The WMAP image shows what the Universe was like 380 000 years after the Big Bang, How is it possible for scientists to 'look back in time?

Agas initially at p1 = 1 bar and occupying a volume of 0.5 liter is compressed within a piston–cylinder assembly to a final pressure p2 = 4 bar. (a) if the relationship between pressure and volume during the compression is pv = constant, determine the volume, in liters, at a pressure of 3 bar. (b) repeat for a linear pressure–volume relationship between the same end states. reference

In positive numbers less than 1, the zeros between the decimal point and a non-zero number are blank significant

Atomic nuclei of almost all elements consist of