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A - level physics > Cosmology > Flashcards

Cosmology Flashcards

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1
Q

What is the astronomical unit?

A

The average distance from the earth to the sun (1.5x10^11)

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2
Q

What is a light year?

A

The distance travelled by light in a vacuum in the time of one year

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3
Q

What is a parsec?

A

The distance at which a radius of one AU subtends at an angle of 1 arcsecond

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4
Q

If a galaxy is moving towards earth?

A

the absorbtion lines will be blue shifted because the wavelength appears shorter

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5
Q

If a galaxy is moving away from earth?

A

the absorbtion lines will be red shifted because the wavelength appears longer

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6
Q

What is the Doppler effect?

A

The change in frequency and wavelength of waves received from an object moving relative to the observer compared to what would be observed without relative motion

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7
Q

What is the cosmological principle?

A

The assumption that when viewed on a large enough scale the universe is homogeneous and isotropic and the laws of physics are universal

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8
Q

What is meant by the word isotropic?

A

the same in all directions

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9
Q

What is meant by the word homogeneous?

A

matter is distributed uniformly across the universe when viewed on a large enough scale

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10
Q

What are the two key pieces of evidence for the big bang theory?

A

Hubble’s law and microwave background radiation

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11
Q

What is microwave background radiation?

A

The microwave signal of uniform intensity detected from all directions in the sky, which fits the profile for a black body at a temperature of 2.7K

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12
Q

What was the universe like during the big bang?

A

Time and space created

singularity - infinitely dense and hot

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13
Q

What was the nature of the universe 10^-35 seconds after the big bang?

A

The universe expands rapidly (inflation)
there is no matter in the universe just full of em radiation in the form of high energy gamma photons
temperature is about 10^28K

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14
Q

describe the nature of the universe after 10^-6 seconds

A

The first fundamental particles begin to gain mass by a mechanism which isn’t fully understood but involves the higgs boson

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15
Q

What happened 10^-3 seconds after the big bang?

A

Quarks combine to form the first hadrons such as protons and neutrons, most mass in the universe was created within the first second by pair production

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16
Q

1 second after the big bang …

A

the creation of matter stops, and the temperature drops to around 10^9K

17
Q

Describe the universe after 100 seconds

A

Protons and neutrons fuse together to form deuterium and helium nuclei along with a small quantity of lithium and beryllium. The expansion of the universe is so rapid that no heavier elements are created.

A - level physics (17 decks)

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