And then you have the bright spots that appear in front of your eyes ("seeing stars") when your body suddenly strains really hard. Maybe you sneezed, or pulled an intense, full-body Valsalva maneuver trying to squeeze out a dissident turd, or just rubbed your eyeball.

Both phenomena are completely normal, yet the explanations are weirder than you think.

It Happens Because ...

First of all, "eye floaters" are not a) just lint and shit that fell into your eye or b) unusually upstart sperm that got really really lost.

Your eyes are mostly made up of a jelly called vitreous fluid, and this gel undergoes many changes as you age. As it slowly shrinks, it loses its smoothness and starts to look stringy. The vitreous can also become more liquid, and this allows for tiny fibers in your eye to come together and form (relatively) large clumps. These get big enough to become visible and freak us out, but they eventually sink down and settle at the bottom of your eyes where you can't see them. So technically, they're your little buddies for life.

Dundanim/Photos.com
Everyone you love will die, leaving ocular degeneration your only friend.

As for the bright dots that flash and move in front of your eyes, they're called phosphenes, and they're caused when cells in your retina are messed with (by rubbing your eyes or having a large person slap you in the dark), causing them to misfire. Strangely, scientists have found that they can also stimulate phosphenes by running electricity across the visual cortex part of your brain. Try it on a friend!

But wait, it gets weirder: Have you ever gone out and stared up at a clear blue sky, only to see faint white dots dancing around the edge of your vision? Most people can see it if they really look, and it's worth it because you are seeing the goddamned white blood cells shooting through the blood vessels in your fucking eyeball. The blue light causes the vessels and other cells to be invisible to your eye, so you wind up seeing the white blood cells zipping around like tiny ghosts, just chasing diseases and shit. Maybe there's a tiny ship full of scientists in there.

It Happens Because ...

Researchers at Harvard, the University of Ireland, and the U.S. Department of Veterans' Affairs teamed up to figure out why the hell such a great thing can be so unpleasant (we guess it's marginally better than spending your tax dollars on another bank bailout). They came to realize that they could trigger the headaches just by placing an ice cube in the subject's mouth and pushing it to the top of the palate, which messes with the brain's thermostat.

The brain wants to keep a constant temperature, so when you're stuffing your head with ice cream, your palate gets chilled and your brain freaks out, thinking you're trapped somewhere near the peak of Mount Everest ("Holy shit, it's so cold here that the inside of his mouth is freezing!"). It opens up arteries to pump more blood to the area to warm it up, but instead of making you super smart, the increased blood pressure just causes an "ice cream headache."

Arvind Jain/Wikimedia
Eating fire's similar; your brain assumes you're in Phoenix.

People usually respond to these shooting pains by pressing their hands to their head, as if manually warming the skull will fix it (which, as you can guess, does nothing). No, the only known way of getting rid of the brain freeze is to warm up the top palate and constrict those arteries back to normal size. Sometimes pressing your tongue against the top of your mouth can help. Or you can shove a Hot Pocket in there, whatever.

It Happens Because ...

Actually, this bizarre reaction was, for some of us, our first childhood introduction to chemistry. The weird horriblization that occurs with orange juice and lots of other foods after brushing is due to a chemical called sodium lauryl sulfate. The white coats making your hygiene products know just how much you like it when your cleaning products foam up, so they have to add totally useless enfoameners (may not be the actual name). The aforementioned SLS is one such animal, and gives you that great frothy mouth-feel you need to make it seem like your toothpaste is doing something.

Jana Lumley/Photos.com
If you're rabidly foaming, it has to be working.

But one side effect of SLS is that it wreaks havoc on your tongue's taste receptors -- it numbs the little guys in your mouth that detect sweetness and erodes the fatty shield that blunts the taste of bitterness. For a while, anyway.

So your mouth is getting double-teamed into a gustatory lethargy, which has the effect of significantly changing the way certain foods or drinks taste to you. Obviously it's more noticeable on substances that are normally super sweet yet acidic (other foods may just taste a little lifeless). If this bothers you, there are actually toothpaste brands that don't have SLS or its sweet foaming action. But if you live with someone else, you've got about one day before they start screaming from the bathroom that your toothpaste is broken.

