Question

The further out into the universe we are looking, the "further back in time" we are seeing due to the time light takes to travel to us.

Assuming the expansion of the universe is uniform throughout all space, the further away something is, the faster it is expanding away from us.

So, couldnt we say that the universe is expanding faster in the past, and, therefore, slower in the present?

While I know it has something to do with speed of expansion relative to an observer as well as the perception of looking into the past versus something actually being in the past, I am having a hard time articulating an answer to the question.

Answer 1

astronomer Edwin Hubble discovered the expansion of the universe by observing that other galaxies are moving away from ours. He noted that the more distant galaxies were receding faster than nearby ones, in accordance with what is now known as Hubble's law (relative velocity equals distance multiplied by Hubble's constant). Viewed in the context of Einstein's general theory of relativity, Hubble's law arises because of the uniform expansion of space, which is merely a scaling up the size of the universe. In Einstein's theory, the notion of gravity as an attractive force still holds for all known forms of matter and energy, even on the cosmic scale. Therefore, general relativity predicts that the expansion of the universe should slow down at a rate determined by the density of matter and energy within it. But general relativity also allows for the possibility of forms of energy with strange properties that produce repulsive gravity. The discovery of accelerating rather than decelerating expansion has apparently revealed the presence of such an energy form, referred to as dark energy. Whether or not the expansion is slowing down or speeding up depends on a battle between two titans: the attractive gravitational pull of matter and the repulsive gravitational push of dark energy. What counts in this contest is the density of each. The density of matter decreases as the universe expands because the volume of space increases. (Only a small fraction of matter is in the form of luminous stars; the bulk is believed to be dark matter, which does not interact in a noticeable way with ordinary matter or light but has attractive gravity.) Although little is known about dark energy, its density is expected to change slowiy or not at all as the universe expands. Currently the density of dark energy is higher than that of matter, but in the distant past the density of matter should have been greater, so the expansion should have been slowing down then. Cosmologists have other reasons to expect that the expansion of the universe has not always been speeding up. If it had been, scientists would be at a loss to explain the existence of the cosmic structures observed in the universe today. According to cosmological theory, galaxies, galaxy clusters and larger structures evolved from small inhomogeneities in the matter density of the early universe, which are revealed by variations in the temperature of the cosmic microwave background (CMB). The stronger attractive gravity of the overdense regions of matter stopped their expansion, allowing them to form gravitationally bound objects from galaxies such as our own to great clusters of galaxies. But if the expansion of the universe had always been accelerating, it would have pulled apart the structures before they could be assembled. Furthermore, if the expansion had been accelerating, two key aspects of the early universe-the pattern of CMB variations and the abundances of light elements produced seconds after the big bang-would not agree with current observations.