Questions About Relativity - Esp. Time Dilation

[Nique]

I'm trying to decipher Wikipedia's articles on these subjects but they're pretty mathy which kind of divorces the concept from being understood by me in more detail.

I'm also looking for the answer/ understanding to specific questions about relativity's effects on our perception of the universe.

So, from my understanding;

Gravity curves/ contracts space-time, or rather, gravity IS the curvature of space-time. Time 'slows down' in the vicinity of gravitational bodies like the earth, sun, or at the very extreme, black holes, and inversely moves faster in low gravity (or '0' gravity, if there is truly such a thing) environments.

Some things I don't quite understand:

-It's also said that moving near the speed of light (or at any velocity greater than the observer's) would cause time to 'slow'. Am I right in understanding that this is due to the greater gravitational forces being invoked due to the greater speed of the mass in question?

-This may be mathy, however; How would one (simply) calculate or estimate how much 'faster' or 'slower' time moves at different speeds or in different gravitational environments (like the sun vs the earth, or 1/2 the speed of light vs 99% the speed of light, etc)

-Also, how much does speed effect gravity, or how do these forces interact? For example, what causes the gravity (and it's effects on the passage of time from an objective observer's viewpoint) of the earth to be exactly how it is? The spin of the earth? It's rotation around the greater gravitational pull of the sun? Our solar system's rotation around the center of the galaxy? The mass of the earth?

-Is there a theoretical 'anti-gravity' environment in which time would actually 'speed' up significantly? What is the difference in time between the earth's environment and a true Zero-G environment?

-Inversely, could gravity be so great that time would literally stop? Or move in reverse? I realize we don't really have any way of knowing what happens in a singularity, but is there any theory that substantially supports such an idea? Since light cannot escape a black hole, I imagine there must be an environment where 'time' cannot escape either?

-Light: If it's measured rate of speed is constant from any viewpoint, what about two light beams coming at each other from opposite directions? Their rate of speed relative to each other isn't 2x the speed of light? The fuck?

---------- Post added at 10:08 PM ---------- Previous post was at 10:05 PM ----------

Tertiary question: If time in a universe moved in reverse from the viewpoint of another universe, wouldn't that mean that cause and effect are really just the same thing? Like, a being in such a universe wouldn't perceive it as 'backwards'.

[Aerozord]

Keep in mind I was studying engineering which didn't get into astrophysics, so this is stuff I learned on my own not through formal education so take it as you will.


-It's also said that moving near the speed of light (or at any velocity greater than the observer's) would cause time to 'slow'. Am I right in understanding that this is due to the greater gravitational forces being invoked due to the greater speed of the mass in question?

No this is a different phenomenon that just has the same effect. Though through inductive reasoning the effect might be caused by an objects mass affecting space-time but since the initial mass of the accelerating object doesn't affect the degree of dilution I dont think they are related.

-This may be mathy, however; How would one (simply) calculate or estimate how much 'faster' or 'slower' time moves at different speeds or in different gravitational environments (like the sun vs the earth, or 1/2 the speed of light vs 99% the speed of light, etc)

I'm too sleepy to check, so I hope someone has the actual formulas but I think if you apply the acceleration formula for relativistic speeds it is proportional to that.

-Also, how much does speed effect gravity, or how do these forces interact? For example, what causes the gravity (and it's effects on the passage of time from an objective observer's viewpoint) of the earth to be exactly how it is? The spin of the earth? It's rotation around the greater gravitational pull of the sun? Our solar system's rotation around the center of the galaxy? The mass of the earth?
like I said the speed and gravity effects are independent, if you mean because speed increases mass. For celestial bodies they are, as a rule, moving far too slow for their kinetic energy to have a noticeable affect on their mass. In otherwords an objects stationary mass will overwhelmingly affect its gravity.

-Is there a theoretical 'anti-gravity' environment in which time would actually 'speed' up significantly? What is the difference in time between the earth's environment and a true Zero-G environment?
significantly? No. We know this affect happens thanks to time keeping devices but its so minor we humans cannot even perceive it.

-Inversely, could gravity be so great that time would literally stop? Or move in reverse? I realize we don't really have any way of knowing what happens in a singularity, but is there any theory that substantially supports such an idea? Since light cannot escape a black hole, I imagine there must be an environment where 'time' cannot escape either?
Gravity? I dont believe so. If you somehow moved faster than the speed of light time would reverse, but good luck with that. And I dont mean like with wormholes I'm saying if you did it by actually somehow accelerating faster than light.


-Light: If it's measured rate of speed is constant from any viewpoint, what about two light beams coming at each other from opposite directions? Their rate of speed relative to each other isn't 2x the speed of light? The fuck?
its constant in a vacuum in relation to a stationary observer. Its not constant to a moving observer or if the source is moving but the observer stationary. Look up the doppler effect.

Tertiary question: If time in a universe moved in reverse from the viewpoint of another universe, wouldn't that mean that cause and effect are really just the same thing? Like, a being in such a universe wouldn't perceive it as 'backwards'.
as a thought experiment. Yes cause and effect if reversed would be seen that way.

Although this is my own crazy ramblings, but my view of temporal continuity is that cause and effect are independent of chronological events. I describe it as watching a train go by. Someone pushes a button that turns on a light in the front. The observer would see a light turning on and then the button being pushed. To them the light turned on first even though objectively the button was pressed first.

[Amake]

For your second question, I haven't actually looked into it at all, but it seems logical a body's movement through time would be directly opposed to its movement through space, that is, since the equator of the Earth is moving at about 1666 km/h faster than the poles you'd gain something like one second in twenty or thirty years, whereas if you moved at 10% of the speed of light you'd have 10% slower time relative to wherever you were moving from, and so on as you approach the speed of light and get ever slower in time.

And you'd simply extend that to gravity by counting how fast a body would move on, for instance, the earth's surface if the earth's surface wasn't there to block that movement. Now you'd think the familiar formula of 9.8 meters per second per second would help, though it's probably not that simple. But it's plain to see we're not getting any relativistic speeds from the gravity of any regular heavenly bodies. I'd be curious about a black hole.

Now for some crazier ramblings, I was thinking about how our understanding of light is that it changes from a quantum wave-or-particle state to either a wave or a particle if observed by a conscious observer. Moving at the speed of light, as light does, one perceives perfectly frozen time and cannot possess consciousness. If light was conscious of itself it wouldn't reach that quantum state and probably wouldn't work anything like light as we know it. Besides having mass, it could be having consciousness that keeps us from light speed travel; maybe the light of consciousness and the light of the stars are mutually exclusive, singular sides of a quantum dual state coin.

[Sithdarth]

Ok this might take awhile but here goes:

Gravity curves/ contracts space-time, or rather, gravity IS the curvature of space-time. Time 'slows down' in the vicinity of gravitational bodies like the earth, sun, or at the very extreme, black holes, and inversely moves faster in low gravity (or '0' gravity, if there is truly such a thing) environments.

The number one fundamental thing to remember about either special or general relativity is that things are usually relative to other things. To put it another way phrases like "time 'slows down' in the vicinity of gravitational bodies" are better phrased more like "the tick rate of a clock near a large gravitational mass will be less (the clock is ticking slower) relative to an identical clock far from any gravitational mass."

It's also said that moving near the speed of light (or at any velocity greater than the observer's) would cause time to 'slow'. Am I right in understanding that this is due to the greater gravitational forces being invoked due to the greater speed of the mass in question?

This line of reasoning would lead you to conclude that a fast enough object would eventually have enough mass to become a black hole. This cannot happen simply because it would cause a paradox as the object would be traveling slow enough in some inertial frames that it could not collapse into a black hole. So observers in those frames would have a totally different reality which cannot happen. The only way to keep the black hole collapse and remove the paradox is to postulate a universal rest frame which violates relativity. Which is a sort of hand wavy argument that says high relative velocity doesn't necessarily mean more gravitation. In reality it just means different gravitation.

Also, special relativistic effects are purely an effect of the need to keep the speed of light constant and the laws of physics the same in all inertial frames. Anything beyond that is pretty much basically speculation.

