ASTRON 2B03 Lecture Notes - Lecture 7: Before Present, Cosmic Distance Ladder, Blueshift
12 Oct 2018
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Hubble"s law: speed: measured from the amount of doppler shift, distance: measured with standard candle technique (fainter = further away, v= hd, hubble had discovered the expanding universe, cosmology is the study of the origins of the universe. The look-back time to an object is the number of years between when the object emitted the light we see and the present. What piece of information does not affect the look-back time for a distant object: its distance, the speed of light, the rate of expansion of the universe, the wavelength of light being observed. The expanding universe: the space between galaxies are growing, carrying the galaxies along, when measuring this through the doppler shift we are measuring the space expanding, not the galaxies, which are not themselves expanding. In a small scale (i. e. molecules): the expansion does not matter because the bonding attraction forces between atoms overcomes the expansion.
