From: physfitfreak@gmail.com   
      
   On 11/1/24 23:52, Sylvia Else wrote:   
   > On 30-Oct-24 12:53 pm, Sylvia Else wrote:   
   >> NASA has a mission to the Jovian system, to study Europa. That moon is   
   >> interesting because it appears to have liquid water under an icy   
   >> surface. The heat need to keep the water liquid comes from the   
   >> stretching and compression Europa experiences during its orbit around   
   >> Jupiter, the orbit not been exactly circular.   
   >>   
   >> So much, so simple.   
   >>   
   >> Some thought made me realise that although the tidal forces on Europa   
   >> mean that it is not exactly spherical, its two bulges cannot remain   
   >> perfectly aligned with Jupiter, because Europa's angular velocity   
   >> relative to Jupiter is higher at periapsis than at apoapsis. The   
   >> result is that the nearer bulge is sometimes ahead, and sometimes   
   >> behind, relative to Europa's orbital motion, resulting in a net force   
   >> backwards along the orbit, or forward along the orbit.   
   >>   
   >> Again, certainly stuff that's already well known.   
   >>   
   >> As far as I can see, the energy that is being dissipated as heat   
   >> inside Europa has to come from changes to Europa's orbit. Further, if   
   >> Europa were either perfectly rigid, or perfectly elastic, there would   
   >> be no energy transfer, and consequently no change to the orbit.   
   >>   
   >> It would make no difference if Jupiter itself were perfectly rigid, so   
   >> the transfer cannot involve tides on Jupiter generated by Europa.   
   >>   
   >> So the existence of the orbital energy transfer depends on Europa   
   >> being neither perfectly rigid nor perfectly elastic.   
   >>   
   >> What escapes me is the mechanism.   
   >>   
   >> Any thoughts?   
   >   
   > Perhaps I was naive to think anyone would address the essence of my   
   > post, rather than going off at massive tangent.   
   >   
   > Sylvia.   
      
      
   Yes. You were naive to think sci.physics is a classroom.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)