What energy does the earth use for its solar orbit and will it run out.

Kinetic energy. And yes, it will run out by dissipating energy through tidal interactions with the Sun. However, that will take a much longer time than would be required for Sun to become a red giant and destroy the Earth by engulfing it.

P.S. Such questions more properly belong in the General Astronomy forum...

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I am; therefore I think.

[This message has been edited by Boris (edited October 06, 1999).]