Humans are kind of dumb. Like, okay, we’ve invented the wheel and the Internet and sliced bread, but there are some really basic things we don’t understand.

Did you ever wonder why your bike stays upright? Why anesthesia knocks you out? Or how cats purr? So have plenty of other people, and no one has an answer.

Yes, it turns out that when it comes to some basic everyday things, we’re about as knowledgeable as the current US president.

So let’s take a look at some of the weird stuff science just can’t explain. Some of it might surprise you.

Why does anesthesia knock you out?

If you’ve had an operation, you’ve probably experienced some form of anesthetic. That might have been local, numbing a part of your body, or general, putting your whole body to sleep.

The bizarre thing, though, is that scientists aren’t sure why this is the case. Local anesthetics can involve injecting a drug or using a spray to numb an area, whereas general anesthetics often involve injecting a drug like propofol or isoflurane to make you lose consciousness.

We know that anesthetics stop nerves in your body sending signals to your brain. How exactly that happens though, well, we’re just not sure. They even work on plants, for God’s sake.

“The truth is, no one knows,” New Scientist noted in an article from 2011. But recent research does suggest we might be getting closer to a clear answer.

How do cats purr?

Cats can purr for a whole number of reasons. They purr when they’re pleased, or content, or even when they’re under duress. But WHY do they purr? Well, that’s another matter.

“Frustratingly, nobody is really quite sure what causes the purring noise in cats,” noted io9. “There is no ‘purring organ’, or specialized part of the cat throat that's responsible for this irresistible noise.”

Yes, that’s right. We don’t know how these adorable creatures are able to maintain a purring noise for minutes on end. Some suggest cats may have some sort of “neural oscillator” involved with the larynx, but no one knows for sure.

There may even be some health benefits to them doing so, although that’s a bit contentious. Out of all the things on this list, scientists, we’d really like you to figure this one out ASAP.

What causes a hangover?

After a night on the town, you’ve probably at some point or other experienced the splitting headache, sickness, and dizziness that heralds a hangover.

You might expect science would have an answer for why you feel so terrible. But we’re afraid to say you’re on your own – it doesn’t.

Technically known as veisalgia, the commonly held belief about a hangover is that dehydration is the cause. But studies have found few links between dehydration and hangovers.

At the moment, the best theory is that alcohol produces a toxic compound called acetaldehyde as a byproduct, which can cause some of the symptoms associated with hangovers. But we aren’t sure.

So the next time you reach for that beer, remember that come the following morning, science won’t be able to help you feel any better.

Why is ice slippery?

Arrggghhhhhhh, splat. That’s roughly the sound of someone stepping on ice and falling over. But why? All together now – we don’t know.

Scientists think it might be something to do with ice forming a liquid layer of water on its surface. The blade of an ice skater, for example, may generate enough heat to melt the ice and form this layer.

But ice can be slippery even when you’re standing still, so that’s clearly not the whole answer. Instead, it might be due to a “supersolid skin” producing an electrostatic force that pushes things away.

For the moment, this is a mystery that has left scientists in the cold (haha).

How do bicycles stay upright?

“Everybody knows how to ride a bike, but nobody knows how we ride bikes,” Mont Hubbard, an engineer at the University of California, Davis, said in Nature in 2016.

That might sound incredible, but it’s true. We have a few ideas, but we don’t have a full picture yet. We just don't know how a bike is able to stay upright with or without a person on it.

One possibility is the gyroscope theory, which suggests a spinning wheel produces a force that keeps the bike running straight. Another, the caster theory, involves the steering axis of the wheel contacting the ground.

While both help a bike remain stable, they do not fully explain how a bike self-balances. We know this because researchers have built bikes that don’t adhere to these rules, but still stay upright.

For now, the jury's out. Although we haven't heard anyone discount “magic” being the answer yet.

 

What causes static electricity?

In 2012 a Scottish man rubbed a balloon on Donald Trump’s head, causing his hair to stick up. It was very amusing. But like the man himself, the cause of this is baffling.

Now, we hear you. “Static electricity!” you scream, while also preparing an angry comment because we’ve mentioned Trump twice in an article that has nothing to do with politics. Make that three times now.

But we do not know how static electricity works. We’d thought it was an imbalance of charges, but then another theory came along and suggested it may involve a transfer of actual material.

“Tiny bits of balloon actually adhere to the hair, disrupting the electrical patchwork on the balloon and causing that strange attraction between it and other objects that we all know as static electricity,” noted Popular Science.

However, if that’s the case, we still don’t know why this occurs. In fact, there’s a lot we don’t know about static electricity. And it’d be a good idea to find out, as it can be rather troublesome at times – not just for future presidents, but for machinery too.

Is the universe a simulation?

Elon Musk once said it was possible we were living in a simulation. He’s not the first to put forward that theory. The argument goes that if the simulation is good enough, we’d never know for sure.

Quite a few people think this might be the case, based mostly on the fact that, well, why not? Our computers are getting more and more powerful, so who’s to say we won’t be able to produce our own mini-universe in the future?

“If one progresses at the current rate of technology a few decades into the future, very quickly we will be a society where there are artificial entities living in simulations that are much more abundant than human beings,” NASA scientist Rich Terrile told The Guardian.

More recently, however, a group of scientists said they had ruled out the theory, basically because of quantum mechanics. So we might not be in a simulation just yet – unless that's what they want us to think.