What is ‘matter’? It is the real substance of which actual physical objects – the ‘things’ of this world – are composed. It is what you, I and our houses are made of. How does one quantify this substance? Our elementary physics text-books provide us with Newton’s clear answer. It is the mass of an object, or of a system of objects, which measures the quantity of matter that it contains. This indeed seems right – there is no other physical quantity that can seriously compete with mass as the true measure of total substance. Moreover it is conserved: the mass, and therefore the total matter
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Mass is the best source of energy to measure since its conservational.
