# What would a physically correct term be for “artificial gravity by rotation”?

Microgravity causes some health concerns in the long run, so it has been proposed that one could create what is often called "artificial gravity" by rotating the space station. This is not strictly physically correct and may spread misunderstandings about physics. So what should we call it?

"Artificial" refers to something humans create. We can't create gravity, so the word artificial has sometimes been exchanged for "simulated" or "emulated". But I think that the problem is that it isn't gravity, it is an acceleration which we do create artificially, so it is rather that word which needs replacement. However, "artificial acceleration" doesn't reveal that it is a rotating acceleration. How is this confusion clarified in a physically correct terminology which still can work as "a term" consisting of at most three or so words?

"-Is it gravity?" "-Nope!"

"-Is it centrifugal force?" "-Nope, that stuff doesn't even exist."

• – Andrew Thompson Mar 30 '15 at 16:55
• @DYM Centripetal force is only one of the two components of the movement. It needs to somehow be combined with the tangential velocity into what could be used as "a term". The effect of interest is that astronauts' feet are pushed towards what becomes a floor. It's open for terminology which refers to this from the reference frame of the astronaut, leaving out general concepts like gravity and velocity. – LocalFluff Mar 30 '15 at 17:02
• Centrifugal force does exist, just not in inertial reference frames. The most reasonable reference frame, however, would be the astronaut, even though it's not an inertial frame. – raptortech97 Mar 30 '15 at 19:56
• xkcd.com/123 – Philipp Apr 17 '15 at 13:58

It is entirely correct to replace "artificial" with "simulated" or even "emulated" or "imitated". Simulated can be defined as "imitating the conditions of something".

In that vain, simulated gravity would in no way imply that we are somehow creating actual gravity. It simply means that we are creating conditions similar to gravity.

Replacing "gravity" with some other word loses the point of why we are doing it. Simulated gravity has the clear purpose of simulating gravity. Artificial acceleration could mean anything (Even firing rockets to move a spacecraft forward), so that is not a good term to use.

• If you want to specifically refer to the effect created by rotating a spacecraft, you can use "centrifuge simulated gravity" to describe the effect and "simulated gravity centrifuge" to describe the device, because you are using a centrifuge to simulate gravity. – neelsg Mar 31 '15 at 9:01
• Sorry, but I removed my approval of your answer, although it is great, because I think that Taemyr's new answer needs to be considered. It is the astronauts who need microgravity mitigation, so maybe centrifugal force is the relevant terminology? Might contain the coriolis effect which in "simulated gravity" depends on the method used, like linear acceleration without it for a while. @Taemyr – LocalFluff Apr 17 '15 at 12:18

The correct term is centrifugal force. It's correct that centrifugal forces does not exist in an inertial reference frame, but the inside of the station is not inertial. Hence when you are using that as your reference frame you would see centrifugal forces.

If you are using an inertial reference frame the physically correct term for what is pulling you towards the floor is inertia.

• Hi Taemyr, welcome to Space Exploration SE. Nice answer, but could you add a reference? – ForgeMonkey Apr 17 '15 at 10:48

The proper phrase is "centripetal force", because that is only created in a rotating system where release is inhibited. Linear force upward would be simply acceleration, and it would lack the vertical force differential from top to bottom and Coriolis forces applied on axial movement.

• I'm removing the CW status of this answer, there's no good reason to use it here. – TildalWave Sep 29 '15 at 19:30
• This is the right answer. The astronaut in the spinning space station exerts a notional "centrifugal force" on the space station due to newton's law that their body should continue in a straight line. The space station wall exerts a real Centripetal Force that prevents them from continuing in a straight line. – Level River St Nov 27 '17 at 12:05

I'm amazed no one else has suggested it by now, but one term I've heard used for this is "pseudogravity". The prefix "pseudo" is defined by Merriam-Webster as "being apparently rather than actually as stated", which acts as a built-in caveat that it's not really gravity.

The term occurs mostly in science fiction, admittedly, but then again, so does the concept it names. It's also used in passing in a couple of Wikipedia articles.

Given that a tenet of general relativity is the equivalence of inertial mass and gravitational mass, I'd suggest 'rotationally induced gravity' as opposed to 'mass induced gravity'. The difference was fatal in Ringworld.

• Hi rdt2. This answer is based on opinion. What we seek are facts, with a strong preference for things that can be demonstrated with links to authoritative references, or by showing the math. When you have more points, commentary like this can be placed in comment sections. – kim holder Aug 27 '15 at 14:15

Centripete is the correct term. Etymologically from the centripetal force. That is, the force that pulls you into the center of rotation. No, there is no centrifuge.

• This answer is very short, could you please expand on your idea? Maybe provide some references? – ForgeMonkey Mar 31 '15 at 8:53
• All sources I have looked up having the word centripete is in French. – Erkin Alp Güney Mar 31 '15 at 9:02
• Artificial gravity (or a centrifuge), on the other hand, would be a force directed away from the center. – Octopus Mar 31 '15 at 19:42