

 

[gururu2]

the bodies of both parties(traveler and his twin) will age normally. the traveler however would have gone a distance very quickly that would have taken his earthbound twin much longer to complete. his twin would have literally waited many years for the traveler to complete the journey, whereas the traveler would have completed it in seconds.
if for example, we were waiting on the traveler to let us know the instant he arrived at his destination, it would take us several years before we heard of his arrival.
now the flaw in this theory is that there would realistically be no way for the traveler to 'return' to compare ages. this hypothetical scenario is what often leads to a general misunderstanding of the concept. if you can accept the fact that the twins could no longer exist on the same time/space continuum, then it is easier to see how the aging over distance traveled processes relate to time.

 

[BadRobot]

Originally posted by: gururu2
the bodies of both parties(traveler and his twin) will age normally. the traveler however would have gone a distance very quickly that would have taken his earthbound twin much longer to complete. his twin would have literally waited many years for the traveler to complete the journey, whereas the traveler would have completed it in seconds.
if for example, we were waiting on the traveler to let us know the instant he arrived at his destination, it would take us several years before we heard of his arrival.
now the flaw in this theory is that there would realistically be no way for the traveler to 'return' to compare ages. this hypothetical scenario is what often leads to a general misunderstanding of the concept. if you can accept the fact that the twins could no longer exist on the same time/space continuum, then it is easier to see how the aging over distance traveled processes relate to time.

I agree with what you say but it does not relate to what is being debated here.

See post above in which he mentions the atomic clock.

You are debating on the logistics of how we gather, handle, and read information; they are speaking of actual time passed according to atomic clocks etc...

 

[mruffin75]

Originally posted by: f95toli

Originally posted by: Baloo
Time itself does not change, rather, it's ones perception of time that changes.

NO, time DOES slow down by a factor is sqrt(1-v^2/c^2). This is real effect, not a percieved one. A rather fun (but pointless) experiment is to take two atomic clocks, leave one at home and then fly with the other around the world in a fast plane. When you come home and compare the clocks you will find that the clock you took with you is "running behind" compared to the one that wasn't moving.
This has actually been tested and the effect is large enought to be measured.

Or could it be that the equipment we use to "measure" time changes instead of time itself?

Time is a measurement.. light, water etc. are all physical items..

 

[Biftheunderstudy]

But thats the whole point. All of our perceptions and machines used to measure time are affected by special relativity ( frequency, length, momentum....). Last I checked, the human body is a machine for all intents and purposes and is also affected by SR. We don't have a good grasp on what exactly time is, and quite frankly, as a scientist you don't care. Science is only concerned with the laws which govern it. Time is not constant.

 

[BadRobot]

Originally posted by: Biftheunderstudy
But thats the whole point. All of our perceptions and machines used to measure time are affected by special relativity ( frequency, length, momentum....). Last I checked, the human body is a machine for all intents and purposes and is also affected by SR. We don't have a good grasp on what exactly time is, and quite frankly, as a scientist you don't care. Science is only concerned with the laws which govern it. Time is not constant.

But a scientist is concerned with at what rate atoms decay and they use a standard term called "time." We could call it "the rate at which things change" if it will make you feel better but time is much shorter to say and a term that many more people are already familiar with.

The theory goes that "the rate at which things change" can change in a manner similiar to location and some theorize that they are in fact linked.

 

[Biftheunderstudy]

Don't get me wrong, I am a physicist and have worked in the frequency and standards devision of the NRC. I was merely pointing out that fundamental meaning of time is a more philosophical point than scientific. The machines we use to measure time are also the ones we use to define it, so what is the difference if it's only the machines ( frequency, decay of atoms and other particles, etc.) that are affected.

 

[BadRobot]

I agree, people assign to much of a philosphical meaning to time.