Kurzgesagt - In a Nutshell Season 13, Episode 5: Your Time Machine Broke - At The Worst Time In History

1

Alien Whales On Planet Nimbus - What Aliens Might Look Like

Humans assume aliens look human. But why would they? Let's explore what life might actually look like in strange, distant worlds.

16 min

2

This Is NOT An Anti Meat Video

Most of us love animals but also eat meat. Unfortunately, most animals we eat live in truly horrible conditions. We don’t torture them for better meat, just for cheaper meat. If we all paid just a bit more, we could avoid most animal suffering – often just for a few cents per meal. What would it truly cost us to avoid animal torture and still eat meat?

15 min

3

Why Your Brain Blinds You For 2 Hours Every Day

Reality is not real. Your world is a prediction. Every sight, sound, and touch you experience is the result of calculations your brain makes before reality even reaches you. It fills in gaps, fabricates details, and even alters time itself so you feel like you’re in control. But if everything you know is an illusion… what does that say about you? What does it mean for your choices? Is there even free will?

13 min

4

SOUTH KOREA IS OVER

South Korea is heading toward a demographic collapse unlike anything the world has seen before. With the lowest fertility rate ever recorded and a rapidly aging population, the country faces a future of economic decline, shrinking cities, cultural erosion, and a vanishing workforce. By 2060, nearly half of South Koreans could be over the age of 65, and entire regions may be abandoned as the population continues to shrink. How did South Korea reach this point? Why might it no longer be possible to reverse the trend? And what does this mean for other countries on a similar path?

15 min

5

Your Time Machine Broke - At The Worst Time In History

What happens when your time machine breaks and you end up stranded millions of years ago? You’ve landed in a world that’s nothing like today, facing deadly storms and unbearable heat, breathing toxic air. How can you survive long enough to make it back home?

12 min

6

We Finally Answered the MOST Important Question

Can jellyfish power Tokyo? What would happen if it rained bananas for a day? We're taking two of your most absurd (and brilliant) questions and answer them with real science.

11 min

7

Why Does Fentanyl Feel So Good?

Fentanyl is the deadliest illegal drug in US history by far. It’s often described as the ultimate high, but it’s actually an inferior, short-lived, and brutally addictive version of heroin. In this video, we explore what opioids do to your brain and body, what it feels like to take them, and why so many people are dying from Fentanyl overdoses without ever choosing to take it.

15 min

8

Why Is The US Dropping Billions Of Mutant Flies From The Sky?

A war has been raging for decades in the jungles of Panama, as we fight one of the most terrifying parasites on Earth. It is so relentless that our best defense is to drop 100 million radiation-blasted, flesh-eating flies from the sky – every week. It’s one of the most successful biological campaigns in history, but it’s a war we can never stop fighting… and one we can’t afford to lose.

11 min

9

The Betrayal of Autoimmune Diseases

What happens when the immune system meant to protect you becomes your worst enemy? This is the betrayal of autoimmune diseases like Type 1 diabetes, multiple sclerosis, celiac disease, lupus, Crohn’s disease, and many others. What exactly goes on in your body and why does it happen in the first place?

11 min

10

Let's Kill You a Billion Times to Make You Immortal

No matter how likely your death is, there will always be a version of you that survives. At least according to one of the most bizarre interpretations of quantum mechanics, known as Quantum Immortality. Can science prove that you are unkillable? And does this mean our reality is split into an endless number of copies?

13 min

11

Alcohol is AMAZING

Alcohol kills more people each year than wars, terrorism, homicides, and car accidents combined. It destroys bodies, relationships, and lives. Yet we toast with it at weddings, sip it at parties, and unwind with it after work. Why do we cling to something so harmful?

15 min

12

The Drug That Works TOO Well?

From study sessions to dance floors, amphetamines can feel like a shortcut to superhuman focus and energy. Why do they work so well? What happens to your body once you take them? And what toll does it take on your health?

12 min

13

The Dumbest Animal Alive

The ocean sunfish, or Mola, is one of the strangest animals alive. A massive, flat, derpy giant that eats jellyfish, drifts aimlessly, and carries parasites that even have smaller parasites of their own. Somehow, this awkward creature that feels like evolution’s inside joke doesn’t just survive in the world’s oceans… it thrives. But how? Like actually how?

11 min

14

Can Humanity Stop A Planet-Killing Asteroid?

Some killer asteroids were found only days before flyby. If they had struck Earth, the power of thousands of nuclear bombs would have flattened cities and killed millions. What if we spotted a 100-meter asteroid just two weeks before collision? Can humanity be saved?

12 min

15

Pregnancy is Insane

Pregnancy is not gentle. Babies begin as invaders, growing a brand-new organ inside another human. For months, they sap energy, hack the immune system, and fight for survival. Out of this struggle emerges the most magical thing there is: new life. This is the brutal and beautiful story of how you and all of us came to be.

13 min

16

We Found a Loophole to Survive the End of the Universe

Can we survive the heat death of the universe? One day, the last star will die, galaxies will dissolve, and black holes will evaporate. The universe becomes a cold, empty void where nothing happens. Forever. But there might be a loophole that lets life keep going.

13 min

17

AI Slop Is Killing Our Channel

AI-generated content is flooding the internet, from videos and music to news and books. On top of that, generative AI is making false information look more convincing than ever. We're entering a new era of information overload, and figuring out what's real and what's not is becoming more and more of a challenge. While AI slop is slowly changing the internet as we know it, one thing is certain: kurzgesagt videos will always remain human-made.

12 min

18

You Need To Quit Weed.

Weed is often seen as harmless, and in some cases, even helpful. But for many people, it can slowly become a serious problem, especially as they approach their twenties or thirties. Today, we take a closer look at how long-term daily use can affect your relationships, motivation, mental health, and life in general. Can it really be used safely? How easy is it for weed to turn into an addiction?

14 min

19

You're More Stressed Than Ever - Let's Change That

Stress is a biological superpower that helped your ancestors outrun predators, fight off enemies, and survive extreme situations. In the past, it helped us survive, but today, it’s quietly damaging millions of lives. What exactly is stress, how did it evolve, and is it even possible to use it in a healthy way

12 min

20

Let's Talk About Fat

Fat is not just stored energy, it’s a complex organ that controls crucial hormones and communicates with your brain, immune system, and metabolism. It's one of the most powerful organs, but it can be one of the most dangerous ones, as well. When there’s too much of it, fat can trigger inflammation, disrupt hormonal balance, increase your risk for nearly every major disease, and significantly shorten your life. What is fat really, and how does it function? When does it become dangerous and can the damage caused by excessive amounts of fat be reversed?

12 min

21

Trees Are So Weird

Trees are among the most extreme and successful forms of life on Earth. They build their bodies from thin air, move water with pressures that would crush a human, and grow using a fascinating system of living cables wrapped in layers of corpses. Under their bark lies a razor-thin strip of living cells, working endlessly to move water hundreds of meters, build indestructible wood, and coordinate millions of functions. How do trees work, and what are they even made of? What makes these ancient giants so resilient, and maybe even immortal?

13 min

22

Astronomy Is In Crisis...And It's Incredibly Exciting

Our best theory of the universe might be breaking apart! The new data we're receiving from space telescopes is creating more and more cracks in our current understanding of the universe, and some scientists believe we could be standing on the edge of the next great revolution in physics. When did the first galaxies really form? How fast does our universe really move and why are the huge cosmic voids not following the cosmic principles?

12 min

23

All Of Human History In One Hour

Modern humans have been around for around 200,000 years. With Earth being 4.5 billion years old, this might seem like only a small speck of time, yet our story is long, rich, and full of transformation. And now, we've turned the entire history of humanity into our second animated movie! From the first humans in Africa to ancient tools, art, rituals, catastrophes, and civilizations, experience all of human history in just one hour, one second at a time.

64 min

24

Tattoo Removal Is Insane

Getting a tattoo itself might be a dramatic event for your immune system, but things get even crazier when you try to remove them! From intense lasers, to shockwaves and exploding cells, laser removal is one of the most intense things your body can go through. What happens when the powerful lasers hit your skin, how do they destroy the ink, and how does your immune system clean up the aftermath of a tattoo removal?

13 min