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My planet has an atmospheric density 12x that of earth with 0.8 Earth Gravity. Someone pointed out a while back that this would increase the wind strength proportionally. Now this is a problem as a light breeze on my planet would be comparable to hurricanes on Earth.

Firstly, how much can expected wind speeds be organically reduced by?

The thick atmosphere would be efficient at regulating heat so I could have the planet orbit further away from the star to reduce temperature, other than that I can't think of anything else that doesn't compromise the air pressure.

Secondly, how well could Earth-like species adapt to the wind strength?

The creatures are very Earth-like in which amphibians, reptiles, mammals, birds and dinosaurs all have similar counterparts, although they are hexapodal in origin. 'Mammals' and 'Birds' lost the 3rd limb set as have many groups of 'dinosaurs'. Gigantism is also very prevalent. I know I'm kind of answering my own question but plants would be stronger, small animals may burrow whilst forests could be very dense to shelter for larger animals and the true megafauna wouldn't be too effected.

Would the environment prove to extreme for earth-like animals to evolve?

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    $\begingroup$ Seems to favor streamlined ground-dwellers and burrowers. Turtles and tortoises, in particular, may flourish as the wind keeps them firmly on the ground. Long-distance soaring birds may do well, if they can catch food. Tree-climbers would seem to have a rough go...except flying squirrels. $\endgroup$ – user535733 Mar 25 '17 at 18:32
  • $\begingroup$ how can you keep more atmosphere while having less gravity? $\endgroup$ – L.Dutch - Reinstate Monica Mar 25 '17 at 19:53
  • $\begingroup$ @L.Dutch Titan and Venus are a couple examples in our solar system. Earth's atmosphere is believed to have been much thicker 150 million years ago despite having the same gravity. High volcanic activity for example can make up for the loss of gas. $\endgroup$ – Zac Walton Mar 25 '17 at 20:31
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    $\begingroup$ Turtles are a good point. That also helps most reptiles. If I could reduce the likelyhood of storms glyptodon-style mammals could work well. I'm not sure how well more conventional mammals would fare in constant gale-force winds though. $\endgroup$ – Zac Walton Mar 25 '17 at 20:41
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Earth is a very, very windy place as well; ask any pilot. It's just not that way on the surface.

I don't agree it would increase wind force proportionally. Ultimately it's about energy. Wind is simply a manifestation of the energy hitting the planet from the sun(s). 12x the density takes 12x the energy to move, and so it'll move slower and impact with the same original force.

Ground effect

For instance ground effect is why windmill towers are taller than they strictly need to be to keep blades from hitting the ground; to get up in the good fast air. I would think denser air is going to be more impacted by ground effect. Proximity to the ground will slow the wind. Or, the wind up high will be worse - might matter to the trees.

Trees

I seem to recall seeing another recent post on here that discusses how trees and gravity relate. Your weaker gravity means trees will be able to more easily lift the water they need to thrive.

However the wind will present a real challenge for them and require they build themselves beefy. Keep in mind the limiting factor isn't daily wind, it's peak wind - as in the peak wind in a tree's productive lifetime.

As a practical manner, it's likely the planet's fauna would evolve** within the forests, using them for protection from the elements. As such, they may not need developments to help them with the wind. You would have to ask whether such developments would give them advantage. Is there stuff beyond the islands of forests which would give reason to leave?

The redwood forests depend very strongly on each other to resist the wind: alone they cannot stand, as a forest they help each other break the wind. That's why it's a big deal when a forest company clearcuts to a property line; they stress and endanger the trees on the far edge of the line. For your society that means there may need to live amongst the forest as the open areas may be inhospitable. The stewardship of the forest would be a survival priority, the forest would effectively be community property, which would mean property ownership would work differently.

It would certainly change the nature of war: does the enemy routinely destroy your forest to defeat you, or is that so uncomprehensively destructive as to be considered a war crime akin to nuclear war? Would the latter be the domain of the civilized Great Powers, whilst ruined forests are the mark of the civil-war-ravaged third world?

Structures

Perhaps cities would have complexes of high walls which do the same thing as the trees, breaking the wind so wind speeds are workable on the surface. Perhaps this is done with usable buildings as much as practicable, resulting in a unique, interlocked style of city-building.

