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?

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.

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?

How will the Universe die?

So what is the difference between you and a rock? This seems like an easy, even stupid question. But even the smartest people on Earth have no idea where to draw the line between living and dead things. Which leads to mind-blowing implications. What is life after all? And is death really a thing? Let's look into it together.

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?

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.

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.

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?

Nuclear war, cat gifs and reddit? Wait, what?

The current crisis in Iraq explained in under 5 minutes.

Black holes. Lets talk about them.

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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.

The universe is unbelievably big – trillions of stars and even more planets. So… there just has to be life out there, right? But where is it? Why don’t we see any aliens? Where are they? And more importantly, what does this tell us about our own fate in this gigantic and scary universe?

A war has been raging for billions of years, killing trillions every single day, while we don’t even notice. This war involves the single deadliest being on our planet: the bacteriophage.

Today we are answering an age-old very scientific and important question: What if the moon crashes into earth? It’s more interesting and weird than you probably think. Let's start with the basics: Why isn't the Moon on its way to crash into us already?

Humans. We have been around for a while now. When we think about our past we think about ancient civilizations, the pyramids, stuff like that. But this is only a tiny, tiny part of our history.

We are trapped on Earth. Controlled by an ancient debt to the universe...

Black holes are scary things. But they also might reveal the true nature of the universe to us.

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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.

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?

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?

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.