CaptainPanic

What is affected by the gravitational constant?

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Hey all,

It’s been too long since I showed my digital face around here! But I am stuck on a question and this seems the #1 place to get some quality feedback, so I dug up the password and logged in. All is well on my end, hope you’re all doing great too.

 

Tl;dr

Other than gravity itself, orbits of celestial bodies and the attraction of objects (i.e. people) to the celestial bodies, what else would be affected if you change the gravitational constant from 6.67*10E-11 to something a lot larger (say 6.67*10E-9)?

Longer version

In a fantasy universe, such as exists in the Kerbal Space Program universe, planets tend to be 10x smaller than in our real-life universe and solar system. The reason that the programmers did this is to make the gaming experience nicer: you can orbit a planet in just 30-40 min, rather than hours.

In a pub discussion, we were discussing how the physics of this would work. The gravitational acceleration at the surface seems unaffected, and is still something around 9.81 m/s2. Since the planet is so tiny, you’d expect that the gravitational acceleration at the surface is much lower. But it isn’t. So either the planet is incredibly dense (maybe some fantasy-elements in the core?) or the actual gravitational constant (G = 6.67*10E-11 m3 kg-1 s-2) is different in this universe.

Of course, in a fantasy universe, you can write whatever you want. Kerbal Space Program is just a game, and the programmers have total freedom. But if you’re expanding the game to include more models of physics phenomena, would you run into problems because the gravitational constant is different? The orbits of planets and my space ships are stable, so those would work with a different gravitational constant. But would there be any other phenomena in which the gravitational constant plays a role?

 

p.s. Kerbals are one of the reasons for my inactivity here. Been rather occupied launching rockets. That, and life just got busy in general. :)

 

 

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Posted (edited)
35 minutes ago, CaptainPanic said:

Of course, in a fantasy universe, you can write whatever you want.

Oh, no.. we have one fantasy universe already in which D.T. became POTUS...

Edited by Sensei

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1 hour ago, Sensei said:

Oh, no.. we have one fantasy universe already in which D.T. became POTUS...

Actually, you'd be surprised how politically neutral Kerbal Space Program is. No mention of any POTUS, or even of countries. :)

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Posted (edited)

It goes back to one of your earlier points but both Atmospheric and seawater pressure could change.

Edited by Endy0816

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If you change nothing but the gravitational constant, the universe would collapse before planets could form. Hence the fine tuning problem associated with Universe models as to why our universe is so finely tuned.

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7 hours ago, CaptainPanic said:

Other than gravity itself, orbits of celestial bodies and the attraction of objects (i.e. people) to the celestial bodies, what else would be affected if you change the gravitational constant from 6.67*10E-11 to something a lot larger (say 6.67*10E-9)?

In addition to what Mordred said, consider stellar fusion, where you get a balance between nuclear interaction rates and gravitational attraction. If you increase the gravitational attraction, you get fusion at much smaller gas densities, and would get to heavier elements fusing (up to iron; that shouldn't change) instead of stopping at an earlier stage.

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40 minutes ago, swansont said:

In addition to what Mordred said, consider stellar fusion, where you get a balance between nuclear interaction rates and gravitational attraction. If you increase the gravitational attraction, you get fusion at much smaller gas densities, and would get to heavier elements fusing (up to iron; that shouldn't change) instead of stopping at an earlier stage.

This is exactly why I posted here. :) Thanks!

In our discussion, we were arguing whether the Kerbal Space Program solar system would be possible at all. We'll just ignore whether interstellar gas clouds want to form such solar systems at all, but just assume they did and now we want to check whether this solar system makes any sense at all.

So stars could possibly be much smaller, but burn as bright as our Sun. In the Kerbal Space Program solar system, the central star is also scaled down, probably with a factor 10 (I think in radius!), but it shines like our own Sun. Under the assumption that this is governed by a smaller gravitational constant, I read that this would be actually expected.

Also, assuming the universe is as old, heavier elements should (start to) become more common than in our universe. The game predicts very little about this, but it is interesting to know! Would elements heavier than iron also be expected to be more common?

 

Anyway, thanks for helping out in our pub discussion! Much appreciated!

 

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3 hours ago, CaptainPanic said:

 Also, assuming the universe is as old, heavier elements should (start to) become more common than in our universe. The game predicts very little about this, but it is interesting to know! Would elements heavier than iron also be expected to be more common?

Heavy nuclei are formed in neutron star mergers, but I can't say if you'd end up with more heavy elements from that since it should be easier to make black holes. 

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Posted (edited)

Star fusion isn't something I spent a lot of time studying but assuming faster processes are involved the metal percentages of the cosmos would show higher metal contents. I wouldn't know if the heavier than iron processes involved would have an easier or more difficult time.

Edited by Mordred

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In a fantasy universe G needn't be the same for all materials- or even for all configurations of materials.
You could, for example, make it "magically" temperature dependent in order o get the stars to work.

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Guys, my question is answered, with some extra's as a bonus! Thanks!

Of course, if you're interested to continue a discussion, feel free! :)

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