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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?.
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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
Hubble’s Law The relationship (slope of the line) is characterized by Hubble’s constant H0: 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.
Hubble’s Law This puts the final step on our distance ladder: If we measure the redshift of a faraway galaxy, we can determine its distance.
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 2.36x10-18 If we convert that from seconds into years: