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(He clearly enjoys these kinds of counterfactual scenarios.)Īs it is, Earth’s day is a reassuring 24 hours, though not a constant one. Or, Murray says, humans might alternately have evolved much sooner than they did, and might even now have died out and been replaced by something else. Since atmospheric oxygen is required for animal life as we know it, any change in concentrations could have delayed or even halted the evolution of land animals. The so-called Great Oxidation Event began at about the same time Murray’s calculations show the Earth’s rotation stalling at 19.5 hours.

It suggests a possible link between the length of the day and the creation of oxygen by bacteria. Murray points to another paper, “Possible link between Earth’s rotation rate and oxygenation,” published last year by Judith Klatt in the journal Nature Geoscience. Of greater concern is whether humans - or indeed complex life - would have evolved at all on a planet with a longer day. “The days would be awful long, but if they’d always been that long you’d be used to it,” he notes. He says there’s no reason humans couldn’t have evolved to live on a planet with a 60-hour day. That’s what happened with the atmospheric resonance and tide.” But if they’re in sync and you’re pushing just as the swing stops at one end of its travel, the push will add to the momentum of the swing and it will go further and higher. “If your push and the period of the swing are out of sync, it’s not going to go very high. “It’s like pushing a child on a swing,” Murray explains.

This two-to-one synchronization created a torque that balanced out the slowing effect of the moon, and kept the day at about the same length for a billion and a half years, until it started to gradually lengthen to its current 24 hours. So the day was about 19.5 hours long, and the natural resonance of the atmosphere almost exactly half that. Two billion years ago, the Earth was warmer than it is now, and spinning a little faster. Astronomer predicts Betelgeuse could go supernova soon.What time is it on the moon? One small step for lunar time.This advertisement has not loaded yet, but your article continues below. Manage Print Subscription / Tax Receipt.