CCC planet and system discussion

[Lyhoko Leaci]

Should we just assume a single Moon-like moon for when dealing with spiritual beliefs? (And how about the sun and other, visible with the naked eye, planets)?

[Haplogy]

I'd like to have at least two clearly visible moons, if at all possible.

[finlay]

I wouldn't mind trying to do a planet system, given a bit of time to randomise it and stuff.

[Lyhoko Leaci]

We could also just have multiple people come up with ideas for the solar system and then vote on them, like what we're doing with everything else. Though in this case, only the winner's will get used, as combining multiple solar systems would just make a mess.

[finlay]

I've kinda done it already. I already had a planet system of my own laid out in a spreadsheet and all it takes is twiddling all the numbers to something a bit different. I've tried to make it a little more like our solar system than the one I'd made already. I dunno how to properly display the data, though. I'll give it a try in the next post.

[Lyhoko Leaci]

Something like this? (This is from an older collab conworld, not this one.)
Some of the details like day length won't be as important though at this point in time. (except for the CCCP, and maybe its moon(s).) Maybe just orbital radius/year length, size, and basic description.

P I: Orbital radius: 0.35 AU Day length: 0.189 Earth years Year Length: 0.189 Earth years Radius: 3982km Description: Small, tidally locked rocky planet

Losna's Planet: Orbital radius: 1.49 AU Day length: 5.43 hours Year Length: 1.66 Earth years Radius: 70,041km Description: Large gas giant, 5 times the mass of Jupiter.

P III: Orbital radius: 1.95 AU Day length: 26.64 hours Year Length: 2.48 Earth years Radius: 6683km Description: Dry dusty planet, similar to M IV. Orbits 2 times for every 3 orbits of Losna's Planet, has an inclined and eccentric orbit.

[finlay]

I should start this with the caveat that when I made my calculator (several years ago) I took all the formulas from Geoff's website (wherever it is now), and I'm not 100% sure how accurate they are. I also haven't calculated all the possible data, and I'm not sure how much to include here. I also don't know how the planets would affect each other. My innermost planet may be too close to the sun, for instance, or the gas giants may be too close together. Or like I want there to be an asteroid belt, but such a thing IRL apparently exists because of Jupiter's gravity, meaning that I should probably take that into account.

So as I envisage it, there are ten planets: 5 inner rock planets, 4 gas giants and 1 outer rock planet (unlike Pluto we should actually consider it a planet because it's bigger and stuff). There are also two asteroid belts which I haven't actually done any calculations for but I envisage being there. The CCCP is the 3rd, just like Earth. The two planets closer to the sun and four planets further away should be readily visible. The 8th planet's maximum magnitude is 5.4, so it will be on the edge of visibility in good conditions, but many cultures may not know about it. The 9th and 10th planets are invisible to the naked eye.

The sun is a little bigger than our sun. It should be G1 to our G2. The planet is a little hotter but only slightly – I think if we really want to make it hotter it should be done by altering the atmosphere to cause a greenhouse effect (however, I haven't looked at atmospheres just now). However I actually think we shouldn't make it hotter, because that would cause the ice caps to melt and it would invalidate Lyhoko's map.

Anyway, here's some data for each planet (selectively displayed; my spreadsheet has more):

Planet #1: Rock planet ("Mercury")
Mean distance from sun: 0.278 AU
Average insolation: 14.88 * Earth (I haven't calculated what temperature this works out at, though. It's a lot hotter than Mercury)
Year: 0.144 * Earth, 52.474 days, 2.010 local days
Local day (sunrise to sunrise): 26.111 days, 626.67 hours
Sidereal day: 51.974 days
Diameter: 3465 km (smaller than the Moon)
Density: 5.37 g/cm³
Mass: 0.0195 * Earth (1.1657E23 kg)
Gravity: 0.2645 * Earth (2.592 m/s²)
Magnitude at greatest elongation: -2.833 (brighter than Mercury)
Tilt: 169.9° (meaning it rotates "back to front" – but scrap this if it's incompatible with tidal locking)

Planet #2: Rock planet ("Venus")
Mean distance from sun: 0.634 AU
Average insolation: 2.858 * Earth
Year: 0.495 * Earth, 180.8 days, 148.6 local days
Local day (sunrise to sunrise): 1.217 days, 29.20 hours
Sidereal day: 1.209 days
Diameter: 10813 km (not as big as Venus)
Density: 5.6 g/cm³
Mass: 0.618 * Earth (3.6944E24 kg)
Gravity: 0.8607 * Earth (8.435 m/s²)
Magnitude at greatest elongation: -3.747 (not as bright as Venus)
Tilt: 3.01°


