The "Time" thread.

[Neogaia777]

If you don't recognize the "delta" symbol in "delta tee", then perhaps you are dabbling in something you are not prepared to understand. "Delta" in standard mathematical and physical notation stands for a difference. In this case "delta t" means a difference in time between two events. They combine into one symbol and there is multiplication involved.

Take care and be prepared.

Everywhere in the universe is the same age, or is all in or at it's same equal now everywhere, is it not? And the only difference is only in what can be seen, correct? And nothing changes the current now for anybody wherever anyone is at, correct? But the only difference, or the only thing that changes, is only in what can be seen from being at a distance from one another, or from the other one, and that is the only thing that changes, correct? So that what you are seeing of the other one, is never of them in their now, correct? Because no one's now, actually ever changes, correct?

Take Care/God Bless.

 

[BeyondET]

Time is an illusion .... outside of planet earth there is no time

Time is a function of our relationship with the physical world and although we might rely on it in our everyday lives, it does not exist outside us. Like a ruler or a weighing scale, clocks offer us merely a symbol of reality, not reality itself.

So death or aging is just an illusion of a period of time? My body seems to tell me differently.

 

[Neogaia777]

I don't think the alien's now changes just because he changed from being stationary to being in motion, etc, and I don't think the man's now changes just because the alien's view of him temporarily changes, etc. And I don't think the time when something sent from the alien to the man would change, or changes, just because the alien's view of the man temporarily changes, etc.

Take Care/God Bless.

 

[SelfSim]

So death or aging is just an illusion of a period of time? My body seems to tell me differently.

Time is our theoretical explanation for the kind of death you're observing there.

Time is a necessary ingredient of the theory that correctly describes what we observe ... and thus, is objectively real, in science.

 

[BeyondET]

Time is our theoretical explanation for the kind of death you're observing there.

Time is a necessary ingredient of the theory that correctly describes what we observe ... and thus, is objectively real, in science.

Just like an atomic clock, time based on an actual event that takes place in certain atoms.

 

[SelfSim]

Just like an atomic clock, time based on an actual event that takes place in certain atoms.

Yes .. the transition frequency there, is operationally measurable and therefore is objectively real in science.
This is critical for us to make (scientific) sense of the notion of atoms having discrete energy levels.
We go further and use this as the basis of meaning behind 'what a second is'.

 

[BeyondET]

Yes .. the transition frequency there, is operationally measurable and therefore is objectively real in science.
This is critical for us to make (scientific) sense of the notion of atoms having discrete energy levels.
We go further and use this as the basis of meaning behind 'what a second is'.

Indeed like in the beginning time frequency was created. It is what we call the universe.

 

[SelfSim]

Indeed like in the beginning time frequency was created. It is what we call the universe.

No .. the human mind invented all the meanings behind all the terms you're using there. They're all our meanings. Its just what our minds do and have been doing all along .. and there's abundant evidence supporting that.
There's no objective evidence for the notion that any of those things were 'created' independently from what us humans have been doing in order to make sense of our own perceptions.

 

[Neogaia777]

I have a question or two that I'm wondering if someone more knowledgeable can answer for me?

We know that time, and the flow of time is a real thing, and that at most places and situations in the universe, it varies most of the time only slightly, but that it does vary a little bit almost everywhere depending on the things situation and/or conditions or circumstances, etc.

But I'm wondering if it varies say for planets/moons/solar systems/galaxies slightly, etc, and if it does, could that make something like planetary orbits slower or faster in some places, or maybe solar systems aging or traveling through a galaxy slower or faster or something, or galaxies moving through the universe faster or slower or something? Anyway, because they are all moving, and all have, or are affected by some gravity, or each have their own unique gravity wells and gravitational pulls in different places, etc, could planetary orbits be faster or slower slightly, or could a solar system be aging or moving slower or faster through a galaxy maybe or something? Or maybe galaxies moving around/through/about the universe maybe or something, etc?

Anyway, does the speed or gravity of these things affect them slightly to where it might make them in a different time slightly, or age or move slower or faster in their orbits or in their moving or aging maybe?

We know it's only very drastic when the speed or gravity is only very, very fast or very, very strong, etc, but could these other things be affected slightly by weaker forces/effects maybe, to where they might maybe age differently maybe? Or be in a slightly different time, or flow of time maybe? But that effects whole planets, or galaxies, or star systems, or something like that maybe?

Much thanks.

Take Care/God Bless.

 

[sjastro]

I have a question or two that I'm wondering if someone more knowledgeable can answer for me?

