massive stars iron-56 fusion gravitational collapse

Fusing atoms heavier than iron costs a star energy

Stars release energy by joining light atomic nuclei into heavier ones. But once a massive star reaches iron, joining nuclei into still heavier elements requires energy instead of releasing it. The star can no longer support itself through this kind of fusion.

The U.S. used far more energy than its share of the world's population

In 2022, the United States had about 4% of the world's population but used about 16% of the world's energy.

Perfect encryption can still reveal who is talking to whom

A one-time pad can be impossible to break if its key is truly random, secret, as long as the message, and never reused. But an observer may still learn from when messages are sent, how often they are sent, and between whom. Encryption can hide the message without hiding the pattern of communication.

massive stars iron-56 fusion gravitational collapse

Fusing atoms heavier than iron costs a star energy

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