Question about planetary gravity

[Saber]

Is  these  things tat  i  write   right ? 

If  there is a  part in a  planet  that  have bulged out too much  or  concaved  in  too much............

 

The  gravity  of the planet  would pull in the  bulged  out part  and  fill in the  concavity and  add the volume of the bulgness to  the   radius of the  planet  equally   and also  the volume of the concavity  would  be equally  reduced  from the radius  .....

 

[Genady]

If the material of the planet is fluid, yes.

[studiot]

36 minutes ago, Genady said:

If the material of the planet is fluid, yes.

May I add the word sufficiently ?

If the material of the planet is sufficiently fluid, yes.

Note also that the pull will always be present, regardless of the state of the planetary material.

Ice for instance will flow under quite small pressure. So if an ice planet is large enough the gravitational pull will be large enough to create flow pressure.

 

But there are other mechanisms at work as well. Some of them in conjunction with gravity, some of them opposed.
 

For instance if the planet spins the pull experinced will vary from equator to pole.

Also if the planet surface is subject to weathering, eg by heating and cooling causing cracking, then gravity will pull the broken off pieces into the concavities.

 

Good question, @Saber . +1

 

Edited February 5, 2023 by studiot

[swansont]

Note that the earth, to a very large extent, is sufficiently fluid. The solid earth deforms from tidal effects of the sun and moon, the surface deviation from smooth is quite small - some km-scale bumps and valleys on a ~6400 km radius, and planet deforms because it is spinning.

[Genady]

Without rotation and other affecting bodies, the outcome depends on 3 factors: material of the planet, mass of the planet, and time. Any other?

[Genady]

1 hour ago, Genady said:

Without rotation and other affecting bodies, the outcome depends on 3 factors: material of the planet, mass of the planet, and time. Any other?

@Saber, can you think of any other physical effect that could affect the process you've described? (Even if it is purely theoretical and does not occur in practice.)

[Saber]

F****
Its been  half  a day  im  trying  to  reach  the  site  as  they have  partially banned  the  net  here.................you  can  only   reach  religious  sites   over here  the  other  ones  are Haram.............

[studiot]

Hope they are not looking over your shoulder then.

[J.C.MacSwell]

9 hours ago, Genady said:

Without rotation and other affecting bodies, the outcome depends on 3 factors: material of the planet, mass of the planet, and time. Any other?

Temperature

[Genady]

29 minutes ago, J.C.MacSwell said:

Temperature

In what way? By affecting properties of the material? Then it does not count

Or something else?

Edited February 6, 2023 by Genady

[Saber]

On 2/5/2023 at 7:18 PM, Genady said:

@Saber, can you think of any other physical effect that could affect the process you've described? (Even if it is purely theoretical and does not occur in practice.)

guess i have to  wait  until weekend  to be able to  think...............You  know   thinkning  is a luxury nowadays.......that  the working class people  cant afford............

Add my country's   internet situation to it........they  want to  cut off all international connections and   we would be able to have an internal domestic network  like china......

[Genady]

31 minutes ago, Saber said:

guess i have to  wait  until weekend  to be able to  think...............You  know   thinkning  is a luxury nowadays.......that  the working class people  cant afford............

Add my country's   internet situation to it........they  want to  cut off all international connections and   we would be able to have an internal domestic network  like china......

I am very sorry to hear that.

BTW, I was born and grew up in your vicinity, in Baku, Azerbaijan. That was many years ago, though.

Good luck.

[mistermack]

On 2/5/2023 at 2:42 PM, Genady said:

Without rotation and other affecting bodies, the outcome depends on 3 factors: material of the planet, mass of the planet, and time. Any other?

A moon might have an effect. Causing internal tidal stresses, making earthquakes more likely. The earthquakes will let settling occur.  

[Genady]

2 minutes ago, mistermack said:

A moon might have an effect. Causing internal tidal stresses, making earthquakes more likely. The earthquakes will let settling occur.  

Yes, certainly.

But,

3 minutes ago, mistermack said:

  On 2/5/2023 at 10:42 AM, Genady said:

Without ... other affecting bodies ...

(As I said above to Saber,

On 2/5/2023 at 11:48 AM, Genady said:

Even if it is purely theoretical and does not occur in practice.

)

[Saber]

7 hours ago, Genady said:

I am very sorry to hear that.

BTW, I was born and grew up in your vicinity, in Baku, Azerbaijan. That was many years ago, though.

Good luck.

You   are Azeri ???

[Genady]

1 hour ago, Saber said:

You   are Azeri ???

Ethnically, no, I'm not. 

