Suppose you can velocity up Earth’s rotation so {that a} day was solely half as lengthy? What would occur? Nicely, for starters we’d need to make new clocks that solely have hours 1 to six for am and pm. For those who 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? Nicely, right here’s the deal. Serious about counterfactual situations 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 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 automobile would experience up and down, identical to an everyday elevator. Principally it’s a approach of getting out to area as simply and routinely as you experience 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 may’t get extra primary than that. However the reply isn’t easy. For those who stated a day is 24 hours, you’re proper—and flawed. For those who’re standing exterior, the time at which the solar is at its highest level within the sky known as native midday. For those who 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. For those who 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 seem 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 consequence 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 known as a sidereal day. Here is a completely not-to-scale diagram that may assist you to perceive the distinction: