That Time Problem??

[LJP07]

You'd often see in textbooks and even in internet articles that common fact that clocks move at different rates, one up in space and one on Earth etc. But how can a mechanical clock move slower or quicker or time move slower or quicker, even as an educated person in science, I can't seem to fathom such a simple problem?

 

Plus, if time moves at different rates, and you go further and further into space, aren't you effectively heading into the future and likewise if time moved slower you'd be heading into a "Past" sense??

[sanctus]

You are actually heading to the future. think of the twin paradox, the one who goes to space and comes back is in a future earth on which he wouldn't have been otherwise.

[Jet2]

I think Space has its own time standard / concept which should be different from ours on Earth and that was something we don't know yet or may not be able to know easily. After all Science is not a 'All Can Do' thing.

[CHADS]

Look at gravity potentials too ... but the doppler effect in the twin paradox will give you the general overveiw.

 

Its basicaly like the faster you go the more you move into suspended animation in comparison to the comparible clock on earth i think.

[Shubee]

How can a mechanical clock move slower or quicker or time move slower or quicker, even as an educated person in science, I can't seem to fathom such a simple problem?

 

You need to add one curious fact. Forgetting gravity for a second, the slowing down and quickening of time works in such a way such that the measuring of these effects are the same everywhere in the universe. Also, the effect is exactly the same no matter how fast you’re traveling through space. In a sense, all the laws of physics are conspiring against us. This is called the principle of relativity. The outcome of all tests on moving clocks are independent of our location and velocity through space.

 

The mathematics of the time dilation effect is contained in the Lorentz transformation equations. If you have mastered high school algebra, then you can begin to understand the physics. See A Derivation of the Lorentz Transformation From a Simple Definition of Time.

[Becca]

Didn't somebody do this with atomic clocks? There was one stationary and one was accelerated to high speeds on some sort of (monorail style) track. The two clocks recorded different durations for the moving clock's trip. The difference was very small but thought to be accurate because of the nature of the clocks. Can anybody back me up on this?

 

Becca

[HydrogenBond]

Times is always moving forward but can move forward at different rates depending on the reference. Time dilation means the flow of time has slowed in that reference. But it is still moving forward. This is easier to explain if you look at time as a type of potential. Relative to the twin paradox, we give them both a gallon of time potential. The one on the stationary reference drinks faster. The one on the moving reference drinks slower (time dilation) so when he returns to earth he has extra left over.

 

Time potential is not a established concept. The alternative never seems to create a meeting of minds for many because it gets too abstract. It require too many assumptions. Time potential only needs one assumption.

[freeztar]

Can anybody back me up on this?

 

Becca

 

Perhaps you're thinking of the Hafele-Keating experiment?

[InfiniteNow]

Hi Becca,

 

I haven't heard of it being done on trains (this does not, however, mean that it has not, just that I haven't heard of it). It has, however, been done on planes (specifically, as Freezy mentioned with the Hafele-Keating experiment).

 

 

YouTube - Time dilation experiment http://www.youtube.com/watch?v=gdRmCqylsME

 

 

 

Also, automobiles. :rolleyes:

 

 

 

 

This site does a quick, but accessible, overview:

 

ticks 'n bricks

[Southtown]

At present time, to me time is the flip-side of the space coin. Space is the distance between locations, and time is the distance between moments, however dynamic the relation amongst the things about which we know very little may be.

 

But the guy was asking about gravity. How could time pass by differently in orbit than it does on the surface. I can't answer, so I share in his desire to realize such an explanation.

[InfiniteNow]

But the guy was asking about gravity. How could time pass by differently in orbit than it does on the surface. I can't answer, so I share in his desire to realize such an explanation.

 

It's more about gravitational potential.

 

Try starting here, and then come back with a more specific question. :rolleyes:

 

Gravitational time dilation - Wikipedia, the free encyclopedia

[modest]

At present time, to me time is the flip-side of the space coin. Space is the distance between locations, and time is the distance between moments, however dynamic the relation amongst the things about which we know very little may be.

 

But the guy was asking about gravity. How could time pass by differently in orbit than it does on the surface. I can't answer, so I share in his desire to realize such an explanation.

 

According to the equivalence principle of general relativity there is no descriptive difference between an accelerating frame of reference and a stationary frame in the presence of a gravitational field.

 

This means a person on a rocket ship with constant acceleration will feel like they are standing on the surface of a planet. In either case a person feels weight. Also, someone in an elevator that is free falling toward a massive body like earth will feel weightless just like someone who is stationary in deep space outside the influence of any gravitational field.

 

In fact, general relativity proposes that someone who conducts experiments of special relativity in a free falling elevator will get the same results as someone who does the same experiments in a stationary elevator in deep space.

 

This idea can be used to derive all the laws of General Relativity including gravitational time dilation. GR tells us that if we are on earth's surface looking up at a clock higher in the gravity well then the clock will appear to run faster than our clock.

