I watched a debate recently between Mark Sargent and a lawyer Viva Freito discuss the Flat Earth conspiracy. In that video, Mark Sargent started by asking, “If the Earth is a globe, surrounded by the vacuum of space, why doesn’t the vacuuum of space suck all the atmosphere away?” The video is here. (If you watch it, watch how deftly Mark shifts the focus of the debate every time he is cornered by raising an unrelated objection and interrupting his debater. The minute he starts to get an answer he doesn’t like, he interrupts.)

Viva mentions that he thinks the atmosphere doesn’t get sucked away by the vacuum of space because the vacuum of space doesn’t work like a vacuum on Earth. On another video, I saw someone respond to this objection saying the atmosphere doesn’t get sucked away because “That’s not how vacuums work.” Answers like these aren’t satisfying because they ultimately appeal to authority. It’s a very simple question, with a very simple answer, so I wanted to try my hand at answering it.

What Is a Vacuum

Mark starts by asking, if space is a vacuum, why doesn’t it suck the atmosphere away. He also cleverly starts with the false premise: “You need a container to make a vacuum,” and then concludes that space must have a container. Leaving alone that Mark doesn’t think space is even real, let’s start with describing what a vacuum is.

A vacuum is nothing. Really, that’s it. A vacuum is really just an absence of particles. In order to create a vacuum, you need to remove all of the matter from a particular point in the Universe. If you can do that, you have a vacuum.

Here on Earth, when we try to make a vacuum, we can feel the vacuum “sucking” the air around it inside. Why? If a vacuum is literally nothing, then why does a vacuum suck?

Why does a Vacuum Suck?

A vacuum doesn’t suck. Let me explain.

A vacuum, in and of itself has no power. There is nothing inside of a vacuum, so there is nothing there to generate a force on the objects around it. If that is so, then why is a vacuum so powerful? The answer to that is something Mark won’t like at all – Gravitation. But how?

Let’s start with what happens in a vacuum. Mark is almost right that in order to create a vacuum on Earth, you need a container. But note that I said “on Earth.” If you are on Earth, and you try to build a vacuum, you have to build a container, and then remove all of the matter inside that container. If you poke a hole in the container, the air around will get “sucked” into the vacuum. So, vacuums suck. Right? No, not really.

Why was it important for me to say that in order to build a vacuum on Earth, you need to start by building a container? Well, picture a cardboard box, one meter tall, 1 meter wide, and 1 meter long. (Roughly three feet by three feet by three feet.) That box is 1 cubic meter in volume. How much does this box weigh? Well, we don’t know because I haven’t told you what is in the box.

If the box is full of packing peanuts, it will weigh about 3 kg. (8 pounds). If the box is full of gold, it will weigh 44,67,200 kilograms (98,033,395. pounds).

What happens if I put a box of gold on top of a box of packing peanuts? We don’t know – because I haven’t told you how strong our box is.

So, let’s say it’s a standard cardboard box. What will happen if you put a box of gold on top of a box of packing peanuts? We don’t know – because I haven’t told you where the box is.

If it’s a standard cardboard box, on the Earth, at sea level, then the box of gold will crush the box of packing peanuts. But if you put a box of gold on top of a box of packing peanuts in outer space, they will sit happily by each other because there is no gravitational force pulling the box of gold down to crush the box of packing peanuts. This is the crux of it.

Now, imagine we have one standard cardboard box, at sea level, and it’s full of regular old air. In that case, the box will weigh as much as the cardboard it’s made of – right? Well – no. We all know air isn’t nothing. Air has weight, and the air inside our box weighs about 1.29 kg (2.8 pounds) because the atmosphere has a density of roughly 1.29 kg per cubic meter.

“But wait!” the Flat Earther might say, “If I put a box on a scale – and zero out the weight of the box – the scale reads zero. How can I say there is over a kilogram of air in there?”

What happens when you zero out (or tare) a scale? You put something on the scale – and then you tell the scale “pretend that weight equals zero.” We do this because we don’t care about the weight of the container, we only want to know the weight of the stuff we put in it. Why does the scale read zero before I put the box on it? Because we started by telling the scale to pretend that the air on top of the scale equals zero. For most experiments we don’t care about the weight of the air on the scale. But in actuality, air has mass. If it has mass, it must have weight. Here on Earth, one cubic meter of air weighs roughly 1.29 kg per cubic meter at sea level.

