Suppose you may velocity up Earth’s rotation so {that a} day was solely half as lengthy? What would occur? Nicely, for starters we’d must 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 now not exists.
However 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? Nicely, right here’s the deal. Desirous about counterfactual situations offers us perception into how issues work right here in actuality. Plus, it’s enjoyable! Want I say extra? OK, it would even assist us construct a working area 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 area station in geosynchronous orbit. A cable-climbing automotive would trip up and down, similar to a daily elevator. Principally it’s a means of getting out to area as simply and routinely as you trip 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’ll be able to’t get extra primary than that. However the reply isn’t easy. When you mentioned a day is 24 hours, you’re proper—and improper. When you’re standing exterior, the time at which the solar is at its highest level within the sky is named native midday. When you stand there till the subsequent 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 a whole revolution of the Earth. When you measured the time of a whole revolution, you’d discover that it’s not precisely 24 hours. The reason being that the Earth is doing two issues directly: It is spinning on its axis, which causes the solar to look to maneuver throughout the sky. But it surely’s additionally orbiting the solar over the course of a yr, which implies a whole rotation won’t end result 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 opposite sort is named a sidereal day. Here is a completely not-to-scale diagram that can aid you perceive the distinction:
