I probably learned that back in university when studying general relativity, but I forgot so I want to ask: As far as I understand it, any energy concentration creates a gravitational field, whether that energy is matter, electromagnetism or other energy, right?
The unit of gravity is meters per second^2.
Issac Newton's Law of Universal Gravitation tells us that the force of attraction between two objects is proportional the product of their masses divided by the square of the distance between their centers of mass - but this only accounts for mass and no other energies.
So what I want to ask is: if I add energy to a body not by adding matter but, for example, by heating it up, then based on my understanding the gravitational pull it creates increases too.
But does that also mean that its mass has now increased? Is mass solely defined via the gravitational field generated at a certain distance? Are they equivalent?