Cosmology
| Cosmological Timeline Cosmology is the study of the history of the universe, its birth, its past and its future. This timeline was developed by astronomers and cosmologists after many hundreds of years of the analysis of our night sky and years of asking: "how could we play the major trends that we see backwards and forwards through time." Because of spectral analysis and the insights of Edwin Hubble we know that the large bodies in our universe are all moving away from each other. Because we can tell that all of the mass and energy in the universe is now spreading apart- we can assume that at one time in the distant past, all of the matter and energy were at one time very close together. Actually all of the matter and the energy in the universe were, 14 billion years ago, squeezed into a point of zero volume and infinite density. This timeline follows the path of this energy (and the matter that it creates) as it spread out, cooled and assumed different forms. As the energy in the universe dissipated some of it began to take on the form of matter. The process of expansion and cooling has created both the physical universe in which we live and the material components of our own bodies and minds. 0 Seconds After the Big Bang: Everything that we can see in space, and all of the distant energy and matter that we cannot see (but can infer the existence of) make up our universe. From the way that our galaxy is moving in relationship to other galaxies and from other clues that we can observe with high powered telescopes, we can tell that around 14 billion years ago, our universe exploded outwards from an infintesimally small point, at an incredibly fast rate. Roger Penrose applied general relativity to show that a giant star may collapse to a singularity and become a black hole. Stephen Hawking used some of the same mathematical procedures and a few generally accepted premises to go on to show that a similar singularity must have been what gave rise to the big bang. As Einstein’s general relativity tells us energy, matter, space and time are inextricably related, it is almost impossible to physically describe one without the others. For this reason and for many others we believe that neither energy, space or time existed prior to the big bang. Because the big bang generated the dimensions of space and time, it was the first event to happen in the history of our universe. 10 ^-43 Seconds: Plank Time and the GUT era At this time, a very small fraction of a second after the big bang, the universe was still very small. The universe may have had a radius of 10^-35 centimeters. Prior to this time- Plank Time- each of the four forces in the universe were unified. After this point in time the gravitational force became distinct from the other three forces which, even today, are still undifferentiated. The other three forces are the electromagnetic force, the weak nuclear force and the strong nuclear force. These three forces are unified as the Grand Unified Theory (GUT) force. Because we do not know how the laws of the universe worked before gravity became differentiated, it is impossible for us to know how the energy released by the big bang behaved before Plank Time. 10^-35 Seconds: The universe has been expanding rapidly since the big bang. The energy that was released from it is observable in many forms including gravitational energy, and electromagnetic energy. The temperature has fallen to 1028K and the universe is about the size of our solar system. 10^-32 Seconds: The Electro-Weak Era The strong nuclear force along with the electroweak force, which is a combination of the weak nuclear force and the electromagnetic force, become distinct. The electro- weak era is marked by the smoothing of inflation. 10^-10 seconds The electro-weak force breaks up into its aforementioned component forces and so by now the energy released by the big bang is present primarily as electromagnetic radiation. Because of the findings of Einstein we know that matter and energy are equivalent. A very small amount of matter is equal to huge amount of energy. The tremendous amounts of energy released by the big bang begin to reorganize and form some of the subatomic particles (forms of matter) that make up atoms. Basically, highly energetic photons (rays of light) turn into particles of matter. For every particle that is created though, an antiparticle is also created. When these two opposing forms of matter meet, they annihilate and turn back into energy in the form of photons. The matter that makes up the majority of our solar system is made of particles whose corresponding antiparticles have already been annihilated. (For every 109 particle/antiparticle pairs one extra particle is created. For this reason, after every pair undergoes annihilation, there are some normal particles left over, leaving 109 photons for every particle in the universe. Because particles occur slightly more often than antiparticles, most of our material universe is made of particles. 10^-3 seconds Not even one second of the universe has passed and it is already much bigger than our solar system. Because the universe has cooled to 1012K the energy density is no longer high enough to create protons, the building blocks of matter. 