Suppose you would pace up Earth’s rotation so {that a} day was solely half as lengthy? What would occur? Effectively, for starters we’d should make new clocks that solely have hours 1 to six for am and pm. When you had tickets to an 8 o’clock live performance, you’d be out of luck: 8 o’clock not exists.
However perhaps a extra germane query is, why do physicists ask nutty questions like this? It’s by no means going to occur—simply transfer on, proper? Effectively, right here’s the deal. Fascinated by counterfactual eventualities provides us perception into how issues work right here in actuality. Plus, it’s enjoyable! Want I say extra? OK, it’d even assist us construct a working house elevator.
Oh, you don’t know what an area elevator is? It’s a sci-fi staple, a tether from Earth as much as an orbiting house station in geosynchronous orbit. A cable-climbing automobile would journey up and down, similar to a daily elevator. Mainly it’s a manner of getting out to house as simply and routinely as you journey an elevator to your workplace within the morning—no rockets required.
Let’s begin off with some primary questions and construct as much as some extra sophisticated physics.
What Is a Day?
You possibly can’t get extra primary than that. However the reply isn’t easy. When you stated a day is 24 hours, you’re proper—and mistaken. When you’re standing exterior, the time at which the solar is at its highest level within the sky known as native midday. When you stand there till the following native midday, the quantity of elapsed time is outlined as 24 hours. So an hour is 1/twenty fourth of the time between two native noons.
However wait! This isn’t the identical as an entire revolution of the Earth. When you measured the time of an entire revolution, you’d discover that it’s not precisely 24 hours. The reason being that the Earth is doing two issues without delay: It is spinning on its axis, which causes the solar to look to maneuver throughout the sky. Nevertheless it’s additionally orbiting the solar over the course of a 12 months, which suggests an entire rotation is not going to outcome within the solar being in the identical place within the sky.
There are literally two several types of days. The photo voltaic day is the one you might be considering of, and it’s the one described above. The opposite sort known as a sidereal day. This is a very not-to-scale diagram that can enable you perceive the distinction:
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