How does the expansion of the universe affect time?

The theory of the Big Bang implies that there was a superdense ball of matter. Before the ball started its expansion there was no time or space. Time and space are created by the expansion of the universe.

The theory of relativity and the equations that are part of the theory shows that time is meaningless at the speed of light. At the speed of light time ceases to exist or become infinite. One day is the same as the duration of 1000 years and 1000 years is the same as 1 day.

Also time is affected by the presence of mass. At the boundary of a black hole mass is so great that light can not escape from the black hole. At the boundary of a black hole time slows down to the point that time stops.

Time and the expansion of the universe are linked. The stars that are billions of light years away, may have light that left the star just yesterday.

Time dilation is the effect of the universe's expansion on time, meaning that as it expands, observers' relative motion and the gravitational fields they are in affect how quickly time appears to pass. Specifically, time appears to pass more slowly in regions with higher gravitational potential or greater relative velocity than it does in regions with lower gravitational potential or less relative velocity.

The expansion of the universe affects time through a concept known as cosmological time dilation. As the universe expands, the space between galaxies, clusters of galaxies, and other cosmic structures also increases. This expansion leads to a stretching of the wavelengths of light traveling through space, which affects the perception of time.

In regions of the universe where the expansion is significant, such as between galaxy clusters, time appears to pass more slowly for observers in one region compared to another. This effect is due to the stretching of space itself, which results in a slower passage of time as observed by distant observers. Conversely, time appears to pass more quickly for observers in regions with less expansion.

This phenomenon has been confirmed through observations of distant supernovae and cosmic microwave background radiation, which show that light from these distant sources has been subject to cosmological time dilation. It's important to note that while cosmological time dilation affects the perception of time on cosmic scales, its effects are generally negligible in everyday life on Earth.