Planet #3: Rock planet (CCCP)
Mean distance from sun: 1.064 AU
Average insolation: 1.015 * Earth
Year: 1.076 * Earth, 393.1204 days, 379.3409 local days
Local day (sunrise to sunrise): 1.036 days, 24.872 hours
Sidereal day: 1.034 days
Diameter: 15279 km (bigger than Earth)
Equatorial circumference: 48002 km (because I can't bring myself to make it a round number sorry)
Polar circumference: 47921 km
Density: 5.12 g/cm³ (this is lighter than Earth but it's necessary so's the gravity is not too high)
Mass: 1.595 * Earth (9.5305E24 kg)
Gravity: 1.112 * Earth (10.898 m/s²)
Tilt: 24.18°
Apparent diameter of the sun: 0.968 * Earth

Moon #1: Light Moon (Modelled after the Moon)
Mean distance from CCCP: 332354 km (a bit closer than the Moon)
Diameter: 3215 km (smaller than the Moon)
Apparent diameter: 0.994 * Moon
Rotation period: 0.638 * Moon, 17.42 days, 16.81 local days
Lunar month (New moon to New moon): 18.23 days, 17.5887 local days
Solar year in lunar months: 21.57 months
Tides caused: 0.97 * Moon
Gravity: 1.482 m/s²
Magnitude at full moon: -12.76 (slightly brighter than the Moon)

Moon #2: Dark Moon (Modelled after a smaller Ganymede)
Mean distance from CCCP: 987874 km (about 2.6 times further than the Moon)
Diameter: 1737 km
Apparent diameter: 0.181 * Moon
Rotation period: 3.276 * Moon, 89.51 days, 86.38 local days
Lunar month: 115.9 days, 111.8414 local days
Solar year: 3.392 months
Tides: 0.00323 * Moon
Gravity: 0.443 m/s²
Magnitude at full moon: -10.35 (still very bright)


Planet #4: Rock planet (Backwards Mars)
Mean distance from sun: 1.791 AU
Year: 2.349 * Earth, 858.1 days
Sidereal day: 0.708 days
Diameter: 7989 km
Mass: 0.167 * Earth
Gravity: 0.426 * Earth
Magnitude at opposition: -1.859
Tilt: 178.1°

Planet #5: Rock planet ("Mars")
Mean distance from sun: 2.485 AU
Year: 3.841 * Earth, 1403 days
Sidereal day: 1.305 days
Diameter: 5874 km
Mass: 0.102 * Earth
Gravity: 0.481 * Earth
Magnitude at opposition: 1.286
Tilt: 8.32°

~Asteroid belt~

Planet #6: Gas giant (Small Saturn)
Mean distance from sun: 6.768 AU
Year: 17.259 * Earth, 6304 days
Sidereal day: 0.408 days
Diameter: 93233 km
Mass: 67.254 * Earth
Gravity: 1.259 * Earth
Magnitude at opposition: -0.236
Tilt: 5.77°

Planet #7: Gas giant (Big Jupiter)
Mean distance from sun: 10.487 AU
Year: 33.289 * Earth, 12158 days
Sidereal day: 0.915 days
Diameter: 164234 km
Mass: 526.3 * Earth
Gravity: 3.175 * Earth
Magnitude at opposition: 0.940
Tilt: 141.1°

Planet #8: Gas giant (Small Uranus)
Mean distance from sun: 16.233 AU
Year: 64.11 * Earth, 23416 days
Sidereal day: 0.520 days
Diameter: 45642 km
Mass: 6.146 * Earth
Gravity: 0.480 * Earth
Magnitude at opposition: 5.473
Tilt: 9.57°

~2nd asteroid belt~

Planet #9: Gas giant (Big Neptune)
Mean distance from sun: 27.423 AU
Year: 140.8 * Earth, 51415 days
Sidereal day: 0.817 days
Diameter: 69670 km
Mass: 29.84 * Earth
Gravity: 1.0002 * Earth
Magnitude at opposition: 7.460
Tilt: 24.9°

Planet #10: Rock planet (Big Pluto)
Mean distance from sun: 35.32368 AU
Year: 205.8 * Earth, 75164 days
Sidereal day: 1.234 days
Diameter: 9874 km (bigger than Mars)
Mass: 0.331 * Earth
Gravity: 0.553 * Earth
Magnitude at opposition: 12.443
Tilt: 15.3°

That took longer than I expected. Oops, better head to bed.

