What do you say to this?
The universe is also slowly running out of usable hydrogen. The gas and dust used to form stars is contained in very large and very cold molecular clouds. These clouds need to be “shunted” in order for them to begin to condense down to form more stars. Early in the universe's history these clouds were all over the place and they were immense but now there isn't quite as many, as you would expect. Also as the universe expands the mean density of hydrogen molecules per cubic centimeter decreases.
So with the theories around in relation to this subject, you are probably looking at something like 100–120 trillion years before the last star dies out. This is by no means the end of the universe, only the end of the age of hydrogen fusing stars. There is a lot more to happen before the universe “ends” but that is another story.
Observations suggest that the
expansion of the
universe will continue forever. The prevailing theory is that the universe will cool as it expands, eventually becoming too cold to sustain life. For this reason, this future scenario once popularly called "
Heat Death" is now known as the "Big Chill" or "Big Freeze".
But if it's eternal how is this possible?
If
dark energy—represented by the
cosmological constant, a
constant energy density filling space homogeneously,
[3] or
scalar fields, such as
quintessence or
moduli,
dynamicquantities whose energy density can vary in time and space—accelerates the expansion of the universe, then the space between clusters of
galaxies will grow at an increasing rate.
Redshift will stretch ancient, incoming photons (even gamma rays) to undetectably long wavelengths and low energies.
[4]Stars are expected to form normally for 1012 to 1014 (1–100 trillion) years, but eventually the supply of gas needed for
star formation will be exhausted. As existing stars run out of fuel and cease to shine, the universe will slowly and inexorably grow darker.
[5][6] According to theories that predict
proton decay, the
stellar remnants left behind will disappear, leaving behind only
black holes, which themselves eventually disappear as they emit
Hawking radiation.
[7] Ultimately, if the universe reaches
thermodynamic equilibrium, a state in which the temperature approaches a uniform value, no further
work will be possible, resulting in a final heat death of the universe.
[8]