[Saber]

13 minutes ago, Genady said:

Ethnically, no, I'm not. 

I  was  named  after  this  person...................it  was  your  fellow citizen...........

https://en.wikipedia.org/wiki/Mirza_Alakbar_Sabir

 

Edited February 7, 2023 by Saber

[Genady]

27 minutes ago, Saber said:

I  was  named  after  this  person...................it  was  your  fellow citizen...........

https://en.wikipedia.org/wiki/Mirza_Alakbar_Sabir

 

I remember learning about Sabir in school. Also, Sabir street in Baku.

I have been to Shamakhy, Sabir's birthplace, but not because of that, but rather on a tour to Shamakhy Astrophysical Observatory - Wikipedia.

Are you Azeri?

[Saber]

54 minutes ago, Genady said:

I remember learning about Sabir in school. Also, Sabir street in Baku.

I have been to Shamakhy, Sabir's birthplace, but not because of that, but rather on a tour to Shamakhy Astrophysical Observatory - Wikipedia.

Are you Azeri?

My  ethics   are   75%  Azeri   some where near  Urmia lake   3 of my  grand parents ............25%  From Hamadan    ( the other one ) ...........But fr  ....they  came  to  Tehran....about  1940's  and 50's.....

Can i  Ask  your   ethics  too ?

Edited February 7, 2023 by Saber

[joigus]

On 2/5/2023 at 1:55 PM, Saber said:

Is  these  things tat  i  write   right ? 

If  there is a  part in a  planet  that  have bulged out too much  or  concaved  in  too much............

 

The  gravity  of the planet  would pull in the  bulged  out part  and  fill in the  concavity and  add the volume of the bulgness to  the   radius of the  planet  equally   and also  the volume of the concavity  would  be equally  reduced  from the radius  .....

 

Good thinking. +1

In recent years, a cosmological theory to explain why the cosmos looks so flat --up to very large scales-- is being developed --Latham Boyle, Kieran Finn, Neil Turok, and others. The mechanism they propose is similar to what you're saying here. In fact, they use the Earth as an analogy. It's a combination of gravity and dissipative processes that does it. You need some fluidity, as Genady and Swansont said. So you need temperature, as J.C.Macswell pointed out.

Because of plate tectonics, it would appear that bulges could potentially regenerate, thereby frustrating this process, and perhaps --from constant cooling of the Earth-- grinding the process to a halt. But dissipative mechanisms are constantly counteracting this tendency, with the result of flattening it out. Gravity does the final trick, depositing the ground pieces as close to the centre as it can.

[Genady]

2 minutes ago, Saber said:

My  ethics   are   75%  Azeri   some where near  Urmia lake   3 of my  grand parents ............25%  From Hamadan    ( the other one ) ...........But from  two  generation ago....they  came  to  Tehran....about  1940's  and 50's.....

Can i  Ask  your   ethics  too ?

No problem, although it's a bit complicated. I assume you mean ethnicity rather than ethics.

My grandparents on the father's side ran away from pogroms in Belorussia and eventually settled in Baku. My father was born in Baku.

My mother's family, including my mother, ran away from advancing German army in Ukraine, in the WWII. They too settled in Baku, after running around for some time.

All the great-grandparents were Jewish, but starting with the grandparents, none were religious. My grandparents spoke Yiddish and Russian. My mother spoke Ukranian and Russian. My father, some Azeri and Russian. My first language was Russian, although I remember some words and phrases in Azeri. So, I'm not sure what is my ethnicity. Also, Baku, at least at that time, was a very cosmopolitan city. 

[Perhaps, the later part of this thread should be moved to The Lounge forum.]  

[sethoflagos]

15 minutes ago, joigus said:

Because of plate tectonics, it would appear that bulges could potentially regenerate, thereby frustrating this process, and perhaps --from constant cooling of the Earth-- grinding the process to a halt. But dissipative mechanisms are constantly counteracting this tendency, with the result of flattening it out. Gravity does the final trick, depositing the ground pieces as close to the centre as it can.

Interesting thoughts. If we take the Martian volcano Olympus Mons as an example: a 22 km high pyramid of basalt formed mainly around 3 billion years ago that is certainly taking its time to dissipate. If vulcanism were somehow to restart on Mars, might it not follow the old channels and lines of weakness and extend Olympus Mons even further from isostatic equilibrium? Gravity may always be there lurking in the background, but if changes to surface topography are dominated by 'random' events (asteroid impacts are another obvious example) the long term trend towards regularity may not be apparent.

Elsewhere in the solar system I think the 396 km diameter Mimas is the smallest body with a gravity strong enough to deform itself. 

