Tuesday, October 16, 2012

Is the Universe Infinite?

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--------------------- #1500 - The Infinite Universe
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- See Review #1499 “ Using Supernovae to Measure Dark Energy”. These measurements conclude that the Universe is 30% Matter and 70% Dark Energy. The 70% is vacuum energy that is expanding the Universe at an ever accelerating rate. The expansion of the Universe is gaining speed.
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- OK, but, what is the Universe expanding into?
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- There is evidence to suggest that the answer is simply more Universe. That the Universe is infinite in size. This is an idea totally inconsistent with logic. However, the idea is consistent with measurements made of sound waves in the Cosmic Microwave Background radiation, with redshifts in Type 1a Supernovae, with calculations of the Hubble Constant, and with the conclusion that space has a flat topology. So an infinite Universe is not contrary to evidence so far.
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- The Hubble Constant measures how fast galaxies are moving away from us. The more distant the galaxy the faster the recession velocity. It may not be a constant over time, or distance, but, in our neighborhood of the Universe the Hubble Constant is 47,000 miles per hour for every million lightyears distance. That is 13 miles per second per million light years of space.
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- If space never ends there is no limit to the number of galaxies, stars, planets, and energy in the Universe. The constant does remain with the speed of light. So, we can only see over the space of so many lightyears distance. Called our “ Observable Universe” it contains at least 200,000,000,000 galaxies. If the Universe is infinite then this is a very small fraction that we can see. In fact, it is essentially zero.
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- Where did this infinite Universe come from? Well, it came from nothing. You take all the mass and gravity and balance that against the negative repulsive force of Dark Energy and the balance equals zero.
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- I told you that it was inconsistent with logic.---------------
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- With these assumptions of the mass being zero and the volume being infinite the density of the Universe is zero/infinity. That ratio would drive a mathematician nuts.
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- We certainly live in a special part of the Universe where the density of things make up our natural world . Take the density of the air we breath for example. The total volume of the Earth’s atmosphere is 4.2 * 10^18 cubic meters. The total mass is 5.1*10^18 kilograms. The average density is 1.214 kilograms per cubic meter. That is equivalent to the average being 0.000044 pounds per cubic inch.
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- But, all that atmosphere is over our head. It is sitting on our shoulders with an atmospheric pressure of 14.7 pounds per square inch.
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- An interesting way to compare the densities in the Universe is to use the units of the number of hydrogen atoms per cubic meter. A hydrogen atom weighs 1.6*10^-27 kilograms. The Earth’s atmosphere then has an average density of 7.5*10^26 hydrogen atoms per cubic meter. That is a lot of atoms weighing down on us.
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- That is an average. If you go up in elevation from 600 miles to 4,000 miles you can measure density at 53 hydrogen atoms per cubic meter. That region is called the Van Allen Radiation Belt, or more recently simply the “magnetosphere“. It is the magnetic shield around the Earth that protects us from the Solar Wind.
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- The Solar Wind coming at us from the Sun has a volume of 1.4 * 10^34 cubic meters. It has a total mass of 4.5*10^14 kilograms. So the average density of the Solar Wind between us and the Sun is 20,000,000 hydrogen atoms per cubic meter.
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- The average density of the total Milky Way Galaxy is the ratio of 1.6 *10^60 cubic meters divided by 2*10^39 kilograms. The gives us an average density of 81,000 atoms per cubic meter.
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- Here is a table of densities measured in the number of hydrogen atoms:
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------------------------- Earth’s atmosphere ------------------- 7.5*10^26 atoms
------------------------- Sun’s atmosphere -------------------- 6.2*10^13 atoms
------------------------- Sun’s surface ------------------------ 1.3*10^23 atoms
------------------------- Orion Nebula ------------------------ 1.5*10^8 atoms
------------------------- Milky Way Galaxy ------------------- 8.1*10^4 atoms
------------------------- The Universe ------------------------- 0 atoms / infinite volume = nothing. I like our part of the Universe the best.
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- An announcement will be made shortly, stay tuned.
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707-536-3272, Tuesday, October 16, 2012

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