I'm afraid that there are a few minor mistakes in the article, though overall it's pretty accurate from a physics perspective. In order to see where those mistakes are, consider these two facts:

a) the "vacuum of space" is pretty empty, although not totally empty. What that means is that its pressure is very very low compared to the pressure exerted by the atmosphere at sea level (ie, the pressure we have evolved to live with).

b) the human body (or any other living organism, other than certain plants) has cavities (some filled with gasses and/or liquid fluids), cells (which have an internal osmotic pressure), and tissues (which have both liquids and gasses dissolved in them, at various concentrations and partial pressures). Certain plants have cells with rigid walls, so they're not as easily deformable as human cells.

So, on to the article.

1. Exploding eyeballs

"Fortunately, eyeballs wouldn't explode in a vacuum, any more than they'd cave in under 33 feet of water."

This is entirely correct, and the comparison is a good one.

At 33 feet/10 meters of (sea) water, you are already exposed to an entire extra atmosphere's worth of pressure. In fact, you gain one atmosphere of pressure for every 10 meters of sea water. Since the ocular pressure (the pressure of the liquid inside your eyes, called aqueous humor) is about 1 atm, and the water pressure outside is 2 atm, the relative pressure is 1 atm, the same relative pressure between the inside of your eyes and the vacuum of space.

From personal experience, we all know that 10 meters underwater won't have much of an effect on anyone. (Well, those of us who like diving know that) Therefore, being in the vacuum of space won't make your eyeballs explode.

What's likely to happen is that the aqueous humor will start sipping through the walls of the eyeballs, decreasing the internal ocular pressure. This will happen very slowly, however, because 1 atm of differential pressure is not all that much. You'll also have some rupturing blood vessels in the eyes (for the same reason, the blood would start sipping through the arteries in an attempt to equalize the pressure inside the arteries with the pressure outside), but the eyes themselves won't explode. They might, in fact, shrink a little, due to the escaping aqueous humor, which would alleviate possible glaucoma symptoms. You may die in space, but you'll not go blind with glaucoma. (Glaucoma is the condition where the ocular pressure is larger than normal, large enough to make an eyeball swell, putting pressure over the corresponding ocular nerve, cutting off its blood supply, and causing it to die. The condition is neither reversible nor curable but it is preventable)

"The body wouldn't swell up and explode like a marshmallow in a microwave, either. There's just not enough pressure inside of us to blow us up."

Again, this is entirely correct. And for the same reasons as above. The differential pressure is 1 atm and that's fairly small to do anything to the body.

Just as before, however, fluids that are inside the body (both liquid and gasses) will start sipping through the interstices between the cells, attempting to escape the body. You won't notice the liquid sipping, though, because it will happen way too gradually.

The gas sipping, on the other hand, might be noticeable depending on the concentrations under which they're dissolved in your tissues and blood.

If you're a scuba diver, you know about "the bends" which is a sudden release of gasses dissolved in your blood (usually Nitrogen) into your muscles. When you dive to even moderate depths and stay there for a long time, nitrogen in the air you breathe gets dissolved into your blood. Since the air you breathe is under high pressure (to compensate for the high pressure of the outside water, or else your lungs would collapse and you wouldn't be able to breathe at all), the Nitrogen is also under high pressure. As you breathe, it gets dissolved into your blood and accumulates there. If too much accumulates, you may suffer from something called Nitrogen narcosis, which causes (typically temporary) neurological effects. Essentially, you go nuts for a while.

Now, as you rise up to the surface, the outside pressure is decreasing, so the high-pressure dissolved Nitrogen boils off the blood into the surrounding tissues. If you come up too quickly, that boiling off can be extremely painful and may cause serious injuries. Note that it's not your blood that is boiling, and neither is anything boiling because of increased temperatures. The Nitrogen in your blood is boiling off because it is dissolved at a higher pressure than the surrounding areas. It's exactly like when you open a bottle of coke after you've shaken it up.

So, yeah, when you're thrown off the airlock, gasses dissolved in the tissue under your skin will start boiling off, and that's probably much more painful than just tickling.

