Megaton

A megaton (symbol MT or Mt) is 1,000,000 tons, i.e. 10⁹ kg.

It is also used as a unit of energy, approximately equivalent to the energy released in the detonation of this amount of TNT. A kiloton is one-thousandth of a megaton -- approximately equivalent to 1,000 tons of TNT. The megaton has traditionally been used to rate the energy output, and hence destructive power, of nuclear weapons. More recently, it has been used to describe the energy released in other highly destructive events, such as asteroid impacts.

A megaton is defined as:

• 10¹⁵ calories
• 4.2 x 10¹⁵ joule = 4.2 PJ (petajoule)

The Little Boy weapon dropped on Hiroshima had a yield of approximately 13 kilotons. Thus, a megaton is equivalent to roughly 77 Hiroshima bombs.

The largest nuclear weapon ever detonated was the Tsar Bomba, which had a yield of 57 megatons.

The impact of a roughly kilometre-wide meteorite with the Earth can yield upward of 10 million megatons. Such impacts have been hypothesized to be the cause of prehistoric extinction events.

See also

• 1 E15 J for comparisons with other energies.

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