Suppose you would pace up Earth’s rotation so {that a} day was solely half as lengthy? What would occur? Well, for starters we’d should make new clocks that solely have hours 1 to six for am and pm. If you had tickets to an 8 o’clock live performance, you’d be out of luck: 8 o’clock now not exists.
But possibly 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? Well, right here’s the deal. Thinking about counterfactual eventualities offers us perception into how issues work right here in actuality. Plus, it’s enjoyable! Need 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, identical to an everyday elevator. Basically 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 difficult physics.
What Is a Day?
You can’t get extra primary than that. But the reply isn’t easy. If you stated a day is 24 hours, you’re proper—and mistaken. If you’re standing outdoors, the time at which the solar is at its highest level within the sky is named native midday. If 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.
But wait! This isn’t the identical as a whole revolution of the Earth. If you measured the time of a whole revolution, you’d discover that it’s not precisely 24 hours. The purpose is that the Earth is doing two issues without delay: It’s spinning on its axis, which causes the solar to look to maneuver throughout the sky. But it is also orbiting the solar over the course of a 12 months, which suggests a whole rotation won’t outcome within the solar being in the identical place within the sky.
There are literally two various kinds of days. The photo voltaic day is the one you might be pondering of, and it’s the one described above. The different sort is named a sidereal day. Here’s a completely not-to-scale diagram that may enable you perceive the distinction: