Earth’s Unique Atmosphere - Solving the Supply Problem

          We take it for granted that when we breathe in (inhale), air is going to enter our lungs.    Go ahead, do it now. Breathe in. How nice to feel the air entering our lungs! The next time you are visiting the Moon or the planet Mercury go ahead and take off your helmet. Take a deep breath and . . . Quick! Put it back on! Did you notice that no air entered your lungs? In fact the opposite happened! When you opened your mouth to breath, the higher pressure air in your lungs was sucked out. Why?  Breathing is useless if there is no air out there for us to breathe in. That’s the case with both Mercury and the Moon.   On these bodies there is a vacuum, no air at all. 

How about our two closest neighbors, Venus and Mars?  Surely they offer better chances for survival! Venus, the beautiful morning and evening star, is surrounded by a wonderfully thick atmosphere teeming with air moleules, but dont even think about taking off your space helmet to enjoy a breath there. Let’s overlook the 800-900 F temperatures right now and focus on the atmosphere.    Your first breath might very well be your last! When you opened your mouth to breathe so much air would rush in that your lungs would be crushed due to this intense pressure, which is 90 times greater than Earth’s atmosphere. Watch the video of atmospheric pressure crushing a can to help you realize what would happen to an unprotected body on Venus.

Well, Mars has to be much better than Venus, right? Well, yes in that it doesn’t have too much air.   However, its thin atmosphere has a pressure 100 times less than that of Earth.  If we didn’t have a pressurized suit our bodies would inflate like a balloon.   "Within minutes the skin and organs would rupture, outgas, and produce a quick, painful death." says Chris Webster from Nasa’s Jet Propulsion Laboratory. (1) Not a pretty picture! There is something special about Earth’s atmosphere which has just the right amount of air molecules in it to support breathing, unlike Venus and Mars.

    Will any air do in keeping us alive? Air is air, right? Not by a long shot! There are around 30 common gases which are either elemental (like helium, hydrogen, nitrogen, oxygen, etc) or compounds (like carbon dioxide, methane, butane, etc).   Of these 30 only one is capable of sustaining life – that’s right, oxygen, and only Earth has an abundant supply. What is so special about oxygen? You will find out the answer to that question when you read the next article, “Why Breathing Keeps Us Alive”. Not only are the atmospheric pressures deadly on Venus and Mars, but the air they do possess is deadly also, consisting of roughly 95% carbon dioxide (CO2).  Experts have determined that concentrations of CO­2 over 5% would make it impossible to eliminate the CO2 that builds up in our bodies and we would die from CO2 poisoning. (2) To learn more about how our “exhale” keeps us alive read the 6th article in the series, “Solving the Trash Problem”.

Watch this video to see what an atmosphere of CO2 would mean for living organisms. You can try Activity 1 to do this yourself (see endnotes)

  When I consider Earth and its two closest neighbors, Venus and Mars, the story of Goldilocks and the Three Bears comes to mind.  Earth’s atmosphere is “just right” for keeping us alive!

The Precious 21%

          So, how much oxygen do you need on any given day? Take another breath and prepare yourself for some math! Of the 500 mL of air you just breathed in (the size of a small water bottle) 105 mL is oxygen (21%). That’s the stuff that keeps us alive!  But not all of that actually gets into our bloodstream. Of that 105 mL of oxygen, roughly 25 mL actually makes it into our bloodstream during each breath.  The rest we breathe out when we exhale. The weight of those precious oxygen molecules in each breath is around 0.0357 grams. (3) That’s around 28 times lighter than an 8 1/2 x 11 inch piece of paper.   Multiply that by 21,600 breaths per day, however, and you get almost 800 grams (1.7 pounds) of pure oxygen your body needs to stay alive,  and that’s not considering when your body demands more because you are playing soccer, or working in the yard, or swimming or playing tag.  That’s the same as the weight of a loaf of bread, which is impressive because this is air we’re talking about, and everyone knows that air doesn’t weight anything. Or does it? Yes, air molecules, though they are light, do have mass! You can try Activity 2 to prove this.

Will the Earth Run Out of Oxygen?

“That’s not that much”, you say.  “Just think about how big the atmosphere is!”. Yet, when you factor in earth’s population, a whopping 6.4 million TONS of oxygen are being removed from the air every day!  How heavy is 6.4 million tons?  It is the approximate weight of the Great Pyramid of Giza. (4) This is the daily requirement to keep the world population alive, not counting animals! Another way to look at it is to consider that almost 1 cubic mile of pure oxygen is being removed from the air every day. (5) Now, are you worried about the Earth running out of oxygen? 

So, why is the atmosphere of Earth not depleted of oxygen?  The short answer is that God gave us plants with green leaves.  During the process of photosynthesis these seemingly simple leaves manufacture glucose by combining carbon dioxide removed from the air with sunlight and water.  That’s right – plants take air and water and turn it into food to feed the whole world!  A by-product of this reaction is oxygen.  One tree can produce roughly 260 pounds of oxygen per year, so it would take 2-3 trees to support 1 person with oxygen. (6)  Scientists believe that microscopic plants that float in the ocean (phytoplankton and seaweed) are responsible for around 1/2 of the oxygen created by plants. (Morsink, 2017)

We didn’t know anything at all about the gas that keeps us alive until 1774 when Joseph Priestly conducted experiments to prove that oxygen existed. A mouse placed in an airtight jar eventually dies, he wrote, and a lit candle burns out in the jar. However, when a sprig from a mint plant was placed in with the mouse it remained alive. Can you figure out why?