It Happens Because ...

Once again we can blame blood vessels. When the man is fully aroused and ready to unleash a payload of DNA, the arteries open, allowing blood to flow into the genitals, but then restricting the blood flow going away -- one result of this is what scientists call a "boner." When an orgasm occurs, the arteries almost immediately open, allowing the blood to leave because the deed is done.

But when sexual activity stops all of a sudden, the body gets all confused and can't figure out how you didn't seal the deal. This means that the blood lingers, and since it isn't oxygenated, it is "blue" -- and thus the term "blue balls" came into the vocabulary. The pressure of that blood is what makes the experience painful and causes tension in the man's balls -- that's right, it's basically getting an ice cream headache to the junk.

Andrzej Szalapata/Photos.com
Which feels worse than it sounds.

Fun bonus fact: This blood-trapping mechanism is the reason why Viagra, a pill originally intended to treat high blood pressure, also helps erectile dysfunction.

The Weirdness:

A sunburn is the point at which something desirable progresses into something painful and annoying. It's a suntan that's gotten too buff and now has to use a claw attached to a bent plastic handle just to wipe its own ass. A modest amount of sunlight to your skin yields a light roast and therefore a nice golden sheen that is absolutely painless (along with scoring you some free vitamin D). A little too much exposure, however, and you're in a world of hurt where suddenly your skin is hypersensitive to even the gentlest of caresses.

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At first, you may think you're fine. Then you shower.

So why would something that isn't painful while you're experiencing it be excruciating when you're recovering afterward? And why would it change the color of your skin in the process?

It Happens Because ...

First of all, what you're seeing is a radiation burn. Blast yourself with radiation from a leaking nuclear reactor or certain medical procedures and your skin will look the same angry red. In this case, it's UV radiation, but it's still directly damaging your DNA and your body still responds with inflammation, increasing blood flow to the site and bringing with it all of your body's tiny repair crews. The angry red color is your body's attempt to heal it before tumors and mutations start sprouting everywhere.

Ralf Hettler/Photos.com
Your body fears the responsibilities that superpowers bring.

All right, so why is your skin suddenly hypersensitive to touch? If you roll your eyes and say, "Duh, because it's a sunburn," not so fast -- it's actually always been a mystery to scientists. Recent research says it might all be due to one obscure protein that helps manage the immune response, which happens to have the side effect of aggravating nerve receptors. Figuring out how to counteract that protein could one day actually fix the pain of sunburns (and other types of inflammation) instead of the current lotions and sprays that work for about the amount of time it takes to apply them.

What the hell? Does asparagus change our body chemistry so fundamentally that our own fluids start to smell like the discharge from a chemical plant? Then why do they allow us to eat it?

It Happens Because ...

The odor is the result of an organosulfur (an organic compound containing sulfur) called asparagusic acid. And yes, that's the real name, we're not joking -- we're told that at least one person in the world calls it that. You might be asking yourself why asparagus doesn't smell like that, then, and the answer is that asparagusic acid itself isn't so potent -- the smell mainly comes from the compounds it breaks down into, which can manifest themselves in urine in as little as 15 minutes. Sulfur, of course, is the same stuff that makes your farts (and skunks) smell bad.

Parents: If your little boy refuses to eat his asparagus, tell him it will let him pee farts. It'll work wonders!

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For more bodily mysteries, check out 6 Things Your Body Does Every Day That Science Can't Explain and 6 Things Your Body Does Every Day (That Can Destroy You).

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Related Reading: Science hasn't solved every mystery of the body. For example: we still don't understand the placebo effect. And did you know laughter is the body's drug dealer? Because that's totally how it works. With all this knowledge, science has figured out how to hack some shit. They can even change your eye color.

And to further expand your noggin, check out Cracked's De-Textbook: The Stuff You Didn't Know About the Stuff You Thought You Knew.

It's loaded with facts about history, your body, and the world around you that your teachers didn't want you to know. And as a bonus? We've also included the kinkiest sex acts ever described in the Bible.