# Hubble Constant Lab Report

Satisfactory Essays
Hubble Constant: Measuring the Expansion of the Universe
By J. Leavy (2239104L)
November 16, 2017
The rate of expansion of the universe, first derived as a possibility by Alexander Friedmann through his work with general relativity and his own Friedmann equations [1], was first observationally confirmed and roughly estimated by Edwin Hubble in 1929 [2], and has since appropriately come to be known as the Hubble Constant. Hubble’s work & observational data confirmed that the recessional velocity of a given galaxy was linearly related to the distance between the observed galaxy and the observer, and this relationship could be expressed (as Hubble’s Law):
V=HD
Where V is the recessional velocity, D is the distance, and H is the scaling factor that equates the two, known as the Hubble Constant [3].

Additionally, through unit analysis of these variables, Hubble provided a means for approximating the time the universe has been expanding: D/V=1/H
Since velocity is a distance unit by a time unit, unit analysis yields that the inverse of the Hubble Constant is an estimation for the time the universe has been expanding, and if one assumes the universe expands linearly for its life, an estimate of the age of the universe, known as the Hubble Time [3]:
If H=530s^(-1),D=〖(7.8*〖10〗^6〗_(in parsecs))*(〖30.857*〖10〗^12〗_(conversion to km) ),and V=3779
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With the 1991 launch of the Hubble Space Telescope (HST), astronomers have been given access to data orders of magnitude more accurate and plentiful. In 2001, Wendy Freedman and other researchers, using data obtained via the HST, calculated the value of H to 72 + 8 [6]. Working with data collected from the Chandra X-Ray Observatory in 2006, researcher Massimiliano Bonamente and his team derived a value for H of 77.6 +14.9, -12.5 [7]. Most recently at the LIGO observatory, the value for H was calculated to be 70.0 +12.0, -8.0