Chapter 1 - Overview Flashcards
Test Review for Chapter 1 (12 cards)
Astronomical unit
The average distance from Earth to the Sun
(150 million km)
Big Bang
A period of rapid expansion that gave birth to our universe
Created the elements hydrogen and helium
Light year
The distance light travels in one year
(9.46 trillion km)
Lookback time
How deep into the past we are looking when we observe an object
(how long it has taken the light from that object to reach us)
Observable universe
The portion of the universe that we can observe because light from the objects there has had sufficient time to reach us
When observing an object, are we seeing it as it is now or as it was at some point in the past?
We see it as it was in the past, because the light from that object has had to travel to reach us
How does the object’s distance in light years relate to the fact that we observe objects as they were in the past?
For an object X light-years away, we are seeing it as it was X years in the past
What does it mean to say we are made of “star stuff”?
All elements except hydrogen and helium were made in the cores of stars
How does the “raisin bread” model help explain the expansion of the universe?
As the bread bakes, the raisins spread out. An observer at one raisin sees the other raisins moving away from them. Raisins that are further away appear to be moving away faster.
If two objects cover the same distance in different times, which has the higher speed?
The object that covered the distance in the shorter time
If two objects travel different distances at the same speed, which traveled farthest?
The object that continued moving for the most time
If two objects have the same orbital period, but one has a larger orbital radius, which one has the higher average speed?
The object with the larger orbital radius
