When you get a sunburn, your cells are dying to avoid becoming cancerous.

more like a theory, the “orangutan paradox”, when we film a documentary on orangutans, they can’t realize that we are observing them, yet they are the most intelligent species of their category, so aliens might be watching us and we are as oblivious as an orangutan

That things we thought were stars (or fuzzy stars) a century ago are actually entire galaxies. Who knows who or what the F is out there?

If a person gets bitten by an animal who has rabies, he will continue to live on a normal life for 12 weeks, and after the symptoms develop, there is no way he's making out alive. You'll know you're gonna die.

brain-eating amoebas

Prions, horrific and totally unpredictable.

30-50% of people don’t have an internal monologue.

Deep time.The Earth was alive a million years ago. And a million years before that. A thousand million years before that.Even if our civilization is miraculously successful and we live for 20 thousand more years and colonize thousands of planets like in Dune it's still nothing. A blink of an eye. The Earth would barely notice.

That a person can be killed by organisms so tiny that we can't even see them

Climate Change

Ageing. I'm content with death but the idea of my body growing old, frail and eventually falling apart before the end game gives me goosebumps.

Every child's jaw is packed with teeth which sounds normal until you realize this is what it looks like.

dementia

How little human scientists actually know relative to the amount of things in the universe

Finding substances that can change your behaviour, memories and general personality.

Gamma ray bursts can happen at any time. No warning, no escape, no defense, no survivors.

The Yellowstone super volcano.

The capability to harness nuclear explosions

Sometimes during brain surgery, they'll peel your face forward like the peel of a banana.

The size of our galaxy, how many *other* galaxies there are and how far away they are. When you can actually see something that incomprehensible..

Time, it's not scary until you start thinking about it

Some tumors have teeth, hair and even eyes.

Since you shed about 40,000 skin cells a day, the dust you see in your house actually used to be part of you. Which means every time you breathe in someone else's house, you could be inhaling 1000s of somebody else's skin flakes.

That weird feeling you get on a roller coaster is actually your internal organs slightly shifting around inside you, especially the ones not secured by ligaments like the intestines.

cracking your neck could cause you to have a stroke but its rare

How the brain is literally rewired and chemically altered by childhood neglect and abuse.

Giant squids. Suddenly the old sailor story's of krakens wrapping tentacles around a ship and pulling it into the ocean doesn't seem like fiction.

Lead in gasoline may very-well have decreased the human IQ on a global scale while in use.

That we've only explored (numbers might not be quite right) 2% of the oceans and that the oceans makes up 78% of the world. I wonder what's in there

Zombifying fungi as depicted in games like The Last Of Us exist, and are very potentially even scarier than how they appear in there.The fungi of the genus Condyceps like to infect insects by scattering spores on them. After a while these insects will start to behave erratically. Eventually they try to reach a high place, like a stalk, where they lock their legs and then die. The fungus then sprouts from their body, scattering its spores below to infect the animal's brothers and sisters.A theory currently is that the fungus doesn't even affect the brain, but rather that it cuts off the brain from the muscles. If this is the case, it means that the brain of the infected animal still functions normally, but its body just doesn't follow its commands, leaving the animal to die a slow but somewhat conscious death in order to infect more of its kind.

that hearing is the last sense to leave, when dying.

The scariest thing for me, is that we have scientifically mapped human psychology. We know social habits, and evolutionary survival instincts that we've carried over from our ancient past. We have extensive knowledge on how to elicit the exact response out of a human on command. And the scary thing is that corporations use this information to sell things to us.Everything about a product's design from it's shape, to it's color pallet to it's odor is specifically and intricately designed to hack our brains and trigger the exact specific response that they want from us.Once you are aware of how much human psychology goes into advertising, you will never look at an add the same way again.

Microplastics found in newborn babies

Not the scariest, but thought I should add because it's kinda suspicious.Many governments are increasingly admitting that UFOs (which means unidentified flying objects, not aliens!) are real. They have been detected by many advanced military systems. They have been observed to seriously outperform our best technology/jets.Now of course, what's a UFO conversation without bringing in the possibility of extraterrestrials watching us? Creepy but fascinating.

If you decapitated someone, the disembodied head will be conscious for 15 to 20 seconds, long enough for them to realize what you did to them.

The infinite expansion of the universe. Everything in the universe is not only getting farther and farther apart, but accelerating in it's expansion, such that one day in the distant future, whatever creatures are left to look up from their planets and wonder, will see an empty sky devoid of stars and galaxies as they've all expanded beyond the cosmic horizon. All worlds will be alone, drifting in the infinite dark, with no possible way of knowing the scale and beauty of what was.