Could aliens destroy us from light years away? Another day at Kurzgesagt Labs, where we answer the most important questions with science. Today: how might civilizations wage war across light years? What kind of devastating weapons could they use and what would they look like?

A breathtaking scientific revolution is taking place – biotechnology has been progressing at stunning speed, giving us the tools to eventually gain control over biology. On the one hand solving the deadliest diseases while also creating viruses more dangerous than nuclear bombs, able to devastate humanity. What is going on?

In 2022 nearly half of Americans expected a civil war in the next few years, one in five now believes political violence is justified. And it is not just the US but around the world. People increasingly see themselves as part of opposing teams. There are many different reasons for this, but one gets blamed a lot: social media. Social media divides us, makes us more extreme and less empathetic, it riles us up or sucks us into doom scrolling, making us stressed and depressed. It feels like we need to touch grass and escape to the real world. New research shows that we might have largely misinterpreted why this is the case. It turns out that the social media internet may uniquely undermine the way our brains work but not in the way you think.

Life has existed on one planet for about 4 billion years, for all we know. But it might have started right after the Big Bang, when the universe was much stranger and more fantastic than today. A universe that might have allowed life to develop absolutely anywhere. The cosmos might be full of the seeds of life, sleeping in a dead desert, waiting for a few drops of rain to explosively bloom and grow. Tiny and not so tiny aliens might be everywhere.

Few of the monsters that evolution created have been so successful at hurting us as the variola virus, responsible for smallpox. The carnage it caused was so terrible and merciless that it compelled humankind, for the first time, to act truly globally. It was one of the greatest wins of our species over the ancient powers of nature, all made possible by… cows.

An undead city under siege, soldiers and police ruthlessly shooting down waves of zombies that flood from infected streets, trying to escape and infect more cities. This is what happens when your body fights cancer, more exciting than any movie. How does this battle for survival unfold?

Somewhere in your body, your immune system just quietly killed one of your own cells, stopping it from becoming cancer, and saving your life. It does that all the time. The vast majority of cancer cells you develop will be killed without you ever noticing. Which is an incredibly hard job because of what cancer cells are: parts of yourself that start to behave as individuals even if it hurts you. What is cancer and how does your body kill it all the time?

Mr. President! Nuclear missiles will strike our country in 14 minutes. I know it’s your first day in office so I’m going to walk you through it, but you’re the only one who can authorize our nuclear retaliation in response and you’ve only got a few minutes to make a decision!

Black holes can destroy everything – but can they be destroyed? What happens if we push physics to the absolute limits, maybe even break it and the universe in the process? Let’s create a tiny black hole, about the mass of our moon, in the Kurzgesagt Labs and try to rip it apart.

Every two years one million Japanese disappear, China’s population will halve by the end of the century, the median age in Italy has reached 48. All around the world birth rates are crashing – Is humanity dying out? What is going on and how bad is it?

The universe is going to die one day, and a fight between two titans will decide our cosmic fate. On one side of this galactic battlefield, we have all the matter in the universe; on the other side, empty space infused with dark energy. Whoever wins will kill the universe in fun ways. But who will that be? We're looking at three possible ways to destroy the universe in our newest video.

You are in the middle of everything in the Universe. Let us go on a fantastical journey together - to the impossibly small and the incomprehensibly large!

There is this idea floating around that what doesn’t kill you, makes you stronger. That surviving a disease leaves you better off. And it seems to make sense because we have all experienced this. When you go through hardship, often you come out more resilient, more ready to face a difficult situation in the future. But it turns out that sometimes, what doesn’t kill you makes you weaker. So, what happens when you get sick?

You are cells. Your muscles, organs, skin and hair. They are in your blood and in your bones. Cells are biological robots. They don’t want anything, they don’t feel anything. They are never sad or happy. They just are, right here, right now. They are as conscious as a stone or a chair or a neutron star. Cells just follow their programming that has been evolving and changing for billions of years, molded by natural selection. They are impossible machines and yet, here they are, driven entirely by the fundamental forces of the universe. The smallest unit of life, right at the border where physics becomes biology. Sometimes, to get a truer understanding of how amazing something is, you need to hold your breath and dive in really deep. So, what are cells and how do they work?

The universe isn't just a vast empty ocean sprinkled with galaxies – most of the atoms are actually drifting in between, in the intergalactic medium. If we look closely, we can see who is in charge here: Quasars, the single most powerful objects in existence. As small as a grain of sand compared to the amazon river, they reside in the centers of some galaxies, shining with the power of a trillion stars, blasting out huge jets of matter, completely reshaping the cosmos around them. They are so powerful that they can kill a galaxy. What are they, and how do they mold the structure of the universe at their whim?

The universe is magnificent and vast. Hundreds of billions of galaxies, trillions of stars, and even more planets. If even the tiniest fraction are habitable, then the Universe should be teeming with life. And yet we see nothing, only vast emptiness. Where is everyone else? The answer to this riddle could be as exciting as it is creepy: we are early, born before almost all other life – but very soon this may change. Not only might aliens appear, they could quickly surround us. An irreversible competition for the universe might be about to begin.

The universe today is happy and healthy, with exciting things going on – but at some point the night will turn dark. Everything that once was, will peacefully sleep forever. But what is the last thing that will ever happen? Let's travel to the end of the universe…

Absolutely everything you think about yourself and the universe could be an illusion. As far as you know, you are real and exist in a universe that was born 14 billion years ago and that gave rise to galaxies, stars, the Earth, and finally you. Except, maybe not.

Earth is 4.5 billion years old - which is approximately the same amount of time it took us to create this video. We’ve scaled the complete timeline of our Earth’s life into our first animated movie! Every second shows about a million years of the planet’s evolution. Hop on a musical train ride and experience how long a billion years really is. It’s the perfect background for your next party, a great way to take a break from studying, or a fascinating companion while you’re on the go … and our celebration of 10 years of kurzgesagt.

In 2023, Kurzgesagt has existed for 10 years (which is insanely long in internet years). We are among the largest sciencey channels on Youtube and still a bit of a black box to people. So let us talk about ourselves in three parts: Our backstory, how we finance our work, and the values of Kurzgesagt!

Your tattoos are inside your immune system, literally. With each very tasteful piece of art, you kick start a drama with millions of deaths, grand sacrifices and your immune system stepping in to protect you from yourself. Let us get under your skin with our newest video.