2. Freezing to death.

"For one thing, space isn't freezing. Space isn't any temperature. Temperature is the measurement of the movement of atoms. There aren't many atoms in a vacuum, so technically there can't be a temperature."

The above isn't quite correct. You are correct that temperature is a measure of the kinetic energy of a collection of moving objects, but even a small number of objects can have a large temperature, if they have a large average kinetic energy. If you're in a region of space with lots of radiation, then it's possible for the temperature of vacuum to be above freezing.

If there aren't any sources of radiation, then it *is* pretty cold in space. However, that has little effect on you because there aren't enough atoms to exchange energy with the atoms in your body (and not because there isn't a temperature, as claimed).

Think of it this way. A thermometer works (ie, measures temperature) because it robs some energy from what you're trying to measure the temperature of. You don't want a large thermometer because it will rob so much energy that the measurement will be incorrect. So, by making the thermometer small, little energy is robbed, just enough to sample the object's temperature. Now, if the thermometer is too small, it will rob so little energy that there will be no noticeable effect in the object. And this is true regardless of the initial temperature of the thermometer itself.

The vacuum of space is like a tiny but very cold thermometer. It's very cold, but there are so few atoms that they won't rob enough energy from you in a reasonable amount of time for you to notice.

3. Boiling Blood.

Everything mentioned in this section is correct, but something was not mentioned that should have been. The gasses that are dissolved in the various tissues, in the blood, and which occupy various cavities of the body. As I mentioned a couple of paragraphs above, those gasses will boil off, and that's both painful and potentially fatal.

4. Lung Shredding

"They also happen to hold gas that expands quite a bit when external pressure is dropped."

Indeed, and that's what I've already explained above. When these gasses expand and boil off the various tissues, those tissues can be damaged. The alveoli are some of the most fragile macroscopic organelles in the body. Imagine that they're tiny coke bottles. You can imagine the rest.

"Because a vacuum does not carry sound very well"

Not just not very well, but not at all. Sound does not travel in a vacuum.

"Fortunately, this only happens if you hold your breath,"

Quite possibly not true. Your eardrums will probably burst, which is an excruciatingly painful experience (I know, because I punctured my right eardrum in an accident in 1993). They'll pop, not because of the pressure differential - it's only 1 atm - but because of the sudden change in pressure. You're being thrown out the airlock, going from a pressure differential of 0 to that of 1 atm, in a matter of seconds. Your eardrums will bend outward and will likely pop, exposing the so-called Eustachian tube to the vacuum of space.

Now, the Eustachian tube is connected to your larynx, which is connected to your lungs through the trachea. Ergo, say goodbye to your alveoli. And once your alveoli burst, exposing your blood to the vacuum of space, then the gasses dissolved in your blood and surrounding tissue will start boiling off at a faster rate.

Of course, if you don't hold your breath, it's even worse, because your lungs will be exposed right away, and will collapse and start bleeding rather quickly.

Heart failure.

"Once a heart stops, the pressure inside of small blood vessels drops, allowing the vacuum to damage them faster. Once the tissue dissolves and the liquid is exposed, well, that's when the blood boiling happens."

Much of the above isn't correct, actually. For instance, if the pressure inside of a vessel drops, then it's going in the direction of equalizing the pressures inside and out, which means that *less* damage would be caused by the differential pressure, not more. Also, there is no dissolving tissue.

Stuff happens in the opposite direction. First, stuff happens and then the heart fails, not the heart fails and then stuff happens.

As I already pointed out, what first happens is that the differential pressure causes fluids and gasses to start sipping through the skin and your lungs start collapsing and bleeding (as a result of the exposure of the Eustachian tube, whether or not you hold your breath - of course, if you don't hold your breath, it's even faster because your lungs will collapse right away).

The leaking of gasses from blood to tissues and through the tissues causes the blood vessels to dilate, which decreases blood pressure.

The natural response of the body to both a decreased lung capacity and a decreased blood pressure is to increase the heart rate. With no blood circulating back to the heart from the lungs (they're collapsed!) and with blood loss, the heart simply can't keep up and eventually fails.

Apparently, that happens fairly quickly, quickly enough that you die of heart failure before you asphyxiate.