Trillions of years in the future, long after Earth is destroyed, the universe will drift apart until galaxy and star formation ceases.
Slowly, stars will fizzle out, turning night skies black.
All lingering matter will be gobbled up by black holes until there's nothing left..
The ultimate fate of the universe depends on the amount of mass contained within it, that is, the mean density of the universe.
There is a critical density, which if reached will be sufficient to just stop the expansion of the universe..
In the simplest cosmological models, the fate of the Universe depends on its rate of expansion, expressed by the Hubble parameter, and the amount of matter it contains.
Qualitatively, the Hubble constant gives us an idea of the kinetic energy associated with the expansion of space..
Physical cosmology seeks to understand the content of the universe, its history, and its ultimate fate..
The Universe will expand forever: If the mean density is less than the critical density, then there is insufficient mass within the universe to stop the expansion - the universe will expand forever.
Ultimately, the galaxies will move increasingly further apart..