Also the main thing I need to fill in now is the descriptions of the worlds themselves but the basis is there.

[Torco]

i wonder if two big moons like that is a stable arrangement.
[he said, with regards to the planet with golems and dragons in it]

[zompist]

I entered finlay's specs into Universe Sandbox. Here's a picture of the system with trails indicating 2.2 years.

[CatDoom]

Hmm... if the planet's less dense than earth, would that tend to imply that it's poorer in metallic elements?

[finlay]

Hmm... if the planet's less dense than earth, would that tend to imply that it's poorer in metallic elements?

Not necessarily, as the metallic elements we have access to are only in the crust, which is but a tiny sliver of the planet. The bulk of the planet is made up inside. This would probably imply that there's less iron in the mantle maybe? I dunno if it's realistic though.

[Hydroeccentricity]

Hmm... if the planet's less dense than earth, would that tend to imply that it's poorer in metallic elements?

Not necessarily, as the metallic elements we have access to are only in the crust, which is but a tiny sliver of the planet. The bulk of the planet is made up inside. This would probably imply that there's less iron in the mantle maybe? I dunno if it's realistic though.

You can just say the planet has Earth density and a slightly large radius. The net effect on surface gravity is minimal, and there's no reason to assume that the species we've come up with would be implausible in a 1.1 G setting.

EDIT: so I did some calculation and it seems I may have been wrong. If we increase the radius by 20%, then we increase the mass of the planet by about 77%, given Earth-like density. But we're standing 44% farther away due to the increased radius. So the actual gravity on the surface would be 1.23 G. Unfortunately, that is not negligible. Does anyone have any ideas?

[Torco]

1,1 gees sounds trivially dissimilar to earth normal. "everything is 10% heavier", however, which means the same, sounds quite more significant. we could also go with the planet is less dense but also younger, which means its metal-poor but since its more volcanic, there's more of it thrown into the crust. also, more volcanoes, and since volcanoes are awesome it all works out for the best.

[Hydroeccentricity]

Maybe it's just not worth this hassle to have round numbers on our grid map?

[Lyhoko Leaci]

Finlay's planet #1 will almost certainly be tidally locked in some form, which means it can't rotate backwards. (Unless it goes around the star backwards...)

Also, a less dense planet, even if it does have plenty of metals at the surface, will likely have a reduced magnetic field.

My idea for the system also has 10 planets, with 5 rocky planets closer in, and then 5 gas planets. The sun is slightly dimmer than our own (0.948x) but not too much so. An interesting case is easily visible moons around other planets, as well as two moons around the CCCP.

Planet #1: Rocky planet; fully tidally locked Mercury-like planet
Semi-major axis: 0.31 AU
Average insolation: 9.87*Earth
Year: 0.174*Earth, 63.521 days
Local day (sunrise to sunrise): N/A
Sidereal day: 1525 hours, 63.521 days
Radius: 3564.3 km (bit bigger than Mars)
Density: 4.643 g/cm³
Mass: 0.147*Earth (8.807E23 kg)
Gravity: 0.471*Earth (4.624 m/s²)
Magnitude at greatest elongation: -3.548 (significantly brighter than Mercury)
Tilt: 4.2°

Planet #2: Rocky planet; fully tidally locked Venus-like planet
Semi-major axis: 0.54 AU
Average insolation: 3.253*Earth
Year: 0.400*Earth, 146.037 days
Local day (sunrise to sunrise): N/A
Sidereal day: 3504 hours, 146.037 days
Radius: 5325.4 km (slightly smaller than Venus)
Density: 4.952 g/cm³
Mass: 0.525*Earth (3.133E24 kg)
Gravity: 0.751*Earth (7.368 m/s²)
Magnitude at greatest elongation: -4.648 (slightly dimmer than Venus)
Tilt: 8.3°

Planet #3: Rocky planet; Venus-like planet
Semi-major axis: 0.78 AU
Average insolation: 1.559*Earth
Year: 0.694*Earth, 253.521 days, 84.273 local days
Local day (sunrise to sunrise): 73.1 hours
Sidereal day: 72.2 hours
Radius: 6350.6 km (slightly smaller than Venus)
Density: 5.042 g/cm³
Mass: 0.906*Earth (5.409E24 kg)
Gravity: 0.912*Earth (8.946 m/s²)
Magnitude at greatest elongation: -5.248 (somewhat brighter than Venus)
Tilt: 67.2°