We know that time, and the flow of time is a real thing, and that at most places and situations in the universe, it varies most of the time only slightly, but that it does vary a little bit almost everywhere depending on the things situation and/or conditions or circumstances, etc.

But I'm wondering if it varies say for planets/moons/solar systems/galaxies slightly, etc, and if it does, could that make something like planetary orbits slower or faster in some places, or maybe solar systems aging or traveling through a galaxy slower or faster or something, or galaxies moving through the universe faster or slower or something? Anyway, because they are all moving, and all have, or are affected by some gravity, or each have their own unique gravity wells and gravitational pulls in different places, etc, could planetary orbits be faster or slower slightly, or could a solar system be aging or moving slower or faster through a galaxy maybe or something? Or maybe galaxies moving around/through/about the universe maybe or something, etc?

Anyway, does the speed or gravity of these things affect them slightly to where it might make them in a different time slightly, or age or move slower or faster in their orbits or in their moving or aging maybe?

We know it's only very drastic when the speed or gravity is only very, very fast or very, very strong, etc, but could these other things be affected slightly by weaker forces/effects maybe, to where they might maybe age differently maybe? Or be in a slightly different time, or flow of time maybe? But that effects whole planets, or galaxies, or star systems, or something like that maybe?

Much thanks.

Take Care/God Bless.

Here is the answer I gave in another thread complete with mathematics why time dilation is a local not a global effect.

This is where a knowledge of mathematics is essential to understand why time dilation due to gravity is a local effect and not a universal effect.
The Schwarzschild metric describes the local curvature of space due to gravity and time dilation due to gravity is determined as follows:

This equation shows if M/r₂ > M/r₁ then dτ₂ < dτ₁ where the clock at r₂ shows a smaller reading than the clock at r₁ in a given interval dt.
This is interpreted to mean the clock at the smaller radius runs more slowly than the other as it sits deeper in the gravitational field.
Note that r₁ and r₂ represent local scales not cosmological scales.

 

[Neogaia777]

Andanother question maybe?

If you put a very strong gravitational pull in front of some photons traveling at the speed of light, will they start to move faster than the speed of light? Or if you put it behind them, will they go slower than the speed of light? I know, photons don't have mass, right. But why then are they affected by strong gravitational pulls like black holes in other ways then, etc? If they have no mass at all, then they shouldn't be affected those things at all, right?

Then as to my previous questions in my post above this one, if a locale like a whole solar system can age faster or slower, then is light affected by that change in time as it goes or passes through it, or is sent from it, etc?

Much thanks.

Take Care/God Bless.

 

[Neogaia777]

Here is the answer I gave in another thread complete with mathematics why time dilation is a local not a global effect.

Are there varying opinions on this?

Much thanks.

Take Care/God Bless.

 

[SelfSim]

Are there varying opinions on this?

Much thanks.

Take Care/God Bless.

I hope you also get that the proper time, 'τ' (tau), is the time measured by a clock in a rest frame. So, if we describe the clock as not being in motion, then the time it measures is the proper time. Regardless of the speed, or position of other observers, proper time, or the time measured by an observer moving along with a clock, is always the same(?)

 

[sjastro]

Andanother question maybe?

If you put a very strong gravitational pull in front of some photons traveling at the speed of light, will they start to move faster than the speed of light? Or if you put it behind them, will they go slower than the speed of light? I know, photons don't have mass, right. But why then are they affected by strong gravitational pulls like black holes in other ways then, etc? If they have no mass at all, then they shouldn't be affected those things at all, right?

Then as to my previous questions in my post above this one, if a locale like a whole solar system can age faster or slower, then is light affected by that change in time as it goes or passes through it, or is sent from it, etc?

Much thanks.

Take Care/God Bless.

Light doesn't speed up or slow down in a gravitational field, it is deflected in a gravitational field as has been observed in solar eclipses.
The light follows the path in a gravitational field known as a null geodesic.

Once again the mathematics shows how light travels along null geodesics as explained in another thread.

The results were good enough to provide the one of the first verifications of general relativity.
In this post the differential equation for the perihelion advance of Mercury's orbit from Schwarzschild's metric was found to be.

Since light travels on a null geodesic ds = 0, the first term on the right hand side of the equation vanishes and the equation reduces to;

A solution for this equation is;

u = sin ϕ/R + [(3MG)/c²R²](1 + 1/3cos 2ϕ)

where R and M are the radius and mass of of the Sun respectively.

