物理学专题 (获评列表級、极高重要度)
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請幫忙把以下這段從英文版轉過來的簡介譯成中文,再放在前頭。謝謝。--石添小草 07:05 2004年4月30日 (UTC)

In science, a physical constant is a physical quantity whose numerical value does not change. It can be contrasted with a mathematical constant, which is a fixed value that does not directly involve a physical measurement.

There are many physical constants in science, some of the most famous being: Planck's constant, the gravitational constant, and Avogadro's constant (better known as Avogadro's number). Constants can take many forms: the Planck length represents a fundamental physical distance; the speed of light in a vacuum signifies a maximum speed limit of the universe; and the fine-structure constant, which characterizes the interaction between electrons and photons, is dimensionless.

Beginning with Dirac in 1937, some scientists have speculated that physical constants may actually decrease in proportion to the age of the universe. Scientific experiments have not yet pinpointed any definite evidence that this is the case, although they have placed upper bounds on the maximum possible change per year at very small amounts (roughly 10-5 per year for the fine structure constant α and 10-11 for the gravitational constant G).

If the physical constants had slighlty different values, our universe would be so different that intelligent life would probably not have emerged: our universe seems to be fine-tuned for intelligent life.






這樣對物理系的學生 沒有幫助吧!