What is a light year? Bill Nye explains

(CNN) Whatever the James Webb Space Telescope, the Hubble Space Telescope, or our other space exploration instruments discover next, it’s likely to be several light years away.

But how far is a light year away – really? The circumference of our planet is 24,873.6 miles (40,030.2 km) and our planet is 93 million miles (149.6 million km) from the Sun.

A light year is much more than that – it’s the distance light travels in one year, and it is 5.88 trillion miles (9.46 trillion km).

At just one light-year from Earth, it’s mind-bogglingly far away. CNN spoke to an educator and science engineer Bill Nye To try to understand the magnitude of the universe and how we measure it.

This conversation has been lightly edited and condensed for clarity.



Bill Nye arrives at the Los Angeles premiere of National Geographic’s “Cosmos: Possible Worlds” at Royce Hall, UCLA, on February 26, 2020.

CNN: What is a light year?

Bill Nye: A light year is the distance a ray of light travels in a year – (more than) 5.88 trillion miles. When scientists or astronomers use the acronym “light,” what we mean is the speed of light for a year. If you drive 60 mph for an hour, you will travel 60 miles.

Now, don’t come running to me about “I can’t do algebra, I hated math. Bill Nye, you bad guy.” No – distance is the rate (speed of light) times time (years). It’s a long way! And what has 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.

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

flute: There is a lot of space in the space. It’s vast, and you have people like us trying to make sense of it. Astronomers wanted manageable units of measurement. Writing millions and millions or billions and billions of miles and kilometers is very difficult! You start getting zero, after zero, after zero, after zero — just lots of zeros, and you lose track. After that, these spaces start to have less meaning. Space becomes more difficult to understand.

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

Since space is gigantic and celestial bodies are so far away from each other, it can take some time for the light from these bodies to reach each other. The Sun is 8.3 light-minutes away from Earth, which means if you look at the Sun – please don’t – you see it as it was 8.3 minutes ago.

according to NASAIf you were to make the journey from the sun to the edge of our solar system, it would take about 1.87 years at the speed of light. But to get to the nearest neighboring galaxy at the speed of light, andromeda, It will take 2.5 million years. This does not cover a fraction of the total real estate in the universe.

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

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flute: It’s the coolest thing of all that there’s so much we don’t know! There is a lot to discover yet and the notion that we can’t know is probably wrong. Maybe there is a way to find out. Maybe there’s a way to see if we can find out or not, you know?

It’s easy to throw away huge numbers with a bunch of zeros, but it’s very difficult to really make sense of them The vastness of the universe sincerely.

CNN: When we’re talking about large numbers like millions and billions, especially in terms of light years, how can we try to visualize that size?

flute: If you can stay awake, not sleep, and count once a second—one, two, three, four—to get to a million, it will take you more than 11 days. This is staying up all night too. To get to 1 billion, it takes more than 31 years. The Earth was about three points worth a billion years. Now, you’re talking about 120 years of not taking naps, not having milkshakes, and counting for a billion. So getting to 13.7 billion, the age of the universe, is literally — and when I say literally, I mean literally — unimaginable.

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

flute: This conversation that we’re having right now (on Zoom) is based entirely on space exploration. We wouldn’t have this global communication without space technology in any way. And the storm systems sweeping through North America — we wouldn’t know about the ones that don’t have satellites and all the ground systems we’ve built to get data up and down from them.

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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 in cosmological terms—that is, what it means for the two big questions: Are we alone? And where did we come from?

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