Planet #3's moon: Rocky moon; Moon-like
Semi-major axis: 302312 km (somewhat closer than the Moon)
Local day (sunrise to sunrise): 519.773 hours
Sidereal day: 479.012 hours
Lunar month: 21.657 days, 7.11 local days
Radius: 1783.1 km (slightly larger than the moon)
Density: 3.445 g/cm³
Mass: 0.014*Earth (8.181E22 kg)
Gravity: 0.175*Earth (1.716 m/s²)
Magnitude at greatest elongation: -0.848 (Easily visible from CCCP!)
Tilt: 11.4°

Planet #4: Rocky planet; CCCP
Semi-major axis: 0.97 AU
Average insolation: 1.008*Earth
Year: 0.963*Earth, 351.584 days, 356.939 local days
Local day (sunrise to sunrise): 23.706 hours
Sidereal day: 23.64 hours
Equatorial Radius: 7639.3 km
Polar radius: 7616.4 km
Circumference: 47999.1 (close enough)
Surface Area: 7.318E8 km^2
Density: 5.524 g/cm³ (slightly higher than the Earth)
Mass: 1.727*Earth (1.032E25 kg)
Gravity: 1.202*Earth (11.79 m/s²) (A bit high, but should be tolerable, maximum for habitability by humans seems to be 1.5 Earth, could also just say that the species here have adapted, even the humans.)
Tilt: 22.4°
Atmospheric Pressure: 1.532 Earths (Flying will probably be easier here than on Earth by a little bit)
14% Oxygen (due to higher total pressure, this is very slightly more than the Earth)
85% Nitrogen
1% Argon
+trace other things

Moon 1: Rocky moon, smaller and closer in
Semi-major axis: 102304 km (way closer than the Moon)
Local day (sunrise to sunrise): 69.384 hours
Sidereal day: 68.819 hours
Lunar month: 2.891 days, 2.927 CCCP days
Solar year in lunar months: 121.947 months
Radius: 535.3 km
Density: 3.053 g/cm³
Mass: 0.000328*Earth (1.962E21 kg)
Gravity: 0.047*Earth (0.457 m/s²)
Magnitude at full moon: -13.3 (somewhat brighter than the full Moon)
Tilt: 2.7°
Angular size: 0.600° (1.2xMoon)
Tides: 1.58xMoon

Moon 2: Rocky moon, more like Earth's Moon
Semi-major axis: 295643 km (somewhat closer than the Moon)
Local day (sunrise to sunrise): 351.125 hours
Sidereal day: 337.139 hours
Lunar month: 14.63 days, 14.812 CCCP days
Solar year in lunar months: 24.098 months
Radius: 1636.2 km (slightly larger than the moon)
Density: 3.394 g/cm³
Mass: 0.010*Earth (6.227E22 kg)
Gravity: 0.158*Earth (1.552 m/s²)
Magnitude at full moon: -13.3 (somewhat brighter than the full Moon) ...It's the same?
Tilt: 3.5°
Angular size: 0.634° (1.27xMoon)
Tides: 2.08xMoon

Planet #5: Rocky planet; Mars-like planet
Semi-major axis: 1.63 AU
Average insolation: 0.357*Earth
Year: 2.097*Earth, 765.867 days, 625.198 local days
Local day (sunrise to sunrise): 29.5 hours
Sidereal day: 29.4 hours
Radius: 4253.5 km (larger than Mars)
Density: 4.563 g/cm³
Mass: 0.246*Earth (1.471E24 kg)
Gravity: 0.553*Earth (5.423 m/s²)
Magnitude at opposition: -2.3 (slightly dimmer than Mars)
Tilt: 16.3°

Planet #5's moon: Rocky moon; similar to CCCP's closer moon
Semi-major axis: 91312 km
Local day (sunrise to sunrise): 155.003 hours
Sidereal day: 153.708 hours
Lunar month: 6.458 days, 5.254 local days
Radius: 456.2 km (slightly larger than the moon)
Density: 3.134 g/cm³
Mass: 0.000209*Earth (1.246E21 kg)
Gravity: 0.041*Earth (.399 m/s²)
Magnitude at opposition: 3.3 (visible, but a bit dim)
Tilt: 2.4°

*Asteroid Belt*

Planet #6: Gas giant, Saturn-like
Semi-major axis: 5.95 AU
Year: 14.624 years
Sidereal day: 9.8 hours
Radius: 58463 km
Density: 0.695 g/cm³
Mass: 97.405*Earth (5.817E26 kg)
Gravity: 1.158*Earth (11.352 m/s²)
Magnitude at opposition: -1.3 (dimmer than Jupiter, but brighter than Saturn)
Tilt: 21.3°

