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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,696

A new page on Gravity

Would value your feedback.

Any ideas on how to best present space-time curvature will be welcome!

Also help in tightening up the wording is welcome, too.

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**ganesh****Administrator**- Registered: 2005-06-28
- Posts: 30,276

Hi MathsIsFun,

The page on Gravity is very well made.

The units of 'g' and 'G' in other systems (other than SI), whether they are scalar or vector, and affect on Altitude and Latitude may be included.

The presentation is flawless.

Great work!

*Last edited by ganesh (2016-04-13 21:11:56)*

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi MIF;

Any ideas on how to best present space-time curvature will be welcome!

That is the standard way to illustrate space-time curvature. Sometimes, you see an animation of two balls (planets) on a sheet.

All in all a nice page.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,828

hi MathsIsFun

Good page. I found the animation tricky to use but I think this has great potential. Mostly, new particles either zoomed off or just crashed into the growing central mass. After some practice I managed to get one particle to orbit the central mass. The 'ellipse' had an axis progression (Mercury type orbit?). Have you built in some Einsteinian relativity element or is this just an accuracy issue? Would it be possible to provide greater control of each particle so it's easier to set up orbits? eg create a new particle, then specify its direction of motion, then the magnitude of this motion. That would allow controllable experimentation.

I made the central mass about 10 x 10^25 and the satellite 1 x 10^23. I say 'about' because most of my attempted satellites just crashed into the 'planet'. It took a while before I managed to get this one with the right tangential velocity.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,696

I was thinking of a popup edit screen, one line per object, with mass, x and y position and velocity magnitude and direction (0-360 degrees). The animation would pause while editing. Can also delete a particle.

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,696

Updated Gravity Freeplay with an edit option, how is it?

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi;

Could be a firefox issue but I can not produce an image like Bob did.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,828

Oh that's great!!!

I chose 2 x 10^23 and 6 x 10^17 for a Sun and Earth system (scaled down mass-wise) and managed this straight away. Think I need to adjust the velocity so that we don't all burn up on closest approach!

Nice demonstration of Kepler's laws too.

Oh joy. I've just added Mars. Shows opposition and all that. This is better than 'sliced bread' !

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

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