Microgravity

Warning: What follows is completely pointless. I often take a break from contemplating the truly meaningful problems that the world is dealing with by deeply contemplating some truly meaningless ones. I find that thinking about things that don’t actually have real consequences from time to time is a nice way to take a break from thinking about our very troubled world and the very troubling real problems that we face. I decided to write this down in case you also wanted to take a break from thinking about things that matter.

The term microgravity has always bothered me a little bit. It shouldn’t. I suppose it’s a reasonable word to use, but after giving it an admittedly excessive amount of thought, here are a few reasons why I think it has always kinda rubbed me the wrong way.

First, it seems a little pedantic not to just call the thing that astronauts experience while in orbit, zero-g. Normally I’m all for pedantry but in this case, the subjective experience of astronauts is so close to zero gravity that it’s almost not worth mentioning the difference in the context of the astronaut’s frame of reference.

But in reality, there are always extremely subtle net gravitational forces acting on bodies in space so at first glance, the term microgravity does seem to be more accurate than zero gravity. If this were all there were to consider then I think I’d actually be quite happy with the term microgravity.

The other piece of information that I think greatly complicates the matter is that the force of gravity at the altitude of the ISS is actually roughly 90% as strong as it is for you and I on Earth’s surface. The astronauts “feel” weightless because they are essentially in perpetual free fall, but their lateral velocity is high enough that they endlessly fall around the earth without ever hitting it.

With this added context, the term zero gravity is wildly inaccurate and clearly has no place in the conversation. But in this context, microgravity seems similarly out of place. 90% of Earth’s gravity hardly seems like an appropriate excuse to throw around the “micro” prefix.

So we have two ways to look at this: To the astronauts, it feels like zero gravity and using the term microgravity feels unnecessarily precise. But in the context of the orbital system as a whole, microgravity doesn’t seem adequate to capture the very “macro” seeming amount of gravity that an object in low Earth orbit is subjected to.

I guess the final thing that doesn’t feel right for some reason (although I don’t yet have a good handle on why yet), is the fact that microgravity gets used to describe everything from the thing astronauts are subjected to in orbit to the thing they are subjected to in deep space to the thing you feel in a plane flying a parabolic arc and even the experience you have in one of those free-fall drop towers at an amusement park. While it’s true that all of those situations give you the subjective feeling of weightlessness, they seem too dramatically different to all get the same very technical and precise sounding yet wholly ambiguous term “microgravity”.

The thing is, I don’t actually have a better suggestion. I’m not comfortable using the term zero-g when describing a system that is subjected to only 10% less gravity than we are and simply saying that astronauts are experiencing 0.9g also feels misleading so I guess I’ll stick to referring to it as microgravity unless you have a better suggestion.