Apparently you do not understand that the astronauts in the ISS are subject to about the same gravitional force as on the ground. The reason they are weightless is that the ISS is actually 'falling' towards the Earth, in free fall.
So, if it is falling towards the Earth, why doesn't it hit the Earth?: Good question. Because it has sufficient horizontal velocity, relative to ground, to insure that it always falls towards (and above) the ground horizon. This keeps it in permanent orbit around the Earth.
Here, design your own satellites and try to keep them in orbit.
Sort of. They orbit a common center of mass, which is usually inside the larger body (like the Earth and the Moon). However, Pluto and its moons are close enough in mass that they all orbit a point somewhere above Pluto's surface. A good demonstration of this can be found here - http://www.stefanom.org/spc/#
That's fantastic! If they get bored, some issues I noticed:
No way to access highscores. It said my score of 30.6 million on the default template was #1 but I have no way of accessing the boards to see how I compared to others.
Highscores don't always work, or at least they didn't work when I won one of the Templates . Not sure if intended; maybe highscores in Templates are disabled? I scored 213.6 million over 500 years in Kepler-18 and it didn't give me the option to submit the score.
The link to get a replay of your game only worked once for me, after that it stopped. It just gives me: "http://www.stefanom.org/spc/?view=" In fact, now my old link won't even work. One of my first games sucked but I grabbed the link just for the hell of it and it worked the first time, but now it won't replay.
Habitability bonus doesn't always work, at least in the Templates... edit: even though the Crowdedness bonus seems to work just fine in Templates.
Not sure if intended or not, but it doesn't run in the background. You have to be on the page viewing the game, and you can't click outside the browser or it'll pause until you're back. Even keeping the browser maximized and having a smaller window alt+tabbed over top will pause the game.
Great project though! Props to your kids. I played it obsessively for a while before tearing myself away. And I don't really care if my scores are saved haha I'm just offering some feedback in case it's an ongoing project of theirs. If they found a way to make it progressively difficult, it'd make a great game app.
It will be possible, but with a ver specific conditions.
A moon is fomed when objects orbiting a planet start to stick togeather in an object with a considerable size.
Maybe some moon actualla had a moon, but it will be ejected with a gravitational wave caused by the planet and the moon, like a slingshot.
Here is a site when you can mess up with planets in an orbit and try that: http://www.stefanom.org/spc/#
Astrophysics isn't necessary for a question like this. Most of that stuff is about particle and energy flows in stellar interiors. Tides are just gravity acting on fluids.
If you want to get an intuitive sense of how orbital mechanics works, there's a fun game worth playing where you create solar systems, and score points the more stable they are, the longer, and the more and heavier objects you put into them:
Super Planet Crash:
A game where you build a solar system using a combination of various masses of planets in orbits you choose. The higher the mass, the more points. The longer the system runs stably, the more points. But every planet you add can produce gravitational dynamics that destabilize the system over time.
Regarding the orbital stability, you can check it out by yourself with the awesome (and dangerously addictive!) Super Planet Crash, an online game designed by astronomer/data scientist Stefano Meschiari:
I'm curious how you think the sun's existence would magically protect the earth in the event of a collision/merging of two solar systems? Or even just a large star passing nearby could disrupt the planetary orbits enough to send us straight into Jupiter or something. Orbits are surprisingly fragile.
I've seen many people (foolishly) try to make analogies between entropy and evil in the universe or, like the AiG folks, suggest that the past is somehow discontinuous with the present on the basis of the Fall (or something else). But as a scientist, there are many reasons and much evidence to suggest that things have, excluding maybe the 1st second of the Big Bang, been pretty much the same in terms of physical laws.
If physical laws were previously different, we would see many discontinuities between the anthropocene (era when humans are active) and the pre-anthropocene times:
Emission spectra of distant stars, which travel at a finite speed to us. Note that the speed of light being changed would change everything else, as it factors into numerous other equations.
Minerals in older, pre-anthropocene deposits, asmineral formation is governed by geochemistry, which is dependent on physical laws.
Processes involving radioisotope decay would show evidence of changes.
Orbits of planets would be rather wonky. (Play this, it's fun.)
Numerous, unimaginable changes to the stability of everything (based on chemistry).
The laws governing the universe are an intricate and complex piece of work. Any fiddling with any one (or all) aspects would throw a lot of things out of whack. And we would see the consequences in every recorded trace of the past.
Some bored studying on Wikipedia after playing this for a few hours about orbit and gravity made me recognize a few words, I didn't understand them, but I recognized them.
Damn. Made it to 158k over the course of 337 years before crashing. The rules state that the game ends when either a planet crashes into another one or the barrier, however I've yet to crash 2 planets together. I always lose when one hits the barrier, and I swear there have been times when it looks like 2 planets hit each other.
Oh well. Still fun.
http://www.stefanom.org/spc/?view=1287185 (takes a while, recommend fast fowarding)
edit: Well screw my previous score. Made it to 759k in 34 years.
edit 2: I won!