Outer Space
When you look up at the night sky, you are looking at something so massive that our human brains struggle to even comprehend it. Outer space goes on and on, filled with billions of glowing stars, freezing comets, and swirling galaxies. Let us blast off and discover the mind-boggling scale of the cosmos!
Just How Big is the Universe?
Light! It travels at an unbelievable 300,000 kilometres per second. But space is so mind-bogglingly huge that even at that maximum speed, it still takes light over four years just to reach us from the nearest star to our solar system, Proxima Centauri!
Over 100 billion! The Milky Way is packed with an estimated 100 to 400 billion stars. And to make the scale even more incredible, our universe contains hundreds of billions of galaxies just like ours.
Put Your Instincts to the Test
Think about what you already know about the night sky. Pick an answer for each question, then see if your instincts were right.
The massive distance that light travels in one year! Because space is so enormous, measuring in kilometres would mean using too many zeros. Instead, scientists measure space by how far light can travel in 365 days.
The Sun! It looks so different from the other stars in the sky simply because we are incredibly close to it.
No, it is an optical illusion! One star in a constellation might be 10 light years away, while the star right next to it could be 1,000 light years away. They only look close together from our specific viewpoint on Earth.
Understanding the Science
Let us explore the stars, the planets, and the incredible speed of light with Bill Nye the Science Guy.
Key Concepts
Light Year
Tap to learn moreA light year is a unit of distance, not a measurement of time. It is the vast distance that light travels in one Earth year, which equals roughly 9.5 trillion kilometres!
Star
Tap to learn moreA star is a massive, glowing ball of burning gas suspended in space. Our sun is a perfectly average, medium-sized star, but there are others that are thousands of times larger.
Constellation
Tap to learn moreA constellation is a pattern of stars in the night sky. Because the Earth is round, people in the Northern Hemisphere see entirely different constellations than people in the Southern Hemisphere.
Asteroid
Tap to learn moreAn asteroid is a large, rocky object floating in space. Millions of them orbit our sun in a giant ring called the Asteroid Belt, located between Mars and Jupiter.
Comet
Tap to learn moreA comet is a giant, dirty snowball made of rock, ice, and frozen gas. When they travel close to the sun, they heat up and leave a beautiful glowing tail across the sky.
Meteor
Tap to learn moreA meteor is a small space rock that enters the Earth's atmosphere. It travels so fast that the friction of the air makes it burn up, creating a bright streak we often call a "shooting star".
Galaxy
Tap to learn moreA galaxy is a massive collection of billions of stars, gas, and dust all held together by gravity. We live in a beautiful spiral-shaped galaxy called the Milky Way.
Expanding Universe
Tap to learn moreThe universe is getting larger every single second! Scientists know this because they can use telescopes to measure that distant galaxies are slowly moving further and further apart from one another.
Try It: Interactive 3D Constellation Viewer
We see the "Big Dipper" flat against our night sky, but the stars are actually scattered deep into space! Use the yellow slider to rotate your viewing angle and watch the optical illusion completely break apart.
Apply Your Knowledge
Let us see if you can classify these massive objects found in outer space.
Match the Concepts
Click an object to select it, then click the matching description to place it.
Real-World Challenge
Imagine you are tasked with designing a message to send out into deep space for alien life to find. Because they do not speak English, how would you use mathematics and science to explain where the Earth is located in our solar system?
What Has Changed Since This Episode Aired
This episode first aired in 1994. Since then, we have launched incredible new telescopes and discovered things that completely changed our understanding of the cosmos!
Updated: Yes! Thanks to highly advanced satellite measurements of ancient cosmic light, we now know the universe is closer to 13.8 billion years old. While it might still be refined slightly, as our tools get better, our answers become incredibly precise.
Updated: We have launched the magnificent James Webb Space Telescope! Using infrared technology, this massive golden mirror can peer directly through thick space dust to see the very first galaxies that formed right after the Big Bang.
Updated: We have discovered over 6,000 confirmed "exoplanets" orbiting distant stars! Some are gas giants like Jupiter, while others are rocky worlds that might even contain liquid water.
Updated: As telescopes improved, scientists found many other icy bodies out near Pluto. To keep things organised properly, astronomers created a brand new category. Today, Pluto has been reclassified as a "dwarf planet".
Updated: Sadly, the Arecibo telescope suffered a structural failure and collapsed in 2020. However, its incredible legacy lives on as new, even larger arrays (like the FAST telescope in China) continue the vital work of mapping the universe using radio waves.
Test Your Understanding
Answer these questions and get instant feedback. How many can you get right?
Results
Your score:
Reflection
Science is always improving, and the things we know about the universe change as we build better tools. What is one mysterious thing about outer space that you hope scientists figure out during your lifetime?
Episode Discussion
Share your thoughts on this Bill Nye episode