Where do people get the idea that rotation is needed for gravity?

I believed this when I was 8 or so years old. The reason was that I read an article about gravity: how things stay in orbit, why there is "zero gravity" in space, and how gravity can be simulated there. I was born in 1960, and folks were landing on the moon soon, so kids like me needed to know this stuff. The article explained that the effect of gravity can be simulated by centripetal acceleration. There was a drawing of a guy swinging a bucket full of water around on a rope, and the water stayed in the bucket when it was overhead. I immediately jumped to the conclusion that spinning was the key to gravity. It took a while (a year or so), I swung the bucket myself, and argued with my little brother. We eventually realized that it would be in the wrong direction, and what about the poles? He concluded finally and I agreed that the earth must just attract stuff.

Now, keep in mind that my brother went on to Cal Tech and became a geneticist, and I grew up to be a physicist. We both have PhD's. Most people would have never got past the first impression.

They know the Earth rotates (they know the Sun rises and sets, even if they don't know which direction to look for it).

They know the Earth has gravity (well, a few think the Earth sucks, but most of them turn to alcohol or drugs).

They know astronauts are weightless (they've seen them on TV).

They know the shuttle doesn't rotate (they've seen them on TV).

They know a spinning carnival ride pushes you against the wall (they've ridden on carnival rides).

Based on personal observation, it isn't a completely illogical conclusion. It's just an ill informed one.

Well, it's not illogical as long they ignore one key fact:

They know the Moon orbits the Earth because of gravity. That may not be a direct conflict, but they apparently never wonder how the Earth's gravity can affect the Moon, but ignore astronauts.

I've thought about this a lot (I'm actually writing my doctoral thesis on misconceptions about gravity, but I still have a lot of work to do). Part of it, I think, is from the fact that a spinning space station is the only way to simulate gravity (except the centrifugal force pushes out, not in). And part of it is from the fact that no one really knows what *causes* gravity - it depends on mass, but the average person wants to see a direct cause.

The education system is going wrong by requiring students to only memorize facts, and not to actually think about concepts.

It is not the educational system, it is sci-fi movies. The spacecraft has to have a spin in order to generate gravity. [For all you Trekkies out there, yes except for the Star trek universe's ships, they have gravity field generators or whatever.]

Yes, I know this only works in the proper direction due to centripetal force, but EVERY movie uses the premise. People seem to remember information they see and hear in movies more readily than what they read in books or learn in school.

I saw one question the other day where people thought gravity was induced by the magnetic field.

Talk about being hard headed!!

In outer space, centrifugal force can be used to simulate gravity, but not on Earth. It's a function of mass.

Really? I see no term involving rotational motion in Newton's law of gravitation. These people must be applying their intuitive notions about motion and forces on Earth without thinking. Or they watched that abominable movie Armageddon. Remember that scene where the cosmonaut flips a switch to rotate the Mir space station and they all appear to walk around just fine? Pure rubbish! That concept certainly doesn't work as perfectly as they presented it.

2001 a Space Odyssey probably sticks in most peoples minds. Movies and pop culture icons have a very powerful effect on the perceptions of people. If a movie depicts something incorrectly or fantastically, it can become a popular misnomer.

The school systems, especially American, are extremely deficient... Teachers who are under-paid and hate their lives... Students who get lazier by the day... And a growing general apathy towards education...

It's ridiculous what people will believe these days just cause some guy who looks like a professional says something...

So many idiots... So few to counter them...

From carnival rides where centripital acceleration is used to hold their bodies against a spinning wall while the floor drops out.

gravity is a function of mass. more mass, more gravity.