the force on parts of a extended body in a non-uniform gravitational field due to residual of the gravitational attraction between the overall effect on the body and the expected effect on the point in question. Tidal forces are most notably in large moons orbiting near their primaries.

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88 views

Synchronized rotation of the moon

Does the moon rotates? Yes. The rotation matches exactly the orbit of the Earth. Which means in 28 days the moon makes one rotation. Shouldn't this be also happening with the Earth rotation around the ...
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3answers
4k views

How quickly was the Earth rotating 250 million years ago?

The Earth is slowing at a rate of $4.7\times10^{-4}$ miles per second every 100 years due to tidal forces of the moon. See: http://en.wikipedia.org/wiki/Earth%27s_rotation ...
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1answer
278 views

Tidal force of Sun?

As I understand, satellites and the Moon orbiting Earth are in free fall. Isn't the same true for Earth orbiting the Sun? My question is then: How can the Sun's gravity affect tides? Aren't the ...
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0answers
37 views

Would a large, small mass object in orbit experience induced rotation

Imagine a large (multiple earth radii), very small-mass ring orbiting The Sun. Half of the ring would be closer to The Sun than the outer half. Since orbital velocity decreases with distance, two free ...
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1answer
161 views

Sun's tidal force on Earth

My question is regarding effect of Sun's gravity on earth. I want to know that if Sun's gravity can change Earth's landscape in long duration (i.e. billion of years) or not? Means if earth is dead ...
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29 views

What will change if we have another Earth in the space near Earth? [duplicate]

If a new Earth came and orbit our Earth within 300,000 km to Earth? I just did not know. thanks.
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4answers
278 views

Dark matter and tides

As I understand, "dark matter" is what they call a theoretical substance which is only known by it's influence upon velocity curve of the galaxy. If indeed the gravity of "dark matter" is so strong ...
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1answer
52 views

Simple question about the tidal force (Leibniz's notation confuses me)

I started going through Taylor and Wheeler's Spacetime physics (standard textbook on special relativity). This is from exercise 2.8. Basically we're dropping a bearing ball from a 315 m height above ...
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1answer
702 views

True or false: the Moon was touching the Earth 1.2 billion years ago

A creationist website makes this argument for the 6,000 year old earth. I'm embarrassed to say I don't know how to do the math to evaluate the claim myself. However, the time scales involved seems ...
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2answers
253 views

Would a considerably big asteroid be disintegrated by the Earth's Roche limit?

If there was a big asteroid with a diameter of say 50km+ in a collision course with the Earth (not orbiting), would it disintegrate into smaller chunks due to the Earth's Roche limit, or the time it ...
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2answers
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If the moon was twice as big but twice as far away, would there be any difference?

I'm just going to go ahead and steal this question question directly of Reddit since I have more trust in the answers I get on this site. So, if the moon was twice as big but also twice as far way, ...
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0answers
297 views

Why is the orbital resonance of the Galilean moons stable?

It is well known that the orbits of Ganymede, Europa and Io are in a 4:2:1 resonance. Most online sources (including but not limited to Wikipedia) say that such an orbital resonance, along with the ...
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0answers
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Calculating the gravity gradient of a black hole [duplicate]

Given a black hole of, say, $10^8 \odot$ (solar masses), how can I calculate the gravity gradient ($\frac{\Delta g}{m}$?) at a given distance from it?
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4answers
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Does the moon affect the Earth's climate?

So, this morning I was talking to a friend about astronomical observations, and he told me that lately there has only been good weather when there was a full moon in the sky, which was a shame. I ...
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1answer
125 views

Is the trajectory of the Moon around the Earth stable? [duplicate]

I understand how mathematically is possible to have one object with elliptical or circular orbit around another object in space. so can I think of it as a limit cycle? If yes, then is it stable or ...
3
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1answer
203 views

How can you calculate the tidal gradient for an orbit?

In the movie Gravity, two characters are dangling from the international space station by a long tether. I've previously wondered exactly how you could calculate the tidal forces that act on an ...
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0answers
140 views

Is the equivalence principle in General Relativity an approximation?

