Edwin Hubble In 1925 Hubble proved that those

Edwin Hubble • In 1925, Hubble proved that those fuzzy spiral nebulae were actually other galaxies, separate from our Milky Way • He then pioneered the use of Doppler Shift to study how those galaxies move.

What possible ways can the Universe behave? • A steady universe where nothing moves or changes relative position. • A constantly expanding or contracting universe • A random universe with no pattern. • How can we find out?

What we’ll do: • We are going to graph the velocity of galaxies vs. the distance to them. • We’ll use the Galaxy and Cosmos Exploration Tool (GCET) to choose and measure galaxies – Each person will select 5 galaxies and look up their distance and redshift – Use the Redshift Velocity Calculator to determine each one’s velocity • Enter your data into the google form

Our data

Hubble’s Law The relationship (slope of the line) is characterized by Hubble’s constant H 0: The currently accepted value for Hubble’s constant: Measuring distances using Hubble’s law actually works better the farther away the object is; random motions are overwhelmed by the recessional velocity.

This puts the final step on our distance ladder: If we measure the redshift of a faraway galaxy, we can determine its distance. Hubble’s Law

Another Meaning for Ho • Okay, we can use Hubble’s constant to determine distance REALLY far out • That slope is also a relationship between distance and velocity – What else is related to “d” and “v”? – A little algebra rearranges this to – So Hubble’s Constant • But what time is “t”

How much time? Well, our slope was 2. 36 x 10 -18 If we convert that from seconds into years: