v2.1.1 Bugs Thread

[jamac41]

A possible bug, though it may also be `the wonders of space': I've found a planet of unusually low density - included in the attached screenshot, it has the same gravity as Mars but over 13 times the volume.  By my calculations, it has a density of a little under 0. 29g/m³.  For comparison, pumice has a density of 0. 25 g/m³.  Maybe it's a Naboo-style planet with a cave system at its centre?

[nuclearslurpee]

A possible bug, though it may also be `the wonders of space': I've found a planet of unusually low density - included in the attached screenshot, it has the same gravity as Mars but over 13 times the volume.  By my calculations, it has a density of a little under 0. 29g/m³.  For comparison, pumice has a density of 0. 25 g/m³.  Maybe it's a Naboo-style planet with a cave system at its centre?

By my calculations, the planet in question appears to have a density of 2.2 g/cm³ which seems reasonable. Mars is 3.9 g/cm³ for comparison.

Quick maths:
    M = (a_g * D²) / (4 * G)    where G = 6.67E-11 in SI units.
    V = (PI / 6) * D³
  rho = M / V = (3 * a_g) / (2 * PI * G * D)


Mars: rho = (3 * 0.38 * 9.81) / (2 * PI * 6.67E-11 * 6.8E6) = 3.9 g/cm³.
Tau Ceti VII: rho = (3 * 0.91 * 9.81) / (2 * PI * 6.67E-11 * 29E6) = 2.2 g/cm³.

Note that the gravity isn't actually the same as Mars (0.91 Gs vs 0.38 Gs), but if it were the density would still be a comfortable 0.92 g/cm³.

You can also check the density in SM mode by selecting the body and clocking the "Modify Body" button in the lower-right panel. I'm fairly sure this density is used to compute the gravity, not vice-versa, so you can be assured that the range of values is reasonably realistic. 

[jamac41]

By my calculations, the planet in question appears to have a density of 2. 2 g/cm³ which seems reasonable.  Mars is 3. 9 g/cm³ for comparison.

Quick maths:
    M = (a_g * D²) / (4 * G)    where G = 6. 67E-11 in SI units.
    V = (PI / 6) * D³
  rho = M / V = (3 * a_g) / (2 * PI * G * D)


Mars: rho = (3 * 0. 38 * 9. 81) / (2 * PI * 6. 67E-11 * 6. 8E6) = 3. 9 g/cm³.
Tau Ceti VII: rho = (3 * 0. 91 * 9. 81) / (2 * PI * 6. 67E-11 * 29E6) = 2. 2 g/cm³.

Note that the gravity isn't actually the same as Mars (0. 91 Gs vs 0. 38 Gs), but if it were the density would still be a comfortable 0. 92 g/cm³.

You can also check the density in SM mode by selecting the body and clocking the "Modify Body" button in the lower-right panel.  I'm fairly sure this density is used to compute the gravity, not vice-versa, so you can be assured that the range of values is reasonably realistic.   

You're right, I was meaning Venus and typing too late at night.  And its density is indeed . 4 of Earth's, which is 2. 2g/cm³ as you say.  I think I was just thrown off a bit by the 62b max population, which is about three times higher than the next largest I've seen, at a lower gravity than Earth's.