... later ?¹

Let us postpone, for the moment, the fact that protons and neutrons are themselves made from yet smaller entities, quarks and gluons, and to complete our story we will need to consider their creation as well.

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... fuels).²

For the purist : I've used ``weight'' and ``brightness'' in preference to the more accurate terms ``mass'' and ``luminosity''.

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... galaxies.³

In case you are wondering how we can know the composition of distant objects : their light carries this information encoded in its spectrum.

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