If the size of the universe is infinite and the speed of light is constant, are there places light has not reached?

Asked by: Enzo

Answer

Despite a century of hard work by many great geniuses, the large-scale structure of the universe is still not completely understood. Nevertheless, we can try to speculate intelligently on the nature of the entire universe.

There are important observational facts which are not in dispute. When we look out as far as possible with our best telescopes, we observe a universe which is homogeneous, expanding according to Hubble's Law, and filled with cosmic microwave background radiation. It is not known if the homogeneity we observe within about 12 billion light-years of the earth extends all the way to infinity. If it does, then there is no part of the universe which lacks light, matter, or galaxies. This means that the hot, dense, big-bang beginning of our universe occurred everywhere throughout all of infinite space. There was no empty place for light to travel to.

The universe has a finite age, so it is certainly true light has traveled only a finite distance since the big-bang. Undoubtedly there are remote objects in the universe which have sent light in our direction and that light has not yet arrived. Indeed, that light may never arrive if the expansion rate of the universe does not slow down. Recent evidence indicates the expansion rate of the universe is actually accelerating. This has an army of cosmologists working overtime, trying to understand it. If the universe is accelerating, then we will never get to see most of it. Even objects that we can now see will disappear as they recede beyond the speed of light.
Answered by: Hugh Mongus, M.S., Retired teacher