Editing Hubble's law (section)

=== Cosmological constant abandoned ===
{{main|Cosmological constant}}
After Hubble's discovery was published, [[Albert Einstein]] abandoned his work on the [[cosmological constant]], a [[Term (logic)|term]] he had inserted into his equations of general relativity to coerce them into producing the static solution he previously considered the correct state of the universe. The Einstein equations in their simplest form model either an expanding or contracting universe, so Einstein introduced the constant to counter expansion or contraction and lead to a static and flat universe.<ref name="mapcc">{{cite web |title=What is a Cosmological Constant? |url=http://map.gsfc.nasa.gov/universe/uni_accel.html |publisher=[[Goddard Space Flight Center]] |access-date=2013-10-17 }}</ref> After Hubble's discovery that the universe was, in fact, expanding, Einstein called his faulty assumption that the universe is static his "greatest mistake".<ref name=mapcc /> On its own, general relativity could predict the expansion of the universe, which (through [[Tests of general relativity|observations]] such as the [[Gravitational lens|bending of light by large masses]], or the [[Perihelion precession of Mercury|precession of the orbit of Mercury]]) could be experimentally observed and compared to his theoretical calculations using particular solutions of the equations he had originally formulated.

In 1931, Einstein went to Mount Wilson Observatory to thank Hubble for providing the observational basis for modern cosmology.<ref>{{cite book |last=Isaacson |first=W. |date=2007 |title=Einstein: His Life and Universe |url=https://archive.org/details/einsteinhislifeu0000isaa |url-access=registration |page=[https://archive.org/details/einsteinhislifeu0000isaa/page/n395 354] |publisher=[[Simon & Schuster]] |isbn=978-0-7432-6473-0 }}</ref>

The cosmological constant has regained attention in recent decades as a hypothetical explanation for [[dark energy]].<ref>{{cite web |date=28 November 2007 |title=Einstein's Biggest Blunder? Dark Energy May Be Consistent With Cosmological Constant |url=https://www.sciencedaily.com/releases/2007/11/071127142128.htm |website=[[Science Daily]] |access-date=2013-06-02 }}</ref>

{{anchor|redshift}}