Universe Sandbox2 broke :[

[GreyGeek]

A couple of weeks ago, or so, I installed Universe Sandbox2 beta from SteamLinux.

It ran beautifully and gave me between 30 and 60 fps. I fired it up today to experiment with some planetary collisions I was studying, and it downloaded an update. The update KILLED the speed. Now I can't get any better than 3 fps, making the simulation worthless.

I decided to see if the update spoiled the Windows version and booted into my Win7 partition and installed US2. It ran well, giving me about 40 fps on average. Very usable. For two hours I experimented with an Earth size planet entering our solar system and looping inside Earth's orbit and back out to the vicinity of Jupiter.

So, I logged back into Kubuntu to see if there was anything else I could try besides the recommendations given by the US2 forum. However, when I run US2 it immediately presents me with "Can not run program (missing executables)".
Unfortunately, SteamLinux didn't offer an option to reinstall US2.

I suspect it is SteamLinux's paranoia about someone running a bootleg copy of their games. When I installed the Windows version I suspect that SteamLinux deleted the Linux executable from my account inventory.

My other steam games run just fine in Kubuntu.

[GreyGeek]

Well, today I logged into Universe Sandbox2 and there was another download waiting. Installed it and got US2 back!
Not only that, it runs faster than it did before! So, US2 not currently broke in Kubuntu!

[GreyGeek]

About 50 years ago I read a book called "Worlds In Collision", by Emmanuel Velikosky. His premise is that Jupiter ejected a body about the size of venus, which had close passes with the Earth and Mars around 800-700 BC, before flinging Mars to its present orbit and itself to where it is now.

I've been using Universe Sandbox2 to try and replicate that scenario. So far no success, but it has been a lot of fun trying!

[Silent Observer]

I haven't read that book. Did Velikovsky explain how the orbits of Venus and Mars (and most likely Earth) could have gone from unavoidable high levels of eccentricity to their current near-circular condition in less than 3000 years? Or have a hypothesis for where Jupiter could have gotten the energy to eject an object massing very slightly more than Earth? Or why such antics left the Moon in so nearly circular an orbit around Earth?

Sorry, not meaning to rain on Universe Sandbox, just extremely skeptical about the orbital mechanics and energy budgets of Velikovsky's fiction.

[GreyGeek]

I haven't read that book. Did Velikovsky explain how the orbits of Venus and Mars (and most likely Earth) could have gone from unavoidable high levels of eccentricity to their current near-circular condition in less than 3000 years? Or have a hypothesis for where Jupiter could have gotten the energy to eject an object massing very slightly more than Earth? Or why such antics left the Moon in so nearly circular an orbit around Earth?

Sorry, not meaning to rain on Universe Sandbox, just extremely skeptical about the orbital mechanics and energy budgets of Velikovsky's fiction.

Those questions are exactly those I considered while reading the book. The "ejection" of a glob from Jupiter the size of Venus, would have had to be in line with the plane of the orbits of Mars and Earth and in a retrograde direction so as to reduce the velocity of the blob to allow it to be drawn toward the Sun. Also the velocity of the ejection would have to be such that "Venus" would have looped around the far side of the Sun but very near to or inside the orbit of Mars which, according to Velikovsky, was between Mercury and Earth. It would have to pass by once close enough to disturb the rotation of the Earth on its axis, causing it to flip while making a line from Israel to the Sun the temporary axis of the rotation to make the Sun appear to stand still for a day. (By drawing part of the molten core of the Earth towards the blob, thus unbalancing the Earth and causing it to flip - like some tops do). Fifteen years later "Venus" passes by the Earth again, flipping the axis again, before being drawn back towards the Sun and an encounter with Mars which flips Mars out of its orbit into an elliptical orbit with an aphelion near Mar's present orbit, and leaving the blob, as Venus, where it is now. At that moment another body would have had to pass Mars at aphelion, close enough to impart an additional velocity vector perpendicular to the radius and with such magnitude as to produce a circular orbit. Ditto for Venus. The second (and 3rd?) body is not mentioned or implied.

Anyway, I've been trying for a couple weeks, letting US2 run for hours and even over night, "500 years" in model time, with various ejection velocities and have NEVER gotten "Venus" to so much as nudge Mars or Earth. On one occasion, after an overnight run, I found "Venus" in an elliptical orbit perpendicular to the plane of the orbits of Earth and Mars, and looped out to an aphelion half way between Jupiter and Saturn. I got tired of that and decided to eject a mass equal to Jupiter itself. Even in that scenario Jupiter's orbit, repeatedly passing by Earth and Mars as it looped around the sun, but not inside Mercury's orbit, never got close enough to nudge either Earth or Mars. I suspected that a body the size of Jupiter would have no problem flipping a puny Mars out of its supposed position (where Venus is now) into a highly elliptical orbit, if not a solar system leaving hyperbolic orbit. No such luck. Yet. If Jupiter isn't likely to do it then Saturn, which is 14% smaller, is even less likely.

Regardless, it has been a lot of fun tinkering with the six elements of orbit to see what can and cannot be done in such an hypothesis. At this point I am concluding it would take divine intervention to create such a series of events that could flip the Earth twice (without stopping it rotation), have the blog assume a near circular orbit where it is now, and Mars to flip out of where Mars was and into a near circular orbit where it is now. But, it's fun and I am going to continue to tinker. Anyway, my 8 year old grandson is having a blast throwing planets into the mix. When you toss two Jupiters and two Venus' into the mix and make all of them have elliptical orbits that move them between Mercury and Mars, all sorts of things happen. The next thing I am going to experiment with are Earth-like planets in a binary star system and see what kind of configuration would keep Earth stably in the goldi-locks zone.