Following up the ideas given in this question, we introduce a new gas to the mix of air.

Meta: Assume an Earth-like planet. The proposed change is a pre-development change (meaning it's there since the forming this planet).

As most known gases will do their best to anesthetize air-breathing beings and because this is about creating new worlds; we will introduce a new gas with no nasty side effects, basically Nitrogen 2.0 - and we'll call it inventigas.

Inventigas has a weight of approx. 20 kg/m^3 at sea level and is inert at normal temperatures (basically a heavier version of nitrogen).

Now that we have this new gas, we replace as much of the air's nitrogen with it as we can (say about 90% of it).

Regarding the development of life: What effects would the proposed change have on flora/fauna in comparison to Earth?

  • $\begingroup$ Would this be a sudden mid-development injection, or pre-development natural process? $\endgroup$
    – Frostfyre
    Jul 6, 2015 at 17:06
  • $\begingroup$ @Frostfyre that would be a natural process (wil update) $\endgroup$
    – dot_Sp0T
    Jul 6, 2015 at 17:47
  • $\begingroup$ is this "inventigas" a radioactive isotopes of Nitrogen? as bowlturner pointed out the soil bacteria is responsible for fixing Nitrogen to make protein for edible plants, all radioactive isotopes are basically useless except for nitrogen-15 used to trace/detect the path of nitrogen in a system. If soil bacteria can adapt to use these isotopes, note that nitrogen can make nucleic acids for storing genetic information the rest I'll leave as homework for the readers. $\endgroup$
    – user6760
    Jul 7, 2015 at 2:18
  • $\begingroup$ @user6760 as mentioned in the question itself already; the gas is basically a heavier nitrogen. So assume it to replace/complement Earth-nitrogen in all the ways that Earth-nitrogen does things $\endgroup$
    – dot_Sp0T
    Jul 7, 2015 at 6:55
  • $\begingroup$ a couple of protons or neutrons more or missing isn't going to make any different at all however a single electron more or missing changes the property of Nitrogen greatly. A heavy nitrogen (isotope) shares similar property with normal nitrogen but a nitrogen ion is different the world we know might not exist as it is today! $\endgroup$
    – user6760
    Jul 7, 2015 at 7:14

2 Answers 2


Plants need nitrogen to live and grow, replacing nitrogen with an inert alternative regardless of its other effects, would make it much more difficult for healthy plants to flourish. Bacteria fix nitrogen into the soil where it is used by plants, and farmers use fertilizer to add nitrogen in order to keep the nutrients in the soil since the process of nitrogen fixing is slower to replenish than yearly harvesting will remove it.

Next issue is the weight of the air, That is an extremely heavy gas. Xenon is less than $6\ \mathrm{kg/m^3}$. It would be heavy enough that it would tend to settle and might displace most other gases needed for life. Oxygen, CO2, water vapor.

Last if it was actually a gas, weather would be absolutely horrendous when it got going, light winds would be almost impossible to walk in. Good strong winds would likely knock down buildings easily. Hurricanes would scour the lands clean.

  • $\begingroup$ Why would buildings be knocked down so easily? I don't understand how increasing air density would create worse storms. $\endgroup$ Jul 8, 2015 at 15:04
  • $\begingroup$ What's the difference between throwing a small pebble at a window at 15mph and a rock the size of your hand? There is a LOT more mass slamming into everything. The new gas is almost 20 times more massive than our current air. $\endgroup$
    – bowlturner
    Jul 8, 2015 at 15:14
  • $\begingroup$ Yes, but it won't be able to pick up as much speed. $\endgroup$ Jul 8, 2015 at 19:27
  • $\begingroup$ @theonlygusti I consider that a large assumption. It might not happen as often, but it will still happen. It might also take longer for things to settle down once they get going. $\endgroup$
    – bowlturner
    Jul 8, 2015 at 19:31
  • $\begingroup$ Wind is created by convection currents in the atmosphere, movement of hot, low-density air upwards as cooler, higher-density air rushes in to replace it. If, however, the bottom layer of atmosphere (this gas) is 20x more dense than other air, the air above it, it will never become hot enough (without cooking populations alive) to rise above any other air. Thus, the surface of the planet will have stagnated weather patterns. You will still get winds above this layer. However, I agree with the rest of your answer, so don't think I'm trying to attack you ;) $\endgroup$ Jul 8, 2015 at 20:26

I imagine that the weight of the air bearing down on living things, both plants and animals would tend to make them stocky, rather than tall. So there will probably be fewer giraffe-like animals and more hippo-like animals. Humanoids would also tend to be short and stocky -- maybe like dwarves in the Tolkien-esque sense.

For plants in particular, the weight of the air would add pressure that would make it relatively difficult to draw water up from the ground. As an evolutionary strategy, plants would either keep low or develop new strategies for drawing up water, such as harder outer covers to maintain a favorable internal pressure.

Animals would also adopt similar strategies. they would also likely have bigger lungs and rib-cages (or gills).

  • 1
    $\begingroup$ I dont believe, pressure works from any direction, not from top to bottom. $\endgroup$
    – Jorge Aldo
    Jul 7, 2015 at 6:12

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