The Weight of the Air

So, what is above my box of air, nothing? No. There’s more air there. Stacked immediately on top of my box of air is one cubic meter of air, which weighs 1.29 kg. On top of that, there is another 1.29 kg of air. And another and another all the way up to the clouds, above the clouds the air is thinner, and weighs less, but it still weighs something. Each box of air is stacked one on top of the other, all the way up to the vacuum of space. Once we are in the vacuum of space, we finally get to the point where there is a box of zero weight on top of our box of air.

But why did I have to say that the air in the box weighs 1.29 kg “at sea level?” Well, its because as you move up towards outer space, the air thins. As the air thins, it becomes less dense. This is because at sea level the air is composed of hydrogen, nitrogen, oxygen etcetera. Oxygen is denser than hydrogen, so there is more oxygen at sea level than there is at the top of Mount Everest. Once we get to the top of Mount Everest, there is so little oxygen that we can’t breathe, and we die. The air there weighs less than the air at sea level. If we keep moving up and up, each cubic meter of atmosphere becomes thinner and thinner and weighs less and less.

The first 1,600 boxes make up the troposhere, and they all weigh about the same amount. The ones at the top are lighter than the ones at the bottom because the air thins gradually.

On top of the boxes that make up the troposphere, there are 36,000 boxes of even thinner air that make up the Stratosphere. Then there are 30,000 boxes of even thinner air in the Mesosphere (where asteroids burn up and create shooting stars.) Then there are a whopping 140,000 boxes in the Thermosphere (where you’ll find a number of satellites). And then there are another 100,000-200,000 boxes containing the last layer of the Ionosphere where the air is so thin each box is mostly full of just electrically charged particles. Finally, the last trace particles of atmosphere can be found in the 200,000 boxes in the Exosphere. Eventually, you’ll get to the point in the Exosphere where each box has no atmospheric particles at all, and you’ll finally be in outer space.

This means that on our tiny box of cardboard, there are about 400,000 boxes of increasingly thinner air, all being pulled down to the Earth by the forces of gravitiation. The sum total of these boxes comes to about 10,000 kg (22,000 pounds). That flimsy cardboard box can support all of that weight because it is not empty. It’s full of air, and the air inside the box is roughly just as dense as the air outside the box, so it helps support the weight of all the air from the ground to outer space. If you remove that air, now you have a flimsy cardboard box trying to hold up a garbage truck. The box will be crushed.

Why Doesn’t the Atmosphere Get Sucked Away?

If you want a true vacuum here on earth, you need to create a wall that will hold up 10,000 kg of air on every square meter of surface area. If the top of your box is two meters wide, now you have to support two garbage trucks. This isn’t because the vacuum inside your container is “sucking” the air into it, it’s because gravitation is pulling 400,000 boxes of increasingly rareified air down to the ground, where they are trying to fill up the empty space you’ve made.

So, why doesn’t the atmosphere get sucked into outer space? Think about it – what is there in outer space? Nothing. (Well, actually a lot more than nothing, but for the purposes of this exercise – essentially nothing.) Because outer space is basically empty, there’s nothing out there to “suck” the atmosphere away.

So – outer space doesn’t suck because vacuums don’t suck. The perception that a vacuum sucks is due to the fact that we are building them here on Earth, and the gravitational force of the Earth “sucks” the air down. There is so much air in the atmosphere that it has a significant amount of weight that we need to counteract. If you get far enough away from the Earth’s gravitational field, then you can create a vacuum pretty easily – you just need a material that will keep out the increasingly rarefied air around you. If you are in outer space, where there are no air particles to keep out, you can create a vacuum with no barrier at all – because there is nothing to fill in the vacuum.

Interestingly, the solar winds could blow away our atmosphere – like they did to the moon – if it weren’t for all those electrically charged particles in the ionosphere protecting us from the solar wind.

Doubly interesting – this also explains why the clouds and helium balloons don’t “defy gravity.” Wator vapor and helium are less dense than air at sea level. Because air is a gas, and gasses behave like fluids in how they move, the balloon and the cloud float above the denser atmosphere like oil floating on water. Eventually, they get high enough that the air above them is less dense than they are, and they float there. The clouds float there until the water vapor condenses around microscopic dust particles until they become heavier than the air around them, when they fall as rain. The balloon floats there until the gas escapes from the balloon enough that it can no longer support the weight of the rubber that the balloon is made of, and then it falls back to Earth.