54
votes
Accepted
Does gravity increase the closer to the core you get?
The below figure, taken from Wikipedia shows a model of the free fall acceleration, i.e., 'gravity'. The left-most point corresponds to the center of the Earth; then further right at $6.3\cdot1000$ km ...
- 2,009
38
votes
What is the pressure at the center of the Earth?
It is the pressure gradient that is proportional to the local gravitational force. When that force is integrated over a distance, the pressure gradient is integrated to accumulate a total pressure.
...
- 4,041
24
votes
Accepted
What is the fastest the Earth has ever spun?
The speed of rotation of Earth is controlled by its angular momentum. And the conservation of angular momentum is a very serious law of physics (perhaps even stricter than conservation of mass). So in ...
- 17.7k
19
votes
Accepted
Are we experiencing lower level of gravity now compared to past?
Earth's radius is about 6400 kilometres. That's 6400000 metres. Let's say that you have a mound 20 metres high, burying an older settlement. Your new "radius" is now 6400020 metres.
Let's say that $g ...
- 23.1k
15
votes
Accepted
Hudson Bay Has Low Gravity?
Gravitational acceleration does vary. It tends to be strongest at the poles and weakest at the equator, this is due to the oblate shape of the Earth which means that at the Equator you are further ...
- 787
14
votes
What is the pressure at the center of the Earth?
The previous answers do a fine job already. But I'll try to add a simple thought experiment. Imagine three objects floating in space, clumping together by gravity:
...
- 241
13
votes
How is the atmosphere expanding in all directions if Gravity is holding the atmosphere down to earth?
A couple thought experiments up front:
If you breathe on a cold day, the air doesn't rush up, despite the
vacuum of space above it. Why? It's not just because of its own gravity... but because of ...
- 8,802
11
votes
Variations in Gravity over Time
Is there any consensus about the conjecture that gravitational force on Earth may have changed significantly over geological time;
No, Earth's gravity did not change significantly over time. Yes, ...
- 23.1k
11
votes
Hudson Bay Has Low Gravity?
The link you give seems largely plausible about the cause of the anomaly in that area:
a 2007 study found that now-melted glaciers were to blame. The ice that once covered the area during the last ...
- 211
10
votes
Accepted
If Earth had rings would gravity exerted by Earth decrease?
Rings wouldn't decrease the gravity much, but the exact amount would depend on the exact geometry of the rings. One reason is that the gravity of one side of the ring would partially cancel the ...
- 17.7k
9
votes
What is the pressure at the center of the Earth?
Pressure at the center of the earth is non-zero. You're correct that there's no gravitational force at the center of the earth, but that doesn't mean pressure is zero - the pressure comes from the ...
- 380
8
votes
Accepted
Why doesn't Wolfram Alpha show low gravitational acceleration for the Hudson Bay?
Wolfram Alpha reports values between 9.78 and 9.88 m/s2 depending on the location, which is odd because it should stay within the range 9.76 - 9.83 all over the world. It also seems to be using the ...
- 224
8
votes
Accepted
How high is too high for hydrogen to rise?
I had a similar question, and then I learned that at the molecular level it is diffusion what dominates, that means that despite Hydrogen is lighter, it won't rise to the top of the atmosphere. ...
- 17.7k
8
votes
How is the atmosphere expanding in all directions if Gravity is holding the atmosphere down to earth?
However, observable reality shows us that the atmosphere expands in all directions as it fills any and all available volume
A very close measurement will reveal that in the presence of gravity the ...
- 81
7
votes
Accepted
Why does the moon orbit the earth and not the sun instead?
The moon does orbit the sun but it also orbits the earth. But your assertion that the earth's gravity is weaker than the sun's is not universally true. If the sun's gravitational pull were greater ...
- 186
7
votes
How is the atmosphere expanding in all directions if Gravity is holding the atmosphere down to earth?
The Earth's atmosphere is held in place because it is more or less in hydrostatic equilibrium, where the pressure that would buoy it upward were it not for gravitation is in balance with the Earth's ...
- 23.9k
6
votes
Accepted
A balloon falling from space?
You cannot leave "temperature outside", as temperature is the key factor to know if the balloon would pop or not.
Let's set up some assumptions about the problem so we can calculate something:
The ...
- 17.7k
6
votes
Does gravity increase the closer to the core you get?
This is a companion answer to both Erik's and tfb's answers.
tfb's answer assumes a uniform density throughout the Earth. This is highly inaccurate. Not to disparage tfb's answer; I've run across ...
- 23.9k
6
votes
How to make a Python function return the Moon's gravitational force (acceleration) to calculate orbits?
From my understanding, it should be possible to follow a similar procedure as what is done for calculating the gradient of gravity potential for the Earth (ignoring the potential corrections due to ...
- 233
6
votes
How is the atmosphere expanding in all directions if Gravity is holding the atmosphere down to earth?
In the radial direction (upwards), the atmosphere is very close to hydrostatic balance, and allows only very small fluctuations in velocity (Mach number <0.1%).
In the horizontal direction the ...
- 3,172
5
votes
Are we experiencing lower level of gravity now compared to past?
To address your original concern, no, the fact that there are buildings underground does NOT mean that the surface of the earth is higher than in the past. What is actually happening is that these ...
- 51
5
votes
Realtime planetary gravity maps?
For sure this is not available.
To create those maps takes several dozens Earth orbits by GOCE (one orbit ~90 minutes) and possibly many more to bring up the signal to noise
Which gravitational ...
- 3,172
5
votes
Accepted
What does the degree and order of Spherical Harmonics mean?
Citing from Wikipedia: $Y_l^m$ is called a spherical harmonic function of degree $l$ and order $m$. If we take the real part of the spherical harmonics only, there is a nice visual explanation for ...
- 1,165
4
votes
Accepted
Plate Tectonics vs Gravity for Creating Highs and Lows
I think this question is less intuitively obvious than it appears. and I like @Universal_learner 's answer. I thought I'd give a different approach to the question.
Earth is the only object in the ...
- 5,897
4
votes
What does the degree and order of Spherical Harmonics mean?
It's Legendre polynomials, not Lagrangian.
The zonal harmonics (the $Y^0_l$ terms) depend only on latitude. These zonal harmonics are closely associated with the Legendre polynomials $P_l(x)$, where $...
- 23.9k
4
votes
How is the atmosphere expanding in all directions if Gravity is holding the atmosphere down to earth?
The simple answer is that it does not rise and expand in all directions. In your house or outside, the air is generally not expanding or contracting, and, on balance, neither rising nor sinking. ...
- 213
4
votes
How is the atmosphere expanding in all directions if Gravity is holding the atmosphere down to earth?
Air at the same temperature and density released into (still) air at the same pressure will result in diffusion; it is an exchange of molecules where the individual molecules rarely go far in one go ...
- 2,110
4
votes
Do gravity and magnetic field change along a geographic latitude or not?
They can both change along any direction.
Here's Earth's magnetic field strength in early 2014, from ESA via NASA.
And here's Earth's gravitational field strength courtesy of NASA's GRACE satellite. ...
- 895
Only top scored, non community-wiki answers of a minimum length are eligible