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Questions tagged [tidal-forces]

Questions about the apparent force stretching a body towards and away from the center of mass of another body due to the variance in acceleration due to gravity

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A moon in eccentric orbit dipping below Roche limit

Let's imagine (or do we know one?) a moon in a very eccentric orbit around a planet, with periapsis below the Roche Limit. How would it behave? Would it break apart when speeding past the planet, then ...
SF.'s user avatar
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27 votes
3 answers
5k views

Why don't the inner moons of Jupiter have tidally-induced volcanism?

Volcanism on Io is caused by the fact that it is tidally heated. There are four moons that are closer to Jupiter than Io with higher eccentricities, yet they don't seem to have any volcanism at their ...
usernumber's user avatar
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27 votes
8 answers
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Why, since Earth is in free fall towards Sun, are tides affected by Sun's gravity? Why aren't the oceans "weightless" like astronauts?

Astronauts on the space station do not feel the Earth's gravity at all; they are in free fall. Since the Earth and all that's on it is in free fall toward the Sun, why would the oceans "feel"...
GulbenkianD's user avatar
25 votes
2 answers
3k views

How can Io be tidally heated while it is in tidal lock?

According to its Wikipedia page: Rotation period: synchronous Eccentricity: 0.0041 But also ...extreme geologic activity is the result of tidal heating... How is it possible? It should not be ...
peterh's user avatar
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23 votes
3 answers
5k views

If we replaced the Moon with Ceres, how close would Ceres have to orbit to cause the same tides?

How close to Earth would Ceres have to be to cause tides of the same strength as by the Moon, above the region it orbits? Ceres has 1.3% the Moon's mass, but that doesn't mean it must be at 1.3% the ...
John's user avatar
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22 votes
1 answer
5k views

How did Mars come to have a 24 hour 39 minute day?

Mercury rotates three times for every two revolutions around the Sun, apparently due to a gravitational resonance with the Sun.Venus takes about 225 days to rotate, and rotates in the opposite ...
Howard Miller's user avatar
16 votes
7 answers
4k views

Why there are no terrestrial planets with a subsurface ocean?

Subsurface oceans in satellites are pretty common: Europa, Enceladus, Ganymede, Callisto, maybe Pluto... This is due to tidal heating of their host planet, Jupiter and Saturn, which heats up the inner ...
Carlos Vázquez Monzón's user avatar
16 votes
3 answers
3k views

Under which conditions could a planet's massive moon's orbit get closer to the planet?

The recent question How do we know the Moon was much closer than it is now? has piqued my interest. The answers are numerous and clear. But I started to wonder. The question includes the following ...
uhoh's user avatar
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16 votes
3 answers
7k views

What causes the antipodal bulge?

The Wikipedia article on tides shows a diagram with a tidal bulge both towards the Moon and on the antipodal point (the Sun isn't included in the diagram). Surely that's wrong - what would cause the ...
rdt2's user avatar
  • 169
16 votes
2 answers
4k views

Will the Earth ever be tidally locked to the Moon?

From my basic understating, Momentum is being transfered from the Earth's rotation to the Moon's orbit by tidal friction. The Earth's rotation slows down and the Moon receedes from the Earth as it ...
TheWhaleOnPluto's user avatar
16 votes
2 answers
880 views

How was Io not torn apart by tidal forces during its formation?

Jupiter's moon Io is arguably one of the most volcanically active bodies in the Solar System. The reason, according to NASA's page Scientists to Io: Your Volcanoes Are in the Wrong Place is believed ...
user avatar
15 votes
4 answers
1k views

Why do Earth and moon move apart but binary black holes move closer?

According to the accepted answer on Is the moon moving further away from Earth and closer to the Sun? Why?, the moon is receding from Earth because tidal forces and friction cause energy to be lost. ...
Gnubie's user avatar
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14 votes
2 answers
6k views

How does the Moon's gravity affect Earth's oceans despite Earth's stronger gravitational pull?

Given that Earth has a much stronger gravitational pull than the Moon, how does the Moon have any influence on Earth's oceans?
Steve's user avatar
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14 votes
5 answers
2k views

Is there any way for a planet orbiting a red dwarf in the habitable zone to not be tidally locked?

Is there any way to avoid the tidal locking of a planet orbiting a red dwarf in the habitable zone? For example, could a planet with a 90° obliquity and large moon avoid such a situation?
Soba's user avatar
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12 votes
1 answer
2k views

Would the Earth and Moon still have tides after the Earth tidally locks to the Moon?

Ignore the Sun's expansion. From my understanding, tidal locking happens from torque as a result of tidal bulges being offset from the line between the two planets. So when the Earth and Moon tidally ...
user138890's user avatar
12 votes
2 answers
9k views

When did the Moon become tidally locked to Earth?

According to various theories the Moon was created around 4.5 billion years ago. About all of these theories suggest that it was rotating around its axis at that time though. Currently, Moon is at ...
SF.'s user avatar
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12 votes
1 answer
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How much of an effect does the moon have on Earth's liquid mantle?

The gravitational pull of the moon is enough to create tidal forces of large bodies of liquid, i.e the sea. I was having a conversation the other day about how to terraform Mars, and someone ...
user avatar
11 votes
2 answers
558 views

Does Saturn raise tides on Titan's lakes?

Titan is the only body in the Solar System other than Earth to have large bodies of surface liquid. Since Saturn is much more massive than the Moon, I would expect for tides, if they're present to ...
ChristieToWin's user avatar
10 votes
1 answer
243 views

Does the orbital decay of Triton affect Neptune's rotation?

Just a quick question regarding Neptune. Because Phobos is spiraling in towards Mars, Mars' rotation speeds up. Does the same thing happen with Neptune's rotation?
StellarExile's user avatar
9 votes
4 answers
2k views

Is there any difference between tidal locking and synchronous rotation?

I'm trying to understand more about orbital mechanics, and I'm encountering a few terms which I'm not sure if they are exactly the same. The two terms are Tidal Locking and Synchronous Rotation. To my ...
ValientProcess's user avatar
9 votes
2 answers
3k views

How would ocean tides work on a tidally-locked planet?

Since the tidal bulge is always in the same place, how would that affect ocean tides? Would they change throughout an elliptical orbit, due to changing distance from the star? How exactly would they ...
Elhammo's user avatar
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9 votes
1 answer
841 views

Why do planets in red dwarf star systems tend to have a higher probability to get tidally locked?

I have read about about the habitability of red dwarf systems on Wikipedia, as well as some web articles on similar topics. The problem is, it does not explain why and how it happened. Google search ...
Yudhi G.'s user avatar
  • 201
9 votes
1 answer
364 views

If Saturn's rings cannot coalesce into a moon because of tidal forces, then how are shepherd moons able to exist?

From Wikipedia: In celestial mechanics, the Roche limit, also called Roche radius, is the distance within which a celestial body, held together only by its own force of gravity, will disintegrate due ...
user177107's user avatar
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9 votes
2 answers
792 views

Why does Saturn have both moons and rings?

From my understanding, a ring can form around a planet when a moon gets too close to its Roche limit, and gets ripped appart by the planet's gravity pull. That makes sense to me, but I don't ...
Nico's user avatar
  • 803
8 votes
2 answers
1k views

Do tidal forces on moons cause them to emit gravitational waves?

As moons orbit planets, they get squashed by uneven gravitational forces acting on them. Does this make a moon emit gravitational waves?
user avatar
8 votes
1 answer
1k views

How strong are the tides raised by Io on Jupiter relative to the ones raised by the Moon on Earth?

There seems to be 2 ways of calculating tidal forces that appear contradictory. Either: By calculating the difference of Io's gravitational acceleration on a point on Jupiter's near side and the ...
user267545's user avatar
8 votes
2 answers
807 views

Eventual outcome of tidal acceleration and deceleration

So, I know the Moon experiences tidal acceleration from the Earth. And, from what I've read, if not for the fact that the sun would boil away the oceans and engulf both of them first, about 50 billion ...
user1410910's user avatar
8 votes
2 answers
657 views

Are the Trappist-1 planets close enough to be tidally heated?

According to the NASA press release, the Trappist planets are close enough (only a few million kilometers) that "the tidal forces between the planets are not negligible". The speaker says that this ...
Phiteros's user avatar
  • 3,166
8 votes
2 answers
755 views

How does gradual crossing over of the Roche limit transform a planet or moon?

Some cartoon simulations (an example) of an object (assume here a large moon with Earth-like density) which crosses the Roche limit of a much more massive giant planet, illustrate a circle suddenly ...
LocalFluff's user avatar
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8 votes
2 answers
431 views

Are many exoplanets nonsynchronously tidally locked like Mercury?

The only tidally locked planet in the Solar system is Mercury. But it is synchronously tidally locked 3:2, because of the relatively high eccentricity of its orbit, so doesn't turn the same side ...
LocalFluff's user avatar
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8 votes
1 answer
512 views

How can we tell that a short-period binary is tidally locked?

Observationally, how can this be established? What is known theoretically about the process? Are there any reference papers to read?
questionhang's user avatar
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7 votes
3 answers
3k views

Jacobi vs tidal radius for star cluster

The tidal radius is defined in King (1962) as: the value of r (the radius) at which f (the density profile) reaches zero... This also referred by King as the "limiting radius" written as (Eq 3): $...
Gabriel's user avatar
  • 822
7 votes
1 answer
881 views

Effects of the solar tide on planets

It’s well known that (lunar) tides on Earth result in a transfer of angular momentum from Earth proper to the Earth–Moon orbital motion. That’s why the Moon resides now in a high Earth orbit, and ...
Incnis Mrsi's user avatar
7 votes
1 answer
76 views

Does Earth changes angular velocity in 24 hours evaluation?

I am trying to detect tidal forces influence on a pendulum. I use a laser interferometer that is able to detect very tiny space changes. The pendulum never stops even after long times quiet and ...
Anderson Alves's user avatar
7 votes
1 answer
441 views

Wouldn't the rings of Saturn experience tidal effect?

The "Lord of the Rings" has more than 60 moons, some of which are larger than Mercury. My question is, wouldn't the ring, which is mostly comprised of rocks, experience tidal effect whenever a moon is ...
user6760's user avatar
  • 2,501
6 votes
4 answers
2k views

Do tides occur on planets like Neptune, having water?

I mean, we experience tides here on earth because of combined effect of gravitational field of moon and sun. So I thought that tides could also occur on other planets. Let us consider Neptune where ...
Gamira's user avatar
  • 209
6 votes
4 answers
3k views

Does the Earth orbiting around the Earth-Moon barycenter cause a measurable centrifugal force?

I just realized the Earth is not a stationary object with the moon orbiting around it. As shown in this minimalist animation from Wikipedia, the Earth actually orbits a common barycenter with the ...
JPhi1618's user avatar
  • 163
6 votes
2 answers
6k views

Trisolar syzygy and it's effects on the planet

Slightly spoilers here, but in the novel The Three-Body Problem, there's a scene in which Civilization #184 is destroyed by the stacked gravitational attraction of the planet's (aptly named Trisolaris)...
Yuri-M-Dias's user avatar
6 votes
1 answer
268 views

Tidally locked Venus, is it possible and consequences?

Suppose, Venus becomes tidally locked. Will its dark side cool enough so that the CO2 from the atmosphere to precipitate in liquid form to make an ocean? Also, I wonder, how close Venus is to becoming ...
Anixx's user avatar
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6 votes
1 answer
5k views

What causes objects to become tidally locked?

I'm trying to write a gravity simulation (suns planets etc), and was hoping tidal locking could be one feature demonstrated. Using a simple equation for gravity has produced some interesting results, ...
Ninjanoel's user avatar
  • 171
6 votes
3 answers
449 views

Does the Sun impose back it's tidal forces onto the Earth (such as the Earth's to the Moon)?

It is known that each year the Moon is moving away from the Earth due to tidal forces. What about the Earth relative to the Sun?
Atom of Universe's user avatar
6 votes
1 answer
198 views

Do moons of rocky oblate planets migrate to low inclination over time? If so, does the time it takes depend on the Moon's size?

Discussions elsewhere suggest that this happens and that smaller moons would tend to low inclination with respect to the planet's equator faster than larger ones. For example, Mars' small moons are ...
uhoh's user avatar
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6 votes
2 answers
1k views

Can moons exist inside a planet's roche limit?

Saturn's rings are inside its own Roche Limit - the limit beyond which bodies start disintegrating due to the tidal forces of the parent body. But as every rock in the ring can be regarded as a ...
Astro Noob's user avatar
6 votes
2 answers
169 views

What's the equation for moon-moon tidal heating?

Between a moon and the primary, the equation for tidal heating is: $$\dot E_\mathit{Tidal} = - Im(k_2) \frac{21}{2} \frac{GM_h^2 R^5 n e^2}{a^6}$$ But how does one calculate the tidal heating between ...
SE - stop firing the good guys's user avatar
6 votes
1 answer
99 views

Physical Meaning of the Principal Tidal Fourier Modes and Their Integers

I'm trying to understand tides evolution of planets, and I often come across the Prinicipal Tidal Fourier Modes expressed as: $$ \omega_{lmpq}$$ For example, see the discussion after Eq. A15 in ...
ValientProcess's user avatar
6 votes
2 answers
265 views

Why would tidal forces on planets become more intense when a star becomes a white dwarf?

I was puzzled by this press release by the Royal Astronomical Society: "Small, hardy planets most likely to survive death of their stars" - phys.org, May 14, 2019 Astrophysicists from the Warwick ...
Jacob C.'s user avatar
  • 387
6 votes
1 answer
82 views

Calculating the radial tidal amplitude on a planet from the fluid Love numbers

How do you calculate tidal amplitudes from the fluid Love numbers? In my course on planetary physics I saw an approximate expression for the displacement from equilibrium tide: $$\Big|\frac{V_T}{g}\...
theWrongAlice's user avatar
6 votes
2 answers
341 views

Tide on the Moon

If the Earth's Moon had a water ocean of depth 2-4 Km, how high would the tides rise due to the Earth's gravity? (Just a hypothetical question.)
Devgeet Patel's user avatar
5 votes
2 answers
2k views

Can you create an orbit in a space station using balls?

Would it be possible to spin a ball in a space station, and for it to create its own orbit for a smaller ball to rotate around it?
user6579's user avatar
5 votes
3 answers
524 views

Question about tidal forces and the Roche limit

As we know, an object that is beyond the Roche limit doesn't disintegrate (obviously) because the tidal forces upon the object are weaker than the gravitational pull of the object towards its centre, ...
Carlos Vázquez Monzón's user avatar