cosmologists think the mass of the universe is not enough to hold stars to forum present galaxies.

we don't even sure if mars has liquid water. how do they know the mass of the universe?

dark matter? dark energy? it is all bs.

NO scientists know what is energy exactly. till now.

energy is vibrating/moving electrostatic force/coulomb force stored within matter/charged particles.

gravity is like water container, water is like energy. bigger mass carries more energy.