What If #001: What if the Earth’s oxygen level doubled?

Presenting a new series ‘What If?’ where you, the students, get to ask us your questions. It can be anything in the whole wide world but there’s just one condition: it should start with ‘What if?’ We’ll pick the most intriguing questions and feature it along with an illustrated explanation on The Learning Tree Blog. 

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The first question in the What If? series comes to us from 11-year-old Manav Variar of Bengaluru. He asks:

What if the Earth’s oxygen level doubled?

The Earth’s atmosphere is made up of about 21% oxygen. Most of the air we breathe is actually Nitrogen – around 78%.

The thing about oxygen is that not only is it an essential gas for life as we know it to survive, but it is also the gas that facilitates all forms of burning and combustion. So would your birthday candle glow twice as brightly if the Earth’s oxygen was increased to 42%? Maybe. But there are bigger implications here!

Our human lungs have adapted perfectly to our current atmospheric setting. Just because oxygen is essential for respiration, it doesn’t mean too much of it is an improvement. Our bodies and indeed all life forms on Earth are finely tuned to the 21% Oxygen supply in the air. But it wasn’t always like this.

Scientists have discovered that around 300 million years ago, during prehistoric times oxygen levels were as high as 30%. During that time, insects were much, much larger! This means spiders were the size of eagles. And lizards were the size of dinosaurs! Scary, right? If the Earth’s oxygen levels would double, at 42%, these creepy-crawlies would be even bigger than before.

But don’t worry! Double the oxygen ensures that you can out-run all of these scary spiders! Due to the availability of more oxygen to the lungs, with every breath you take, your stamina would increase tremendously. Oxygen-rich blood would pump through your veins, fueling your muscles with energy, while increased blood circulation will give you greater agility and focus!

But don’t get too happy yet! Wait till the excess oxygen starts to weigh you down! With double the oxygen, the air density would also vastly increase. This means we will all experience increased air pressure and our ears will pop way more often! But that’s not the only problem.

While running away from all the giant creepy crawlies, we’ll have to watch out for something called ‘oxygen toxicity’. Too much oxygen in your bloodstream will cause rampant harmful oxidation in your cells causing them to die. So with double the oxygen levels, deaths due to fatigue and exhaustion will be more common than deaths from diseases!

A higher oxygen concentration would lead to a thicker atmosphere, which would scatter more sunlight. So the sky would look beautifully bluer but you may feel colder as the overall temperature drops.  

Going back to our birthday candle, one of the most significant changes will be the increase in the rate of fires and combustion. Forest fires will spread much faster and flames will rise much higher than usual. Meanwhile, plants will get lesser carbon dioxide from the atmosphere so photosynthesis will slow down. Most of the earth’s green vegetation might be replaced with moss and fungi.

We should actually consider ourselves lucky to find ourselves at a time with such a finely balanced atmosphere. Too little oxygen and harmful radiation from space would have burnt everything crisp. Too much oxygen and all the dreadful possibilities described above could become a reality. We are, in a way, extremely lucky to have just the right amount of oxygen and we should do everything we can to keep it that way!

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