Big bang and time

[TungstenX]

Good day All,

Our current understanding of time is that it is not linear or constant; just add gravity.

I've heard a lot about the time scale of the big bang. Now do science take into account the vast difference of gravity (concentration of gravity) during the first few minutes of the big bang?

What is the reference point use in measuring the universe's age / time scales? (Earth? - it was not there when all this started)

As the universe expanse, does the universe's average / general time accelerate? (Gravity diluting in space)

Just a few thoughts on time.

Best regards,
TX

[Chalnoth]

Good day All,

Our current understanding of time is that it is not linear or constant; just add gravity.

I've heard a lot about the time scale of the big bang. Now do science take into account the vast difference of gravity (concentration of gravity) during the first few minutes of the big bang?

What is the reference point use in measuring the universe's age / time scales? (Earth? - it was not there when all this started)

As the universe expanse, does the universe's average / general time accelerate? (Gravity diluting in space)

Just a few thoughts on time.

Best regards,
TX
This doesn't make any sense to me. Time isn't a thing that can move or accelerate. Time is a direction of motion.

[granpa]

yes time does dilate in a gravity well and it dilates for rapidly moving objects.
your question is reasonable but I dont know that anyone will be able to answer you.

the 'official' answer is that space wasnt expanding into a pre-existing space and therefore it shouldnt have had a velocity nor should it have experienced any gravity.
but nobody really knows.

[Tanelorn]

An 8 Billion year old alien civilisation may know :)

[Ich]

(Earth? - it was not there when all this started)
Of course it was there. Everything was.
Cosmological time is the proper time measured by observers at rest with, say, galaxies. So every galaxy has its own time, and you define "the universe at cosmological time 13.7 Gy" is the set of all events (at all the galaxies) where the respective proper time since Big Bang is 13.7 Gy. That's just a definition so far.
The remarkable thing is that all these events seem to be simultaneous with their respective neighbouring events. So you can define a reasonable notion of "now", and you find that - using this notion - every component of the universe is of the same age, and born at the same time. That's nontrivial, and the basis of the Standard Model.

Gravitational time dilation uses a different definition of "now". Using this definition, the Big Bang happens now and is ~25 Gly away. That's not "cosmological" time.

[Kevin_Axion]

Time is constant just not with respect to others in motion or those near massive bodies, it is always constant for you though.

[TungstenX]

I don't think time is constant (either is the perception of time). Atomic clocks runs at different times when at different gravities. (gravity field strengths)

[zonde]

I googled "cosmological time" and I found this definition:
"This way there is also cosmological time, which for an observer at a fixed spatial point in comoving coordinates is identical to her local measurement of time."
(Comoving distance (http://www.fact-index.com/c/co/comoving_distance.html))

So it's proper time not coordinate time.
If you would use coordinate time then Big Bang should have happened at infinite past.

[Deuterium2H]

I don't think time is constant (either is the perception of time). Atomic clocks runs at different times when at different gravities. (gravity field strengths)

TungstenX,

The Universe contains Space and Time and does not exist in Space and Time. The central tenant in Cosmology is the Cosmological principle, which states that the Universe is homogeneous and isotropic. All places are alike. A consequence of this principle is that all clocks in the Universe, apart from local irregularities, agree in their intervals of time. This universal time is also known as cosmic time, and departures from cosmic time are caused by local irregularities (e.g. massive, compact objects).

Instead of focusing on time, by itself, one must also incorporate space. The fusion of these two yields an invariant quantity. All space-time intervals are invariant. All observers, independent of their relative motion, will measure the same space-time interval between events.

[universe11]

From where started the Universe in the quantum world?
Started from a volume = mass of the universe divided by Planck density

[Deuterium2H]

From where started the Universe in the quantum world?
Started from a volume = mass of the universe divided by Planck density

The simple answer to where the Universe began is that it began everywhere.