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Astronomy Ch. 18

Categories: Astronomy
. What did Einstein consider was the greatest blunder of his career?
Not predicting that the universe is expanding

Where in the universe does the “general” expansion occur?
Only in the space that separates clusters of galaxies

. What causes the cosmological redshift of light?
The wavelength of photons from a distant galaxy becomes stretched by the expansion of space while the photons are traveling toward us

Suppose it was discovered that Hubble’s constant, H0, was smaller than previously thought. How would this affect our estimate of the age of the universe?
The age of the universe would be larger.

Penzias and Wilson were the scientists who
first observed the cosmic background radiation.

How many basic forces are there in the universe today?
Four: the gravitational, electromagnetic, strong nuclear, and weak nuclear forces

At the extremely high temperatures of the first moments of the Big Bang, the four forces of nature seem to have had the same strength and operated together in a unified way.

At what stage and time in the evolution of the universe during the Big Bang did the strong nuclear force separate out and begin to operate independently?

10^-35 s, T = 1027 K

What happened at the end of the Planck time, when the age of the universe was 10^-43 s?
The laws of physics became applicable in our universe for the first time

What solution has been proposed by cosmologists to explain the remarkable uniformity of temperature throughout our universe?
Space expanded by a very large factor during a very brief period soon after the time of creation.

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What important development occurred in the early universe at about 380,000 years after the Big Bang?
Protons and electrons combined to form neutral atoms, with the result that the universe became transparent for the first time.

When was most of the helium that exists in the universe today created?
During a period of intense nuclear reactions that ended about three minutes after the start of the Big Bang.

Which component appears to contain the majority of the overall mass of the universe?
Dark energy, which causes the universal expansion to accelerate with time

The key piece of evidence showing that the expansion of the universe is accelerating is that the
most distant type Ia supernovae are fainter than they would be if the expansion is not accelerating.

Our present universe is dominated by dark energy, but at much earlier times the universe was matter-dominated. How did dark energy come to dominate matter?
The density of dark energy remains constant as the universe expands, whereas the density of matter in the universe decreases. Therefore, the density of matter eventually decreased below that of the dark energy.

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Astronomy Ch. 18. (2018, Jan 24). Retrieved from

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