I read in web that Einstein used the principle of equivalence to explain General Relativity but we know the gravitation is approximately equal in all of rested frame in gravitional field. In ...
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1answer
66 views

About Earth Gravity and its characteristics in different scenarios

Earth's gravitational field gives rise to a typical acceleration of 9.80 m/s². If you say gravity changes with altitude, then what will be the gravity at per say 8900 meters. Is there any specific ...
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2answers
2k views

Where does tidal energy come from?

Kind of an odd, random question that popped into my head. Tidal energy - earth's ocean movement, volcanism on some of Jupiter's moons, etc. - obviously comes from the gravitational interaction between ...
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1answer
127 views

Lunar and solar tides [closed]

I just read the following statement in a book: If the diameter of the earth increased by 20%, both lunar and solar tides would be weakened with lunar tides weakening more than solar tides. What ...
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2answers
562 views

Is the tide on Earth caused by curvature of spacetime

The tide on Earth appears absolutely whenever the moon is overhead. Is that tide caused by spacetime, re-curvature in space or attraction gravity?
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0answers
115 views

Relation between the period of rotation and the period of revolution of a satellite

I read somewhere that the tidal forces between the earth and the moon causes the equality between the 2 periods of the moon and that every planet-satellite system will evolve to this condition (like ...
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2answers
447 views

How large can planets or moons appear?

In many artistic impressions or movies there are pictures or scenes where the sky is filled with an enormous moon (as seen from a planet) or vice versa. I wonder if there is an upper limit to the ...
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1answer
880 views

Has anyone on Earth ever seen the dark side of the moon and if so where are the pictures? [duplicate]

If the Moon rotates then we should see the dark side right? But as far as I know the Moon only shows one side to Earth, how can this be if it is rotating?
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2answers
339 views

If the moon was rapid enough would it be able to orbit the earth from a close distance?

If the moon was close in orbit that it's surface was like 100 km away from the earth's surface. And it had a large enough angular velocity will it be able to hold orbit? If this was possible, is ...
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2answers
237 views

Saturn ring stabilization

The rings of Saturn are the most extensive planetary ring system of any planet in the Solar System. I'm wondering, what power is primarily responsible for that stability? © Public Image by NASA ...
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1answer
58 views

Question about tide

Let's say a canal is built in the middle of Kansas in the shape of a ring that stretches 100 miles in diameter. The band of water is 100 feet wide and 10 feet deep throughout the entire canal, and the ...
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3answers
136 views

Stresses in asteroid during close flyby

The acceleration of an asteroid (such as 2012DA14) as it approaches earth is proportional to the reciprocal of distance $r$ from earth center, squared. the derivative of the acceleration, or jerk, is ...
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1answer
115 views

Relationship between angular momentum of Earth and recession rate of the Moon

So the problem goes like this: Two masses $m_1$ and $m_2$ orbit each other with semimajor axis $a$. The orbit is circular, and $m_1 \gg m_2$. The body $m_1$ has a rotational moment of intertia $I_1$ ...
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1answer
174 views

How do the “tidal forces warming moons” theories hold when apart from heating from expansion, there may be also cooling from contraction?

I can understand a temporary heating, from the tital forces exerted on the moon but wouldn't there be cooling as well eventually when particles "give in" to contraction? Wouldn't they eventually net a ...
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1answer
1k views

How can the Moon have such a strong effect on the ocean?

The gravitational acceleration on Earth is approximately $ 10 \mathrm{m}/\mathrm{s}^2 $. Compared to this, the tidal effect of the Moon's gravity gives a local variation in the acceleration of ...
6
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1answer
664 views

Can you tell just from its gravity whether the Moon is above or below you?

If you are on a place of Earth where the Moon is currently directly above or directly below you, you experience a slightly reduced gravitational acceleration because of Moon's gravity. This is what ...
5
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1answer
330 views

Tidal force when planets and smaller objects collide

There are lots of animations on the Web of planet collisions. In most, the planets maintain their (almost perfectly) spherical shape and their surface features right up to the point of impact. In ...
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1answer
497 views

Where does energy for high and low tides come from?

