Pythagoras’s theorem
For a triangle in the plane (or in a more general flat space), two of whose sides form an angle of 90 degrees, the following holds: The lengths a and b of the two sides that form the 90 degrees angle and the length c of the third side are related by the ...
pulsar
Rotating neutron star from which regular pulses of radiation reach the Earth. Behind those pulses is the fact that the pulsar sends out narrowly focussed beams of radiation that, due to the pulsar's rotation, sweep through space like the beam of a ...
PSR1913+16
A specific binary system consisting of two orbiting neutron stars, one of which is a pulsar from which we here on Earth receive regularly spaced radio pulses. From the point of view of general relativity, the system is interesting not only because, using the ...
proton
Particle that carries positive electric charge and is comparatively massive; the atomic nuclei consist of protons and neutrons. Protons are not elementary particles, they are compound particles consisting of quarks that are bound together through the ...
primordial
In cosmology: At, from, or relating to the beginning (or at least the early phases) of the universe. For example, the primordial abundances of the chemical elements are the abundances right after Big Bang Nucleosynthesis, at a cosmic time of a few ...
pressure
A measure for the strength of the resistance with which matter (for instance a gas) resists attempts to decrease the volume it occupies. ...
potential energy
When an object is being acted upon by a force like the electric or gravitational force, then it can be assigned an energy that depends only on its location relative to the source of the force. This energy is called the potential energy - "potential" as it can ...
post-Newtonian formalism
For situations in which gravity is very weak, general relativity and Newton’s theory of gravity lead to very similar predictions for the motion of bodies (e.g. the planets in our solar system) and the propagation of light. Such situations can be described ...
