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

How can Io be tidally heated while it is in tidal lock? It is tidally locked in a mean motion sense of "tidally locked". That Io is in an eccentric orbit rather than a circular orbit means ...
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27 votes
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Shouldn't tidal locking be impossible for a satellite that has a considerably eccentric orbit?

You are right, that would be weird if the Moon speeds up and slows down this way to always show the exact same side to the Earth. That's why it doesn't. At some point in the orbit the Moon's rotation (...
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  • 2,400
17 votes

Will the Earth ever be tidally locked to the Moon?

As the moon orbits Earth, tidal forces slow down the Earth's rotation by 2 milliseconds per century. Eventually, in tens of billions of years, the Earth and Moon would achieve a double tidal lock, ...
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  • 6,084
13 votes

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

That sentence on wikipedia continues "from friction generated within Io's interior as it is pulled between Jupiter and the other Galilean moons". There's an orbital resonance (with the other ...
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  • 478
11 votes

Is the moon "perfectly" tidally locked and, if not, how long would it take us to observe it's rotation?

The Moon indeed "wobbles" about in its orbit because it goes around the Earth in an ellipse and not a circle. From our point of view, it wobbles a little back and forth such that over a lunar cycle, ...
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11 votes
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Is the moon "perfectly" tidally locked and, if not, how long would it take us to observe it's rotation?

The question is interesting, but I suspect the answer is that the Moon will never show its "far side" to the Earth, because there are differences between the side that faces us and the far ...
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  • 5,142
9 votes
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Is it coincident that all planets with tight orbit are tidally locked to their parent body?

This is a physical result: The change in rotation rate necessary to tidally lock a body B to a larger body A is caused by the torque applied by A's gravity on bulges it has induced on B by tidal ...
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  • 1,392
9 votes
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Has the Earth-facing side of the Moon that we see today always faced us ever since the Moon got tidally locked? Or does it precess?

The Earth-facing side of the Moon doesn’t change currently due to any of the forces on it by other bodies (excepting librations). From Gladman et. al.: “tidal dissipation in the satellite drives it to ...
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8 votes

Shouldn't tidal locking be impossible for a satellite that has a considerably eccentric orbit?

With a more eccentric orbit, tidal control of the rotation does not lead to a librating lock. Mercury is in a 3:2 spin-orbit resonance. Hyperion's spin is chaotic: it gets a quasi-random kick each ...
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  • 787
7 votes
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A "tidally locked" double planet?

Your scenario isn't stable. A simple way to explain this is to imagine that the planet's orbit each other at the same rate they orbit the star (your scenario has them orbiting even slower). At the ...
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7 votes
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Why isn't Earth tidally locked to the sun?

Really, it's just because the tidal locking timescale is so long for Earth: $$t\propto\frac{a^6m_{s}}{m_{p}^2R_s^3}$$ where $a$ is semi-major axis, $m_s$ is the mass of the secondary object, $m_p$ is ...
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7 votes
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Why circularization of an orbit has longer time scale than tidal locking?

Tidal locking is a primary effect due to a direct torque on a body from its tidal bulge lagging its rotation. This is pictured nicely on wikipedia with an example from the Earth/Moon system. Tidal ...
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6 votes
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Earth rising and setting from moon's perspective

You're quite right. The Earth is (nearly) stationary in the Moon's sky. (I say "nearly" because the Moon is in a slightly elliptical orbit around the Earth, but rotates perfectly smoothly. This ...
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  • 7,390
6 votes
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Would a tidally locked planet be always increasing in temperature?

Hot objects radiate heat. The hotter something is, the faster it radiates heat. The side of the planet that faces the sun would heat up until the rate at which it is absorbing heat from the star is ...
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6 votes
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Is there any residual oscillation left from the Moon rotation?

This is called "physical libration". The Moon’s physical librations and determination of its free modes (2011) estimates it using the Apollo mission retroreflectors. Their result is very small. They ...
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6 votes
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Tidally locked Venus, is it possible and consequences?

It may not be possible for Venus to become tidal locked I don't think we know if it's possible for Venus to become tidally locked. Correia et al. 2008 expect the equilibrium rotation to differ from ...
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5 votes

How is Mercury tidally locked if the ratio is not 1:1?

It's not tidally locked like the moon is because it is in a 3:2 resonance with the sun. It rotates three times for every two orbits it makes. So it isn't considered a tidal lock because it means they ...
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5 votes

How is Mercury tidally locked if the ratio is not 1:1?

The reason that Mercury is not locked into a 1:1 spin orbit resonance is its eccentric orbit. In fact, the 3:2 resonance is the result of weak tides in conjunction with the orbital eccentricity. This ...
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  • 5,276
5 votes

How is Mercury tidally locked if the ratio is not 1:1?

The simple answer to your question is that Mercury is not tidally locked. You may have seen old books (before 1965) that said it was tidally locked, because it was once assumed to be so. Alternatively,...
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  • 2,525
5 votes
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Eventual outcome of tidal acceleration and deceleration

So that's question 1: Is it really possible for tidal acceleration to throw a satellite into space before the planet is tidally locked, and if so, does either objects' size impact it, or just ...
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  • 1,405
5 votes

Can a solar system exist where the second planet rotates fast, and the third planet is tidally locked to their star?

The tidal locking timescale depends on several factors: $$\tau_{lock} \approx \frac{0.4 \omega_0 a^5 m Q}{3 G M^2 k_2 r^3}$$ such as the initial spin rate $\omega_0$, the semimajor axis $a$, the mass $...
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5 votes

Is the moon's revolution speed increasing or decreasing

From the cited article, The slowing of the speed of rotation of Earth also results in the increase in speed of revolution of moon around the Earth. I suspect that this is the statement that is ...
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5 votes
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Tidally locked, and yet spinning?

I think what you are envisioning is having one pole always pointed towards the primary star. So the planet would rotate about that pole, but then the direction of the pole would change over the course ...
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  • 2,525
5 votes

Lunar phases if Earth was tidally locked to the Moon

tl;dr: An observer on the "Moon side" would see only half the phases during the fortnight-long night: from waxing half-moon to waning half-moon. They would also see the Moon during the day (early ...
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5 votes

Will Mercury ever become locked to the Sun?

Mercury is tidally locked; it has a 3:2 resonance with the Sun, where it rotates three times for every two orbits. It is well understood that Mercury is tidally locked, but modern explanations for how ...
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  • 2,147
5 votes
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Is an extreme precession on a tidally locked planet possible?

Yes. Our own Moon is tidally locked to the Earth, but has an axial precession with a period of about 18.6 years. This precession is due to the 1.5 degree offset angle between the Moon's rotational ...
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4 votes

Is the moon's revolution speed increasing or decreasing

Some confusion may have arisen in parts of the literature due to the facts that (a) the moon's mean rate of angular motion (and revolution speed) does appear to be speeding up if it is measured by ...
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  • 726
4 votes

Would a tidally locked planet be always increasing in temperature?

You're asking if the temperature of the side facing the star will increase without bound. Almost anytime you're talking about a real, physical system, "without bound" just doesn't happen. Think about ...
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4 votes

Eventual outcome of tidal acceleration and deceleration

You missed the the most important factor, which is, how close the sun is and as a result of the distance to the sun and relative mass, the Hill sphere and the approximate distance where the stable ...
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