On the other hand, isn't a sphere the optimum shape of a given volume for collision avoidance? That may provide some statistic bias towards 'roundish' shapes for smaller bodies.   

[joigus]

21 minutes ago, sethoflagos said:

Interesting thoughts. If we take the Martian volcano Olympus Mons as an example: a 22 km high pyramid of basalt formed mainly around 3 billion years ago that is certainly taking its time to dissipate. If vulcanism were somehow to restart on Mars, might it not follow the old channels and lines of weakness and extend Olympus Mons even further from isostatic equilibrium? Gravity may always be there lurking in the background, but if changes to surface topography are dominated by 'random' events (asteroid impacts are another obvious example) the long term trend towards regularity may not be apparent.

Elsewhere in the solar system I think the 396 km diameter Mimas is the smallest body with a gravity strong enough to deform itself. 

On the other hand, isn't a sphere the optimum shape of a given volume for collision avoidance? That may provide some statistic bias towards 'roundish' shapes for smaller bodies.   

You're right in that it's not just a matter of hinging together a bunch of qualitative concepts. I'm sure it depends on how much dissipation, gravity, tectonic energy at play... So the quantitative argument is lacking there.

The case of Mars is interesting because of the relatively low gravity, as compared to Earth. That's probably why Mount Olimpus and Valles Marineris are so huge when considering them with some kind of scale law in mind. Even though Mars has strong dissipation in the atmosphere*. It doesn't have that much dissipation underground --if at all--, as it has no plate tectonics. So in my mind, lower gravity and tectonic dissipation could easily account for it.

It's interesting to notice though that minuscule satellites, like Phobos and Deimos, look more like potatos. Very low gravity and practically no dissipative processes. Seems to bode well with the qualitative idea.

There must be a scale law involved, no doubt.

I'm being quite vague though, I'm aware of it.

-------

* But having had active geology and erosion processes in the remote past. (EDIT)

Edited February 7, 2023 by joigus
Addition

[MigL]

29 minutes ago, sethoflagos said:

On the other hand, isn't a sphere the optimum shape of a given volume for collision avoidance? That may provide some statistic bias towards 'roundish' shapes for smaller bodies.   

A sphere does maximise volume, concetrating the greatest amount of volume, and therefore mass, into the smallest radius/dimensions.
Which is what gravity tends to do.
And all static, non-charged, Black Holes are perfectly spherical.
IOW, if something is big, and massive, enough, all other factors, like fluidity of material, don't matter;it will be spherical.

[Saber]

5 hours ago, Genady said:

No problem, although it's a bit complicated. I assume you mean ethnicity rather than ethics.

My grandparents on the father's side ran away from pogroms in Belorussia and eventually settled in Baku. My father was born in Baku.

My mother's family, including my mother, ran away from advancing German army in Ukraine, in the WWII. They too settled in Baku, after running around for some time.

All the great-grandparents were Jewish, but starting with the grandparents, none were religious. My grandparents spoke Yiddish and Russian. My mother spoke Ukranian and Russian. My father, some Azeri and Russian. My first language was Russian, although I remember some words and phrases in Azeri. So, I'm not sure what is my ethnicity. Also, Baku, at least at that time, was a very cosmopolitan city. 

[Perhaps, the later part of this thread should be moved to The Lounge forum.]  

Very  interesting  to hear.............man....yes i  meant  ethnicity......beg  my pardon.......I   one had a  friend in  Baku  who  was in  Ham  radio .............he  went  to all  remote  islands on  expedition   challenge's   .....he   once  went to   the  Bouvet  Is.

 

3 hours ago, sethoflagos said:

Interesting thoughts. If we take the Martian volcano Olympus Mons as an example: a 22 km high pyramid of basalt formed mainly around 3 billion years ago that is certainly taking its time to dissipate. If vulcanism were somehow to restart on Mars, might it not follow the old channels and lines of weakness and extend Olympus Mons even further from isostatic equilibrium? Gravity may always be there lurking in the background, but if changes to surface topography are dominated by 'random' events (asteroid impacts are another obvious example) the long term trend towards regularity may not be apparent.

Elsewhere in the solar system I think the 396 km diameter Mimas is the smallest body with a gravity strong enough to deform itself. 

On the other hand, isn't a sphere the optimum shape of a given volume for collision avoidance? That may provide some statistic bias towards 'roundish' shapes for smaller bodies.   

you  know   i meant   much  larger displacements  on the  surface of the planet..........22 km's   on  mars  with  6750 km  of  diameter  is  not  even  half a  percent.........i meant  larger   unevennesses .........@  least 10 %  of  the  planets   Diameter.......