physics

Newtonian gravity

1687

Newton's law of universal gravitation states that every particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Planet Vulcan

1859

To explain Mercury’s odd behavior , which orbited closer to the sun. He suggested that the gravity from Vulcan was influencing Mercury’s orbit. But repeated observations revealed no signs of Vulcan.

Special relativity

1905

a theory proposed by Albert Einstein that describes the propagation of matter and light at high speeds

Einstein predicts gravitational redshift

1907

theory of general relativity predicts that the wavelength of electromagnetic radiation will lengthen as it climbs out of a gravitational well. ... As an example, take the white dwarf star Sirius B, with a gravitational field ~100,000 times as strong as the Earth's.

General relativity

1915

General relativity is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics.

Einstein theories stimulated emission

1917

Einstein devised an improved fundamental statistical theory of heat, embracing the quantum of energy. First, Einstein proposed that an excited atom in isolation can return to a lower energy state by emitting photons, a process he dubbed spontaneous emission.

Prediction of frame dragging

1918

Frame-dragging is an effect on space time, predicted by Einstein's general theory of relativity, that is due to non-static stationary distributions of mass–energy. ... They predicted that the rotation of a massive object would distort the space time metric, making the orbit of a nearby test particle precess.

First observation of gravitational lensing

1919

lensing is the bending of light around massive objects, such as a black hole, allowing us to view objects that lie behind it. During a total solar eclipse in May 1919, stars near the sun were observed slightly out of position.

First measurement of gravitational red shift

1925

which measures the redshift of light ... However, if the two systems are in a gravitational field then the photon may undergo gravitational redshift as it travels from the first system to the second.

Prediction of a galactic gravitational lensing

1937

he amount of bending is one of the predictions of Albert Einstein's general theory of relativity. ... Fritz Zwicky posited in 1937 that the effect could allow galaxy clusters to act as gravitational lenses.

Gravitational redshift verified

1959

is the phenomenon that clocks in a gravitational field tick slower when observed by a distant observer. More specifically the term refers to the shift of wavelength of a photon to longer wavelength (the red side in an optical spectrum) when observed from a point in a lower gravitational field. In the latter case the 'clock' is the frequency of the photon and a lower frequency is the same as a longer ("redder") wavelength.

Laser invented using stimulated emission

1960

originated as an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.

First evidence for black holes

1960

The 1960s was the beginning of the renaissance of general relativity, and saw the discovery of galaxies that were powered by the immense pull of black holes in their centres.

First observation of gravitational time delays

1966

effect was observed between 1966-7 by bouncing radar beams off the surface of Venus and measuring the time taken for the signals to return to Earth. The delay measured agreed with Einstein’s theory. We now use time-delays on cosmological scales, looking at the time differences in flashes and flares between gravitationally lensed images to measure the expansion of the universe.

False detection of gravitational waves

1969

First, a bit of history. In February 2016, it was announced that gravitational waves had been found for the first time – ripples in space-time caused by colliding black holes. In June 2016, we found some more. And then we found more again in February 2017.

Indirect evidence for gravitational waves

1974

Two neutron stars orbiting each other should lose a precisely defined amount of energy as they radiate gravitational waves.

LIGO receives funding

1979

The initial LIGO observatories were funded by the National Science Foundation (NSF) and were conceived, built, and are operated by Caltech and MIT.

First observation of a galactic gravitational lens

1979

The first extragalactic gravitational lens was discovered, when observers Dennis Walsh, Bob Carswell and Ray Weymann saw two identical quasi-stellar objects, or “quasars”.

Another false alarm for gravitational waves

1987

The LIGO Laboratory operates two detector sites, one near Hanford in eastern Washington, and another near Livingston, Louisiana. This photo shows the Livingston detector site.

LIGO construction begins

1994

On 11 February 2016, the LIGO and Virgo collaborations announced the first observation of gravitational waves. The signal was named GW150914.

LIGO starts first search

2002

The first observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016.

Frame dragging probe

2004

Thirring effect, the frame of reference in which a clock ticks the fastest is one which is revolving around the object as viewed by a distant observer. ... It is now the best known frame-dragging effect, partly thanks to the Gravity Probe B experiment.

LIGO hunt ends

2005

Earth’s premier gravitational wave hunter turned on for its second science run – and after the first run’s grand success, hopes are high for what this next six-month round of observation may bring.

Enhanced LIGO

2009

The initial LIGO detectors have finished a two year long data run during which a full year of triple-coincidence data was collected at design sensitivity. Much of this run was also coincident with the data runs of interferometers in Europe, GEO600 and Virgo.

Enhanced LIGO hunt ends

2010

This document presents the baseline plan for enhancing aspects of the LIGO detectors in the time period between the end of the fifth Science Run.

Advanced LIGO upgrade completed

2014

An additional data run with the modified Enhanced LIGO detectors reached completion in 2010.

LIGO upgraded again

2015

This remarkable discovery, confirmed by electromagnetic telescopes around the world, illuminates a century-old puzzle about the origins of high-energy cosmic rays and marks a major breakthrough for the emerging new field of multi-messenger astrophysics.

False alarm #3 for gravitational waves

2015

There is a strong rumour that gravitational waves of astronomy’s holy grails have been found. Rumours have been circulating since November that ‘something’ was detected in September 2015. Analysis is currently ongoing and if everything checks out an announcement is expected in February.

Gravitational wave detection confirmed

2016

For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.