Astronomy ch 17
The electromagnetic force is stronger than gravity. Why is it overpowered by gravity on large-scale's?
Most objects are electrically neutral
Helium originates from
Mostly from the Big Bang with a small contribution from Stellar nucleosynthesis.
Which event in the history of the universe happened last?
Neutral atoms formed.
Based on our current understanding of physics, We can understand the conditions that prevailed in the early universe as far back in time as about ____.
One 10 billionth of a second after the Big Bang
Which of the following histories are in the correct order of occurrence?
The Big Bang happen send me tenuously with the start of the expansion of the universe, then stars make the first elements heavier than helium, then the sun forms.
What are the two key observational fax that led to widespread acceptance of the Big Bang model?
The cosmic background radiation in the helium content of the universe
Evidence that the cosmic background radiation is the remnant of the Big Bang comes from predicting characteristics of remnant radiation from the Big Bang Siri and comparing these predictions of the observations. Four of the five statements below are real. which one is fictitious?
The cosmic background radiation is expected to contain redshifted Emission lines from the hydrogen and helium, and it does
The Big Bang predict that the universe should be 25% hydrogen and 75% helium
False
Approximately how long did the nucleosynthesis era last?
Five minutes
The Big Bang theory is supported by two major lines of evidence that alternative models have not successfully explained. What are they?
(1) the theory predicts the existence of and the specific characteristics of the observed cosmic microwave background. (2) the theory correctly predicts the observed overall chemical composition of the primeval universe
Rank these times based on the wavelength of the Peak intensity of the cosmic background radiation at those times, from shortest to longest.
1 million years after the Big Bang, 100 million years after the Big Bang, today.
According the the BBT, how many forces - and which ones - operated in the universe during the GUT era?
2 forces: Gravity and a single force that later became the strong, weak, and electromagnetic forces.
What is the temperature of the universe (as a whole) today?
3 K
What do we mean by inflation?
A sudden and extremely rapid expansion of the universe that occurred in a tiny fraction of a second during the universes first second of existence.
Why might inflation have occurred at the end of the GUT era?
An enormous amount of energy was released when the strong and electroweak forces froze out from the GUT force
What is the significance of the Planck time?
Before it, conditions were so extreme that our current understanding of physics is insufficient to predict what might have occurred.
In principle, if we could see all the way all the way to the cosmological horizon we could see the Big Bang taking place. However, our view is blocked for times prior to about 380,000 years after the Big Bang. Why?
Before that time, the gas in the universe was dense and ionized and therefore did not allow light to travel freely
In stars, helium can sometimes be fused into carbon and heavier elements (in their final stages of life). Why didn't the same fusion processes produce carbon and heavier elements in the early universe?
By the time stable helium nuclei had formed, the temperature and density had already dropped too low for helium fusion to occur
Why is the nucleosynthesis era so important in determining the chemical composition of the universe?
Except for a small amount of elements heavier than helium produced later by stars, the chemical composition of the universe is the same now as at the end of the nucleosynthesis era.
In the cosmic timeline for the universe starting at the Big Bang, we live in the Planck era.
False
The Big Bang produced no elements heavier than helium because it was never hot enough for healing them to undergo fusion.
False
Economic history is easier to write in the history of the universe. Nevertheless, most cosmologists now think that when the universe was formed ____.
First there was the Big Bang and then inflation which caused recession
In the past, the temperature of the universe was ____.
Hotter than it is today
If observations had shown that the cosmic microwave background was perfectly smooth (rather than having very slight variations in temperature), then we would have no way to account for _____.
How galaxies came to exist
What kinds of atomic nuclei form during the nucleosynthesis era?
Hydrogen, helium and trace amounts of Lithium, beryllium, and boron.
How does the idea of inflation account for the existence of the "seeds" of density from which galaxies and other large structures formed?
Inflation would have caused random, microscopic quantum fluctuations to grow so large in size that they became yeh seeds of structure.
Which of the following is not an observed characteristic of the cosmic microwave background?
It contains prominent spectral lines of hydrogen, the primary chemical ingredient of the universe
What happens to gas as it freely expands?
It he's less dense and cools
Which of the following statements about the cosmic background radiation is not true?
It is the result of a mixture of radiation from many independent sources, such as stars and galaxies that formed within the first billion years of the big bang
Which statement about the cosmic microwave background is NOT true?
It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.
Which statement about the cosmic microwave background is not true?
It is the result of a mixture of radiation from the many independent sources, such as stars and galaxies.
What direct evidence do we have that the weekend electromagnetic forces were once unified as a single force?
Particle accelerators on earth can reach energies equivalent to the high temperatures of the electroweak era and have produced particles predicted by the unified theory
How does the serious inflation explain the near uniformity of the cosmic microwave background?