 

To derive this with the equivalence principle we must consider what would happen in an accelerating frame (or elevator) with no gravitational field. Let's say we are in a very large elevator and there is a clock on the ceiling. The elevator is undergoing constant acceleration like a rocket. It is in deep space. Every second the elevator goes faster.

 

To make this situation simple we can consider the clock on the ceiling to simply be a strobe that is programmed to blink sixty times per second. Our own clock is also programmed to blink sixty times per second. If you consider this situation you will realize the person on the floor will not see the strobe on the ceiling flash sixty times a second but faster than that. Because the entire elevator is accelerating there is a Doppler-like effect where the strobe flashes are observed more quickly from flash to flash by the time they get to the floor. The change in velocity from the time of emission to observation accomplishes this.

 

The important things are:

1. If the equivalence principle of general relativity is true then the time dilation I just described for our accelerated frame must extend to gravitational potential as well.
   
2. Can this be described mathematically and applied to gravitational fields.

 

Number one has been found true and verified by atomic clocks (such as GPS)

 

Number two - mathematically, a person can use accelerated coordinates such as the Rindler metric:

 

[math]ds^2 = -(1 + gr) dt^2 + dr^2[/math]

 

This can be used to describe the situation above and it can also be used to derive gravitational time dilation and redshift which is done here:

 

Gravitational redshift - Wikipedia, the free encyclopedia

 

So, I believe the reason for gravitational time dilation can be shown as a result of gravity as "curved spacetime". Actually, it was predicted on that basis. Why gravity curves spacetime? :shrug:

 

-modest

[Southtown]

It's more about gravitational potential.

 

Try starting here, and then come back with a more specific question. ;)

 

Gravitational time dilation - Wikipedia, the free encyclopedia

Hmm... ok, why does gravity affect time?

[Southtown]

So, I believe the reason for gravitational time dilation can be shown as a result of gravity as "curved spacetime". Actually, it was predicted on that basis. Why gravity curves spacetime?

 

-modest

Thank you sir for explaining that so eloquently. Ps why the "eye of Ra" in yer sig?

[InfiniteNow]

Hmm... ok, why does gravity affect time?

 

You will have to bear with me. I only learned some more about this yesterday thanks to a post elsewhere by Janus. In other words, I'll try to answer correctly, but may misspeak and my comments should be checked.

 

 

We know that acceleration results in time dilation/length contraction.

We know that gravity is indistinguishable from acceleration.

 

Now, in this example, when time is dilated in one reference frame relative to another, it is because there is greater "gravitational potential."

 

There ya go.

 

 

 

From the wiki link I shared:

 

Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the higher the local distortion of spacetime due to gravity, the slower time passes.

 

<...>

 

Gravitational time dilation is manifested in accelerated frames of reference or, by virtue of the equivalence principle, in the gravitational field of massive objects. In more simple terms, clocks which are far from massive bodies (or at higher gravitational potentials) run faster, and clocks close to massive bodies (or at lower gravitational potentials) run slower.

 

It can also be manifested by any other kind of accelerated reference frame such as an accelerating dragster or space shuttle. Spinning objects such as merry-go-rounds and ferris wheels are subjected to gravitational time dilation as an effect of their angular spin.

 

This is supported by the general theory of relativity due to the equivalence principle that states that all accelerated reference frames possess a gravitational field. According to general relativity, inertial mass and gravitational mass are the same. Not all gravitational fields are "curved" or "spherical"; some are flat as in the case of an accelerating dragster or space shuttle. Any kind of g-load contributes to gravitational time dilation.

[Southtown]

I read that page. And I understand that time dilation happens by either gravitation or acceleration. But the OP asks how it happens mechanically, and I can't answer. I imagine that both acceleration and gravitation act upon atoms in the same manner. Though I admit, the speed of light being observed equally in all inertial frames of reference kinda tweaks my noodle.

[CHADS]

Would I be right in thinking that as an object accelerates its kinetic Energy increases .. and its this Energy which Contributes to its Gravitational potential?

 

So the faster an object travels the more mass it seems to have so gravity and velocity are similar in some fashion?

 

Whilst moving at large velocities or in greater gravitational wells ;The whole clock and its working mechanisms and moments are dimensionally restricted in doing what it would do if it was on earth. The clocks Mechenisms and moments on Earth would be the comparible clock.

 

Now in comparison on Earth to a clock taken away at 90% speed of light Its Mechanisms and moments would be restricted litrally in dimension. Like a funnel .

A snooker ball can whirl around the top of a funnel .. but one that is deeper in the funnel is heavily restricted in its movement and could only make smaller whirls in relation to the ball at the top of the funnel.

 

So when the ball Travelling at 90% C at the bottom of the funnel returns to earth

Which is represented at the top of the funnel It has only been moving at small circles ... in comparison to the clock on earth ... So Shows a lesser time.

 

The ball has mass so cant pass straight through the funnel but a photon is massless and can occupy the stem of the funnel .

 

Hope this Abstract concept helps in explaining something.