# Gravity in classical energy

It's well understood that matter has mass, and more importantly gravity.

I believe I am correct to say that gravity is more like an affect of matter. And not actually part of it. Ie mass bends space time.

As we know that matter (a form of energy) can be converted into other forms of energy (let's say light) then what happens to the gravitational affect that once was?

Is there now no gravity being 'created' by the light? That seems odd. Or is the gravity simply distributed some how.

Additionally if we could convert matter into kenetic energy, then that surly mean that there is no way for the original gravitational quantity to exist?

This then comes down to the question, can gravity be created and destroyed.

And if it cannot be destroyed then that suggests that gravity is slowly migrating to the outer edge of the universe (along with all the other energy)

## 2 Answers

I believe I am correct to say that gravity is more like an affect of matter. And not actually part of it. Ie mass bends space time.

One must be very clear in what framework the question is expressed. You say "classical".

There is classical, as in Newton's classical gravitational theory within classical mechanics.

There is General Relativity which works with the energy momentum tensor. You say "bends" this is within the framework of general relativity. Newtonian gravitation emerges from the general relativity formalism .

As we know that matter (a form of energy) can be converted into other forms of energy (let's say light) then what happens to the gravitational effect that once was?

Now you are mixing in another framework, the quantum mechanical one where there are particles and special relativity four vectors describing the probabilities of interaction in a quanum mechanical formalism.In this framework all matter is made out of particles from the table in the standard model and though energy and momentum are conserved there are transformations allowed that change mass into energy and vice verso.

As General Relativity uses the energy momentum tensor for "creating" the gravitational effect we see, handwaving one can say that since energy and momentum are conserved the long range newtonian gravitational effects will be the same, during the quantum mechanical transformations of masses to energies. Nevertheless, since there is no definitive quantization of gravity, only effective models, this will be an effective answer that may change depending on the final theory of everything. After all there are "holes" in general relativity, frames where energy conservation does not hold. It holds in special spaces that have to be clearly assumed.

Is there now no gravity being 'created' by the light? That seems odd. Or is the gravity simply distributed some how.

In general relativity there is gravitational distortion by light, because light has energy

Additionally if we could convert matter into kenetic energy, then that surly mean that there is no way for the original gravitational quantity to exist

Kinetic energy is part of the four vector describing a particle . Nothing changes in the general relativity frame.

This then comes down to the question, can gravity be created and destroyed.

In some general relativity space times, there is no conservation of energy, and yes energy may be created or destroyed, and the gravitational effect of the four vector will change. Macroscopically in the newtonian framework one can say that gravity was created, as in the hypothesis of the Big Bang model.

And if it cannot be destroyed then that suggests that gravity is slowly migrating to the outer edge of the universe (along with all the other energy)

In the flat spaces of the present universe, energy and momentum are conserved and their gravitational impact is retained though as it expands, according to some models the density of the effect gets smaller and smaller. This is a research project for cosmology.

There is continuity in the overlaps between frameworks, but one cannot throw statements in one bag and mix an indiscriminate cocktail. If you are a student and are wondering about this stuff you should sit down and study the appropriate courses, with a lot of elbow grease and mathematics. If not a student, you should start by reading the links I have provided to really separate the various models of physics.

Simple answer to your question is: We need quantum gravity, Which we dont have that kind of a theory now.

Long answer: You are actually talking about pair production. Pair production is simply converting energy into matter or vica verse. And in this process energy and momentum is conserved.

If we talk about clasical gravity, but not quantum gravity, then theres no meaning in to say what happens to "gravity" in these processes. You cannot attach a gravity to an electron. That is the crucial point actually. You cannot think an electron as a source of gravitational field.

Even if you try to define classically, the field force would be in order of $$10^-22$$ which that is too small and it has no meaning.

The second point is that in QM the electron is just a wavefunction, which means that all particles have wave properities and they act like it. Its the same thing for a photon. Hence we cannot think electrons as small planets and "attach a gravity" to it (or to any kind of particle). Because they are not just particles. Light is aĺso not only a wave but a particle which we call it photon. That is why we need quantum gravity.

In this sense you cannot just simply ask what happens to gravity.