Q: If the world were to stop spinning, would the people and everything on it be considered ‘lighter’ or ‘heavier’? Would any change take place? And does centrifugal force have an effect on gravity?

Physicist: Centrifugal force* due to the spinning of the Earth is certainly a measurable effect, but it’s a small effect.  While the spinning of the Earth doesn’t directly affect gravity, it does off-set it a little.  At the north and south poles objects weigh exactly what they should, and at the equator things weigh slightly less.

Assuming that the Earth is round (which is a pretty good assumption), with a back of the envelope calculation you can figure out the centrifugal force trying to fling you into space.  At the equator (where it’s strongest) that force is approximately 0.35% as strong as Earth’s gravity (0.0035 g’s).  So, if you weigh 300 pounds in Ecuador you’ll find that you weigh almost 301 pounds at the Amundsen-Scott South Pole Station.  0.35% doesn’t seem like much, but it would have a profound affect on at least a few historical events.

Centrifugal force always points out from the Earth’s axis, whereas gravity always points toward the Earth’s center.  So you’d think that somewhere between the poles, where the centrifugal force is zero, and the equator, where it points straight up, that there would be a place where it points a bit sideways.

The farther you are from the Earth’s axis the more centrifugal force you’ll experience. At a latitude of ±45° it pulls sideways more than anywhere else.

Turns out, that place is at 45° north and south latitudes where you “should” find that things get pulled sideways with a strength of half of the maximum: 0.17% g’s.  If the Earth was perfectly round, then this would be exactly the case, and everything in Europe would have to be built slightly tilted (if you’re wondering, the Tower of Pisa would be leaning the wrong way).  However, fluids (and the ground is basically a fluid) move so that the net force always points directly into their surface.

A spinning trough of water. Gravity points down and is constant, while the centrifugal force points out and increases with distance. The surface of the water is always perpendicular to the combined force.

By being distorted a little (an extra 20 km at the equator) the combined gravitational/centrifugal force always points straight up and down.  So, if the Earth were to stop spinning right now then we’d find that buildings were tilted very slightly, things at the equator would suddenly weigh 0.35% more, and eventually the Earth would settle into a more perfectly spherical shape.

Now, if the Earth were to literally come to a sudden and abrupt stop: that would be lots of bad. Things at the poles would be fine, but the closer to the equator the greater the change in speed.  At the equator everyone and everything would suddenly find themselves moving east at mach 1.4 (1,038 mph), and every land mass near the equator would be thoroughly scrubbed by the oceans washing over them.  The economy would take a real hit if the Earth suddenly came to a stop.


*Any time that centrifugal forces are mentioned in the vast crucible that is the internet, a small but vocal cadre makes it known that the centrifugal force isn’t really a force.  Be cool.

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20 Responses to Q: If the world were to stop spinning, would the people and everything on it be considered ‘lighter’ or ‘heavier’? Would any change take place? And does centrifugal force have an effect on gravity?

  1. ivo says:

    I saw recently a documentary on NatGeo or Discovey, not sure which one, about what would happen if the Earth’s rotation were to slow down and eventually stop. All sort of crazy weirdness happened, of course, but what shocked me the most were the huge bodies of water that would move from the equator to the poles and thus flooding everything in their path. Eventually, the poles would be covered in water and the only land would be a huge piece on the equator. You should try finding that documentary, it was really fun to watch.

  2. Eamonn says:

    Great article.

    How fast would the Earth need to rotate for the centrifugal force produced at the equator to equal Earth’s gravitational pull? How short would this make the average solar day?

  3. The Physicist The Physicist says:

    Assuming that we continue to assume that the Earth is round, the equator would have to be moving at about 7.9 km/s (orbital velocity at ground level). This translates to a day that’s about 84 minutes long.

  4. Kirov says:

    This made me think. If one was standing still at the North pole, then relative to space itself, they would be spinning. Would they get dizzy?

  5. The Physicist The Physicist says:

    Exactly as much as standing on a merry-go-round that takes 24 hours to turn once.

  6. The Wonderer says:

    We would age faster though, wouldn’t we?

  7. Khan says:

    When the earth stop spinning, the value of g at equator will increase. Why?