10^-3 to 100 seconds: The Era of Nucleosynthesis The protons in the universe interact to create helium nuclei, one of the lightest and simplest elements on the elemental chart. By the end of this era the vast majority of nuclear reactions have taken place and the universe contains hydrogen, helium and traces of deuterium, lithium, boron and beryllium. The other elements will be made later inside the burning cores of stars. 100 seconds to 300,000 Years At this point the universe is actually opaque, meaning that radiation can not pass through it. It is opaque because the electrons that occupy much of the available space absorb the photons of light. When we look back into the farthest reaches of space to the light that is finally reaching us from this era, we see completely opaque space. 300,000 Years: Recombination At this point in time the universe changes from being opaque to being translucent. The universe is now matter dominated. Most of the universe that we can see from earth is transparent. Yet when we look into the farthest reaches we can see evidence of the opacity of the early universe. This is apparent to us as the “cosmic microwave background.” It turns out that this cosmic microwave background is actually the explosion of the big bang- and we are enveloped in it. Luckily for us this remaining heat from the big bang is only about three degrees Kelvin or negative 270 degrees Celsius. Scientists predicted that the detection of the microwave background would be evidence for the theory of the big bang. Several years later when radio astronomers (Arno Penzias and Robert Wilson) found this background radiation, seemingly on accident, we were able to be much more secure about our theory of the creation of the universe, our big bang theory. One Billion Years: The Stelliferous Era Stars begin to form from clouds of gas. Through the atom crunching nuclear reactions that they derive their fuel from, stars began to create all of the 92 natural elements in our universe. In other words, the explosion of the big bang began to form the energy into matter- really into just a few of the elements, mainly helium and hydrogen. Stars were responsible for transforming these huge pools of helium and hydrogen into the other elements that are found in space, on our earth and in our bodies. In fact the sun and stars in our universe are still performing these transformations today. The carbon and oxygen in your body was actually made in a star. Soon after, galaxies (large groups of stars) of many shapes and sizes began to form all over the universe. 9 Billion years Our sun and our solar system form. 14 Billion Years: Now We live about 14 billion years after the big bang. 15 Billion Years One billion years from now the sun will be bright enough to heat the earth to very high temperatures. The average temperature on earth will be near the boiling point of water. 19 Billion Years The Sun becomes a red giant and engulfs many of the planets in our solar system including the earth. 20 Billion Years The sun shrinks and becomes a white dwarf 10^13 Years: The Degenerate Era This is a much older universe which has been cooling steadily. By now the average kinetic movement in the molecules of matter is reaching 0 Kelvin. There are no longer any stars shining in the universe. The stelliferous era has come to an end. 10^14 Years Universal Expansion has carried all galaxies out of sight of our own. The universe is getting progressively colder, very quickly. 10^14-10^33 Years All matter in the universe is now in black holes, neutron stars, white dwarfs, brown dwarfs and planets. 10^33- 10^37: The End Of Matter The protons and other particles of matter decay into energy. Matter is a type of potential energy and the universe is too “cold” to sustain it. 10^60 – 10^100 The Black Hole Era Most of the large formations of energy in our universe are in the form of black holes. Before 10^100 years after the big bang most black holes will have completely evaporated. 10^100 The universe is a dilute and ever-expanding mix of photons, neutrinos, electrons, and their antiparticles. Eventually all particles will annihilate with their antiparticles. The shape of the universe is determined by the interaction of two forces. One is the pull of gravity that pulls all of the massive bodies together. The second force is the momentum of expansion that was applied to all of the massive bodies in the original explosion- the big bang. For a long time scientists thought that the gravity of the massive bodies in the universe would have been strong enough to eventually pull all of the matter back together, in what it called the big crunch. But now we know that the matter is moving too fast to ever be pulled back together. Because our universe is inflating above the critical speed, it is actually still accelerating from the blast of the big bang. We know that the force of gravity between the massive objects in our universe is not great enough to pull the universe back together. Our universe will continue expanding after the average temperature of all of the objects within it reaches absolute zero and all atomic and molecular movement stops. It will actually continue to expand forever. . |
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