# Altered Earth Physics

I was researching whether Dragons in Game of Thrones are realistic or not and I found a answer in Quora very interesting about them. In it, the guy said that for a world to be habitable for such large flying animals it would be necessary to increase air pressure by 50% and decrease gravity by 10%. I'm raising dragons for my world and they will be as big as the ones in the series, but I don't know if under conditions like that other life forms (including humans) would live well like this. So, using the Earth as a reference, what would life on Earth be like if gravity decreased by 10% and air pressure increased by 50%?

I want to know if the Earth would still be habitable for humans and other living beings without complications and still allow the existence of giant flying animals(Like those Dragons from Game of Thrones, Balerion would weigh tons in real life and wouldn't be able to fly, Drogon too).

• the thing is - isn't gravity the thing that keeps air pressure up? (also: those numbers seem pretty livable, even for humans that evolved on plain old, boring "regular earth") Dec 11, 2021 at 18:13
• @FranzGleichmann, not necessarily: Venus has a much higher surface pressure with a gravity 90% of Earth
– L.Dutch
Dec 11, 2021 at 18:25
• quora.com/How-much-external-pressure-can-a-human-body-withstand Dec 12, 2021 at 11:51
• well,.. pressure under 2 meter of water is live-able isnt-it?, the gravity thing would impact construction technology, we could build taller buildings, but yet again we as humans we cound get a tat taller as a result.
– Cris
Dec 20, 2021 at 11:56
• When you are submerged in water you have a more relaxing time , i have at least .. Isnt swiming recomended for kids in general for phisical related health problems?.. As a side efect more pressure equates as a need to more muscle and bone mass. Why?, well becouse you need it to handle the same body structure in the high-er pressure
– Cris
Dec 20, 2021 at 12:07

## Pressure

You can start looking at the past, there was a time when oxygen levels on Earth were higher (not sure about overall pressure though).

Plants using photosynthesis would probably have a faster metabolism, because photosynthesis involves gaseous exchanges (of carbon dioxyde & dioxygen), and gaseous exchanges are easier when the pressure builds up.

Regarding the breathing of a pressured gas by humans, you can look at scuba diving (a field dealing with higher-than-atmospheric pressure). Divers are mostly worried by oxygen toxicity and nitrogen narcosis, both occur while breathing the said gas at a high pressure. Nitrogen narcosis can happen below 30 m (so 4 atm) and oxygen toxicity below around 50 m (so 6 atm).

## Gravity

I'm not sure than a difference of only 10 % would be such a big deal (that would give g = 8,9 m²/s). However, if it were to change anything, plants and animals would be able to be higher without any change to their hearts' power or their ability to drive sap upwards. Nonetheless, there might still be other factors (say evolutionnary pressure ?) that could make it a bad choice for a species...

Birds and flying insects could probably be larger and fly higher, for the same reasons as dragons may be able to exist !