For a light ray grazing the Sun;

When r is large, ϕ becomes small and sin ϕ ≈ ϕ, cos 2ϕ ≈ 1.

For the limit u → 0 (or r → ∞), ϕ → ϕ∞ where ϕ∞ = -2MG/c²R.

The total deflection is therefore 4MG/c²R.

Plugging in the values M, G, c and R gives the total deflection of 1.75” which agrees with Eddington’s result.

These days in order to obtain extreme high precision in astrometry the gravitational effects on light need to compensated for as was done during the Hipparcos mission.

 

[Neogaia777]

I hope you also get that the proper time, 'τ' (tau), is the time measured by a clock in a rest frame. So, if we describe the clock as not being in motion, then the time it measures is the proper time. Regardless of the speed, or position of other observers, proper time, or the time measured by an observer moving along with a clock, is always the same(?)

Wouldn't the flow rate of time be different for an observer and a clock that was truly at rest, versus an observer and a clock that was moving? (Or was very close to a strong gravitational pull or well, etc)?

If so, which would be the correct time, etc?

 

[Neogaia777]

Light doesn't speed up or slow down in a gravitational field, it is deflected in a gravitational field as has been observed in solar eclipses.
The light follows the path in a gravitational field known as a null geodesic.

Once again the mathematics shows how light travels along null geodesics as explained in another thread.

Is the light being deflected, or is it being pulled on by gravity, or is it really just following a straight line through spacetime, etc?

Why does light get either trapped along the event horizon of a black hole, or sucked into a black hole, etc?

And finally, does light's course get changed by gravity wells or pulls as it is traveling through spacetime by these things, etc?

Much thanks.

Take Care/God Bless.

 

[SelfSim]

Wouldn't the flow rate of time be different for an observer and a clock that was truly at rest, versus an observer and a clock that was moving? (Or was very close to strong gravitational pull or well, etc)?

If observer A and their clock are in the same frame, then observer A measures the proper time.
There is no such thing as 'truly at rest'.

 

[Neogaia777]

If observer A and their clock are in the same frame, then observer A measures the proper time.
There is no such thing as 'truly at rest'.

But everything is in motion though, and is also usually somewhat close to a gravitational pull, so what makes observer A and their clock in their frame, any more or less correct than observer B and his clock in his frame, that either may or may not be moving and faster or slower than observer A, or might or might not be, close or not close to, etc, a strong gravitational pull or not also, etc? (As compared to observer A, etc).

Whose is correct or not correct, etc?

Take Care/God Bless.

 

[SelfSim]

But everything is in motion though, and is also usually somewhat close to a gravitational pull, so what makes observer A and their clock in their frame, any more or less correct than observer B and his clock in his frame,

Nothing .. 'correct' is not the concept of proper time, (nor is it the point I made).

.. Whose is correct or not correct, etc?

Ok .. I'll go along with the 'correct' thing here .. they are both 'correct'.

 

[sjastro]

Is the light being deflected, or is it being pulled on by gravity, or is it really just following a straight line through spacetime, etc?

Why does light get either trapped along the event horizon of a black hole, or sucked into a black hole, etc?

And finally, does light's course get changed by gravity wells or pulls as it is traveling through spacetime by these things, etc?

Much thanks.

Take Care/God Bless.

As explained the light is travelling along a null geodesic path which results in it being deflected in the gravitational field of the object.
Space-time around the object is curved and the light trajectory follows this geodesic path which is the shortest distance travelled.

In the case of the black hole, referring back to the maths in post #70.

If r₂ is the event horizon of a black hole then r₂ = 2MG/c², the denominator of the equation equals zero and the ratio of the proper time intervals dτ₁/dτ₂ becomes infinitely large.

This corresponds to a object stuck on the event horizon emitting photons away from the event horizon but taking an infinite amount of time to reach the external observer.

When an object or observer reaches a black hole’s event horizon and passes through it is curtains and can never reemerge.
This can be explained with a Minkowski space-time diagram.

The observer’s present time and location is where the observer’s past and future light cones meet.
The region inside the past light cone is where events have occurred in the observer’s past and events which will happen in the observer’s future fall inside the future light cone.

As the observer approaches the event horizon the light cones narrow due to gravitational time dilation and when it passes inside the event horizon at r = rₛ the time like and distance like terms in the Schwarzschild metric are interchanged.
Geometrically the light cones “tip over” and the singularity is in the observer’s future light cone and the event horizon is in the observer’s past light cone.

To travel back towards the event horizon requires the observer to travel back into his past which needless to say is impossible.