FINAL EXAM ESSAY 1 EARTH IN SPACE

A)Our knowledge of Earths location in the universe has been shaped by 400 years of telescopic observations, and has expanded radically in the last century. Initially, Earth was believed to be the center of the universe, which consisted only of those planets visible with the eye and an outlying sphere of stars. After the acceptance of the heliocentric mofdel in the 17th century observations by william h.and others showed that Earth's Sun lay within a vast, disc-shaped galaxy of stars, later revealed to be suns like our own. By the 20th century, observations of nebula revealed that our galaxy was only one of billions in an growing universe grouped into clusters and superclusters. By the 21 centuary the structure of the visible universe was becoming clearer. Superclusters, filaments and voids are likely the largest coherent structures that exist in the Universe. At still larger scales over 1000 megaparsecs the Universe becomes homogeneous meaning that all its parts have on average the same density, composition and structure.
Since there is believed to be no "center" or "edge" of the universe, there is no particular reference point with which to plot the overall location of the Earth in the universe. It is still undetermined whether the universe is infinate and there is speculation that our universe.
(1)http://en.wikipedia.org/wiki/Earth's_location_in_the_universe

 
 B) Motion. The galaxy is moving away from us, this is known as the Doppler effect. The same effect can be detected in sound. When a police car is speeding towards us the sound waves made by its siren are 'squashed' and the pitch sounds higher. As it passes us and starts to move away the sound waves are 'stretched' and the pitch sounds lower. In the 1920's Edwin Hubble observed that all galaxies (apart from a few local ones attracted towards our own and showing blueshift) show red shift. This indicates that the galaxies are all flying away from us, as in a Big Bang explosion. Expansion of the universe. Einstein's famous equations show that the universe should be expanding, not because the galaxies were moving through space, but because the 'empty' space between them (spacetime) is expanding. This cosmological redshift results because the light from the distant galaxies is stretched by the amount that space expands while the light is en route to us. This also reveals that the Earth is not at the centre of the universe with all the galaxies moving away from us, but that due to the expansion of the universe, all the galaxies are moving away from each other, like painted dots on a balloon moving apart as it is inflated. Gravity. This is also explained by Einstein's general theory. Light moving outwards from a star is moving 'uphill' in the star's gravitational field, and loses energy as a result. Because light cannot slow down - it always travels at the same speed - when it loses energy its wavelength increases, in other words, it is redshifted. It does however, require a very powerful gravitational field for this effect to be measurable, such as created by a white dwarf star.
(2) http://www.thekeyboard.org.uk/The%20Big%20Bang%20Theory.htm



C) Measurements by the WMPA satellite can help resolve this crisis. then the detailed structure of the cosmic microwaves will depend on the current density of the universe, the composition of the universe and its expansion rate. WMAP has been able to determine these parameterswith an accuracy of better than than 3% of the critical density. How does WMAP data enable us to determine the age of the universe is 13.7 billion years you may ask? with an uncertainty of 1% The key to this is that by knowing the composition of matter and energy density in the universe, we can use Einstein's General Relativity to compute how fast the universe has been expanding in the past. With that information, we can turn the clock back and determine when the universe had "zero" size, according to Einstein. The time between then and now is the age of the universe. There is one caveat to keep in mind that affects the certainty of the age determination: we assume that the universe is flat, which is well supported by WMAP and other data.

http://www.theresilientearth.com/files/images/cosmic_rays_hit_earth.jpg

(3) http://map.gsfc.nasa.gov/universe/uni_age.html

BIB
(1)
URL- http://en.wikipedia.org/wiki/Earth's_location_in_the_universe
Date updated- 10/16/10
Title-Earths location in the universe
Company- wikipedia

(2)
URL-http://www.thekeyboard.org.uk/The%20Big%20Bang%20Theory.htm
Date updated- 5/13/07
Title- The Big Bang Theory
Company-
(3)
URL- http://map.gsfc.nasa.gov/universe/uni_age.html
Date updated- 7/19/10
Title- WMAP
Company-  NASA