Final

2. the antiparticle of the proton
5. the SI base unit of thermodynamic temperature (equivalent in size to the degree Celsius), first introduced as the unit used in the Kelvin scale.
8. The 'critical density' is the average density of matter required for the Universe to just halt its expansion, but only after an infinite time.
10. of the same or a similar kind or nature.
11. nonluminous material that is postulated to exist in space and that could take any of several forms including weakly interacting particles or high-energy randomly moving particles.
13. the speed of light

1. a particle representing a quantum of light or other electromagnetic radiation.
2. consisting of antiprotons, antineutrons, and positrons.
3. having a physical property which has the same value when measured in different directions.
4. When a body that is emitting radiation has a non-zero radial velocity relative to an observer, the wavelength of the emission will be shortened or lengthened, depending upon whether the body is moving towards or away from an observer.
6. An alternative term for the radiation era in the Big Bang theory, during which the Universe was hot and dense and was dominated by the effects of radiation.
7. basic building block of chemistry.
9. the science of the universe.
12. the era that started when the gravitational effect