Big Bang theory
Redshift and the expansion of the Universe support the idea of a 'Big Bang' but they are not conclusive.
They only show the current movement of the galaxies and not the evidence of the aftermath of any 'Big Bang' itself.
The final piece of evidence depends on the relationship between temperature and emitted radiation.
From everyday life we know that hot metal glows 'red hot' and if it gets hotter still the colour changes to 'white hot' then blue.
The light emitted from stars can be analysed to determine the temperature of the star. Such temperatures are usually measured on the Kelvin scale, where 0 Kelvin is the coldest temperature possible 鈥 absolute zero.
This corresponds to a Celsius temperature of \(-273^\circ C\). The intervals on the Kelvin scale are the same as those on the Celsius scale, so a change of 1 K is equal to a change of \(1 ^\circ C\).鈥
The curves on the graph indicate the distribution of radiation emitted from one object at three different temperatures.
The dotted line shows the peak intensity of radiation (intensity can also be referred to as 'radiation per unit surface'). The higher the temperature of an object the shorter the peak wavelength of its spectrum.
The shorter the wavelength and the higher the frequency, the bluer the colour, so white or bluish stars are hotter than red stars.
This idea is used in the Hertzsprung-Russell diagram which plots the brightness of stars against the temperature.
This graph can be used to tell the life story of a star and importantly predict whether a star can become a red giant or a black hole.