What Causes Eye Floaters?

iStock / Mark_Kuiken
iStock / Mark_Kuiken

Eye floaters — or muscae volitantes, Latin for “hovering flies" — are those tiny, oddly shaped objects that sometimes appear in your vision, most often when you’re looking at the sky on a sunny day. They look like spots, or a squishy little amoeba, and drift aimlessly around in your field of vision. Try to get a fix on one, though, and it seems to disappear.

Floaters aren’t just optical illusions. You’re really seeing them, and they’re actually in your eye, not just on it or in front of it. The weird little squiggles are pieces of the vitreous humor, the fluid that fills the eye, breaking off and then floating about in your eyeball.

A little gross, I know, but completely normal. The vitreous humor fills the gap between your retina and lens and helps maintain the round shape of your eye. It’s made up of water bound up in a little hyaluronic acid and collagen. When you’re young, it’s thick and gel-like, but as you age, the hyaluronic acid network breaks down and releases the trapped water molecules. As this happens, the core of the vitreous humor becomes more watery and little bits of undissolved gel break off and slowly drift around. When light passes through the eye, the shadows of these pieces are thrown up on your retina and you perceive them as floaters.

A Closer Look

Since floaters, well, float, their paths generally follow the motion of the eye. This makes looking right at them difficult, and when you shift your gaze towards them, they often move and stay at the edges. They don’t always float, though, and many of them will sink towards the bottom of the eyeball. To get a good look at them, just lie down looking up at a clear sky. Some of the floaters will settle near the fovea, a small area that sits at the back center of your eye and is responsible for your sharp central vision. The lack of movement and the even, textureless background makes it easy to scope them out and watch the blobs bob around a little.

For the most part, floaters are nothing to worry about — just a sign that you’re not a kid anymore. The sudden appearance of a lot of floaters combined with the onset of other eye weirdness — like flashes of light or blurriness or loss of peripheral vision — could indicate a problem, though. Sometimes, floaters are a symptom of the vitreous humor pulling away from the retina, a retinal tear, or the abnormal growth of blood vessels in the eye. If your floaters cross the line from curiosity to nuisance, it’s time to give the eye doctor a call.

Why Do Dogs Eat Grass?

iStock/K_Thalhofer
iStock/K_Thalhofer

If something is edible (or even if it's not), many dogs will gladly make a meal of it. But if you see your pet grazing on your front lawn like cattle, it may be driven by something more than its undiscerning appetite. Eating grass frantically can be a sign that a dog is sick.

It's not unusual to see a dog vomit after consuming grass, prompting some pet owners to wonder if their dog ate the grass to soothe its own upset stomach or if the grass is what caused its symptoms in the first place. According Dr. Jerry Klein, chief veterinary officer for the American Kennel Club, this behavior is sometimes a response to symptoms that were already present. "When dogs go outside and gobble grass really quickly, there's usually a reason, an instinctual behavior to try to induce some kind of gastrointestinal reaction," he tells Mental Floss. "When they realize they're nauseous or something else, the only thing they know how to do is to force themselves to vomit. Some dogs that eat grass chomp it down without really chewing it, and often times may vomit something up and that's how they treat themselves."

Despite it being a common issue for pet owners, little research has been done into why dogs eat grass. It's likely that stomach problems only explain this behavior part of the time. In other situations, a dog may eat grass for the same reason it eats your shoes or the groceries you left on the kitchen counter: Because it's hungry, anxious, or bored.

So how can you tell when your dog is munching grass for pleasure and when it's trying to induce itself to vomit? Pay attention to the way it eats. Dogs are omnivorous, meaning they eat both plants and animals, so just eating grass alone normally won't be enough to make it sick. But if a dog is gorging on grass faster than it can chew it, that may be an indication that something is wrong. Whole blades of grass can irritate a dog's throat and stomach lining, potentially causing them to throw up if they swallow a lot of them in a short amount of time.

No matter the reason for your dog's grass-eating habits, Klein says that they aren't a major issue. The behavior shouldn't be encouraged, as grass in public places can potentially carry harmful chemicals like pesticides, so stop your dog if you see it grazing. But if it shows no signs of illness or discomfort afterward, there's no need to rush it to the vet. "If I see a dog eating grass, I'm not going to panic. I would try to stop it and then monitor it to see how it acts in the next 15 to 20 minutes. Look at how the dog's acting, its body shape and movement, and the feeling you get from the dog."

One condition related to vomiting that would warrant a trip to the vet is something called bloat. This happens when a dog's stomach fills with air, causing it to retch without actually throwing anything up. This is a medical emergency and can be deadly if left untreated.

A dog who vomits after eating grass and looks happy afterward, on the other hand, is probably not a cause for concern—though you may argue otherwise when you're steam-cleaning your carpet.

Have you got a Big Question you'd like us to answer? If so, send it to bigquestions@mentalfloss.com.

How Do Airplanes Land in Water?

iStock/oblong1
iStock/oblong1

Joe Shelton:

At least in terms of the physical act of landing, seaplanes and floatplanes land on the water pretty much in the same way that land based airplanes land on the ground.

They start with an appropriate approach airspeed, a slight flaring just before touching down, feeling it as the aircraft touches the water, and then it's slightly different. Because of the water's drag the aircraft will slow very quickly and settle into the water. Brakes aren't really needed. And that's good because they don't have any brakes that work in the water.

Once in the water they are as controllable as a boat. Which is to say, not that much. In fact, in the water they are navigated pretty much just like a boat.

Most if not all seaplanes and floatplanes have "water rudders" that allow them to steer in the water just like a boat. But as they approach a pier or beach you'll usually see the engine stopped and the pilot out on the float or leaning out of the aircraft with an oar rowing the boat to shore (sounds like a Peter, Paul, and Mary lyric).

If the question wonders why the aircraft don't sink, it's because they are designed to float.

Floatplanes are typically normal aircraft that have been outfitted with floats, usually two, one under each wing. Seaplanes, on the other hand, are designed specifically for water operations.

Many or even most floatplanes and seaplanes are what's called amphibious. That means that they can land and take off from both water and land. Typically they have retractable/extendable wheels (landing gear).

While it's important that an aircraft's landing gear has been extended when landing on the ground, it's equally important, if not more so, that the landing gear is retracted when landing on water.

Here's why:

The aircraft in the video is a "floatplane" with aftermarket floats.

a firefighting seaplane
iStock/Paolo Seimandi

This is a seaplane where the fuselage is designed to float like a boat. It also has floats, but they are part of the design.

a Piper Apache floatplane
Phil Hollenback, Flickr // CC BY-NC 2.0

This is a Piper Apache on floats. It's also the aircraft that I earned my Commercial Multiengine Seaplane rating in.

This post originally appeared on Quora. Click here to view.

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