Bill Nye explains light-years and the vastness of the universe

By Danya Gainor, CNN

No matter what the James Webb Space Telescope, Hubble Space Telescope or our other tools of space exploration discover next, it’s likely to be located many light-years away.

But how far away is a light-year — really? Our planet’s circumference is 24,873.6 miles (40,030.2 kilometers) and our planet is 93 million miles (149.6 million kilometers) from the sun.

A light-year is so much more — it’s the distance light travels in one year, which is 5.88 trillion miles (9.46 trillion kilometers).

Just one light-year away from Earth is mind-boggling far away. CNN talked to science educator and engineer Bill Nye to attempt to understand the enormity of the universe and how we measure it.

This conversation has been lightly edited and condensed for clarity.

CNN: What is a light-year?

Bill Nye: A light-year is how far a beam of light travels in a year — (over) 5.88 trillion miles. When scientists or astronomers use the shorthand “light,” what we mean is the speed of light for a year. If you’re driving 60 miles per hour for an hour, you’ll go 60 miles.

Now, don’t come running to me about “I can’t do algebra, I hated math. Bill Nye, you’re an evil man.” No — the distance is rate (speed of light) times time (a year). It’s a long way! And, what’s been discovered recently with the James Webb Space Telescope is that we are — as far as we can tell — looking at the light that came from the other side of the universe after the Big Bang.

CNN: Why does outer space have a unique unit of measurement?

Nye: There is a lot of space in space. It’s vast, and you’ve got people like us trying to understand it. Astronomers wanted units of measurement that were manageable. Writing millions and millions or billions and billions of miles and kilometers is very difficult! You start to end up with zero, after zero, after zero, after zero — just a lot of zeros, and you lose track. Then, these distances start to have even less meaning. Space becomes even more difficult to understand.

Like Earth years, a light-year can be broken down into smaller units like a light day, hour, minute, etc. In a light-minute, light travels 11,160,000 miles.

Since space is ginormous and celestial objects are so far from one another, light from these objects can take a while to reach each other. The sun is 8.3 light-minutes away from Earth, meaning if you were to look at the sun — please don’t — you’re seeing it as it was 8.3 minutes ago.

According to NASA, if you were to take a trip from the sun to the edge of our solar system, it would take approximately 1.87 years at light speed. But to get to our nearest neighboring galaxy at light speed, Andromeda, it would take 2.5 million years. That doesn’t cover a fraction of the universe’s total real estate.

CNN: Is it frustrating to think about objects in the universe that are so far away from us we may never be able to study them?

Nye: It is the coolest thing ever that there’s so much we don’t know! There’s so much out there yet to discover and perhaps the idea that we can’t know is wrong. Maybe there is a way to know. Maybe there is a way to know whether or not we can know, you know?

It is easy to throw around huge numbers with a bunch of zeros, but it is much harder to grasp the reality of the universe’s vastness sincerely.

CNN: When we talk about substantial numbers like millions and billions, especially in terms of light-years, how can we try to visualize that magnitude?

Nye: If you could stay awake, no sleeping, and count once per second — one, two, three, four — to get to one million, it would take you well over 11 days. That’s staying up the whole night, too. To get to one billion, that takes more than 31 years. Life on Earth has been around three point something billion years. Now, you’re talking 120 years of not taking a nap, no milkshakes, and counting to get (around 3.7) billion. So, getting to 13.7 billion, the age of the universe, is literally — and I when I say literally, I mean literally — unimaginable.

CNN: Why is it important to understand the meaning of a light-year, and what does it tell us about space?

Nye: This conversation we’re having right now (on Zoom) is fully dependent on space exploration. No way would we have this global communication without space technology. And storm systems that sweep across North America — we wouldn’t know about those without satellites and all the ground systems that we built to get the data up and down from them.

I encourage everyone to take the time to understand what a light-year is. It’s the speed of light for a year. Also understand what it means cosmically — meaning, what it means for the two big questions: Are we alone? And where did we come from?

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Correction: A previous version of this story misstated the number of years life has existed on Earth.