Expansion refers to the idea that the universe is constantly getting larger, with galaxies and other objects moving away from each other. This phenomenon was first observed by Edwin Hubble in the early 20th century and is now widely accepted as a fundamental aspect of the universe.
Redshift is a term used to describe the stretching of light waves as they travel through space. This stretching is a result of the expansion of the universe, as the light waves are being carried along with the expanding space. Redshift is often used as a measure of how much an object is moving away from us due to the expansion of the universe.
No, energy is not lost during expansion. In fact, energy is conserved in the universe and cannot be created or destroyed. The expansion of the universe does not affect the total amount of energy present, it simply causes the energy to be spread out over a larger space.
The expansion of the universe causes the wavelength of light to stretch, which results in a decrease in energy. This is known as cosmological redshift and is one of the key pieces of evidence for the expansion of the universe.
Scientists have determined that the expansion of the universe is currently accelerating, meaning that the rate of expansion is increasing over time. This is due to a mysterious force known as dark energy, which makes up a large portion of the universe and is causing the expansion to speed up.