Measuring black holes by their shadows

The story of diameter

Chapter 1

The math of the middle

Chapter 2

Sizing up the cosmos

Chapter 3

Engineering the everyday

YOUR GOAL

Master of The story of diameter

Ch 2 · Sizing up the cosmos

hue Cosmic Diameters

Our diameter is ninety-three billion light-years, and space is still stretching out!

hue The giant waistline of Earth

The moon illusion in the sky

hue The moon's apparent size, known as its angular diameter, remains constant despite looking larger near the horizon.

How we weigh the stars

hue Astronomers calculate the physical diameter of distant stars by measuring their brightness and temperature.

Wide Wide Space -> The Wide Universe).
* Cosmic S

BETA

hue Sort cosmic objects by diameter to discover the true scale of the universe.

Fun Fact

Cosmic scale: The Sun's diameter is so massive that about 109 Earths could fit lined up side-by-side across its face.

Gossip

Which planet would you most want to visit if size didn't matter?

Quiz

In 2019, scientists imaged the shadow of a black hole in which galaxy to find its diameter?

hue How we weigh the stars

Quiz

What physical property of a star must astronomers combine with temperature to calculate its diameter?

hue Measuring black holes by their shadows

Quiz

What term do astronomers use to describe how big an object looks in the night sky?

hue The moon illusion in the sky

Quiz

What is the approximate equatorial diameter of planet Earth?

Quiz

Which planet in our solar system has the largest physical diameter?

Quiz

What is the angular diameter of both the Sun and the Moon as seen from Earth?

Quiz

Why is Earth's equatorial diameter larger than its polar diameter?

Quiz

Approximately how many Earths could fit side-by-side across the diameter of the Sun?