Cosmology Flashcards
What is one astronomical unit (AU)?
The average distance from the Earth to the Sun (about 150 million km).
What is a light year?
The distance that light travels in a year.
How big an angle is an arc second?
It is a 3600th of 1 degree.
What is a parsec?
The distance at which a radius of 1 AU subtends an angle of 1 arc second.
What is stellar parallax?
The effect where a relatively nearby star shifts its position relative to some much more different stars when viewing from different points.
How is the Doppler Effect used to measure the velocity of receding objects?
The faster the recessional velocity of the object, the more it will redshifted.
What is Hubble’s Law?
The recessional velocity of a galaxy is directly proportional to its distance from Earth.
What is the cosmological principle?
The universe is homogeneous and isotropic (Matter is distributed evenly across the universe and the universe looks the same in all directions).
What are the two pieces of evidence for the Big Bang?
Hubble’s Law and the Cosmic Microwave Background Radiation.
Which constant can be used to give an approximation for the age of the universe?
1/Hubble’s Constant
What percentage of the universe is dark matter?
About 27%.
What percentage of the universe is dark energy?
About 68%.
What percentage of the universe is ordinary matter?
About 5%.
What are the theoretical effects of dark energy?
It causes the expansion of the Universe to accelerate.
Why is dark matter thought to exist?
Observations of spinning galaxies show that they are spinning far faster than they should be able to with just the ordinary matter inside them.
