Are we alone in this universe?

Here are 5 things about the universe that still blow my mind:

1. You're made of dead stars.

Every heavy element in your body — the iron in your blood, the calcium in your bones — was forged inside a star that exploded billions of years ago. You are literally stardust.

2. The observable universe is 93 billion light-years across... and still expanding.

The universe is 13.8 billion years old, but because space itself has been stretching, the farthest things we can see are now 46.5 billion light-years away in every direction.

3. There's a black hole 40 billion times the mass of the Sun.

TON 618 is one of the most massive black holes ever discovered. Its event horizon is larger than our entire solar system.

4. 95% of the universe is invisible.

Everything we can see — every star, planet, and galaxy — is only about 5% of what exists. The rest is dark matter and dark energy, and we barely understand either.

5. Neutron stars are so dense that a teaspoon weighs 6 billion tons.

When massive stars collapse, they compress into city-sized objects where atomic nuclei are crushed together. The result is the densest observable matter in the universe.

If stuff like this fascinates you, I built a full course breaking down the universe from our solar system to the Big Bang. No PhD required — just curiosity.