The Problem of the Quasi-Stellar Objects
The observational evidence on these strange celestial objects presents many mysteries. The central question is still whether they are at the edge of the universe or relatively close to us
Anti-Matter
The discovery of the anti-proton and the anti-neutron raises the following question: Do anti-atoms made of these and other anti-particles exist in the universe?
The Steady-State Universe
Some cosmologists dissent from the evolutionary view, holding that the large-scale features of the expanding universe do not change, and that its density has been maintained by the creation of matter
Ultrahigh Temperatures
They occur in nuclear explosions and in the interiors of stars. In the latter they promote thermonuclear reactions and perhaps convert hydrogen into all other elements on the periodic table