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# Questions tagged [gravity]

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36 votes
3 answers
16k views

### Does gravity increase the closer to the core you get?

Or does the mantle and crust above you counteract the increase at one point and it actually decreases?
• 484
18 votes
5 answers
11k views

### What is the pressure at the center of the Earth?

In the question Does gravity increase the closer to the core you get?, it was determined that gravity reduces to zero at the center of the Earth. That is logical. However if pressure is proportional ...
• 189
12 votes
4 answers
4k views

### Hudson Bay Has Low Gravity?

Is there lower gravity at the Hudson Bay? How does this happen? And where exactly is this because I might want to go.
12 votes
1 answer
2k views

### What is the fastest the Earth has ever spun?

How fast can the Earth rotate and support life? In prehistoric times, dinosaurs were so massive that archeologists wonder how they were not crushed under their own weight. Could a faster spinning ...
• 1
12 votes
2 answers
1k views

### Change in earth mass since the time of the dinosaurs

Is there a significant difference in the mass of the Earth between now and the time of the dinosaurs (250 - 75 million years ago)? I was just wondering if the force of gravity on dinosaurs would have ...
11 votes
4 answers
9k views

### Does gravity differ from place to place on Earth

Does a particular object have the same weight on every part of Earth or does it vary?
• 628
9 votes
2 answers
1k views

### Terrain correction for gravity data using Nagy, 1973

I am working with an algorithm for terrain correction of gravity data. I am using Nagy, 1973. However, I could not get the results I need. So, this is the problem. I have this function where x,y,z ...
7 votes
1 answer
3k views

### Compute direction of gravity vector

As I understand to compute vector of gravity not saficient to compute normal to elipsoid, but we need to computer normal to geoid (by definition geoid is a surface to which the force of gravity is ...
• 173
7 votes
1 answer
226 views

### Can anyone explain the torque that causes the Earth's axial precession?

Looking around on the web, I frequently see explanations like "precession is caused by the action of the Sun's gravity on the Earth's equatorial bulge." That's nice, but I'm interested in a little ...
• 1,023
6 votes
1 answer
854 views

### How to make a Python function return the Moon's gravitational force (acceleration) to calculate orbits?

The Space SE question How much does it cost to land on a lunar mascon? includes the background information below. I am sure it's not too hard to find a link where spherical harmonic coefficients for ...
• 7,072
6 votes
1 answer
236 views

### Why is sealevel higher where gravity is higher?

The EGM96 geoid map depicts hypothetical sealevel due to gravitational variations on the Earth's surface: image source It places one of the highest areas in the northern part of the Atlantic ocean. ...
• 160
5 votes
8 answers
3k views

### How is the atmosphere expanding in all directions if Gravity is holding the atmosphere down to earth?

We are taught that gravity is the force that keeps the atmosphere and everything else binded to Earth. However, observable reality shows us that the atmosphere expands in all directions as it fills ...
• 67
5 votes
3 answers
7k views

### Are we experiencing lower level of gravity now compared to past?

Whole civilizations have been buried underground and we have built new landscapes over them. The fact that tall buildings and houses are being excavated from under the ground means that we are living ...
• 199
5 votes
2 answers
437 views

### Why doesn't Wolfram Alpha show low gravitational acceleration for the Hudson Bay?

I thought I would be clever and add a new answer to Hudson Bay Has Low Gravity? by using Wolfram Alpha to report gravitational acceleration for different locations, but it looks like my cleverness ...
• 7,072
5 votes
1 answer
589 views

### How high is too high for hydrogen to rise?

If hydrogen is the lightest gas known, would it rise making the outermost part of the atmosphere mostly hydrogen? Images to associate with your answer would be much appreciated. Thanks
• 1
5 votes
2 answers
673 views

### Plate Tectonics vs Gravity for Creating Highs and Lows

I have a question that I thought of when discussing a Worldbuilding scenario here. In that question, a super earth with gravity 1.35 times that of earth's is discussed, and is assumed to have shallow ...
• 153
5 votes
1 answer
713 views

