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SPACE PHYSICS NOTES
SUMMARY NOTES CLIPS
The Universe
The speed v at which a galaxy is moving away from the Earth can be found from the change in wavelength of the galaxy’s starlight due to redshift.
The distance of a far galaxy d can be determined using the brightness of asupernova in that galaxy.
The Hubble constant is one of the most important numbers in cosmology because it tells us how fast the universe is expanding, which can be used to determine the age of the universe and its history. It gets its name from UChicago alum Edwin Hubble, who was first to calculate the constant from his measurements of stars in 1929.
Define the Hubble constant 𝐻0 as the ratio of the speed at which the galaxy is moving away from the Earth to its distance from the Earth; recall and use the equation 𝐻0 = 𝑣/d
The current estimate for 𝐻0 is 2.2 x 10power18 per second
The equation 𝑑/𝑣= 1/ 𝐻0 represents an estimate for the age of the Universe and that this is evidence for the idea that all matter in the Universe was present at a single point.
