Kurzgesagt - In a Nutshell Season 12, Episode 22: Black Hole's Evil Twin - Gravastars Explained

1

Did The Future Already Happen? - The Paradox of Time

Is your future already written? Do your past, present, and future all exist right now? Surprisingly, the answer could be yes. Let's take a look at what time is and how it works – in our first video of the year!

13 min

2

What Happens AFTER Nuclear War?

A nuclear bomb is the most devastating explosion ever created. One bomb can end tens of thousands of lives immediately and hundreds of thousands through the radioactive aftermath. However, the worst part comes afterward: a nuclear winter that might kill billions, potentially leading to the complete collapse of our civilization. In a nuclear winter, there are no winners – only starving losers. How exactly does it work and what would it look like?

11 min

3

The Paradox of an Infinite Universe

What is outside of the universe? We know that the universe had a beginning 14 billion years ago and that it has been expanding ever since. But something that is expanding should also have an edge, right? What would you see if you went there?

14 min

4

How The Dinosaurs Actually Died

A ruthless murder was committed! Someone killed the dinosaurs and we have the murderer! Witnesses say that an Everest-sized asteroid hit Earth, devastated the planet and caused a mass extinction. A simple, fascinating and convincing explanation. Or… is it?

12 min

5

There Are Thousands of Alien Empires in The Milky Way

We often assume that advanced technology will make it easy for aliens to colonize space. But what if space exploration is always difficult, no matter how advanced you are? Let’s travel back in human history, to the colonization of Oceania over 5000 years ago, to find parallels between ancient explorers and extraterrestrial civilizations.

14 min

6

Smoking is Awesome

We need to have an honest conversation about smoking: The problem with smoking is that it is way more than just a physical addiction. Smoking creates a temporary problem and offers an instant solution. Once your brain is used to nicotine, for up to 72 hours you are itchy,nervous and stressed – but one drag and instantly, you feel really good. It also helps you focus and take breaks during work, while suppressing your appetite. So why is it such a bad idea?

12 min

7

This Black Hole Could be Bigger Than The Universe

Black holes might create infinite universes while destroying time and space. Everything in existence could be black holes, all the way down. We might live inside a black hole that is inside a black hole, that is inside a black hole. But let’s start at the beginning and build a black hole out of air.

12 min

8

Do You Have a Free Will?

You may think you have free will and can choose what you do, but this might be an illusion. Your body is made up of particles that blindly follow the laws of physics, with every outcome already predetermined. So, you might not have any free will at all. Is free will an illusion, or does it exist? Which philosophical camp is right?

13 min

9

This Disease is Deadlier Than The Plague

The white death has haunted humanity like no other disease following us for thousands, maybe millions of years. In the last 200 years it killed a billion people – way more than all wars and natural disasters combined. Even today it’s the infectious disease with the highest kill count. But what is this horrible disease?

11 min

10

A.I. ‐ Humanity's Final Invention?

Humans rule Earth without competition. But we are about to create something that may change that: our last invention, the most powerful tool, weapon, or maybe even entity: Artificial Super intelligence. This sounds like science fiction, so let’s start at the beginning.

18 min

11

Fever Feels Horrible, but is Actually Awesome!

Fever feels bad. So we take medication to suppress it – but is this a good idea? It turns out fever is one of the oldest defenses against disease. What exactly is a fever, and how does it make your immune defense stronger? Should you take a pill to combat it?

13 min

12

We Traveled Back in Time. Now Physicists Are Angry.

Time travel is possible. In fact, you’ve been doing it since the day you were born. But what if we told you there’s a way to hack the universe and manipulate time itself? We just have to do two simple things to make it happen: 1. Make a lot of physicists grumpy. 2. Shoot one twin through space against their will, while the other chills on Earth. Let's go!

11 min

13

We Need to Rethink Exercise (Updated Version)

Exercising doesn’t help you lose weight. In fact, it barely changes your daily calorie burn. Welcome to the workout paradox! Let’s dive into the science of how your body actually handles calories and sabotages your best efforts to burn them.

13 min

14

Why Scientists Are Puzzled By This Virus

You’ve got trillions of viruses inside you – right now! But these aren’t the viruses you fear. Some of them are your body’s secret protectors, keeping deadly bacteria in check and even killing cancer cells. But what happens when they turn against you? Let's look at the wild world of the human virome.

11 min

15

This Video Might Save 58 Lives Next Week

58 of you watching this video right now will not be alive next week. And it’s not because of some freak accident or rare disease. It’s because of everyday actions you probably think are harmless. Let’s save your life today by looking at what is most likely to kill you next week – so you can avoid it.

13 min

16

There Is Something Hiding Inside Earth

We’ve found a new planet, home to octillions of the most extreme beings living in the most absurd and deadly hellscape. In absolute darkness, crushed by the weight of mountains, starved of oxygen, cooked alive, bathed in acid, salt or radiation. And yet, they live for thousands, perhaps millions of years! It turns out, this planet is not in space – it is inside the crust of Earth! This is the deep biosphere and we basically learned that it exists yesterday. Its volume is at least twice as large as all the Earth’s oceans, home to more microbes than the rest of the entire planet.Their total biomass is more than 20 times greater than all humans, livestock, and animal wildlife. Let’s descend into this mad, deadly world where none of the rules we thought are mandatory for life apply.

12 min

17

Tired of Doomscrolling?

Being a human in the 21st century often feels frustrating. We are clearly at the high point of our species, while at the same time life is incredibly hard! We are divided, unable to solve our problems while creating new ones, destroying our world in the process. In many ways the vibe is that we live in dark times. But as Terry Pratchett said, we are the storytelling ape, we think in narratives and live in a network of stories that make up our world. So without minimizing the darkness, we want to add a story that we find helpful for dealing with the world.

11 min

18

We Fell For The Oldest Lie On The Internet

“Your blood vessels stretch a staggering 100,000 kilometers, enough to wrap around Earth twice!" Sounds amazing, right? We spent over a year trying to confirm this claim, and let's just say – things aren't as they seem. Join us on our year-long journey that uncovered outdated science, speculation, and a lot of dead ends.

13 min

19

The Most Insane Weapon You Never Heard About

At the height of the Cold War, a terrifying concept emerged: a bomb so powerful it wouldn’t need to be dropped. Known as Project Sundial, this doomsday device would have left a 400-km radius in flames and plunged the world into darkness. It was a bomb that would destroy everything – not a weapon, but an apocalypse. How close did we come to pressing the button?

14 min

20

We Have To Talk About Weed

Cannabis is finally being decriminalized in more and more places around the world. And for very good reasons! Compared to other legal drugs such as alcohol, cannabis is pretty mild and most users enjoy it without issue. But there’s a dark side for some. So let’s take an honest look at some of the latest research together.

15 min

21

Vaping Is Too Good To Be True

Vaping is marketed as the “safe” alternative to smoking, but it’s far from being harmless. Unregulated ingredients, hidden toxins, and extreme nicotine levels mean we’re conducting a massive experiment on ourselves. Let’s dive into what we know – and what we don’t know, yet.

14 min

22

Black Hole's Evil Twin - Gravastars Explained

Gravastars could change how we think about the universe. These cosmic objects solve black holes’ biggest problems without breaking physics. From their ultra-thin shell to their energy-filled core, gravastars are both elegant and terrifying. But what exactly are they?

14 min

23

Is The World Getting More Violent?

Ten years ago, in 2014, we released a video titled "Is War Over?". Back then, the question didn’t seem so naive. It seemed violent conflict was on the decline and the world more peaceful than ever. But the last ten years weren’t what we expected. So let's see how our video has held up.

13 min

24

The Real Reason Why You Have Allergies

Allergies are more than just overreactions – they might be an evolutionary relic from a time when worms invaded our bodies daily.

15 min