Hubble’s Law & Expanding Universe

Question 1

What did people assume about the Universe before 1940’s?

Answer 1

Newton: Universe was infinite in time and unchanging

Question 2

Why is Edwin Hubble important?

Answer 2

Used Hooker 100” to discover cepheids of Andromeda—therefore
“Galaxies are very distant”

Cepheids are many kilo parsecs away

Question 3

What did Vesto Slipher discover?

Answer 3

Most galaxies are redshifted (by galaxy’s motion away from us)

Question 4

How does Redshift connect to Hubble?

Answer 4

Discovered correlation between galaxy distance and redshift!

Question 5

Hubble’s Law

Answer 5

Linear relationship between distance and redshift.
The greater the distance in light years a galaxy is, the more redshifted they are.

Question 6

Why is Hubble Law an important discovery?

Answer 6

Celestial objects that are farther away from Earth are moving away faster. Therefore, this Implies that the Universe is Expanding ! !
This also means that the Universe was tiny at some point—a beginning !

Question 7

Hubble Law Equation

Answer 7

v = HoD

v = recessional velocity (redshift)
Ho = Hubble Constant
D = distance

Question 8

Hubble Constant

Answer 8

The slope of the Hubble Plot; the rate of the expansion of the Universe

Question 9

What does the Origin of the Hubble Plot represent?

Answer 9

Milky Way

Question 10

How Can the Age of the Universe be calculated?

Answer 10

ON HUBBLE PLOT

t (Age of Universe) = d/v

d = distance
v = recessional velocity

t(Age of Universe) = 1/Ho

Ho = v/d

Question 11

What type of expansion does the Hubble Law suggest? What does this mean?

Answer 11

An expansion where it is the same anywhere (does not need a center).

This means that the expansion is SPACETIME STRETCHING. Galaxies do not move apart through space; galaxies get farther apart as space EXPANDS.

Question 12

What causes Cosmological Redshift?

Answer 12

Space stretching ! (Wavelength of light is stretched—makes light “shifted” towards red.