Hubble’s Law of the Universe Expanding

Although widely attributed to Edwin Hubble, the notion of the universe expanding at a calculable rate was first derived from the general relativity equations in 1922 by Alexander Friedmann. Friedmann published a set of equations, now known as the Friedmann equations, showing that the universe might expand, and presenting the expansion speed if this was the case. Then Georges Lemaître, in a 1927 article, independently derived that the universe might be expanding, observed the proportionality between recessional velocity of and distance to distant bodies, and suggested an estimated value of the proportionality constant, which when corrected by Hubble became known as the Hubble constant. Though the Hubble constant H0{displaystyle H_{0}} is roughly constant in the velocity-distance space at any given moment in time, the Hubble parameter H{displaystyle H}, which the Hubble constant is the current value of, varies with time, so the term ‘constant’ is sometimes thought of as somewhat of a misnomer. Moreover, two years later Edwin Hubble confirmed the existence of cosmic expansion, and determined a more accurate value for the constant that now bears his name.
Hubble inferred the recession velocity of the objects from their redshifts, many of which were earlier measured and related to velocity by Vesto Slipher in 1917.


What is the difference between a Lunar Eclipse and New Moon? They seem quite similar and there is often confusion between the two. A lunar eclipse happens twice a year whereas a new moon happens once a month. Here is further clarification: Therefore, the results of the new study support the idea that primitive life could potentially have evolved on Ganymede. This is because places where water and rock interact are important for the development of life. For example, some theories suggest that life arose on our planet within hot, bubbling seafloor vents. Before the new study, Ganymede's rocky seafloor was believed to be coated with ice--not liquid. This would have presented a problem for the evolution of living tidbits. The "Dagwood sandwich" findings, however, indicate something else entirely--the first layer on top of Ganymede's rocky core might be made up of precious, life-sustaining salty water. "The near-side of the Moon has been studied for centuries, and yet continues to offer up surprises for scientists with the right tools. We interpret the gravity anomalies discovered by GRAIL as part of the lunar magma plumbing system--the conduits that fed lava to the surface during ancient volcanic eruptions," Dr. Maria Zuber explained in an October 1, 2014 NASA Press Release. Dr. Zuber is from the Massachusetts Institute of Technology (MIT) in Cambridge.