Prior to rapid inflation, all regions of space were close enough to bounce radiation back-and-forth and reach the same temperature.
Which of the following statements CANNOT be tested by science today?
Prior to the Planck time, our universe edged from another universe
Creation science claims that scientific evidence can and does prove God made the universe. Select the statement which does not identify a legitimate objection to this claim.
Scientists are not allowed to believe in God.
Which adjective does not necessarily describe a known feature of the early universe?
Small
Which of the following important events occurred earliest in the history of the universe?
Space time rapidly expanded during a brief period of time
The four fundamental forces that operate in the universe today are ____.
Strong force, weak force, electromagnetic force, gravity
Why does the Big Bang theory predicts that the cosmic background radiation should have a perfect thermal radiation spectrum?
The background radiation came from the heat of the universe, with a pick a corresponding to the temperature of the universe.
What was the significance of the end of the era of nucleosynthesis, when the universe was about 5min old?
The basic chemical composition of the universe had been determined
What happens when a particle of matter meets its corresponding anti-particle of antimatter?
The combined mass of the two particles is completely transformed into energy
What happens when a particle of matter meets its corresponding antiparticle of antimatter?
The combined mass of the two particles is completely transformed into energy (photons)
Why did the era of nucleosynthesis end?
The density of the universe became too low
Which of the following hypothetical observations, if true, what does prove a prediction of the Big Bang theory?
The discovery of a galaxy with 10% helium abundance
The Big Bang theory seems to explain how elements were formed during the first few minutes after the Big Bang. Which hypothetical observation below would call our current theory into question?
The discovery of a galaxy with a helium abundance of only 10% by mass
Which forces have physicist shown to be the same force under conditions of a very high temperature, as confirmed by experiments and particle accelerators?
The electromagnetic and weak forces
Lab experiments conducted with particle accelerators confirm predictions made by the theory that unifies ____.
The electromagnetic and weak forces into the electroweak force
What is postulated to have caused a set inflation of the early universe?
The energy released from the freezing out of the strong force from the GUT force
Which of the following observations cannot be explained by the Big Bang theory unless we assume that an episode of inflation occurred?
The fact that temperature of the cosmic microwave background is almost the same everywhere.
Which of the following observations cannot be explained by the Big Bang theory unless we assume that an episode of inflation occurred?
The fact that the temperature of the cosmic microwave background is almost the same everywhere
What is the Big Bang theory?
The idea that all matter and energy in the universe began in and unimaginably dense state, and then space itself began expanding
Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions?
The overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form.
Why do we think tiny quantum ripples should have been present in the very early universe?
The principles of quantum mechanics required that the energy fields at any point in space be continually fluctuating.
Which of the following statements correctly summarizes the events in the early universe according to the Big Bang theory?
The universe began with the forces unified. During the first fraction of a second, the forces separated and there was a brief but important episode of inflation. Subatomic particle's of both matter and antimatter then began to appear from the energy present in the universe. Most of the particles annihilated to make photons, but some became protons, neutrons, electrons, and neutrinos. The protons and neutrons underwent some fusion during the first five minutes, they are by determining the basic chemical composition of the universe.
Which of the following statements explains why the night sky is dark?
The universe has a finite age
Why did the era of nuclei and when the universe was about 380,000 years old?
The universe has expanded and cooled enough for stable, neutral atoms to form.
Which of the following is not consistent with observations of the cosmic microwave background?
The universe is at lease 20 billion years old
Which of the following statements best explains what we mean when we say that the electroweak and strong forces "froze out" at 10^-38 second after the Big Bang?
These two forces first became distinct at this time
What happened to all of the quarks that existed freely in the particle era?
They combined in groups to make protons, neutrons, into their anti-particles.
If inflation really occurred in our observable universe is only a tiny portion of the entire universe born in the Big Bang
True
In the particle era, particles of matter outnumbered particles of antimatter by about one particle in 1 billion.
True
Observations of the cosmic background radiation for the COBE satellite revealed tiny variations in its temperature by about one part and 100,000.
True
Recent measurements of the temperature fluctuations in the cosmic microwave background radiation support the production of inflation that the overall geometry of the universe is flat
True
The observed composition of ordinary matter in the universe roughly 75% hydrogen and 25% helium by mass closely matches the theoretical predictions based on the Big Bang model
True
A "GUT" (grand unified theory) refers to theories that ____.
Unify the strong force with the electromagnetic and weak nuclear forces
Why can't current theorists describe what happened during the Planck era?
We do not yet have a theory that links quantum mechanics and general relativity
How do we determine the conditions that existed in the very early universe?
We work backward from current conditions to calculate what temperature and densities must have been when the observable universe was much smaller in size
Olbers' paradox is an apparently simple question, but it's resolution suggests that the universe is finite in age. What is the question?
Why is the sky dark at night?
