Letters Made of Light

What this book is about

When you look at a star, you are not looking at the sky. You are looking at the past. The light left that star years, centuries, sometimes millions of years ago, and it has been travelling ever since. Looking up is the only kind of time travel anyone has ever managed.

This book was written because of an argument in a family living room. Someone said that if the Earth were destroyed, the universe would lose its balance. That sentence is the reason these seventy-three pages exist. Not to mock it — it is a completely natural thing to believe if nobody has ever shown you the scale — but to replace it with something you can actually picture.

So every enormous number in here gets turned into an object. The Sun becomes a football and the Earth a mustard seed. The distance to the next star becomes a walk. The Milky Way becomes a city, and the universe becomes a country full of cities. By the last chapter the scale is no longer a number; it is a feeling.

And then the book turns around and argues the other way. Being small in a vast universe is not the same as being worthless. That is where it lands: ছোট মানে তুচ্ছ নয় — small does not mean insignificant.

What is inside

• Light-years, and why the night sky is a photograph of the past
• The Solar System reduced to objects you can put on a table
• Stars, galaxies, and the distances between them, in things you can walk
• How we know any of this, and how we could be wrong
• Activities, a numbers table, a glossary and a quiz