Welcome to the Universe summary

There it is, the sun!

From Earth, it might appear as yellow, but in reality, it’s radiating roughly equal amounts of all the visible colors, which instead gives us white light, not yellow. But burning away somewhere around 6,000 degrees K – it’s quite a bit hotter than your normal white flame.

The enriched gases that explode from a star after its life has ended can eventually form into balls of solid matter containing elements like oxygen, silicon, and iron. In other words: terrestrial planets. In our solar system, we have nine – shoot – I mean, eight planets . . . I’ll get to that miscount momentarily. But first, look outside your windows and you’ll find yourselves passing the first family of planets that our wonderful solar system has to offer.

Those would be Mercury, Venus, Earth, and Mars. All of them are small and rocky objects that orbit the sun. They certainly have many differences, but they’re still closer to each other than they are to anything else in the solar system.

As we start to head outside of our own solar system, you’ll notice that everywhere you turn the sky is full of bright, shining stars.

It’s very likely that you have quite a few misconceptions about them, though. For example, you’ve probably heard it repeated that the North Star –⁠ Polaris –⁠ is the brightest in the sky. That’s actually incorrect. In fact, Polaris isn’t even in the top ten . . . or 20 . . . or 30 brightest stars. It comes in at a lowly 45th place. The brightest is actually Sirius, otherwise known as the Dog Star.

As we begin to dart through the Milky Way galaxy, you’ll notice stars aren’t lone wolves. Instead, they form in clusters.

Some clusters contain just a few hundred stars. In that case, we call them open clusters. Others have hundreds of thousands of stars, in which case we call them globular clusters. In both cases, the stars in any given cluster share a birthday –⁠ they all formed from a gas cloud at the same time.

Objects so massive that not even light can escape them –⁠ these are what lie at the center of galaxies. We’re talking, of course, about black holes.

At the very center of every large galaxy with a significant bulge, there lies a supermassive black hole. That includes the Milky Way. But actually, in comparison, ours is kind of on the wimpy side. Our black hole has a mass of just 4 million suns, while others are worth several billion suns.

If you recall, we dipped our toes into the topic of the big bang earlier on our tour. We briefly discussed the explosion of matter that resulted in the universe we know today –⁠ a universe that will die when all its energy has been used up.

The big bang model makes several predictions. As scientists, we compare those predictions with what we observe. The results we find show us how accurate the predictions are. And so far, the big bang model has passed every test we’ve thrown at it.

Time travel as depicted in most science fiction has one major flaw. In order to return to the past via a time machine, according to Einstein, a time traveler must be able to exceed the speed of light. But we know that traveling faster than light is physically impossible.

However, nothing says you can’t take a shortcut to beat light to the finish line. There are two ways of doing that: going through a wormhole or around a cosmic string.

We’ve been exploring the universe for a while now. How’s everyone feeling?

By this point, you have a solid grasp of the physical material that makes up the universe, as well as some more theoretical concepts. But we’ve saved the best for last: the question of whether there is intelligent life in the universe aside from humanity.

The key message in this Blink is:

The universe is so much bigger, hotter, denser, and weirder than we typically realize. It can be easy to convince ourselves that Earth is somehow special, but in reality, we and our planet occupy a corner of space that’s not much different from any other. Stars, planets, galaxies, black holes, wormholes –⁠ these are just a few of the things that exist, or may exist, in the vast expanse of the universe. And as we grow along with our universe, we continue to discover new things about space, time, and our very existence every day.