Search results
Results From The WOW.Com Content Network
In inflationary models of cosmology, times before the end of inflation (roughly 10 −32 seconds after the Big Bang) do not follow the same timeline as in traditional Big Bang cosmology. Models that aim to describe the universe and physics during the Planck epoch are generally speculative and fall under the umbrella of "New Physics".
A world line is a special type of curve in spacetime. Below an equivalent definition will be explained: A world line is either a time-like or a null curve in spacetime. Each point of a world line is an event that can be labeled with the time and the spatial position of the object at that time.
According to Mach, Newton's examples simply illustrate relative rotation of spheres and the bulk of the universe. [8] When, accordingly, we say that a body preserves unchanged its direction and velocity in space, our assertion is nothing more or less than an abbreviated reference to the entire universe. —Ernst Mach [9]
The physical universe is defined as all of space and time [a] (collectively referred to as spacetime) and their contents. [10] Such contents comprise all of energy in its various forms, including electromagnetic radiation and matter, and therefore planets, moons, stars, galaxies, and the contents of intergalactic space.
An event in the universe is caused by the set of events in its causal past. An event contributes to the occurrence of events in its causal future. Upon choosing a frame of reference, one can assign coordinates to the event: three spatial coordinates x → = ( x , y , z ) {\displaystyle {\vec {x}}=(x,y,z)} to describe the location and one time ...
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. [1] [2] As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space—what they are, rather than where they are", [3] which is studied ...
The parameter usually used to find out whether a process in the very early universe has reached thermal equilibrium is the ratio between the rate of the process (usually rate of collisions between particles) and the Hubble parameter. The larger the ratio, the more time particles had to thermalize before they were too far away from each other. [21]
An infinite universe (unbounded metric space) means that there are points arbitrarily far apart: for any distance d, there are points that are of a distance at least d apart. A finite universe is a bounded metric space, where there is some distance d such that all points are within distance d of each other.