Hubble constant
In an expanding universe such as that of the big bang models, every observer will find: The apparent velocity with which the galaxies around him recede is proportional to their distance; the more distant a galaxy, the more its distance increases in a given ...
horizon
In general relativity: A closed surface that is the boundary of a black hole. Whatever enters through this boundary from the outside can never again leave the inside. Synonym: event horizon. ...
Hertz
Unit of frequency, abbreviation: Hz. One Hertz corresponds to one oscillation per
helium
After hydrogen, the second lightest chemical element. Its atomic nucleus consists of two protons and, ordinarily, two neutrons ("helium-4"); such helium nuclei are also called alpha particles. Another variety of helium, helium-3, has only one neutron in its ...
Heisenberg’s uncertainty principle
Is a fundamental law of quantum theory, which defines the limit of precision with which two complementary physical quantities can be determined. If one of the quantities is measured with high precision, the corresponding other quantity can necessarily only be ...
Hawking temperature
Characteristic temperature of the Hawking radiation of a black hole. For simple, spherically symmetric black holes, it is TH = 6· 10-8 (solar mass/mass of the black hole) Kelvin. [Problems reading expressions such as 10-8? See exponential ...
Hawking radiation
Thermal radiation emitted by black holes due to quantum effects. First calculated by the British physicist Stephen Hawking in the 1970s. The characteristic temperature of the radiation, which depends on the mass and spin of the black hole, is called Hawking ...
