Message from @hgb
Discord ID: 675491088194207765
You can only use centre of mass to estimate gravity when the object is like a point mass
> Perform an experiment. Have a large plane perpendicular to the earth, place an object near it, see where the gravitational force acts on that object.
@hgb Is this plane got more mass then the earth. If so the earth will be attracted to the plane. Also this plane woult crumple in on its centre of mass to create a sphere
Near the dead centre of the earth, the prediction of the centre of mass gravity would be very very very large, in reality, it's close to zero.
Ok you're still not getting my point.
The centre of gravity isnt used to calculate the centre of mass ever. It shows where gravity will be in effect
Lmao
Okay.
You're at 5 meters away from centre of the earth
ok
How much gravity force would there be on you
Would it be larger than or smaller than g
larger
following inverse gravitational square law
That's what the centre of mass method predicts, right?
no?
i just told you
But in reality, if you're there, obviously, your gravity would be less than g
the inverse gravitational law
thats not true
Okay.
You're at the centre of the earth. Inverse square law predicts near infinite force there, correct?
no
Well say 0.0000001 m away from centre of earth
ok
You would have a humongously large force
But
You have equal mass in any direction from you.
See what I mean?
The centre of mass model is good if, well, we consider masses to be point masses.
But not so otherwise.
Because if I cut the earth into two, and stand in the middle, then they would exert equal and opposite force on me
Because they have centres of masses in at different locations
Which contradicts the prediction made by considering solely the centre of the earth
They would now be two different objects. their gravity would be reliant on the mass of each half. It would not be equal as each half of the earth is not equal
Which is I would have a massive force on me, and the immediate moment I cross the centre, that massive force inverts in direction.
Yea
Do you genuinely believe this
That in the dead centre of the earth, I have infinite force
so for a split second you would feel the force decrease to 0 as you have an opposite and equal force applying pushing you into an equilibrium
no