No matter where you go on Earth, the air contains 21% oxygen.  The higher you travel in elevation above the Earth’s surface the air becomes increasingly thinner, however the percentage of oxygen stays constant at 21% (roughly 1 out of every 5 molecules is oxygen)  However, people working in areas with potential oxygen deficiency have to follow strict rules. Healthy individuals can survive but are unable to perform strenuous work and their coordination may be affected in oxygen environments of 15 percent to 19 percent. Oxygen levels of only 10 percent to 12 percent cause an increased breathing rate, lips turning blue, and confusion. Fainting and unconsciousness begin to occur at 8 percent to 10 percent oxygen. Death occurs in 8 minutes at 6 percent to 8 percent oxygen. The Occupational Safety and Health Administration, OSHA, determined the optimal range of oxygen in the air for humans runs between 19.5 and 22 percent. (6)

If oxygen is so necessary for us, why didn’t God give us an atmosphere with at least 50% oxygen, instead of only 21%?  Have you ever heard of the expression, “too much of a good thing?” Check out this video to see why. Imagine what it would be like to try to fight a forest fire with this much oxygen! Now do you see why God wisely created our atmosphere with 78% nitrogen? Nitrogen is a perfect “filler” gas. It is not too reactive, and is also very important for plant health.

A visual that helps me appreciate our wonderful atmosphere is looking at the Earth from space. That thin blue ribbon you see is our atmosphere. It is like a “life-bubble” surrounding Earth, separating us from the blackness and emptiness of space.  This thin blue ribbon of air serves not only as a source of oxygen, but also as a blanket to trap heat from the sun.  It is that thin blue ribbon of air which is keeping you alive right now.

  Take another deep breath and think about the steady flow of air into your lungs. Nitrogen, the non-reactive filler gas, and oxygen, the perfect life-sustainer are flowing in. You can fill your lungs without fear. Not only is there something rather than nothing (like Mercury or the Moon), but it is the perfect something (unlike Venus and Mars).

We take our atmosphere for granted.  We shouldn’t.   God designed it with wisdom and skill to sustain life on planet Earth.

Questions to Consider:

  How did it happen that the planet we call home has a continual supply of 21% oxygen which is perfectly suited for its critical role in keeping us alive? How is it that it exists in exactly the right concentration in our atmosphere? How did the processes which maintain this perfect level come to be? Is this just blind chance, or is this another reason to give thanks to our Creator?   

End Notes:

(1) https://www.businessinsider.com.au/how-to-survive-on-mars-2015-10

(2) https://inspectapedia.com/hazmat/Carbon_Dioxide_Hazards.php

(3) Calculations to convert 25 mL of oxygen into grams per breath:

In one breath we take in 500 mL of air (at rest).  Oxygen is 21% of air, 500 x .21 = 105 mL of O2.  Only 5 % is actually taken into alveoli, so 500 mL x.05  = 25 mL of O2/ 22.4 mol/L = 0.00111607 moles x 32 g/mole = 0.0357 g/breath of O2

(4) http://flash.esva.net/bigthings.htm  “Visual Perspectives of Millions of Tons”

(5) (4)  Calculating the volume of 6.4 million tons of oxygen –

Find the volume by: 6.4 million tons x 2,000 lbs/1 ton x 454g/1 lb x 1 mole/32.0g x 22.4L/1 mole = 4.068 E12 L /4.1682 E12 L/mile = .98 cubic miles

(6) Oxygen Defiency: The Silent Killer; EHS Today; retrieved at: https://www.ehstoday.com/fire_emergencyresponse/ehs_imp_77598

Activity 1: Fire Extinguisher (parent supervision)

Materials: candle taped to a ruler; tall glass; vinegar; baking soda; lighter/matches (see video above for more details

Add around 3 oz of vinegar to glass along with 1 tsp of baking soda. Allow reaction to stop but don’t disturb glass. Light candle and slowly lower into glass. If you want to try to copy the video, pour the CO2 into a second glass. Questions: What percent of the air in the glass was CO2 before the reaction? After? Why did the candle go out? If you can pour CO2, what does that tell you about its density?

Activity 2: The Weight of Air

1) If you have a scale which is sensitive to 0.01 grams, fold a piece of tape and stick it to an empty balloon (you will need the tape to secure the balloon to the scale). Find the mass of the empty balloon and tape. Now blow up and tie the balloon and reweigh it using the tape to secure it to the scale (otherwise it will most likely just roll off the scale). Does the balloon full of air have more mass?

2) Place a yardstick on a table or counter so around 10 inches is hanging off. Strike the end so that the yardstick flips up. Repeat, but this time with an opened newspaper sheet spread out over the part of the yardstick on the table. Why is it harder to move the yardstick now?