### How much energy does the Moon transfer to the Earth, does this affect the Earth's surface temperature?

I'm wondering by how much the gravitation effects, tides etc caused by the moon (and other energy such as moonlight IR) increase the surface temperature of the Earth. So how much warmer than the ...
• 83
5 votes
0 answers
81 views

### How do you choose appropriate parameters for a lowpass filter when filtering a Bouguer anomaly?

I am trying to filter my Bouguer anomaly data to remove the short wavelength features. I have created a lowpass filter to achieve this, but I am wondering how I can more objectively choose my cutoff ...
• 51
4 votes
2 answers
5k views

### What does the degree and order of Spherical Harmonics mean?

I've been reading up about Gravitational Models and Spherical Harmonics. Where I first read about them is in this scholarly article on Autonomous navigation with Gravity Gradients. It talks about ...
• 143
4 votes
1 answer
74 views

### Realtime planetary gravity maps?

I'm trying to find maps of realtime (or at least periodically updated / semi-realtime) gravity maps of Earth. I was hoping that GOCE might have something like this available, but I've been hitting a ...
• 261
4 votes
1 answer
73 views

### Why do ocean tides have negative and positive terms in their effects on Stoke's coefficients for calculating geopotential?

I have recently started working on calculating a Geopotential model based on GGM05C. In order to obtain a model as accurate as possible, some corrections must be applied to the normalized Stokes' ...
• 233
4 votes
2 answers
308 views

### Does the Earth produces measurable gravity waves?

Does the Earth exhibit measurable gravity waves? Note: I'm not asking about gravitational waves. Some recent experiments looking at low-frequency (3$\times 10^{-5}$Hz) accelerometer data are showing ...
• 51
4 votes
1 answer
179 views

### What would be the depth variation of a "water ellipsoid" above a reference ellipsoid Earth?

The question If the Earth was a smooth spheroid how deep would be the ocean? has an excellent answer which explains the shape and surface area of an oblate spheroid before calculating the average ...
• 7,072
3 votes
1 answer
318 views

### A balloon falling from space?

How long would it take for a store bought rubber balloon filled in space with air to fall from space just outside the atmosphere and touch ground? Would it Pop? Added after comments: Ideally you ...
• 1
3 votes
3 answers
630 views

### If the Earth's core were made up of copper/other metals other than iron-nickel alloy, what would the magnetosphere be like?

We know that our earth's core is made up of iron-nickel alloy, and it is spinning to create magnetic flux all around our planet to create our life-saving Magnetosphere. And this also influences our 9....
3 votes
1 answer
213 views

### Expression for the gradient of gravity potential in spherical coordinates

I am currently using the GGM05C Stokes' coefficients to reconstruct the gradient of gravity potential of Earth. I have found an expression for said gradient in spherical coordinates in this technical ...
• 233
3 votes
1 answer
65 views

### Do the 600 satellites that orbit the Earth have any gravitational pull on the tides like the moon?

I know that space is big and satellites are small compared with the moon, but do they have, or will they if we get more, any effect on the sea and ocean water on the earth?
• 121
3 votes
1 answer
2k views

### How much do tides affect earth's rotational velocity?

Many of us are familiar with an exaggerated picture of the Moon's effect on Earth's tides: Since the Earth is not uniformly covered with water, however, I imagine that the tidal effect will depend on ...
• 273
3 votes
0 answers
73 views

### How are mGal-smooth free-air gravity anomaly measurements made exactly? (tiny variations of acceleration on a bumpy airplane ride)

Free-air gravity anomaly measurements from Operation Icebridge aircraft are described in A fault-bounded palaeo-lake basin preserved beneath the Greenland Ice Sheet (open access). Question: These ...
• 7,072
2 votes
0 answers
35 views

### Learn geological properties of the horizon through density of the rocks

It is possible to evaluate the geological structure of a basin based on gravimetric data. But if one doesn't have gravimetric data, how can one learn the geological structure and properties of a ...
2 votes
0 answers
87 views

### Are ramp pumps the solution to the global water problem? [closed]

For the past few years people have been trying to solve the global water problem (especially in Africa), and what better way than being echo friendly. So my question is, can you use the tidal energy ...
• 29
2 votes
0 answers
42 views

