this post was submitted on 08 Aug 2024
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Science Memes

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submitted 3 months ago by [email protected] to c/[email protected]
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[–] [email protected] 105 points 3 months ago (3 children)

A time traveler's survival guide. The vertical green bars are the only times in Earth's history with enough oxygen to breathe (hypoxia) and low enough to avoid oxygen toxicity (hyperoxia):

https://fedia.io/media/cache/resolve/entry_thumb/fa/a9/faa97017c09ebf7d9543fece447951844e5cfbdaa9f491c95763102e987ffc59.jpg

[–] [email protected] 65 points 3 months ago* (last edited 3 months ago) (4 children)

That blue bar is extremely pessimistic. Humans can survive pretty well with 15% oxygen, and do so in several places in the Andes mountains, China and India. I wouldn't recommend doing it without lengthy acclimatizing, especially not considering my last paragraph, but it's completely survivable by itself.

Humans also don't really have a problem with 25% oxygen, although that will definitely bring down the life expectancy.

On the other hand, note how those pointers talk about giant insects, megafauna and other scary things. Those are a much bigger problem than the air you're breathing.

[–] [email protected] 31 points 3 months ago

To add to this: At 3'500 meters above sea level, the pressure is down to 2/3 atmospheres. So instead of 21 kPa of oxygen partial pressure, it is only 14 kPa. So like breathing 14 % oxygen at sea level. People live at that height.

[–] [email protected] 10 points 3 months ago (1 children)

Dumb question, but in a very oxygen rich environment, can you just breathe through a paper bag or something? Mostly just breathe your own exhaled CO2 with a bit of O2 leaking in?

[–] [email protected] 7 points 3 months ago

For short periods maybe. You only use a few percent of the O2 you breathe in each time. But you also increase the CO2 each time. It'd depend on the amount of leak because you need enough O2 coming in but enough CO2 going out.

[–] [email protected] 5 points 3 months ago (1 children)

So like how big mosquitos are we talking about?

About crabhead ticks?

[–] [email protected] 15 points 3 months ago* (last edited 3 months ago) (1 children)

Mosquitos are kind of modern, being only 45 million years old, way after the megafauna bugs died.

but think 40cm long, meter wide "dragonflies", half-meter long "scorpions", 60cm "spiders" with knifelike front legs and 250cm long millipedes (technically not an insect, but eh)

But if you're looking for giant mosquitoes, you're in luck: the very much not-extinct elephant mosquito can grow over 1.5cm long.

[–] [email protected] 7 points 3 months ago (1 children)

Dragonflys don't scare me, but if we got same proportional upgrades to anything that regularly bites, I would move underground.

[–] [email protected] 9 points 3 months ago (1 children)

Dragonflys don't scare me

Dragonflies are possibly the most efficient predator in existence, catching up to 95% of the prey they attempt to catch. And their larvae are utterly terrifying.

I would move underground.

With the 2.5 meter long millipedes..?

[–] [email protected] 5 points 3 months ago

Yes, into a vault.

[–] [email protected] 2 points 3 months ago (1 children)

bring down the life expectancy

why?

[–] [email protected] 2 points 3 months ago (1 children)

Oxygen is really rough on the DNA due to making the cells "rust" which hampers cell division and/or increases risks of mutations or cancers

[–] [email protected] 14 points 3 months ago

I'm super skeptical of this.

You don't get oxygen toxicity, even breathing pure oxygen, unless you're under significantly more pressure than atmospheric pressure...

So either this graphic is wrong/misleading, or the atmosphere was more than double current pressure for most of earth's history... Which I'm pretty skeptical of.

[–] [email protected] 7 points 3 months ago (1 children)

Is there a higher resolution version?

[–] [email protected] 5 points 3 months ago (1 children)

Is there a version with more JPEG?

[–] [email protected] 1 points 2 months ago

Is there a version which actually loads?