The Conservation of Byron Number - Assignment Example

• Galaxy 1 observed to have hydrogen line wavelength of 8204 angstroms.

Galaxy2 observed to have hydrogen line wavelength of 6549 angstroms.

The rest hydrogen line measurement from the lab is 6563 angstroms wavelength.

Therefore the radial velocity of the galaxies is; Vr=cz {speed of light * redshift}

Radial velocity of galaxy 1, 

 redshift z = (8204 – 6563) / 6563 = 0.25

:. Vr = 300000km/s * 0.25 = 75000 Km/s

Radial velocity of galaxy 2,

Redshift z = (6549 - 6563) / 6563 = -0.002

Vr = 300000km/s * - 0.002 = -639.95km/s

A negative radial velocity implies that the distance between galaxy 2 source and the observer was gradually decreasing. 

The expansion of the universe is governed by two competing processes that tend to drive galaxies apart from one another and a gravitational attraction of matter in the universe that assembles galaxies together. Astronomers can notice the changes in the rate of expansion of the universe through measurements of the recession speeds and distances of very distant galaxies (Materrese & Sabino 2010).

The assumption of dark energy is that it is a gravitationally repulsive force that does not appear to cluster in galaxies. It has last been seen to stretch the space-time apart and certainly fits the accelerating-expansion scenario. Therefore acceleration of the expansion implies clearly the existence of some force that acts to push galaxies apart, and the source of this force is the dark energy.

• Scenarios for structure formations: Top-down scenario

In this scenario large structure-size galaxy clusters are formed first then they are segmented into galaxies. This scenario is based on radiation smoothed out the matter density fluctuations to produce large pancakes which then gradually build up the matter after recombination and grow until they collapse and fragment into galaxies.

Bottom-up scenario

In this type, small dwarf Galaxies form first then they merge into clusters of galaxies. The density enhancements at the time of recombination are close to the size of small galaxies and the enhancements collapse from self-gravity to form dwarf galaxies.

• The “Modified Newtonian Dynamics” MOND

This is a theory that was proposed by mordehai Milgrom and it attempts to explain the galaxy rotation problem by modifying Newton’s second law of motion, so as the acceleration at very low values such as between distant stars is not strictly linear. It tries to resolve the problem that when astronomers observe galaxies and apply the current theory of gravity, the result shows the stars within the galaxy should go spinning apart from each other. Most astrophysicists and cosmologists do not believe that MOND fits the evidence. This falls in the somewhat less-informal category of an alternative gravity theory since it proposes fundamental changes to the understanding of the way gravitational force works, as opposed to dark matter theory, which proposes that the understanding of gravity is fine (Mckenney & Jana 2012).