-This may be mathy, however; How would one (simply) calculate or estimate how much 'faster' or 'slower' time moves at different speeds or in different gravitational environments (like the sun vs the earth, or 1/2 the speed of light vs 99% the speed of light, etc)


At what distance from the Earth/Sun? You need at least some idea of the actual conditions. The equations can be somewhat simple for simple cases but can also get very complicated for complicated cases.

-Also, how much does speed effect gravity, or how do these forces interact? For example, what causes the gravity (and it's effects on the passage of time from an objective observer's viewpoint) of the earth to be exactly how it is? The spin of the earth? It's rotation around the greater gravitational pull of the sun? Our solar system's rotation around the center of the galaxy? The mass of the earth?

1) All those motions you listed will only change how someone not undergoing those motions would see our time and each motion would have a unique and independent effect. Again relativity usually means you need at least two frames of references.

2) Speed (or even velocity) is not a force. As for the exact way in which relative velocity impacts observed gravitation that is very complicated and beyond my current knowledge to do anything quantitative. I do know however that it isn't anything like simply plugging in the relativistic mass for the rest mass and then calculating the new gravitational attraction. Its much closer to how the electric field of an electron moving relative to you looks different than one that is stationary relative to you but even that is a rather poor analogy.

3) Earth's gravity is what it is because of the Earth's mass and the effects of that mass on spacetime. Any explanation beyond that is outside the realm of general relativity and thus pure speculation.

-Is there a theoretical 'anti-gravity' environment in which time would actually 'speed' up significantly? What is the difference in time between the earth's environment and a true Zero-G environment?

Theoretically speaking any curvature of spacetime that is opposite the curvature caused by gravity is "anti-gravity" in a sense. It would probably cause a clock to tick faster relative to an identical clock in flat spacetime. The time difference between say the surface of the Earth at the equator and truly flat spacetime is pretty much insignificant unless you're trying to keep some GPS clocks synced to an absurd number of decimal places over several days.

-Inversely, could gravity be so great that time would literally stop? Or move in reverse? I realize we don't really have any way of knowing what happens in a singularity, but is there any theory that substantially supports such an idea? Since light cannot escape a black hole, I imagine there must be an environment where 'time' cannot escape either?

1) Time is not a thing like light. Time is a dimension. The stoppage of the passage of time probably doesn't ever happen because it would require physically measurable quantities to become infinity and physics just doesn't work if physically measurable quantities become infinite because you can't measure something that is infinite.

2) The kinds of intense gravitational fields you are talking about are beyond even the applicability of general relativity. General relativity is predicated on the assumption that you can always divide space into small enough chunks such that each chunk itself is basically flat. However, once fields get strong enough that basically becomes impossible and then you need a new theory which will probably include quantum mechanics.

-Light: If it's measured rate of speed is constant from any viewpoint, what about two light beams coming at each other from opposite directions? Their rate of speed relative to each other isn't 2x the speed of light? The fuck?


What do you mean by "Their rate of speed relative to each other?" If you mean something like the speed of the second light beam in the rest frame of the first light beam then your question is nonsense. The speed of light in a vacuum is the same in all inertial frames and therefore there exists no rest frame for light. Therefore you can't even pose that question as it is a non-sequitur and there is no answer.

If you mean the speed at which the two beams are seen to approach each other by an observer in a third reference frame that is not at rest with respect to either beam than the answer is simple. The closing speed of the beams is twice the speed of light. This is not a real speed of a physical object but a measure of the rate at which the distance between them shrinks and as such the speed of light restriction does not apply. This argument holds even for massive particles moving at say 99% the speed of light. However, in that case each particle does have a rest frame and the speed of the other particle in that rest frame will be less than the speed of light in a vacuum and given by the relativistic addition of velocities formula.

Tertiary question: If time in a universe moved in reverse from the viewpoint of another universe, wouldn't that mean that cause and effect are really just the same thing? Like, a being in such a universe wouldn't perceive it as 'backwards'.

That question probably doesn't have an answer and won't have an answer until we have a grand unified theory that explains why the arrow of time in our universe points the way it does.

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its constant in a vacuum in relation to a stationary observer. Its not constant to a moving observer or if the source is moving but the observer stationary. Look up the doppler effect.