Planet #7: Gas giant, Saturn-like
Semi-major axis: 10.53 AU
Year: 34.429 years
Sidereal day: -11.5 hours
Radius: 61452 km
Density: 1.133 g/cm³
Mass: 184.414*Earth (1.101E27 kg)
Gravity: 1.984*Earth (19.453 m/s²)
Magnitude at opposition: 1.2 (bit dimmer than Saturn)
Tilt: 163.3°

Planet #8: Gas dwarf
Semi-major axis: 15.32 AU
Year: 60.419 years
Sidereal day: 16.3 hours
Radius: 11432 km
Density: 2.654 g/cm³
Mass: 2.781*Earth (1.661E25 kg)
Gravity: 0.864*Earth (8.477 m/s²)
Magnitude at opposition: 6.9 (brighter than Neptune, dimmer than Uranus)
Tilt: 15.3°

Planet #9: Ice giant, Neptune-like
Semi-major axis: 21.43 AU
Year: 99.957 years
Sidereal day: 17.4 hours
Radius: 32542 km
Density: 1.636 g/cm³
Mass: 39.543*Earth (2.362E26 kg)
Gravity: 1.517*Earth (14.874 m/s²)
Magnitude at opposition: 6.2 (somewhat dimmer than Uranus)
Tilt: 11.3°

Planet #10: Gas giant, Saturn-like
Semi-major axis: 36.46 AU
Year: 221.823 years
Sidereal day: 10.4 hours
Radius: 54674 km
Density: 0.943 g/cm³
Mass: 108.096*Earth (6.456E26 kg)
Gravity: 1.469*Earth (14.405 m/s²)
Magnitude at opposition: 6.9 (brighter than Neptune, dimmer than Uranus)
Tilt: 42.5°

~Kuiper belt equivalent~

Any moons around Planet #6 will be around magnitude 6 at the brightest, and likely dimmer. The Ḵsīnesīr and Nightpeople might be able to see the dimmer planets due to their better night vision, or at the very least, Planet #9.

What exactly should we go with? Or possibly combine some ideas? (Visible moons around other planets in Finlay's system?)

[Hydroeccentricity]

The more I read about magnetic fields the more they start to look like unicorns. I think saying "This planet has a magnetosphere" is right up there with "This planet has exactly the right temperature for humans to live" in terms of hand-waving and deliberate world crafting. Take Mars, whose core rotation was stopped by an impact event, or Venus, whose core can't create a dynamo because convection between the core and the mantle isn't great enough. So I don't think "Magnetospheres will be less likely" is a meaningful criticism, since we'll be deus-ex-machina-ing that shit anyway.

[zompist]

If no one else wants a go, perhaps Lyhoko and finlay could work out a combined proposal? They both have 10 planets, with 2 moons for CCCP, so it seems doable.

I like Lyhoko's visible moon on #5, but I also like finlay's super-Jupiter.

[finlay]

I'm happy with that. I deliberately didn't mention any moons or atmospheres of the other planets.

[Torco]

I'd like to express preference for finlay's CCCP, assuming it has a normal atmosphere: Lyhoko's, with 50% more atmosphere and everything 20% heavier would be pretty different from earth in a few meaningful respects <for example, forests would be less common, as would trees in general, both for added flammability and on account of wind breaking them>. large buildings would become harder and harder to construct <since wind forces are larger and also buildings are heavier>, Interestingly,

this is all pretty awesome, I mean, I like not-quite-like-earth conworlds, that's a great feature for scifi to have and its fun to work out how it all works and so on, but I personally think we have enough funk with magical constructs walking around near dragons and divinating frogfolk.

[finlay]

I'd like to express preference for finlay's CCCP, assuming it has a normal atmosphere: Lyhoko's, with 50% more atmosphere and everything 20% heavier would be pretty different from earth in a few meaningful respects <for example, forests would be less common, as would trees in general, both for added flammability and on account of wind breaking them>. large buildings would become harder and harder to construct <since wind forces are larger and also buildings are heavier>, Interestingly,

this is all pretty awesome, I mean, I like not-quite-like-earth conworlds, that's a great feature for scifi to have and its fun to work out how it all works and so on, but I personally think we have enough funk with magical constructs walking around near dragons and divinating frogfolk.

The proportions of gases in the atmosphere are different, though – there's proportionally less oxygen which means that flammability would be the same as Earth.

