Suppose you might velocity up Earth’s rotation so {that a} day was solely half as lengthy? What would occur? Properly, for starters we’d need to make new clocks that solely have hours 1 to six for am and pm. Should you had tickets to an 8 o’clock live performance, you’d be out of luck: 8 o’clock now 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? Properly, right here’s the deal. Serious about counterfactual eventualities offers 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 an everyday elevator. Principally 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 fundamental questions and construct as much as some extra difficult physics.
What Is a Day?
You possibly can’t get extra fundamental than that. However the reply isn’t easy. Should you mentioned a day is 24 hours, you’re proper—and incorrect. Should you’re standing outdoors, the time at which the solar is at its highest level within the sky is known as native midday. Should 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 a whole revolution of the Earth. Should 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 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 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 several types of days. The photo voltaic day is the one you’re considering of, and it’s the one described above. The opposite sort is known as a sidereal day. Here is a very not-to-scale diagram that can assist you perceive the distinction:
