<p>The four big Galilean moons - Io, Europa, Ganymede, and Callisto - they are all tidally locked.</p>
<p>They all wobble a bit (and produce some internal heating) as the moons pass each other in orbit, gravitationally nudging one another.</p>
<p>Is this system stable? Can it be maintained indefinetely? And finally, would there be any way in which a similar system will not collapse or decay due to the emission of gravitational waves over time?</p>

CC BY-SA 4.0
2024-08-08T23:03:05.530Z
I would say that statistically, it is more likely to be stable than not. Otherwise, what would be the chances of humans living at the exact same time as it exists in a (temporarily) stable phase?
Pierre Paquette
CC BY-SA 4.0
2024-08-09T12:41:57.263Z
@PierrePaquette so they can cause tides to each other without affecting their orbits (contrary to what happens to the moon for instance which is receding as it "steals" angular momentum from earth until they get tidally locked)? Also, would there be any way in which a similar system will not collapse or decay due to the emission of gravitational waves over time?
vengaq
CC BY-SA 4.0
2024-08-09T14:38:49.900Z
The Galilean moons gain orbital energy from tidal interaction with Jupiter’s spin.  Gravity waves are a separate question.
eshaya
CC BY-SA 4.0
2024-08-09T15:36:27.283Z
@eshaya but when Jupiter will stop spinning what will happen? Will the moons still be giving tides to one another while being in stable orbits?
vengaq
CC BY-SA 4.0
2024-08-09T16:40:02.057Z
Could be that Jupiter locks and moons spiral in.  But, I would guess that Jupiter’s spin eventually throws the moons away.  Or some combination.
eshaya
CC BY-SA 4.0
2024-08-09T19:16:44.873Z
@eshaya is it physically impossible that they would stay in their orbits if Jupiter stops spinning then?
vengaq
CC BY-SA 4.0
2024-08-10T18:09:30.423Z
@vengaq I don’t know enough to speak about the potential long-term outcomes of the system. As eshaya said, though, gravitational waves are something else. And I’m pretty sure that by the time Jupiter (or any other planet) “stops spinning,” the Sun will have died. And “stop spinning” with respect to what? A reference frame is needed…
Pierre Paquette
<gravity><orbital-mechanics><gravitational-waves><tidal-forces><tidal-locking>
Are systems of multiple moons orbiting a planet where they cause tides to each other stable on the long term?
vengaq
# Are systems of multiple moons orbiting a planet where they cause tides to each other stable on the long term?

(Asked by: username_0 on 2024-08-08)

The four big Galilean moons - Io, Europa, Ganymede, and Callisto - they are all tidally locked.

They all wobble a bit (and produce some internal heating) as the moons pass each other in orbit, gravitationally nudging one another.

Is this system stable? Can it be maintained indefinetely? And finally, would there be any way in which a similar system will not collapse or decay due to the emission of gravitational waves over time?

**Tags:** gravity, orbital-mechanics, gravitational-waves, tidal-forces, tidal-locking

> **Comments:**
> **username_1**: I would say that statistically, it is more likely to be stable than not. Otherwise, what would be the chances of humans living at the exact same time as it exists in a (temporarily) stable phase?  
> **username_0**: @username_1 so they can cause tides to each other without affecting their orbits (contrary to what happens to the moon for instance which is receding as it "steals" angular momentum from earth until they get tidally locked)? Also, would there be any way in which a similar system will not collapse or decay due to the emission of gravitational waves over time?  
> **username_2**: The Galilean moons gain orbital energy from tidal interaction with Jupiter’s spin.  Gravity waves are a separate question.  
> **username_0**: @username_2 but when Jupiter will stop spinning what will happen? Will the moons still be giving tides to one another while being in stable orbits?  
> **username_2**: Could be that Jupiter locks and moons spiral in.  But, I would guess that Jupiter’s spin eventually throws the moons away.  Or some combination.  
> **username_0**: @username_2 is it physically impossible that they would stay in their orbits if Jupiter stops spinning then?  
> **username_1**: @username_0 I don’t know enough to speak about the potential long-term outcomes of the system. As username_2 said, though, gravitational waves are something else. And I’m pretty sure that by the time Jupiter (or any other planet) “stops spinning,” the Sun will have died. And “stop spinning” with respect to what? A reference frame is needed…  

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## 0 answers