The speed of light in a vacuum is constant relative to any movements of either the observer relative to the source or the source relative to the observer. The doppler effect and the relativistic doppler effect only affect the frequency of the light not the speed of its propagation.

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For your second question, I haven't actually looked into it at all, but it seems logical a body's movement through time would be directly opposed to its movement through space, that is, since the equator of the Earth is moving at about 1666 km/h faster than the poles you'd gain something like one second in twenty or thirty years, whereas if you moved at 10% of the speed of light you'd have 10% slower time relative to wherever you were moving from, and so on as you approach the speed of light and get ever slower in time.

Relative to what? You've postulated a preferred stationary rest frame (or aether) without realizing it. Such a thing is contrary to all observations.

And you'd simply extend that to gravity by counting how fast a body would move on, for instance, the earth's surface if the earth's surface wasn't there to block that movement. Now you'd think the familiar formula of 9.8 meters per second per second would help, though it's probably not that simple. But it's plain to see we're not getting any relativistic speeds from the gravity of any regular heavenly bodies. I'd be curious about a black hole.

Sorry but this is pretty much nonsense.

Now for some crazier ramblings, I was thinking about how our understanding of light is that it changes from a quantum wave-or-particle state to either a wave or a particle if observed by a conscious observer.

Nothing like this ever happens. For starters there is no such thing as a particle state. In reality its just another wave with particle like behavior, essentially because it is a very narrow wave packet that is localized enough that it looks to our instruments like a particle. Further, the change between particle like and wave like behavior does not require any conscious observation at all.

Moving at the speed of light, as light does, one perceives perfectly frozen time and cannot possess consciousness.

This is nonsense for reasons I've touched on above. To elaborate further the Lorentz transforms only work when transforming one inertial rest frame into another inertial rest frame. Since light does not have an inertial rest frame the Lorentz transforms cannot be used to predict what one would experience in the inertial rest frame of light. One cannot describe something that does not physically exist and expect the description to have any relation to physical reality. Further, if what I said above wasn't the case the key point of the Lorentz transforms is that you as an observer never notice the tick rate of your clock change. It is always the tick rate of other clocks not at rest that slows relative to your clock. Therefore the statement that "one perceives perfectly frozen time and cannot possess consciousness" is not even consistent with what the Lorentz transform would predict if using them didn't result in nonsense.

If light was conscious of itself it wouldn't reach that quantum state and probably wouldn't work anything like light as we know it. Besides having mass, it could be having consciousness that keeps us from light speed travel; maybe the light of consciousness and the light of the stars are mutually exclusive, singular sides of a quantum dual state coin.

This is of course also nonsense largely because of having been predicated on the proceeding nonsense.

[BitVyper]

So if someone were to travel to Earth from near the centre of the galaxy at near light speed, after detonating a bomb made out of Jupiter to kill all the space monsters, would it take considerably longer for them to reach Earth from the perspective of someone on Earth than from their own perspective?

I ask this because it is very important to me that my cartoons about defeating monsters with hard work and guts use relativity correctly.

Edit: Also they are travelling away from a giant black hole that their bomb made.

[Nique]

In reality it just means different gravitation.

So does this mean that mass at or near light speeds would, in theory, still curve space-time in some way due to it's velocity?

At what distance from the Earth/Sun? You need at least some idea of the actual conditions. The equations can be somewhat simple for simple cases but can also get very complicated for complicated cases.

Well, just for simplicity's sake, I guess we could take the standard '1G' of earth's surface and extrapolate from there? It sounds like from your explanation though that even an environment with literally no gravity would have time moving at a comparable, only marginally faster pace, which definitely answers a few of my questions.


Theoretically speaking any curvature of spacetime that is opposite the curvature caused by gravity is "anti-gravity" in a sense. It would probably cause a clock to tick faster relative to an identical clock in flat spacetime. The time difference between say the surface of the Earth at the equator and truly flat spacetime is pretty much insignificant unless you're trying to keep some GPS clocks synced to an absurd number of decimal places over several days.

Are there such curvatures?


