To the best of our knowledge, energy and mass are always conserved
together in any transformation. This summary of experience has been made
into a keystone of science: the Law of Conservation of Energy and Mass.
It states that the total amount of mass and energy cannot be altered.
This law applies to everything we do, from driving a nail to launching a
space probe. While the conscience of the scientist insists that he
continually recheck the truth of this law, it remains a bulwark of
science.
The Law of Conservation of Energy and Mass is also called the First Law
of Thermodynamics. It is related to the Second Law of Thermodynamics,
which also governs energy transformations. The Second Law says, in
effect, that some energy will unavoidably be lost in all heat engines.
The first two laws of thermodynamics have been paraphrased as (1) You
can’t win; (2) You can’t even break even. Let us look at them further.