Space
Welcome! I'm so excited to explore the cosmos with you. Space is a mind-blowing topic, and we're going to have a lot of fun breaking down its biggest mysteries together.
To make sure we set just the right pace and depth for our journey, could you tell me a bit about what draws you to space, and how much you already know about it?
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It is wonderful to have you here! Since you are just starting out, we will keep things simple, intuitive, and highly visual. Let's begin our journey by looking at the big picture of what we are studying and how we map out the cosmic neighborhood.
Your path
The Solar System
Stars and Stellar Evolution
Galaxies and the Universe
The Boundaries of Space
To understand astronomy, we first have to ask: where does "space" actually begin?
There is no physical ceiling in our sky. Instead, as you travel upward, Earth's atmosphere simply gets thinner and thinner until it fades away. To make things official, scientists decided on an imaginary boundary called the . Located about 100 kilometers (62 miles) above us, this is where we officially say Earth ends and outer space begins.
A vertical transition from Earth's light-blue atmosphere to the dark navy of outer space at the 100 km Kármán Line.
Once you cross that line, you enter a vast, ultra-cold vacuum. But space is far from empty! It is the ultimate stage where planets, stars, and entire galaxies interact.