Sample Astronomy Paper on Hubble’s Law
Hubble’s law does not imply that Earth is at, or even near the center of the universe, if there is such a place, even though from observation it has been noted that other galaxies are almost all increasingly drifting away from us (Kutner 17). This is primarily because from any other galaxy others are seen as drifting away from them too as a result of the fact that the universe is expanding. Galaxies keep to a smooth expansion where the more distant galaxies appear to move faster away compared to those near Earth. However, other motions cause deviations from the smooth line of expansion. The only way for this not to happen, which also makes up the principal exception to Hubble’s law, is if the other galaxies are also part of the same gravitationally bound cluster of galaxies.
The idea that the universe is increasingly expanding prompts the question of whether this expansion will continue for eternity. Hubble’s law allows for the fact that gravity works contrary to the expansion. Given this, Hubble’s law proposes that if the density were sufficiently massive, it would bring the expansion to a stop, and eventually bring the galaxies together again in a big crunch. This would result in what Hubble’s law refers to as a closed universe. On the other hand, if the density were small enough, this would allow expansion to progress for eternity, resulting in an open universe (Kutner 54). However, at a specific critical density, it would become possible for the universe to becoming arbitrarily closed by approaching the limit of zero rate of expansion, but never collapsing. According to Hubble’s law, evidence currently points to the universe being rather close to this critical density.
Kutner, Marc. Astronomy: A Physical Perspective. Cambridge University Press, 2003.