What do you mean by "Their rate of speed relative to each other?" If you mean something like the speed of the second light beam in the rest frame of the first light beam then your question is nonsense. The speed of light in a vacuum is the same in all inertial frames and therefore there exists no rest frame for light. Therefore you can't even pose that question as it is a non-sequitur and there is no answer.

Maybe the phrasing used by others is confusing me - But I thought that light measured from any point at any speed came out to the same (299,792,458 meter's p/ sec?)

I guess what I mean is - Isn't it true that the relative velocity of light is the same from any reference point, even one traveling at 99% the speed of light? Do we know why this is the case?

[Sithdarth]

So if someone were to travel to Earth from near the centre of the galaxy at near light speed, after detonating a bomb made out of Jupiter to kill all the space monsters, would it take considerably longer for them to reach Earth from the perspective of someone on Earth than from their own perspective?

I ask this because it is very important to me that my cartoons about defeating monsters with hard work and guts use relativity correctly.

Edit: Also they are travelling away from a giant black hole that their bomb made.

Pretty much yes. The people back on Earth would say it took them probably millions of years or something and on the spaceship they would say it took decades or something. It all depends on the exact distance and relative velocity. Though a bomb that size would produce a pulse of light strong enough to be pretty deadly even at great distance and would probably have killed everyone on the ship.

So does this mean that mass at or near light speeds would, in theory, still curve space-time in some way due to it's velocity?

I don't know enough to give a very definitive answer but I'm pretty sure the curvature of a mass in relative motion would look a lot like the curvature of the same mass at rest with some modifications that depend on relative velocity. The actual form of those modifications I do not know but it definitely isn't just plugging in some extra mass based on relative velocity.

Well, just for simplicity's sake, I guess we could take the standard '1G' of earth's surface and extrapolate from there? It sounds like from your explanation though that even an environment with literally no gravity would have time moving at a comparable, only marginally faster pace, which definitely answers a few of my questions.

This is a pretty good answer. (http://en.wikipedia.org/wiki/Gravitational_time_dilation#Outside_a_non-rotating_sphere) You might want to try reading the whole page.

Are there such curvatures?

I think that is still up for debate. I'm not sure if anyone has observed them but there is a guy at NASA working on warp drives that may one day confirm that such curvatures are possible. (You need them for warp drives to work.)

Maybe the phrasing used by others is confusing me - But I thought that light measured from any point at any speed came out to the same (299,792,458 meter's p/ sec?)

I guess what I mean is - Isn't it true that the relative velocity of light is the same from any reference point, even one traveling at 99% the speed of light? Do we know why this is the case?

What you say is true with the caveat that the speed of light has to be measured in a vacuum and in a valid inertial reference frame. This specifically excludes talking about the speed at which one would measure a second photon moving when at rest with respect to a first photon because there is no such thing as a valid inertial reference frame that is at rest with respect to any photon. Basically special relativity only works for things with a rest mass.

The other side of that is purely geometrical things like the rate at which two objects are seen to approach each other by an observer in relative motion to both objects or the speed of a laser spot (not the photons but the visible reflection spot you make your cat chase) are not limited to the speed of light because they are not real physical objects. Though the closing speed of two objects (the first thing I mentioned) is limited to 2 times the speed of light by the limitation on the speeds of the two objects by special relativity.

As to why the speed of light is constant for all inertial observers there is no answer to that question in special relativity. There is no answer specifically because one of the axioms from which the entire theory is derived is that the speed of light is constant for all inertial observers. In short, the theory started with the assumption that all inertial observers will measure the same speed of light and therefore cannot explain why that is true. An answer would have to come from another theory that doesn't start with that axiom but such a theory might not exist.

In truth you can say something like the constant speed of light is an extension of the idea that the laws of physics must be identical in all inertial frames but that is usually not very satisfying. If you look at Maxwell's equations of electrodynamics one of them actually is an expression which gives the speed of light in any material including the vacuum. This relation does not depend on any relative velocity which was sort of a hint to scientists at the time that anyone in any arbitrary inertial frame had to measure the speed of light in a vacuum to be the same as anyone in any other different arbitrary inertial frame. So I guess that best answer is that all inertial observers measure the speed of light in a vacuum to be the same because they have to or physics doesn't work.