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Biology! Habitats for Humans



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Wed Aug 14, 2013 1:33 pm
Tenyo says...



Are there any biology buffs who can help me out? I'm trying to make a criteria for what requirements there are for a land to be habitable by humans.

I'm thinking of issues like; oxygen levels, radiation levels, temperature, water toxin levels... e.c.t And how much of an impact they would have.
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Wed Aug 14, 2013 6:45 pm
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Rosendorn says...



One thing to keep in mind is that humans evolved from Earth, and while we're really good at adapting to all parts of the Earth, we're kinda bad at living anywhere else.

Oxygen levels can be varied from really thick air to thin (ocean to mountain), but people will feel sick depending on where they came from originally. It takes some adjustment.

Gravity is also a really important thing. Unlike what comics tell you, different levels of gravity can actually lower (or increase) your muscle/bone density because you're not working them as hard (or working them harder than you're used to). The human body can only take about 20% variation in the gravity of a planet before that becomes a risk. Too much gravity and the planet will be inhospitable. Gravity is also what determines things like how tall trees get (there is a point where a tree's ability to pull water up from its roots will fail because gravity's got too much of a pull) and other such things, such as how much of an atmosphere the planet holds.

Atmosphere is important because that's what protects the earth from radiation and keeps heat in. Atmosphere not only regulates temperature but also temperature extremes. Mercury, with no atmosphere, goes from 400 C to -200 C. Now it's also really close to the sun, but its lack of atmosphere doesn't help.

Another thing to keep in mind is that the atmosphere does have weight. I don't know the number off the top of my head, but it is a few pounds. Different thicknesses of atmosphere would be heavier. It's not really noticeable within earth, but muck around with the atmosphere too much and it'll make a difference.

Also, what really protects Earth from radiation is its rotating iron core and magnetic field. So a hospitable planet must have a core like that, with the magnetic polls (aka, a compass has to work)

There is also what minerals humans need and their concentration in the planet. Each planet has various amounts of minerals which produces radically different environments. This includes the amount of trace minerals in the air.

To even find a planet that works, it must be in the Goldilocks Zone. This is a term astronomers have used that describe planets that are just far enough away from the sun that they don't get bombarded with radiation and heat, but aren't so far away that the planet is too cold.

And an interesting little factoid for you: Most stars revolve in pairs. It's actually "weird", scientifically, that our solar system only has one sun.
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Thu Aug 15, 2013 12:21 pm
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niteowl says...



Rosey covered a lot of the basics, but I have a couple more points to add.

1) A tectonic system. This also relates to size of planet and the rotating iron core Rosey mentioned. Basically, when a planet forms it has so much geothermal energy, which it slowly loses over time. Tectonic activity is crucial for recycling nutrients--if plates stopped moving, the oceans would fill up with sediment and they'd be gone in about 10 million years. If a planet is too small, like Mars, this stops pretty fast (this is part of the reason why Mars is dead now). Also, life most likely started near hydrothermal vents.

2) Microbes and other important life forms. I have trouble believing humans could go onto a lifeless planet and survive for very long. Microbial life had the planet for over 2 billion years, and without the oxygen produced by cyanobacteria (forget trees, little green dudes in the ocean produce half of it), multicellular life has no chance.

I'd have more, but I rarely think about what humans need since I work on anaerobic stuff. :P
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Mon Aug 19, 2013 11:01 am
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StellaThomas says...



Yeah, microbes would be important- remember that 90% of the cells in your body right now actually belong to the bacteria living on/inside you. We *need* these to stop other more dangerous infections but also for digestion.

I'm pretty sure that we need roughly 20% oxygen in our air, anything below 96% oxygen saturation in our blood is dangerous.
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Mon Aug 19, 2013 2:21 pm
Tenyo says...



Ninety percent!

Seriously?

I feel so... used...
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Wed Aug 28, 2013 8:32 pm
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OrionX says...



Last month I came across a National Geographic Documentary called: Evacuate Earth, on youtube. It speculates how humanity could escape from Earth's destruction and travel through space for 80-ish years to reach a new planet. The spaceship has to sustain life, so it's kinda like a human-made planet. Perhaps it can offer you insights in what humans need in order to survive.

Link: http://www.youtube.com/watch?v=95n9BclgBUM
  








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