Expansion of the universe is set at the correct rate for stability
Summary
- The strength of gravity is set exactly right to ensure that the universe expands in a rate that is conducive to life
Details
- If the strength of gravity was slightly higher, the universe would collapse in on itself. If it was too weak, matter would not be able to form into stars and planets.
References
- Signature in the Cell - DNA and the Evidence for Intelligent Design - Stephen Meyer
- See also Astrophysics: A very short introduction by James Binney
Quotes
A homogeneous universe is called “flat” if it is balanced between eventual gravitational collapse and eternal expansion; in such a case its geometry would be precisely Euclidean and space would not be curved. The universe achieves such flatness when the actual mass density in the universe is very close to the critical mass density (the density required to halt the expansion of the universe)—that is, if the ratio between the actual and critical mass densities is close to one. In our universe, the ratio of these two quantities is ever so slightly less than one. As a result, our universe will keep on expanding without a gravitational recollapse, and space has hardly any overall curvature. That these values were so precisely balanced is surprising from the standpoint of standard big-bang theory, because, again, for this balance to arise, the universe would have needed to have very finely tuned initial conditions.