Why does gravity play a role in the energy of the universe?

[Lacy33]

Why is the energy coming as a result of a Big Bang so explosive as to burst into universe(s)?

How can something coming from nothing have so much energy?

Why is it in physics, the smaller something is the more energy it has?

What is, in physics, the exact moment of an explosion?

Please

 

[Chronos]

Unknown. But fun to speculate.

 

[Garth]

Hi Shoshana!

Why is the energy coming as a result of a Big Bang so explosive as to burst into universe(s)?

How can something coming from nothing have so much energy?

Gravitational energy can be thought of as a negative form of energy, the more you use it the bigger it gets, like my overdraft. The total energy of the universe may well be zero, the positive energy of the matter universe being canceled out by the negative energy of the gravitational field and any Dark Energy lying around.

Why is it in physics, the smaller something is the more energy it has?

Because it is more tightly bound by that energy.

What is, in physics, the exact moment of an explosion?

I take it that you are referring to the 'explosion' of the BB?

It all depends on how you measure it.

You cannot speak of anything unless you have some way of experiencing that phenomenon. In physics we measure and compare observables with some definitive standard, a block of platinum in a Paris safe or a specific emission line of a particular caesium atom for example.

At the earliest moments of the BB there were no such atoms around to define mass, length or time and so these physical quantities have to be carefully extrapolated from regions where they do exist and can be measured, basically that means all the way back to planet Earth.

In order to extrapolate from here to there we have to assume and then define something to be constant over that distance. In GR it is energy-momentum that is conserved and the mass of an atom that is defined thereby to be constant. In so doing the energy of a photon is not conserved and so they show red shift when transmitted from 'there to here'. Defining a second by the 'tick' of an atomic clock one finds the universe appears to have a beginning at the BB, at least according to the standard theory of GR unadulterated by quantum effects. It is not only the beginning of the universe but also the beginning of time as there was no time, i.e. no means of measuring time, at t<0.

However if we take, for example, the frequency (inverse) of a photon as the 'tick' of our clock you find the BB is translated into the infinite past and there was no 'beginning'.

It depends on how you measure it.

Garth

 

[Antiphon]

Gravitational energy can be thought of as a negative form of energy, the more you use it the bigger it gets, like my overdraft. The total energy of the universe may well be zero, the positive energy of the matter universe being canceled out by the negative energy of the gravitational field and any Dark Energy lying around.Because it is more tightly bound by that energy.

Attractive Gravity is a "curvature of space" which indicates the presence of energy.

You may be thinking that an "apple on a planet" has less energy than "apple
far off the planet" which is true for the pair of apple+planet. But the
gravity itself is the indiciation of the presence of positive energy density.