- The Observable part of the Universe is inhabited by 100,000,000,000 galaxies. Each of these galaxies contains on average 100,000,000,000 stars and each of these galaxies contains 100,000,000,000 planets. All, as best we can estimate.
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- Galaxies themselves seem to be held together by the gravity of Dark Matter. These galaxies are accelerating away from each other on a wave of expanding space. This anti-gravity in space is called Dark Energy. We do not know what either Dark Matter or Dark Energy is. We just know the two combined occupy 96% of the total matter - energy that composes the Universe. The matter - energy that we are familiar with only occupies 4% of the expanding Universe.
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- Space itself is expanding and galaxies , stars and planets are just being carried along for the ride. This expansion has been going on for 13,725,000,000 years. The rate of expansion today is measure to be 47,000 miles per hour per million light years distance. (called the Hubble Constant at 74 kilometers per second per mega parsec.)
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- Expanding space also means that light traveling through the space is being stretched to longer wavelengths. The energy of light is a direct function of the frequency of the oscillation and indirectly a function of the wavelength. So, expanding wavelengths loose energy. The wavelengths are red-shifted . Consequently the Universe is cooling as it expands. It is today about 3 degrees Kelvin.
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- A light from a distant galaxy is redshifted, stretched out to a longer wavelength. The amount of redshift tells astronomers how much the Universe has grown over the intervening years. The greatest redshift astronomers have measured to date is a redshift of 8.0. At that time the Universe was a few hundred million years old and 1/9th its present size.
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- The measurements indicate that stars and galaxies first emerged in the Universe when it was 100,000,000 years old. At that time the Universe composition was 5 parts Dark Matter and 1 part hydrogen - helium.
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- The quantum fluctuations of particles created slightly uneven density in the plasma at the very beginning of the expansion. The quantum fluctuations come from the Heisenberg Uncertainty Principle which states that particles are also waves and their position is determined by a range of probabilities. The particle’s position and velocity as a product must be less than Planck’s Constant, a very small number, 10^-16. Being a product if one probability increase the other decreases, the better you know velocity the less you know about position.
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------------------ Probability of position * Probability of momentum = < 6.58 * 10^-16 electron volt - seconds. Momentum is mass * velocity.
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- These quantum fluctuations created regions of higher density which in turn created regions of higher gravity. Gravity acted to amplify these denser variations. Denser regions expanded more slowly and eventually the gravity in these clumps became large enough for the matter to collapse. Each region was about 1,000,000 Solar Mass of material. Dark Matter accounted for a bulk of this mass.
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- Because the Dark Matter could not emit or absorb light it remained in an extended cloud. However, hydrogen and helium particles emitted light , lost energy, and became concentrated at the center of the cloud. When the concentrations were great enough stars were born.
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- These first stars were massive, hundreds of Solar Mass. Big stars have short life spans. They go supernovae after a few million years. Supernovae explosion create all the heavier elements in the Periodic Table. So, the next stars that are born out of this new cloud of material will contain the full range of heavier elements. So, when planets form they have all the chemistry and biology needed for life.
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- If we go back as close to the Big Bang as we can get the redshift is 1,100. This light traveling through the expanding Universe has redshifted from visible light into the microwaves. We detect this light as Cosmic Microwave Background radiation, first discovered in 1964. It is light that left 380,000 years after the Big Bang. It is the period when the first atoms were formed and the particle plasma became neutrally charged. The temperature of the plasma had cooled to 3,000 Kelvin at this point in the expansion.
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- In 1992 studies of the Microwave Background Radiation discovered variations in temperature of 0.001%. This slight lumpiness represents the seeds for the formation of the galaxies billions of years later.
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- These studies revealed that prior to 100,000 years after the Big Bang the energy density or radiation exceeded that of matter. This initial radiation kept the matter from clumping and collapsing in the beginning. Prior to 100,000 years the composition of the Universe was 25% helium and 75% hydrogen nuclei. There were very small amounts of lithium and isotopes of deuterium and helium 3. All the heavier elements formed billions of years later in the stars and supernovae explosions. All this “ ordinary matter” comprises only 4.5% of the total Universe matter - energy density.
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- If we take the evolution back to less than one microsecond not even protons and electrons could exist. The plasma was quarks, leptons, and force carriers photons, W and Z bosons and gluons.
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- We know that galaxies are held together by the Dark Matter that is 23% of the Universe. Science has not determined what “ Dark Matter” is. Theories include “ Neutralinos” and “axions” but the answer has yet to be discovered.
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- The theories also require there to be equal parts of matter and anti-matter. When matter and anti-matter meet they both evaporate into a burst of radiation. However, theories also hold that there was an imbalance of one extra quark out of every billion anti-quarks that survived to explain the existence of ordinary matter that exists today.
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- To explain the general uniformity of the overall Universe on the largest scale science uses the theory of Cosmic Inflation that occurred 10^-34 seconds after the Big Bang. When Inflation ceased the decaying energy formed the quarks, anti-quarks, leptons, and other particles. The inflation was faster that the speed of light. So, what we see today appears flat in its geometry, and uniform in all directions.
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- The pattern we see is in the Cosmic Microwave Background radiation is a giant image of this early subatomic world.
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- Going back earlier than 10^-34 seconds is beyond any physics that we understand today. Back to 10^-43 seconds is called Plank Time when space-time were first created. Theories persist that multiple Universes likely formed, not just the one we live in. If Cosmic Inflation happened once it could have happened any number of times. Really, these ideas reside beyond the realm of science. You have to use your imagination.
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- Today, the story above is what science can say about the Universe we live in. The most amazing part about this Universe is that we are here thinking about it. Happy Mother’s Day. An announcement will be made shortly, stay tuned.
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(1) To learn more: http//arixiv.org/abs/0803.0982
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