matter: The Relationship of Matter and Energy

The atomic theory of matter does not answer the question of the basic nature of matter. It is now known that matter and energy are intimately related. According to the law of mass-energy equivalence, developed by Albert Einstein as part of his theory of relativity, a quantity of matter of mass m possesses an intrinsic rest mass energy E given by E = mc², where c is the speed of light. This equivalence is dramatically demonstrated in the phenomena of nuclear fission and fusion (see nuclear energy; nucleus), in which a small amount of matter is converted to a rather large amount of energy. The converse reaction, the conversion of energy to matter, has been observed frequently in the creation of many new elementary particles. The study of elementary particles has not solved the question of the nature of matter but only shifted it to a smaller scale.

Sections in this article:

• Introduction
• The Relationship of Matter and Energy
• Physical and Chemical Changes
• Modern Theory of Matter
• Early Theories of Matter
• The States of Matter
• The Properties of Matter
• Bibliography

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2024, Columbia University Press. All rights reserved.

See more Encyclopedia articles on: Physics