### Phase of S2 constituent in tidal prediction

I ran the ETERNA code for the prediction of tidal gravity at some station. Then I use Fourier analysis to recover the amplitude and phase of the S2 constituent. As I understand, the phase of the S2 ...
1 vote
2 answers
2k views

### Why does the moon orbit the earth and not the sun instead? [closed]

Objects orbit the sun because of the sun's gravity, and Earth's gravity is weaker than the sun's gravitational pull. So why does the moon orbit the Earth instead of the sun?
• 43
1 vote
1 answer
72 views

### Why isn't the acceleration of an object in Earth's gravity related to the object's mass? [closed]

Why isn't the acceleration of an object in Earth's gravity related to the object's mass? Please, try to explain this effect without physical formulas, but using only logical formulation.
1 vote
1 answer
79 views

### How might 25% lower gravity affect precipitation on an Earth-like planet? [closed]

I'm working on a science fiction project and hoping someone who knows something about climate can answer this question for me: if Earth had 25% less gravity, how would that affect precipitation? I ...
• 233
1 vote
1 answer
255 views

### How was the Earth's core made?

All I've heard until now is that when the Earth was very hot and slimy, the relatively heavier elements went down to the center of the Earth to form the core. But lately I've come up a contradiction ...
• 113
1 vote
1 answer
41 views

### How to compute spherical harmonics coefficients using orthogonality?

I use the lunar gravity model GRGM900C to calculate the gravitational potential across a $360{^\circ}*360{^\circ}$ grid. This calculation follows the equation: V(\varphi,\lambda)=\sum_{\mathrm{n=0}}^...
• 21
1 vote
0 answers
63 views

### Why does weaker local gravity cause lower sea level?

The weaker local gravity in the Indian Ocean geoid low (IOGL) causes the sea level to be 106 m below the global mean sea level. Why is that ? "Because of this lower density, the gravitational ...
• 223
1 vote
0 answers
34 views

### Why is there a low gravity anomaly right next to a high gravity anomaly next to mascons on the Moon?

This is from the book "Isosatsy and Flexure of the Atmosphere" by A. B. Watts. According to him, evidence for the isostatic compensation of mascons (i.e. regions of higher density material ...
1 vote
0 answers
29 views

### Would obliquity and precessional changes of Earth affect the accuracy of GPS-based measurement of tectonic movements?

The rate and direction of tectonic movements can be measured by comparing the coordinates of the same GPS receiver over time. The coordinates are obtained using trilateration. All materials I could ...
• 51
1 vote
0 answers
36 views

### Detailed gravity maps

Does anyone know if it is possible to get a gravity map of a specific region of Greenland? The data I've found here http://icgem.gfz-potsdam.de/vis3d/longtime , are simply of to low spatial ...
• 111
0 votes
1 answer
521 views

### If Earth had rings would gravity exerted by Earth decrease?

If Earth had enough mass in its own rings, more than the weight of Earth: What could it decrease the gravity to? Would the atmosphere have more depth or be thinner? What would the weather be like? ...
• 1
0 votes
1 answer
113 views

### Do gravity and magnetic field change along a geographic latitude or not?

Along the same geographic latitude does magnetic field change or not, and the same for the gravitational field, does it change along a geographic latitude? Please explain.
0 votes
1 answer
121 views

### Which forces align objects with the rotation of the Earth and how?

I have a question about which forces cause alignment of objects with the rotation of the Earth and how: It is known to me from public sources that objects up to a height of about 36,000 meters above ...
0 votes
1 answer
95 views

### What is a general formula for Earth gravity as a function of radius, given a spherical shell model?

I'm trying to derive the formula for gravitational acceleration as a function of Earth radius $g(r)$, given a spherical shell model where each shell has a constant density $\rho(r)$. If I set $r=0$ to ...
-1 votes
3 answers
631 views

### Variations in Gravity over Time

Is there any consensus about the conjecture that gravitational force on Earth may have changed significantly over geological time; and in particular in periodic increase associated with mass ...