8 Hubble Law 16f

# 8 Hubble Law 16f

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1 Astronomy 116 Lab 8 The Expanding Universe and Hubble’s Law Based on Voyager:Skygazer CD-ROM Activities (Addison-Wesley), adapted and revised by Emory Physics, 12/12/12 We live in an expanding universe, with galaxies moving further and further away from each other. These increasing distances are not simply due to galaxies moving through space, but rather are caused by space itself expanding. This expansion can be described by Hubble’s Law , which states that a galaxy’s distance and its radial velocity (velocity away from us) are directly proportional. It is expressed by the equation H=V/D where dividing a galaxy’s radial velocity (km/s) by its distance (megaparsecs) gives you H, the Hubble Constant. In this lab, you will determine a value for H by graphing a number of galaxies’ distances and radial velocities. Once you have done this, you will then be able to determine the distances to other galaxies. Using the Hubble Constant, you will also be able to determine an approximate age of the universe. The radial velocities of galaxies used to determine the Hubble Constant are calculated from the red shifts of the galaxies’ spectra. The equation that expresses the relationship between them is Δλ / λ = v / c where λ is the wavelength of spectral line at rest, and Δλ is the difference between the observed wavelength and λ . v is the radial velocity, and c is the speed of light, 300,000 km/s.

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