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relativity and redshift Flashcards

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1
Q

What is Einstein’s theory of relativity primarily about?

A

It describes how space and time work, particularly under conditions of high speed or strong gravity.

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2
Q

How many parts does Einstein’s theory of relativity have?

A

Two: Special Relativity and General Relativity.

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3
Q

What is the key principle of Special Relativity?

A

The speed of light is constant for all observers, regardless of their motion.

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4
Q

What does General Relativity explain?

A

It explains gravity as the curvature of space-time caused by mass.

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5
Q

What does E=mc^2 represent?

A

It represents the equivalence of mass and energy.

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6
Q

What is time dilation?

A

The slowing down of time for an object moving at high speeds relative to a stationary observer.

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7
Q

What is length contraction?

A

The shortening of an object in the direction of its motion as it approaches the speed of light.

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8
Q

What is space-time?

A

A four-dimensional continuum combining the three dimensions of space and one of time.

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9
Q

How does mass affect space-time?

A

Mass causes space-time to curve, which we perceive as gravity.

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10
Q

What is a black hole?

A

A region of space where gravity is so strong that nothing, not even light, can escape.

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11
Q

How does space-time curvature relate to gravity?

A

Gravity is the effect of space-time being curved by mass and energy.

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12
Q

What is the cosmological constant (?)?

A

It represents dark energy and is responsible for the accelerated expansion of the universe.

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13
Q

What is dark matter?

A

An invisible form of matter that makes up most of the universe’s mass and affects its structure.

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14
Q

What is dark energy?

A

A mysterious force driving the accelerated expansion of the universe.

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15
Q

How does General Relativity explain the orbit of planets?

A

Planets move along curved paths in the curved space-time around a star.

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16
Q

What is gravitational lensing?

A

The bending of light as it passes near a massive object due to the curvature of space-time.

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17
Q

What causes time to slow down near massive objects?

A

The stronger gravitational field curves space-time more, causing time to pass more slowly.

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18
Q

Why is space-time considered four-dimensional?

A

It includes three spatial dimensions and one time dimension.

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19
Q

How does the expansion of the universe affect light?

A

It stretches the light waves, causing redshift.

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20
Q

What is the redshift in cosmology?

A

The lengthening of the wavelength of light from distant objects as the universe expands.

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21
Q

What does ?CDM stand for?

A

Lambda Cold Dark Matter model.

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22
Q

What is the significance of the ? in the ?CDM model?

A

It represents the cosmological constant, associated with dark energy.

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23
Q

What does ‘Cold’ in Cold Dark Matter refer to?

A

It refers to dark matter that moves slowly compared to the speed of light.

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24
Q

How much of the universe’s mass-energy content is ordinary matter?

A

About 5%.

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25
Q

What percentage of the universe is made up of dark energy?

A

About 68%.

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26
Q

What role does dark matter play in the universe?

A

It provides the gravitational framework for the formation of galaxies and large structures.

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27
Q

How does the ?CDM model explain cosmic microwave background radiation?

A

It provides a snapshot of the early universe, consistent with the predictions of the ?CDM model.

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28
Q

What is the significance of the Hubble constant in cosmology?

A

It measures the rate of expansion of the universe.

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29
Q

How does dark energy affect the universe’s expansion?

A

It causes the expansion of the universe to accelerate.

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30
Q

What are the key components of the ?CDM model?

A

Ordinary matter, dark matter, dark energy, and the expansion of the universe.

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31
Q

What causes cosmological redshift?

A

The expansion of the universe stretches the light waves from distant galaxies.

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32
Q

What is Doppler redshift?

A

The redshift caused by an object moving away from an observer, stretching the light waves.

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33
Q

How does gravitational redshift occur?

A

Light loses energy and shifts to longer wavelengths as it escapes a strong gravitational field.

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34
Q

Why is infrared light important for studying distant galaxies?

A

Distant galaxies are redshifted into the infrared region, so we observe them in infrared light.

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35
Q

What does ‘z’ represent in cosmology?

A

It represents the redshift, indicating how much the universe has expanded since the light was emitted.

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36
Q

What does a redshift of z=10 signify?

A

The light was emitted when the universe was very young, about 13 billion years ago.

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37
Q

How do we measure the redshift of a galaxy?

A

By analyzing the shift in the wavelength of light emitted from the galaxy.

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38
Q

What is the relationship between redshift and the age of the universe?

