## Gravitational Force Experiment Issues

What did you draw?
OfPowerDerive
Posts: 1
Joined: Fri Jan 06, 2023 8:19 pm

### Gravitational Force Experiment Issues

Essentially I need to recreate the Earth's orbit around the Sun, but I'm having problems keeping all the masses and the radius between the celestial bodies to scale. I need the values to be to scale because I am assessing the gravitational force between the bodies and it would be easiest for me to divide all the masses and radius by the same value as it would result in the same gravitational force had I been working with the the bodies at full size. Scaling it down is mainly so that I don't have to zoom out and move around all the way to 149 597 870 700 meters out for the radius of the Earth's orbit.

My main problem is that every time I get all the masses and radius inputted into the sim the Earth entirely stops its circular orbit and goes shooting off in one direction entirely off of the screen. I don't really know why that it, though I may be entirely missing something as I'm not too familiar with this simulator. If anyone can help out, or give me some pointer with how to fix the orbit of the Earth I would really appreciate it.

testtubegames
Posts: 1139
Joined: Mon Nov 19, 2012 7:54 pm

### Re: Gravitational Force Experiment Issues

Oh, yeah, building things to scale can be tricky.

The full version of the sim actually has different unit-systems you can select. So you could pick Astro-Units,for instance, and put your Earth 1 AU away from the Sun.

But even with the free version, and a little math, I did a writeup about the unit conversions that might be helpful for you: https://testtubegames.com/gsim101/?p=units

My Astro-Units conversion was one of infinite I could pick - but it tends to do a nice job keeping things kinda on screen, moving at a good speed, and also means you don't need to worry about changing the Gravitational Constant at all. So you'd put Earth 2000 m* units away from the Sun, given the conversion. And the Earth's mass would be .002843983 kg*. That kinda thing. Maybe that'll help?

Getting the densities and velocities right will take a little thought - but having the length/time/mass conversion factors could get you started.