Cooling Of The Universe example essay topic

Describe the transformation of radiation into matter where followed the "Big Bang" After the Big Bang... Where the big bang is recorded to begin, the first step was radiation filling the Universe. This took between 10-12 to 10-10 seconds. At this time, the universe is lying in a dense, hot and small state. As proposed by Einstein's theory of general relativity, the expansion of the Universe can be driven by energy density in the form of matter radiation. As the radiation here was exceedingly larger than matter, it can be excluded (ie. matter doesn't exist).

This radiation creates pairs of particles and anti-particles, some of which collide and annihilate back to radiation. These include quarks and anti-quarks, which averaged in number until the cooling of the Universe (and hence the radiation associated with it) which created less off these pairs, and the overall result was quarks greatly outnumbering anti-quarks. As this occurs, the amount of matter present is increasing due to the still highly abundant radiation until eventually the energy density in the matter superceeds the amount of energy density in radiation. The energy density of radiation continues to be in smaller and smaller ratios to that of matter, and so can be counted as negligible in cosmic equations and the further expansion of the Universe can be determined by the actions of matter from this point.

Following this new shift in matter domination, a less efficient energy exchange between matter and radiation is created. Accretion of the stars and galaxies The moment when the expansion began was roughly 14 billion years ago. The universe began in a very hot, dense state, then cooled as it expanded. As distances increase, the average density of the universe decreases. Since matter cools down as it expands (think of the outer layers of an expanding red giant, for instance), the universe is going from a hot dense state to a cool low-density state. As the universe expands, the wavelength of light travelling through the universe expands as well.

If distances double due to the universal expansion, the light from the distant star will be doubled in wavelength. The universe is not infinitely old. Because the universe is about 14 billion years old, we can't see objects more than about 14 billion light-years away. The light from them simply hasn't had time to reach us yet. The "Big Bang Theory" states that the universe was initially very hot and dense, and is currently expanding. As the cooling process continued, average particle energy was falling to the scale of the weak nuclear force.

Particles which transmit these forces today are weak nuclear bosons, which obtain heavy masses from the "spontaneous symmetry breaking" process. Bosons with radiation energy above this force are massless. Hence, with this information, cosmologists hypothesis e that while the Universe was in its massively hot state, the particles created were massless due to their energy being above that of the weak force, which had a range akin to photons and gluons, but as the Universe cooled and the energy dropped, a level was achieved to facilitate the spontaneous symmetry breaking needed for weak nuclear bosons to gain mass. This even slowed the particles and confined their force to shorter range. As the Universe cooled further, the quarks and gluons which were previously travelling individually at high speeds all underwent a phase transformation to become confined together inside mesons and barons (ie protons and neutrons) which now comprise our known Universe. For one second, the newly formed protons and neutrons were changing into each other via emissions and absorption of neutrons.

As the Universe still cooled, a ratio of approximately seven protons for each neutron was fixed. This occurs as neutrons have the capacity to change into protons by decay, but for the reverse to happen a collision with an electron or a positron. With sufficient energy (ie before the Universe had cooled to this point) the collisions required to make neutrons were frequent, hence the previous one to one ratio. As an immediate consequence, hydrogen was abundantly formed (as only one proton was needed for a nucleus) in comparison to helium, which is what is observed today. this further validates the big bang theory. For the next one hundred seconds, energy levels had fallen to allow bonding of protons and neutrons to form atomic nuclei in "nucleosynthesis". Here mainly the lighter elements, e.g. helium and lithium were formed.

As strong nuclear forces hold the elements confined and cannot do so at distances larger than 10-13 cm, protons and neutrons had to be very close in order to form nuclei. Nuclei will not form at high temperatures, as the energy involved would cause them to move to fast for nucleosynthesis to occur. The event of nucleosynthesis has now provided the possibility for the formation of atoms, which in turn makes way for the creation of everything above the atomic level. However, this does not yet occur for an extremely long time, as Universe expands and cools for next ten thousand years.

This occurs as photons scatter increasingly more with other photons than with matter. It is now that the photons thermal ise and now begin acting as thermal black body radiation, which scientists can presently identify and measure today as cosmic background radiation. The temperature of this can be calculated from physical testing and the variance of this temperature at different directions of the Universe can provide us with useful information on the big bang and Particle physics The newly created matter has provided the Universe with a basis to form atoms. The most primitive of which was hydrogen, helium and lithium. These were the first true atoms created over the next five hundred thousand years as the Universe was cool enough to allow electrons (which were until now free in the void) to be captured by the electromagnetic forces working in a nucleus. Conditions were previously too hot for this to occur for long as captured electrons were launched out of orbit around a nucleus by a collision with other high speed particles.

Over the next billion years gravitational forces come into effect (by calculation of matter density) and hydrogen gas is pulled together by these gravitational forces which cause the gas to collapse and therefore ignite. This spawned the first stars, enormous balls of flaming hydrogen gas. The question as to where the heavier elements came from lies, literally, in the stars, and their creation arises in a timeframe of two to thirteen billion years. The stars produce these elements by consuming hydrogen and through the process of nuclear fusion, amalgamate nuclei into heavier atoms. Once created, the new atoms can only escape after the stars lifespan expires (hence the billions of years needed for a star to die and eject the particles) and they explode into supernovas before condensing again into a white dwarf, neutron star or black hole.

Bibliography

web web web web web web web Microsoft, Encarta 98 Encyclopedia The Guinness Encyclopedia, 1990.