A

Higher redshifts correspond to looking further back in time, closer to the universe’s beginning.

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39
Q

How does redshift affect the apparent color of galaxies?

A

It shifts their light toward the red end of the spectrum, making them appear redder.

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40
Q

What is the role of JWST in observing redshifted galaxies?

A

JWST’s infrared capabilities allow it to observe galaxies that are highly redshifted.

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41
Q

How does space-time curvature explain the weight of an object on Earth?

A

The Earth’s mass curves space-time, and the object’s weight is the force felt as it follows this curvature.

42
Q

What happens to space-time near a black hole?

A

It becomes extremely curved, creating a region where gravity is so strong that not even light can escape.

43
Q

How does space-time curvature affect the orbit of planets?

A

Planets follow the curved paths in space-time created by the mass of the Sun.

44
Q

Why do we feel weight on Earth?

A

Because the Earth’s surface prevents us from moving along the curved space-time, creating the sensation of weight.

45
Q

What is gravitational time dilation?

A

The slowing down of time in a strong gravitational field, like near a massive object.

46
Q

How is the curvature of space-time visualized in 2D?

A

It can be imagined as a rubber sheet that bends under the weight of a heavy object.

47
Q

How does Einstein’s theory differ from Newton’s view of gravity?

A

Einstein described gravity as the curvature of space-time, while Newton saw it as a force between masses.

48
Q

What effect does mass have on space-time?

A

Mass curves space-time, affecting the paths of objects moving through it.

49
Q

How does General Relativity explain gravitational lensing?

A

Light bends as it passes through the curved space-time around a massive object.

50
Q

What is a geodesic in space-time?

A

The shortest path an object follows in curved space-time, often appearing as a curved trajectory.

51
Q

What is the event horizon of a black hole?

A

The boundary beyond which nothing can escape the black hole’s gravity.

52
Q

What happens to time near a black hole?

A

Time slows down significantly as you approach a black hole.

53
Q

What is singularity in a black hole?

A

A point where the curvature of space-time becomes infinite, and the laws of physics as we know them break down.

54
Q

Can anything escape a black hole?

A

No, not even light can escape from within the event horizon of a black hole.

55
Q

How are black holes detected if they emit no light?

A

By observing the effects of their gravity on nearby objects and light.

56
Q

What is spaghettification?

A

The stretching and compression of objects into long thin shapes as they fall into a black hole.

57
Q

What is Hawking radiation?

A

Theoretical radiation that black holes could emit due to quantum effects near the event horizon.

58
Q

How does a black hole affect the space-time around it?

A

It causes extreme curvature, creating a deep ‘well’ in space-time.

59
Q

What is the Schwarzschild radius?

A

The radius of the event horizon of a non-rotating black hole, beyond which escape is impossible.

60
Q

How do black holes form?

A

From the collapse of massive stars after they have exhausted their nuclear fuel.

61
Q

How does quantum mechanics challenge General Relativity?

A

Quantum mechanics operates on small scales and doesn’t easily integrate with the large-scale effects of General Relativity.

62
Q

What is the search for quantum gravity?

A

The effort to find a theory that unifies quantum mechanics with General Relativity.

63
Q

What is string theory?

A

A theoretical framework that attempts to reconcile quantum mechanics and General Relativity by describing particles as tiny vibrating strings.

64
Q

What role do higher dimensions play in string theory?

A

String theory suggests that there may be additional dimensions beyond the familiar three spatial and one time dimension.

65
Q

What is the Planck scale?

A

The scale at which quantum gravitational effects are expected to become significant, and space-time may become quantized.

66
Q

How does the Heisenberg Uncertainty Principle relate to quantum mechanics?

A

It states that the more precisely we know a particle’s position, the less precisely we can know its momentum, and vice versa.

67
Q

What are virtual particles?

A

Temporary particle pairs that pop in and out of existence in quantum fields, potentially contributing to phenomena like Hawking radiation.

68
Q

How does quantum entanglement challenge classical physics?

A

It shows that two particles can be instantaneously connected regardless of the distance separating them, defying classical ideas of locality.

69
Q

What is a quantum superposition?

A

The concept that particles can exist in multiple states at once until measured.

70
Q

How might quantum mechanics and General Relativity conflict?

A

General Relativity treats space-time as smooth and continuous, while quantum mechanics suggests it might be discrete at very small scales.

71
Q

What is the Big Bang Theory?

A

The leading explanation for how the universe began, starting from a hot, dense state and expanding over time.

72
Q

What is cosmic inflation?

A

A rapid expansion of the universe immediately after the Big Bang, solving several cosmological puzzles.

73
Q

How old is the universe?

A

Approximately 13.8 billion years.

74
Q

What is the cosmic microwave background (CMB)?

A

The afterglow of the Big Bang, visible as faint microwave radiation permeating the universe.

75
Q

What does the CMB tell us about the early universe?

A

It provides a snapshot of the universe when it was just 380,000 years old, showing temperature fluctuations that led to galaxy formation.

76
Q

What is dark energy’s role in the universe?

A

It drives the accelerated expansion of the universe.

77
Q

What is the observable universe?

A

The portion of the entire universe that we can potentially observe, limited by the speed of light.

78
Q

What is the multiverse theory?

A

The idea that our universe might be one of many, each with its own laws of physics.

79
Q

What is a galaxy cluster?

A

A large group of galaxies bound together by gravity.

80
Q

What is the fate of the universe according to current theories?

A

The universe could continue expanding indefinitely, potentially leading to a ‘Big Freeze’ where stars burn out and the universe grows cold and dark.

81
Q

What is the Einstein field equation?

A

A set of equations in General Relativity that describe how matter and energy determine the curvature of space-time.

82
Q

How does the curvature of space-time affect the path of light?

A

Light follows the curved paths in space-time, which can cause effects like gravitational lensing.

83
Q

What is the cosmological principle?

A

The assumption that the universe is homogeneous and isotropic on large scales, meaning it looks the same in every direction.

84
Q

What is cosmic variance?

A

The statistical uncertainty in observations due to the limited number of cosmic structures we can observe in the universe.

85
Q

How do scientists measure the expansion rate of the universe?

A

By observing distant galaxies and using redshift to determine how fast they are moving away from us.

86
Q

What is the significance of Hubble’s Law?

A

It states that the speed at which a galaxy moves away from us is proportional to its distance, implying the universe is expanding.

87
Q

What is an inflationary universe?

A

A model in which the universe underwent an extremely rapid expansion in the first fractions of a second after the Big Bang.

88
Q

What is the cosmological constant problem?

A

The discrepancy between the observed value of the cosmological constant (dark energy) and the value predicted by quantum field theory.

89
Q

What is the significance of the horizon problem in cosmology?

A

It questions why different regions of the universe, too far apart to have exchanged information, have the same temperature, which inflation theory helps to explain.

90
Q

What is the flatness problem?

A

The puzzle of why the universe appears to be so close to being geometrically flat, which is also explained by inflation.

91
Q

How does the JWST improve our understanding of the universe?

A

By observing in the infrared spectrum, allowing us to see distant, redshifted galaxies and study the early universe.

92
Q

What is the significance of measuring the mass-to-light ratio in galaxies?

A

It helps determine how efficiently galaxies are converting gas into stars, particularly in the early universe.

93
Q

How do scientists use spectral energy distribution (SED) fitting?

A

To estimate the physical properties of galaxies, such as stellar mass, by analyzing their emitted light across different wavelengths.

94
Q

What are the implications of finding more massive galaxies in the early universe than expected?

A

It suggests that star formation may have been more efficient or that the conditions in the early universe were different than current models predict.

95
Q

What role does the IMF (Initial Mass Function) play in understanding star formation?

A

The IMF describes the distribution of masses for a population of stars, affecting the mass-to-light ratio and star formation efficiency.

96
Q

Why is the study of galaxy clustering important?

A

It provides insights into the distribution of dark matter and the efficiency of star formation across cosmic time.

97
Q

What are ‘cosmic variance’ and ‘Poisson errors,’ and why are they considered in cosmological studies?

A

They are sources of uncertainty in observational data, with cosmic variance referring to statistical uncertainties due to the finite size of the observable universe, and Poisson errors arising from the discrete nature of galaxy counts.

98
Q

What does ‘baryon conversion efficiency’ refer to in cosmology?

A

The efficiency with which baryonic matter (normal matter) in a galaxy is converted into stars.

99
Q

What does an excess of massive galaxies at high redshifts imply about the early universe?

A

It may indicate a higher baryon conversion efficiency or changes in the mass-to-light ratios compared to the present-day universe.

100
Q

What could future observations reveal about the nature of dark matter and dark energy?

A

They could help refine our understanding of these components, potentially leading to new physics beyond the ?CDM model.

Relativity (1 decks)

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