Term
| universe was opaque before recombination? |
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Definition
| The universe was unable to see because it was too hot. The temperature was so high that elctrons and protons were unable to combine to form atoms-- too full of particles with no companion. Too bright to see anything like the center of t |
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Term
| What happened at the time of recombination? When did it happen? What is the name of the radiation that was released at that time and which we can still observe today? |
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Definition
| atoms form and the universe became transparent 380,000 year after the big bang. (CMB); Cosmic microwave background radiation is released and we can observe 1% of it through the television. |
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Term
| What is “inflation” and what caused it? |
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Definition
| Inflation is the rapid and sudden dramatic expansion of the universe when the strong force was released and released energy. |
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Term
| What are the four forces that we know today? Which two unify at high temperatures? Which three unify at even higher temperatures? |
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Definition
| (1) Strong force, Weak force, electromagnetism force and gravity. (2) Electromagnetism and weak force. (3) Everything but gravity. |
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Term
| What happened during the Plank Era? How do you know, or why donʼt you know? |
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Definition
| 0 to 10 to the -43 seconds. We don’t know anything about the Planck Era. There are two theories that we haven’t been able to combine; general relativity and quantum physics. This is why we don’t know what happened. |
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Term
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Definition
| Is what causes the universe to accelerate in expansion. |
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Term
| why do we live in a universe that is made of matter rather than antimatter or only photons? |
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Definition
| -There was a tiny bit more of matter than anit-matter. For every one billion pair of proton and anti-proton there was one extra matter. Happened in the first .001 second. If there was a little more matter than the universe would be made up of anti-matter. Good that there was one extra proton for every billion pair of protons/anti-protons. |
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Term
| what are the two competing factors that whether or not the Universe will continue to expand forever |
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Definition
Kinetic energy from expansion-> pulls everything out and gravity from the average density->holds everything
together. |
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Term
| What is the definition of the “critical density” of the Universe? |
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Definition
| The density you would need to balance expansion exactly. |
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Term
| What might dark matter be made of? |
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Definition
-Ordinary matter called MACHOs; massive compact halo objects and extraordinary dark matter called WIMPs; weakly
interacting massive particles. |
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Term
| hat are the three possible kinds of curvature that the Universe might have, depending on its density? |
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Definition
-Positive curvature: when density of universe has more critical matter—closed
- 0 curvature: when density=critical matter—flat
-Negative curvature: when matter is smaller than critical matter—open |
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Term
| What is the composition of the universe in terms of dark energy, dark matter, and matter (atoms)? |
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Definition
Dark Energy 73%
Cold Dark Matter 23%
Atoms 4% |
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Term
| what does the Big Bang Theory describe? |
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Definition
| a study of how the universe changed from when it became cooler, less dense, and bigger. |
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Term
| Cosmological Horizon? Why can’t we see anything beyond it? |
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Definition
-Tells us that space has expanded faster than speed of light. It is a limit on how far we can see, because light from
these objects has not had enough time to reach us. That is why earth has a boundary. |
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Term
| one Hubble time ago? Approximately how long ago was that? |
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Definition
-All matter in the universe was at one point singularity and began to expand. This occurred about 13 to 14 billion
years ago. Expansion called the big bang. |
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Term
| All distant galaxies appear to be moving away from us. Explain why this does not imply that we are at the center of the universe |
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Definition
According to the cosmological principle the universe has no center, no point is different and galaxies are all moving
away from one another. |
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Term
| What does the Cosmological Principle say? |
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Definition
| -All the points in the universe are the same. |
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Term
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Definition
| galaxy is a measure of its recession velocity (or distance) due to the expansion of the universe. The higher, the larger the recession velocity. The further they move from us the bigger they are expanding. |
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Term
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Definition
| -On average the recession velocity of a galaxy is directly proportional to its distance. |
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Term
| What is galactic cannibalism? |
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Definition
| A process where a more massive and more larger galaxy consumes a smaller galaxy and becomes more massive. Galactic cannibalism may explain how giant elliptical galaxies form near the centers of rich clusters of galaxies, where galactic collision are frequent. |
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Term
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Definition
| Extremely bright centers of galaxies they are the most powerful objects in the universe. They emit 100 times as much energy (light) as the entire galaxies, but they are about 100,000 times smaller than the whole galaxies. |
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Term
| Why are stars likely to form when two galaxies collide? |
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Definition
| -The collision between two galaxies compresses the gas and triggers star formation. |
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Term
| List at least five different types of signs of galaxy interactions (or collisions) |
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Definition
| -Tidal tail, bridges, rings, warped disks, counter-rotating gas, polar rings, shells |
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