ASTR 123 – Flashcards

Astronomers believe that nearly all galaxies are moving away from us because:

Current estimates place the value of H0 near 22km/s/Mly giving 14 billion years as the age of the universe. If H0 were in fact 44km/s/Mly, the approximate age of the universe would be:

Suppose Hubble's constant is H0 = 22km/s/Mly. Then we would expect a galaxy located 10 million light years away to be moving away from us at a speed of about:

An astronomer measures the velocities of two galaxies, galaxy A and galaxy B. He finds that galaxy A is moving at twice as fast away from us as galaxy B. Assuming these galaxies are moving because the expansion of space, which statement is true?

Suppose we lived in a Universe that was shrinking rather then expanding. If you measured the velocities of many galaxies, what would you find?

From our vantage point in the Milky Way, we see distant galaxies all moving away from us, and more distant ones moving faster. Suppose you lived in a distant galaxy, what would you observe?

One reason Hubble's constant isn't exactly know today is :

Why do you think we observe a dark space between the galaxies?

Which of the following statements best describes what astronomers mean when they say that the universe is expanding?

Note that an observer located at the Local Raisin would see Raisins 1, 2, and 3 all move away from her during the video. What would an observer located at Raisin 2 see?

The table in the video shows you the speeds of Raisins 1, 2, and 3 as measured from the Local Raisin. Suppose instead that you measured speeds as seen from Raisin 2. An observer at Raisin 2 would measure __________.

The following statements describe ways in which the analogy might apply to the real universe. Which statements are correct?

Based on what you've learned from the raisin cake analogy, which two properties of distant galaxies do astronomers have to measure to show that we live in an expanding universe?

Today, the evidence that we live in an expanding universe is extremely strong because astronomers have measured the motions of millions of galaxies. Nevertheless, in science, we must always remain open to the possibility that some future observation could call even our most strongly supported theories into question. Which of the following hypothetical observations would not be consistent with what we expect in an expanding universe?

The following figures give the approximate distances of five galaxies from Earth. Rank the galaxies based on the speed with which each should be moving away from Earth due to the expansion of the universe, from fastest to slowest.

The following figures give the approximate speeds at which five galaxies are moving away from Earth due to the expansion of the universe. Rank the galaxies based on their distance from Earth, from farthest to closest.

The following figures give the approximate speeds at which five galaxies are moving away from Earth due to the expansion of the universe. Rank the galaxies based on the amount of redshift that would be observed in each galaxy's spectrum, from largest to smallest.

Hubble's law is a relationship between galaxy speeds and galaxy distances. This relationship can be shown as a line on a graph of speed versus distance. Each of the following four graphs shows a possible relationship expressing Hubble's law. Rank the graphs based on their predictions of the speed, from fastest to slowest, for a galaxy located 400 million light-years away from Earth.

The following four graphs are the same as those from Part D, with each showing a possible relationship for Hubble's law. Rank the graphs based on the prediction they each would make for the current age of the universe, from oldest to youngest.

When we observe a distant galaxy whose photons have traveled for 10 billion years before reaching Earth, we are seeing that galaxy as it was when the universe was

I observe a galaxy that is 100 million light years away. Which of the following do I see?

The horizontal axis of the graph measures the time since the Big Bang in seconds. The extreme left of the horizontal axis, where it meets the vertical axis, is labeled 10−45 seconds (that is a decimal point followed by 44 zeroes and then a one). If we move along two tick marks to the right on the horizontal axis, it is labeled 10−35 seconds. By what factor does the time increase from one tick mark on the horizontal axis to the next tick mark toward the right?

The vertical axis of the graph measures the temperature of the universe in kelvin. If we move up one tick mark to the next, by what factor does the temperature increase?

In basic terms, what does the graph show?

To get your bearings on the horizontal time axis of this plot, it is useful to calculate the age of the universe in seconds today. If you multiply the age of the universe in years by the number of seconds in a year, approximately what is the current age of the universe in seconds?

Suppose you want to know what the temperature of the universe was 1 billion years ago. Where along the horizontal axis should you look?

What was the approximate temperature of the universe when the universe was just 1 second old?

From Part C, you know that in basic terms, the graph shows that the temperature of the universe decreases with time. In more specific terms, this graph shows that the temperature of the universe __________.

What happens to gas when it freely expands?

The four fundamental forces that operate in the universe today are ________.

The electromagnetic force is stronger than gravity. Why is it over-powered by gravity on large scales?

According to the Big Bang theory, why do we live in a universe that is made of almost entirely of matter rather than antimatter?

What kind of particle does the Large Hadron Collider accelerate?

The Large Hadronic Collider set a new world record in December, 2009. What was the record for?

What famous (or infamous) United States collider, set to be built in Texas, was cancelled in 1993?

Which of the following accelerators held the record for the highest energy collisions before the Large Hadron Collider broke it?

The Large Hadron Collider is designed to reach high energies. The results of this experiment are relevant to which of the following astrophysical situations?

According to the article, the scientific impact of the Large Hadron Collider can be summarized by which of the following statements?