If you've ever chatted with a curious child, you know how these conversations often unfold. They start by asking questions about the origins of things or how they function—an inquisitiveness that deserves encouragement. However, each answer seems to prompt another question, eventually leading you to the limits of your own understanding, or even humanity's collective knowledge. At some point, you might face inquiries about the very beginning of everything: the Big Bang. This week’s question comes from Tyler Legare, who asks:

How would you explain the Big Bang to a 10-year-old?

Although many adults struggle with grasping the concept of the Big Bang, science has provided us with a clear narrative. Here's how I would explain it to a child.

So, where does everything come from? This includes you, me, and all the planets, stars, and galaxies in the universe. This question has intrigued humanity for millennia. For ages, we relied on myths, guesses, and theories. It wasn't until about the last century that we acquired a scientific answer.

That answer is known as the Big Bang. It describes the origin of everything in our universe and is essential for understanding how the universe has evolved over time. To appreciate its significance, let’s examine what we can see in the universe today.

As we observe the Earth, we encounter a multitude of sights, sounds, smells, tastes, and textures. Everything we interact with—people, food, air, and even light—consists of matter and energy. This principle extends beyond our planet; everywhere we look in the universe, from distant galaxies to stars, we find the same fundamental components: matter and energy, built from the same basic elements found on Earth.

The complex beings we are arise from the countless ways these fundamental particles can combine. The iron in our blood, the calcium in our bones, and the sodium in our nerves are just a few examples of how these atomic building blocks can come together to form the intricate structure of our bodies.

Beyond our planet lies a vast universe filled with countless objects. Our Milky Way galaxy contains hundreds of billions of stars, each likely hosting its own planetary systems. The Milky Way is merely one of an estimated two trillion galaxies in the observable universe. Remarkably, with only a few exceptions, nearly all of these galaxies seem to be moving away from us.

This was a surprising discovery made in the 1920s. Why are most galaxies receding from us? The further away a galaxy is, the faster it appears to be moving away.

To visualize this, imagine a ball of dough filled with raisins.

When you bake raisin bread, you start with dough and raisins. As the dough rises, the raisins remain the same size, yet they seem to move farther apart from each other. If you were one of the raisins, you would observe this increasing distance as the dough expands.

In this analogy, the raisins represent galaxies, and the dough symbolizes the expanding fabric of space.

If space itself is expanding, it means the universe is growing larger, and galaxies are drifting apart over time. This implies that in the past, the universe was more compact. If we look back far enough, we can imagine a time when all the matter and energy in the universe were concentrated in a tiny area.

This is the core idea behind the Big Bang: galaxies that are unbound are moving away from each other as time progresses, indicating they were closer together in the past. If we trace this back, we can envision a time when all matter and energy were contained in a minuscule region.

The Big Bang encompasses the entire history of our universe. Everything that exists today originated billions of years ago from a small region of space that has since expanded. All the matter and energy present then still exists today, albeit more dispersed due to the universe's expansion.

The Big Bang is not merely an origin story; it's the only scientifically validated explanation for the universe's development. To fully understand it, we must consider that as the universe expands, the pure energy within it—like light or radiation—cools down, making it hotter when the universe was smaller.

In the earliest moments of the Big Bang, all the matter was compressed into a tiny space filled with intense radiation. During this time, it was impossible to create different types of atomic nuclei. Only as the universe expanded and cooled could neutral atoms form.

Eventually, the universe cooled enough to allow the formation of neutral atoms. The radiation that once disrupted atomic structures should still be detectable today. In 1964, scientists discovered this cosmic microwave background radiation, confirming the Big Bang theory.

As the universe continued to expand and cool, gravitational forces caused tiny clusters of matter to attract other clumps. Over time, these aggregates evolved into stars and galaxies, generating heavy elements and rocky planets, and ultimately giving rise to intelligent life in at least one instance.

The Big Bang has revealed how our universe came to be. It chronicled the evolution from an ultra-dense initial state to the present day. This incredible journey continues, as the universe expands even now. Scientists are particularly interested in the next great mystery: how will it all end? Perhaps you'll be the one to uncover that answer.

Send in your Ask Ethan questions to startswithabang at gmail dot com!

Starts With A Bang is now on Forbes and republished on Medium on a 7-day delay. Ethan has authored two books, Beyond The Galaxy, and Treknology: The Science of Star Trek from Tricorders to Warp Drive.