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LISA
The concept of LISA (Laser Interferometer Space Antenna), a space-based gravitational wave detector, has been studied jointly by the European and US space ...
quark-gluon-plasma
An exotic form of matter which was in all probability present in the early universe shortly after the big bang. Under ordinary circumstances, quarks only occur ...
lead
Chemical element with the symbol Pb; each lead nucleus contains 82 protons. Lead nuclei, stripped of their electrons, are among the types of heavy ions which ...
gold
Chemical element with the symbol Au; each gold nucleus contains 79 protons. Gold nuclei, stripped of their electrons, are among the types of heavy ions which ...
Relativistic Heavy Ion Collider
A particle accelerator operated by Brookhaven National Laboratory on Long Island, New York. It brings heavy ions - the nuclei of atoms that have been stripped ...
recombination
In the early universe as described by the big bang models: transition that occurs at cosmic time around 300 000 years. At this point, the universe has cooled ...
Compton Gamma Ray Observatory
A satellite observatory for astronomical observations of gamma rays operated by NASA from 1991 to 2000. Scientific aims included the study of gamma ray bursts, ...
gamma-ray burst
Astronomical events visible as extremely strong flashes of gamma rays. Their origin is still unclear; in the context of general relativity they are interesting ...
intergalactic medium
A thin gas that fills some parts of the empty regions between galaxies. The distribution is non-uniform; filaments of intergalactic medium are separated by ...
active galactic nuclei (AGN)
The innermost regions of young galaxies can become very active and radiate away considerable energy. Examples for such active galactic nuclei are radio ...
fluid
State of matter in which the constituent atoms and molecules are connected so loosely that the matter cannot maintain any shape without external support: If ...
microquasar
An astronomical object comparable in size to a star, which emits enormous amounts of energy; the processes responsible for the emission are similar to those ...
gamma rays
The most highly energetic variety of electromagnetic radiation , mit above a quintillion oscillations per second, corresponding to wave-lengths of less than a ...
string(s), string theory
Candidate for a theory of quantum gravity; a quantum theory, where the fundamental building blocks are tiny, one-dimensional, oscillating entities, called ...
XMM Newton
Satellite project of the European space agency ESA. Launched in December 1999, XMM Newton is a space-based X-ray telescope; as such it is especially suited for ...
world-line
The path of a pointlike object in four-dimensional space-time is a line called the object's world-line. To every moment in time corresponds one point of that ...
Wilkinson Microwave Anisotropy Probe
NASA satellite telescope dedicated to observations of the cosmic background radiation. WMAP website
Wien's law
One of the laws governing the properties of the simplest form of thermal radiation - that emitted by a blackbody: the product of such a body's temperature ...
"Why now?" puzzle
From astronomical observations, it follows that the density associated with dark energy in our universe has the same order of magnitude as the density of the ...
White dwarf
When stars with up to ten solar masses have exhausted the fuel of light atomic nuclei they need to sustain nuclear fusion reactions, they collaps to form a ...
Weyl singularity
A type of spacetime singularity (i.e. a boundary of spacetime) that is associated with infinitely strong tidal forces. More information about the different ...
weightlessness
From everyday life, we're used to the Earth's gravity pulling every body down to the ground, and the strength of that force is called its weight. If no such ...
weak force
One of the basic interactions in the standard model of particle physics. It is responsible for certain radioactive decays, such as the one where a neutron is ...
wavelength
For simple wave where maxima and minima, wave crests and troughs follow each other with perfect regularity, one can define a characteristic wave-length: the ...
wave
In a general sense: any travelling pattern, whether or not it involves matter being transported as well. Simple examples are water-waves - wave crests and ...
virgo cluster
The galaxy cluster closest to our own, roughly 50 million light years away. It consists of about 2000 galaxies. In the night sky, as viewed from Earth, it is ...
velocity
In physics, velocity is a combination of two aspects: First of all, how fast an object is, in other words: how long a distance it moves in a given time (its ...
UV radiation
See ultraviolet radiation.
uniqueness
Given a set of physical laws, one interesting class of question is aimed at finding out the variety of situations those laws allow. For example, is there only ...
unified field theory
Collective designation for Einstein's unsuccessful attempts to formulate a theory in which gravity and other interactions, notably electromagnetism, are ...