Why Gravity Fluctuates on the Moon

We need gravity: it anchors us. But the gravity we experience on earth is very different from the gravity on the moon, and both, it turns out, can fluctuate due to a number of things! Looking at new research announced by NASA, Trace upends our notions of gravity.

Read More:
NASA's GRAIL Mission Solves Mystery of Moon's Surface Gravity
"NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission has uncovered the origin of massive invisible regions that make the moon's gravity uneven, a phenomenon that affects the operations of lunar-orbiting spacecraft."

Gravity anomaly map of the conterminous United States
"Measurements of the gravitational field vary slightly from place to place due to the composition and structure of Earth's crust. These digital grids describe the complete Bouguer and isostatic residual gravity anomalies for the conterminous US."

Mascon
"Mascons were first identified by the observation of small anomalies in the orbits of Lunar Orbiter spacecraft launched in 1966--67."

Gal (unit)
"The gal, sometimes called galileo, (symbol Gal) is a unit of acceleration used extensively in the science of gravimetry."

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[Wordavee]

Ooops, To say it fluctuates is to imply that the force of gravity changes, but it is the attraction of varying masses which makes one area have a greater pull.

[Seeker]

1. Not really no. 2. You can absolutely say all of those things. 3. Probably, but it's such a tiny amount it's not really noticeable. -- Trace

[steevf]

I hadn't thought much about this but this totally makes sense.

[Seeker]

9.8m/sec/sec means I'm accelerating by 9.8m every second until I hit terminal velocity. So @ 1sec I'd be falling at 9.8m, then @ 2sec I'd be going 19.6m then @ 3 sec I'd be going 29.4! It's getting faster every second. Great question! -- Trace

[SkyHikerMike]

What's cool is how the pair of spacecraft work. They keep track of the distance to each other to an accuracy of less than a human blood cell. From that they can see when the leading craft get pulled more than the trailing craft, and hence deduce the gravity. Pretty sweet. NASA did the same thing on Earth first.

[DarkRubius]

This is the kind of science that will prevent mistakes in the future.

[xxhellspawnedxx]

On the second question, yes, that is the very definition of stable orbits - One lighter entity is falling towards a heavier entity, but the heavier entity is falling away from the lighter one at the same speed, thereby creating an equilibrium.

[kowhx]

can we say that countries with taller humans have lower gravity?

space station are falling towards Earth, so can we say that moon is falling towards Earth as well? and is Earth falling towards the sun?

can we jump higher if the moon is directly above us?

[amatorif]

Why do we weigh more on Mount Everest. Using weight equal to mg and combining it with the equation for universal gravitation we see that mg = (GmM)/r^2. We can divide out an m to get g=(GM)/r^2 so as we move further from earth gravity will decrease by the inverse square. then we plug it back into the force equation and gravity is decreasing faster than mass.
Can you please explain to me how that works. The only thing I can think of is that the mass (kg) increase faster than the distance(m).

[jameswright]

Periapsis and Apoapsis my friend. When the moon is furthest away from the planet is is pulled in and when it is close it is "slingshot" away/around. This is how orbiting works

[Mummele]

Normally earth's gravity is used as 9, 81m/s². I would suggest you round it to the closer 10 rather the 9...
Anyway ... SpaceNews rule :)

[xxhellspawnedxx]

1 Gal = 1cm/s². As it measures acceleration, it needs an increase over time component. Simple as that.

[LittleSegway]

do one on cordiceps please, the insect controlling fungus

[sroman]

It s the same as m/s^2 which is the si unit of acceleration

[mtb]

Its the same reason that larger planets have more gravity. Their is more mass beneath you to pull you down. You might be farther from sea level, but you are still on the earth and the area you are at has more mass.

[lilshove]

its the common sciences having a impossible time keeping up. untill they accept the elictric universe model, 'gravity fluctuations ' are just one of many rediscoveries we will keep rediscovering

[PlagueXKillR]

You guys are doing a great job. I dono where you come up with so much information to give twice a day. But I love it! Keep it up

[IdoZemach]

The moon is getting further and further away from us. It's speed overcomes Earth's gravity and so it's not falling towards us, it's slowly moving away. Or so I heard...

[ghensold]

This video sort of implies otherwise, but we can measure gravity anomaly on the earth, and in fact do so all the time both for science and business. For example, vulcanologists can figure out the size and shape of a magma chamber by using a gravity anomaly map, and miners look for mineral deposits in the same way.

[TadaGanIarracht]

That's really cool I never would have guessed it was caused by actual impacts. I was thinking maybe early geological activity or uneven distribution of matter during formation. The real answer is much more interesting.