Flashcards in Chapter 1 Deck (17):
According to current scientific estimates, when did the Big Bang occur?
about 14 billion years ago
On the cosmic calendar, which compresses the history of the universe into a single year, about when did Earth form?
in early September
On the cosmic calendar, which compresses the history of the universe into a single year, about when did life arise on Earth?
On the cosmic calendar, which compresses the history of the universe into a single year, about when did early humans first walk on Earth?
just a few hours before midnight on December 31
Which of the following statements best describes what astronomers mean when they say that the universe is expanding?
The average distance between galaxies is increasing with time.
Based on what you’ve learned from the raisin cake analogy, what two properties of distant galaxies do astronomers have to measure to show that we live in an expanding universe?
their distances and speeds
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?
You discover an extremely distant galaxy that is moving toward us.
What is our "cosmic address" from small to large?
Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
When we say the universe is expanding, we mean that:
The average distance between galaxies is growing with time.
If stars existed but galaxies did not:
We would not exist because we are made of material that required recycling in galaxies.
Could we see a galaxy that is 20 billion light-years away?
No, because it would be beyond the bounds of our observable universe.
The star Betelgeuse is about 425 light-years away. If it explodes tonight:
We won't know about it until 425 years from now.
If we represent the solar system on a scale that allows us to walk from the Sun to Pluto in a few minutes, then:
the planets would all be marble size or smaller and the nearest stars would be thousands of miles away.
The total number of stars in the observable universe is roughly equivalent to:
the number of grains of sand on all the beaches on Earth.
The age of our solar system is about:
one-third of the age of the universe
An astronomical unit is:
Earth's average distance from the Sun.