  8. Pingback: O que aconteceria se, de repente, a Terra parasse de girar?

  9. Alicia says:

    If the planet has more mass will gravity be lighter

  10. AALOK RANJAN says:

    On contrary to all above arguments If the rotation of earth is stopped then the magnetic field that is gravity will vanish as the gravity of the earth is due to the metals present at the core which produces magnetic lines of force these are generated due to the difference in the velocity of core and mantle. As soon as the earth’s rotation stops the gravity will disappear.

  11. Andy Harris says:

    “As soon as the earth’s rotation stops the gravity will disappear.”

    The magnetic field might slowly dissipate (thus killing us all) but the Earth would still have the same mass and therefore the same gravity field.

  12. steve says:

    Wake up. The earth doesnt spin, rotate, or move. The earth is stationary. Multiple scientific experiments have been done and are easy to do your self to prove the earth is stationary. Secular science needs the earth to move to propagate their lies about a huge universe, big bang, evolution etc…

  13. Andy Harris says:

    The remarks by Steve “Wake up. The earth doesnt spin, rotate, or move. The earth is stationary…”

    Pity he doesn’t leave more of an explanation for his beliefs. I’d really like to see that including details of the “experiments” he speaks of.

  14. oca says:

    so what if the earth stops spinning?if that happens,what can you do about it?right now,it might make an interesting topic.but,does it matter?what interest me more are mundane problems like converting sea water into clean fuel, or making it fresh for drinking,how to grow more trees by reforestration,how to have fast, clean and safe transportion,and etc.but doing anything scientific to stop the earth from its natural state,forget it.we are being distracted from the important issues.san blague,there are many important things to talk about.ca va?

  15. Buck Rogers says:

    Please, stop the world and let me off of it.

  16. seth says:

    So we all have a center gravity die glocke Butler’s weapon now time travel wouldn’t actually be time travel jest airplanes are fast but they are not attached to the ground but the bell was and to match it it with earth that’s we are allready moving that fast to center ur self inside but actually be moving like we are ow would it slow time

  17. Thomas says:

    Steve, I would really like to know what experiments I could do that proves your theory that the earth doesn’t move. Since you’re claiming it can be done very easily I’d love to conduct this experiment put it on youtube and collect my Nobel Prize. Oh, and the subseuent tornado of cash I’d recieve for having this new information quoted in journal articles and textbooks. So, please if you could tell me how I can help prove your statement I would totally give you credit when I type up the article.

  18. Hans Geiger says:

    Being the devil’s advocate for Steve.. possibly the Michelson-Morley experiment proves a stationary earth as they did not scientifically detect ether? After all, it was the great Michael Faraday that realized the relativity of it all.. an electric current is generated either by a moving coil of copper over a stationary magnetized iron rod or equally – it can be generated by a moving magnetized iron bar through a stationary coil of copper. I cannot prove we are not the center of the universe. If we are not – which of six pointing directions is closer? the mathematics of a fast sun racing across the sky of a stationary earth probably matches the math of an orbit earth around a stationary sun. 1/2 would still equal 8/16 by any other name…

  19. Roy says:

    If our planet were to suddenly stop spinning, the least of our problems would weighing a little bit more. To wit…

    1. First, let’s just ignore that the energies applied to cause such a massive change in momentum would rip the crust away from the mantle and convert the planet a molten state causing the immediate extinction of all life down to and including the microbial level.

    2. The sun would heat only the side of the planet with its face toward it, baking it until all life dies. The dark side of the planet would freeze to death. Everything in between would be killed by storms resulting from the changes to the weather. Any life that managed to burrow deep and avoid an immediate death would probably die when the Earth’s atmosphere burns off completely.

    3. We would lose the magnetic field that protects us all from hard radiation from the sun. But, we would all be long dead before that became a problem.

    So, yeah… it would be a “bad thing”.

  20. Benjamin says:

    Regarding steve’s comment. I am christian and still believe in the big bang, Earth orbiting the sun, etc. The “feeling” of being stationary is simply due to the vastness of our beautiful cosmos. No one can wrap their mind around the size of the Universe.

    Oh, and if you want to clarify for your case, could you give me a link to the evidence to suggest that Earth is stationary?

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