High and low tides are caused by Moon gravity attracting water. Now there's friction, waves cause erosion, their energy is used in power plants yet the tides work for millions of years and are ...
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4answers
1k views

Angular momentum power plant on Earth

If tidal power plants are slowing down Earth's rotation then is it theoretically possible to build a power plant that would drain energy from Earth's angular momentum (thus slowing down it's ...
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3answers
595 views

Tidal force on far side

I have a question about tidal forces on the far side of a body experiencing gravitational attraction from another body. Let's assume we have two spherical bodies $A$ and $B$ whose centers are $D$ ...
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5answers
921 views

Why cant one see tidal effects in a glass of water?

Why cant one see the tidal effect in a glass of water like in an ocean?
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3answers
212 views

Is there any dynamical reason for the winter solstice to happen close to the perihelion?

When the winter solstice arrives, the angular momentum of the Earth, its orbital angular momentum and its radius vector with the orbital focus in the Sun are in the same plane. This happens quite ...
3
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0answers
118 views

Is Earth/Luna tidal lock approaching faster?

Wikipedia pegs the mass of Earth at $5.972\cdot 10^{24}\,\text{kg}$ or $5.972\cdot 10^{21}\,\text{metric tons}$. Assuming Earth accumulates approximately $30,000\,\text{metric tons}$ annually. To ...
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1answer
2k views

What would it be like if we had a planet very close to us?

My desktop background rotates through a bunch of space and nature scenes, and this one came up. What would be the effect on people walking around down here, if another earth was looming overhead ...
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0answers
97 views

Where to go to minimize tidal forces?

Suppose you design an experiment where you need to minimize the effects of tidal forces. Where would you go? There are a few possibilities, and the choice depends on how much effort you are willing to ...
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1answer
124 views

Could tidal effects make matter hot enough for nuclear fusion?

There was a recent question about cosmological firewalls. Putting aside questions of entanglement and information and looking at the problem from a pure mechanical viewpoint, we know that although ...
3
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1answer
348 views

Would the Moon drift away from the Earth due to extraction of tidal energy? [duplicate]

Possible Duplicate: Why does the moon drift away from earth? It seems to me that, due to conservation of energy, the moon would drift away from the Earth if humans began extracting large ...
6
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2answers
375 views

Does a tidally locked planet have seasons?

Could a tidally locked planet have seasons? According to my understanding, a tidally locked planet rotates around itself exactly once per rotation around its sun. However, if the axis of rotation of ...
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1answer
132 views

How should I be thinking about tides?

I am working on a project for physics that involves tides. This is my current mind set when thinking about tides: The earth applies a gravitational force on some mass ...
1
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1answer
851 views

Curvature of spacetime in only required to explain tidal forces?

I'm a bit confused about the equivalence principle in GR. I'm quoting from Wikipedia: An observer in an accelerated reference frame must introduce what physicists call fictitious forces to ...
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2answers
2k views

How gravitation affects tides

I know that tide is caused by the gravitational pull of moon but what I don't know is how it affects water. I have actually these doubts. Why does gravity of the moon creates tides only in water? ...
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2answers
206 views

How important are electromagnetic tidal effects in QFT? Can they be used to determine whether a particle is point-like?

I just did a back-of-the-envelope calculation, which surprised me. I calculated the difference in acceleration (due to repelling like-charges) experienced by two sides of an electron the size of the ...
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1answer
287 views

Stability of moons around tidally locked exoplanets

Can someone send me pointers to work (either theoretical or simulations) showing (in)stability of satellite orbits around tidally locked exoplanets? I want to know firstly if satellite orbits can ...
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1answer
124 views

If a hot Jupiter was not tidally locked, then are there any specific cases where its wind speeds would be milder than those found on Jupiter?

If a hot Jupiter was not tidally locked, are there any specific cases where its wind speeds would be milder than those found on Jupiter? After controlling for the age of the hot Jupiter, of course. ...