OT: I'm confused about gravity

And the Earth isn't a hollow shell

Then you remain doomed to thinking and posting bollocks. Your choice.

Then you obviously didn't have a clue what you were doing.

As you rise up, you become further away from the bits of the Earth, and so their pull on you decreases.

You can't *think* your way to an answer to this. Only by using calculus can you get the correct answer. It's always going to be inverse square, whether above or below ground, but once you go below ground calculus gives you the linear decrease as you go downwards.

Remember that we have landed spacecraft on the planets using *only* Newton's laws, in particular inverse-square.

The force on any body in space and hence how it accelerates at that moment is the sum of all the gravitational forces on it - from the Earth, Moon, Sun, and the planets. Also, in fact (but prolly for calculation purposes, ignorable), all matter in the universe.

That's some contortion if you can pull it off.

Prejudices acquired much later in life through personal experience are far more valuable. A Conservative is just a Liberal that got mugged.

Nah, John McDonnell more like. ;->

I am, but I know my limits. Today my son ran 48 miles. The chances of me understanding calculus are about the same as me running 48 miles.

Occam's Razor works for me.

Bill

I think all that was irrelevant.

Bill

Yes it probably does. But I don't like to boast about it.

Bill

I didn't. I said that it would need to be modified for the conditions near the planet, where gravity pulls in all directions below the horizon. Once you get up in space far enough away the modification would be negligible.

Bill

Maths is comons sense, just in more detail.

If you can catch a ball thrown at you, you can do - are doing - differential calculus.

The point is to do it consciously.

Leprechauns sit inside the middle of everything amd pull it all together...

It was you who introduced the inverse squares buit, That was maths

But I have a final world for you.

Science is about making models of the world. Not the world itself.

Your 'common sense' has failed you the moment you start asking questions about a model of the world as if it where the world itself.

Stuff falls.

That is all common sense tells you. There is no 'gravity' at all.

Thats an invention of theorists.

No. just to them.

Being spoilt and selfish if they go past they try to drag them back again

It does, BUT the combined effect so long as the earth ios approximately spgerical is as if the mass were concentrated at the middle

Newton elt al worked that out from the basic law of gravity by adding up every single bit of planet inside a sphere.

Integral calculus is the tool that allowed them to do that without actually counting every little bit.

In the same way that I can tell you that renewable energy is a crock of s*it without having to build 10,000 windmills and solar panels to prove it.

Gravity is an interesting force, as it seems to me that if indeed it is a force at all, it has to be a monopole, ie there is no negative gravity. Most other forces are forces and can attract or repel, but at the moment Gravity only attracts, at least in a very local system it does, which is why its so very odd that the universe is expanding and getting faster as well. Brian

If you look on it as a distortion of space however it make a little more sense, which is, I suspect why einstien figured out that it can affect the passage of local time as well. Mass is interesting of course as it seems to be a distortion of a field. This is where the Higgs Bozon comes in, in that it is theparticle mostly responsible for the field that bodies of atoms move through of course. Brian

Not right. You feel the full effect of all the mass that can be encompassed by a sphere under your feet. I'm not sure of your level of mathematics but you can look at the diagram and see the argument here:

It includes a full derivation but uses integral calculus to sum up all the contributions.

If the object is a sphere then every piece of matter that forms it will be on one side of the tangent plane to the sphere so it will produce a net attractive force downwards towards the centre of the planet.

Indeed and that was how the gravitational constant was first measured (although they got it a bit wrong at first because the mountain is floating on a denser sublayer of molten rock).

That is because the Earth is spinning and isn't a perfect sphere. In addition there are places where there are higher densities and surface irregularities. The quite substantial masscons on the moon caused some minor irritation for the orbital calculations of Apollo.

The rules of physics are the same in both cases. All the mass contained in a sphere beneath your position acts to attract you as if it were a single point mass at the centre of the object.

Try the diagrams in this article then. You don't have to completely follow the maths to understand that for any given ring of material that forms a part of a sphere the net contribution is always attraction towards the centre of the sphere proportional to the mass of the ring.

Calculus just gives you a way of summing up all the tiny contributions.