** Assuming your planet does evolve. Some are created by powerful beings, especially in fiction.

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There are places on earth that are often very still, with little or no wind. This is not in sheltered ravines or the like, but out on the open ocean. It was a big problem in the sailing ship days.

http://oceanservice.noaa.gov/facts/horse-latitudes.html http://oceanservice.noaa.gov/facts/doldrums.html

From these sites, it looks like high pressure air causes these regions. The doldrums is caused by equatorial heating with the air rising up. Also, the Coriolis effect caused by rotation of the earth does not apply at the equator, but as one moves farther away this effect pushed air towards the poles. https://en.wikipedia.org/wiki/Coriolis_force#Meteorology

I dot not understand why the horse latitudes occur.

Maybe on your world there are latitudes like these where wind is usual not problematic and this is where wind-sensitive ecosystems are concentrated.

Another thing which would diminish wind is to not have your planet rotate: no Coriolis effect. That would mean a day would be half a year.

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Atmospheric density defines the mean inertia, more energy is required to create a wind effect an said wind effect has more energy..but equally at every moment requires more energy to maintain itself against the inertia of standing bodies of air.

Wind is largely the result of different localized average air pressures, or in other words.. the average density alone neither increases nor decreases wind speed nor wind effect.

Atmospheric density is not any different to working with any other density.

Imagine you're in a swimming pool and, with your arms submerged do a "shinku hadoken" maneuver.. water is propelled forward..but it doesn't maintain it's force indefinitely because of the liquid's resistance & the dispersal of energy.

Talking about adaptation, I can't see any land dwelling organism evolved in terran conditions operating under such conditions.

Lungs would need to use [more than] 12 times as much force to expel air from a filled lung in the cycling process. Lungs would be filled, in turn, with air being motivated by that (considerable) difference in force created by the 12* air pressure, which would quickly damage human lungs, for instance.

Organisms would require significant increases in malleability/density or some other mechanism or structural property that diminishes the destructive effects of external pressure. Diving whales are good examples of approaches to this, the replacement of bone with cartilige, using fluids at high density to balance pressure loads etc

Insect approaches to 'breathing'(more like fish respiration than mammalian) would become the norm, I'd imagine, though we could imagine other approaches made viable, large & cavernous lungs probably never would be unless fitted with significantly superior valves to land-base terran life.

Eyes just wouldn't work, or at least.. those formed under terran conditions would degrade quickly, pressure deformations could be adapted to of course, potentially, tho a species transplanted would likely just go permanently blind as it had no use for it's eyes, babies would lose the use of them before they learned to talk.

If we think about heat-exchangers in terran organisms we have more issues, I don't think humans would be able to sweat, for instance and would heat up and die, adaptations would include ..being cold-blooded and restricting the amount of heat generated under normal operating conditions. more efficient heat-exchange mechanisms, or at least those that can operate efficiently at high pressures.

For creatures evolving under such conditions, the emergence of intelligence is massively [even more] unlikely.

I'd go with: The dominant lifeform would be dinosaurs, amphibious and retain piscine eyes.

In fact, wasn't the atmospheric density of earth supposed to be much higher than the modern era due to higher mean temperatures and thus more water in the air? So, are we describing ancient earth? :)

//reply to comment.

Well, I think that's true, because actually you never need to empty the lungs, your 1/12th 'normal breathing effort' is potentially enough to exchange the same number of actual molecules. That is to say..not having to empty your lungs is a factor I was managing to totally overlook.

But we have other problems. Firstly that if we assume the same effort to each breath, it seems reasonable to assume we're exchanging just over 1% of the lung capacity in any given breath.

Whilst we might be getting the effective oxygen/moisture/general goodness content exchange of a normal breath, the proportion of 'stale' air in the lungs will be considerably higher. Then we get to diffusion in the lung membranes and etc, wherein the pressure difference between the interior of the lung (that is to say it's capacity) and the exterior (that is to say the body proper/exchange mechanisms between the lungs and rest of the body is significantly increased.

Whilst I'd suggest that this might increase the rate of uptake, I'd assume this to be 'across the board' and not just goodness..an result in poisoning, if nothing else.

Hearing is another thing of course, naturally sound waves act differently in different densities of matter, they' still work, but what we heard would be different.

I didn't finish high school, so take all that with several pinches of salt.

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  • $\begingroup$ Ancient Earth is very much the inspiration. Think Mesozoic Earth on steroids. What you said about eyes is new so I'll have to think about that one, however air pressure in the lungs is something I've seen discussed quite a few times on here and the conscensus seems to be that the increased pressure in the lungs would be counter-balanced by external pressure? $\endgroup$ – Zac Walton Mar 27 '17 at 13:36
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    $\begingroup$ hearing is another thing of course $\endgroup$ – mensenisevirem Mar 27 '17 at 16:48

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