Albert Einstein's personal letters up for auction

When he wasn't working on the theory of relativity, Albert Einstein seems to have spent a fair amount of time writing letters.

And in some of those letters he touches on such topics as God, his son's geometry studies, even a little toy steam engine he says helped change his life.

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Now, more than two dozen letters from the pre-eminent physicist are going on sale Thursday at California-based auction house Profiles in History.

Some are written in longhand, others on typewriters. Some are in German, others in English.

Einstein discusses such subjects as his complicated feelings about God and cajoles one of his sons to study geometry.

He also wrote to an uncle on the man's 70th birthday, telling him how the toy steam engine the uncle gave him spurred a lifelong interest in science.