[Torco]

Right, excellent point. There still remains the thing about wind impeding tall trees and buildings, but at least flammability looks like it would keep.
But with the same amount of oxygen, a denser atmosphere and heavier grav pull locomotion would be harder... I mean, harder to move, same amount of oxygen = short of breath <which would naturally lead to bigger lungs and hearts, much like it does at higher altitudes on earth>. And its not by any small margin, mind you: 20% heavier means a random human would have to put on a backpack with like a laptop, charger and a couple of notebooks <and for me, it basically means a mountain bike >

[Lyhoko Leaci]

Remember, all of the people here presumably evolved or were created here, so would be used to it. Also, a denser atmosphere won't impede movement noticeably, except at higher speeds, which will only really come into play after cars and planes and stuff are invented.

As for combining the solar systems:
I like that the moons on my CCCP have nearly integer length "months", which both nearly fit into an integer number of months in a year, but then Finlay's not neatly matched up set of moons could create multiple different calendar setups to deal with without everyone likely coming up with similar systems...

Maybe Finaly's 1, my 2 and 3, Finaly's CCCP (as planet 4), my 5, Finaly's 6 and 7, my 8, Finaly's 9, and my 10? (And probably Finaly's sun so the CCCP ends up in the right climate zone)
With some modification to make sure none of the planets end up in too close orbits, and to adjust mine to the different year length of another sun.

That way we end up with the visible moons around a couple other planets, a not quite as heavy CCCP, the giant Jupiter, and a dim runty gas dwarf.

[Hydroeccentricity]

Torco, I think you might be overestimating the force of wind. I don't think we are looking at the same wind speed with extra force. The winds would be slower.

The strength of the wind is caused by solar energy going in. That solar energy has to move X amount of matter at Y speed. If the air is more massive, and the amount of energy coming in is the same, then the wind speed cannot be the same, can it? The wind would have more mass, but a lower speed, sort of the opposite of what happens on Mars, which has very fast winds with very little mass in them. There might be an increase in the force of the wind, but it's not going to be a full 50% increase.

About moons. I think whatever we decide about moons, we should have at least one large enough to create tides. A tideless ocean would have very, very different plants and animals in it, and might be much less rich than our own oceans. I know it sounds boring to have a "moon-like" moon, but maybe we could do something fun with it, like make it a captured body with very low albedo so it's barely visible, or put it on a collision course with CCCP in 100,000 years, or cover it in ice-geysers.

biospheres. Since we have global distribution of sentients, and evidence of a previous advanced civilization, I propose that we assume all areas with similar climate could have access to similar plants and animals. In other words, tomatoes and wheat could appear in the same place if you want them to. Otherwise we'd have to work out the history of plants and animals in great detail before anyone can start making cultures.

[Matrix]

Otherwise we'd have to work out the history of plants and animals in great detail before anyone can start making cultures.

Well, not anyone. Golems FTW

[Salmoneus]

Some things about a denser atmosphere:

- yes, I'd think that winds would be more sluggish
- heat will be distributed more efficiently - the poles will be warmer, the equator will be colder, nights will be warmer, days will be colder
- because of the last, there won't be as violent weather systems (which tend to stem from steep temperature differentials). There will be fewer hurricanes, and less wind in general. This will probably multiply with the first observation
- flight will be easier. Larger creatures will be able to fly, and larger creatures will be able to fly well and rapidly. Humans are likely to invent human-powered flight (which is on the edge of possibility as it is), though not for long distances
- floating in the air will be easier. In the long term that's good news for balloons, but biologically it'll also probably mean more aerial seed dispersal, which may encourage taller trees and fewer fruits
- wind resistance will be higher. Things will be slower, both airborne and on the ground
- everything other than flying will be harder. Things will have to move around less, or sleep longer, or else eat a lot more food. Herbivores can't really do much on the eating more food front, so they'll tend to be slower, which will probably mean they'll either haver to be a lot more numerous to not go extinct (if there's enough of you it doesn't matter if you get eaten a lot), or else they'll become bigger (if you're big enough, it doesn't matter if things can catch up with you). In turn, predators will tend to be bigger, but there'll be fewer endurance predators like humans and wolves, and more things will try to have long periods of idleness punctuated by brief periods of activity (i.e. ambush predators) - bad news for dogs, good news for cats. It'll also be a lot more tempting to be a scavenger. Some of the biggest carnivores will probably be scavengers (particularly since they'll probably have to compete with megacondors).