Question

The Hubble Constant, the density of the universe, and the cosmological constant are all vital to the evolution of our universe. Briefly discuss why each is so important -and- what would happen if we tweaked each one up or down a little. Are there other constants that are equally important? If so, which and why?

Answer 1

Hubble constant is the parameter that gives us an idea about at what the galaxies are moving away from us, ie. we can measure the rate of expansion of universe by using the Hubble constant. From which we can estimate size and age of the universe. The density of the universe is dependent on the Hubble constant, and as the density changes the type of universe changes ie, if the density is high it leads to a closed universe, and as the density decreases it becomes an open universe, with no ends. The cosmological constant was introduced by Einstein into his field equations to match the model of the static universe which was accepted during the time when Einstein derived these equations, then when Hubble proved that the universe is not static and is indeed expanding, he termed the cosmological constant as the biggest blunder for the field equations. Changing Hubble constant will change the size as well as the estimated age of the universe, whereas the density decides the openness of the universe. Some of the other important constants are the Universal Gravitational Constant (determines the force of gravity), The speed of light(determines the limit for speed of transfer of information) and Planck's constant (smallest possible scales are defined by this). These are more fundamental constants and the above discussed constants are indirectly dependent on these constants and these are equally important.