For geniuses, even blunders are triumphs in disguise. A dialogue between Albert Einstein and Erwin Schrödinger, pictured, suggests the pair stumbled upon the idea of dark energy 80 years before its time, while toying with what they thought was an ugly fudge factor.
In 1917, Einstein's novel equations of space-time had geometric terms on the left and energy on the right. A constant on the left kept the universe steady, suiting observations at the time. But in 1929, it became clear that the universe is expanding and Einstein dubbed the constant "the biggest mistake of my life".
Now historian Alex Harvey of New York University has re-analysed papers from the physicists, published in 1918. In one Schrödinger toyed with Einstein's equations, moving the constant from the left to the right.
The simple move transformed the constant from part of the geometry of space-time to a source of energy for the universe. "While mathematically it doesn't make any difference, physically it does," says Harvey.
Einstein responded, rather cheekily, that the properties of this new energy term were either nothing or demand a "non-observable negative density in interstellar spaces".
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