This astronomy book is very rare.

His hobby is observing celestial bodies.

Uranus is the seventh planet in the solar system.

He dreamed of ruling the world.

The sky is clear and blue, it's very beautiful.

The Emperor is the symbol of Japan.

He was staring at the horizon.

In linear algebra, the transposition of a matrix is an important operation.

When you transpose a matrix, the rows and columns are swapped.

Smallpox is a disease that caused a lot of suffering in the past.