Scientists discover how to turn light into matter after 80-year quest
Imperial College London physicists have discovered how to create matter from light - a feat thought impossible when the idea was first theorised 80 years ago.
Imperial College London physicists have discovered how to create matter from light - a feat thought impossible when the idea was first theorised 80 years ago.
Optics & Photonics
May 18, 2014
48
17
The world's most indestructible species, the tardigrade, an eight-legged micro-animal, also known as the water bear, will survive until the Sun dies, according to a new Oxford University collaboration.
Earth Sciences
Jul 14, 2017
14
680
In the early-morning hours of today, 14 October 2022, astronomers using the Gemini South telescope in Chile operated by NSF's NOIRLab observed the unprecedented aftermath of one of the most powerful explosions ever recorded, ...
Astronomy
Oct 15, 2022
9
3097
Earlier this year, astronomers were keeping tabs on data from the Zwicky Transient Facility, an all-sky survey based at the Palomar Observatory in California, when they detected an extraordinary flash in a part of the sky ...
Astronomy
Nov 30, 2022
0
2825
(Phys.org)—A nearby short duration gamma-ray burst may be the cause of an intense blast of high-energy radiation that hit the Earth in the 8th century, according to new research led by astronomers Valeri Hambaryan and Ralph ...
Astronomy
Jan 21, 2013
55
0
A physicist at the University of California, Riverside, has performed calculations showing hollow spherical bubbles filled with a gas of positronium atoms are stable in liquid helium.
General Physics
Dec 6, 2019
19
8263
(Phys.org)—Five billion light years is a distance almost inconceivable, even on a cosmic scale. To better illustrate the extent of this physical quantity, it's enough to say that 35,000 galaxies the size of our Milky Way ...
(Phys.org)—Researchers have identified a burst of high-energy radiation known as 'dark lightning" immediately preceding a flash of ordinary lightning. The new finding provides observational evidence that the two phenomena ...
Earth Sciences
Apr 24, 2013
83
0
For the first time, scientists have witnessed the cataclysmic crash of two ultra-dense neutron stars in a galaxy far away, and concluded that such impacts forged at least half the gold in the Universe.
Astronomy
Oct 16, 2017
201
4589
A new way to test one of the basic principles underlying Einstein's theory of General Relativity using brief blasts of rare radio signals from space called Fast Radio Bursts is ten times, to one-hundred times better than ...
General Physics
Dec 30, 2015
135
3001
Gamma rays (denoted as γ) are electromagnetic radiation of high energy. They are produced by sub-atomic particle interactions, such as electron-positron annihilation, neutral pion decay, radioactive decay, fusion, fission or inverse Compton scattering in astrophysical processes. Gamma rays typically have frequencies above 1019 Hz and therefore energies above 100 keV and wavelength less than 10 picometers, often smaller than an atom. Gamma radioactive decay photons commonly have energies of a few hundred KeV, and are almost always less than 10 MeV in energy.
Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium. Alpha and beta "rays" had already been separated and named by the work of Ernest Rutherford in 1899, and in 1903 Rutherford named Villard's distinct new radiation "gamma rays."
Hard X-rays produced for by linear accelerators ("linacs") and astrophysical processes often have higher energy than gamma rays produced by radioactive gamma decay. In fact, one of the most common gamma-ray emitting isotopes used in nuclear medicine, technetium-99m produces gamma radiation of about the same energy (140 kev) as produced by a diagnostic X-ray machine, and significantly lower energy than the therapeutic treatment X-rays produced by linac machines in cancer radiotherapy.
In the past, distinction between the X-rays and gamma rays was arbitrarily based on energy (or equivalently frequency or wavelength), but because of the wide overlap and increasing use of megavoltage X-ray sources, now the two types of radiation are usually defined by their origin: X-rays are emitted by electrons outside the nucleus (and when produced by therapeutic linacs are often simply called "photons"), while gamma rays are specifically emitted by the nucleus (that is, produced by gamma decay). In theory, there is no lower limit to the energy of such photons, and thus "ultraviolet gamma rays" have been postulated.
In certain fields such as astronomy, gamma rays and X-rays are still sometimes defined by energy, as the processes which produce them may be uncertain.
As a form of ionizing radiation, gamma rays can cause serious damage when absorbed by living tissue, and they are therefore a health hazard.
This text uses material from Wikipedia, licensed under CC BY-SA