The Sky Was Their Screen

Corrections and updates

Last updated: 29 September 2026

This book argues that science is a habit of checking your own answers. That has to apply to the book too.

Every printing of this book is checked again before it goes to press. When something is improved or corrected, it is listed here so readers know exactly what changed and which printing they hold.

If you have an earlier copy, nothing here changes the science you can do with it. The activities, the sky map and the methods all stand.

Third printing

Late September 2026

Page 6A note for readers south of the equator

The shadow-stick activity works identically in both hemispheres, but nothing on the page said so. Readers in Australia, New Zealand and southern Africa now get that confirmed, along with the one thing that looks different from there.

Added

South of the equator — Sydney, Cape Town? Nothing changes. The Sun still rises in the east, so your two marks still work. You will just see it cross the northern half of the sky around midday instead of the southern.

Page 6Plainer wording

The explanation used two words pitched above the book’s reading age.

Was

The Sun’s path is symmetric around noon, so two equal shadows balance around the North–South line.

Now

Morning and afternoon, the Sun climbs and falls the same way, so your two marks mirror each other across North.

Page 6The caption now tells you where to stand

Step 4 said to stand with West on your left, but never said where to stand to do it. The picture caption now completes the instruction.

Was

The Shanku Yantra (YUN-tra, an instrument) — a stick, a circle, and two marks. The whole observatory.

Now

The Shanku Yantra (YUN-tra, an instrument) — a stick, a circle, two marks. The dashes across the grass are your East–West line. Stand at the stick with the West mark on your left, and you are facing North.

Pages 90 and 92Making the Stump the Adult cards last

The blank backs of the card pages now carry a tip for readers who want to keep their cards.

Added

Want them to last? Glue this page onto a piece of cereal box first, then cut along the dotted lines.

Copyright pageIllustration credit

The illustrator is now credited by name on the copyright page, as she should have been from the first printing.

Added

Illustrations by Kavya Muniswamappa.

Second printing

Early September 2026

After the first printing I went back through the whole text looking for places where a claim was stronger than the evidence behind it, or where two pages disagreed with each other. These were corrections of wording and of dates that were more precise than the evidence allows.

Contents, chapter openers, page 10How old is the sky in Chapter 1?

Was

Lagadha dated to around 1350 BCE, on the contents page, the timeline strip in every chapter opener, and his letter on page 10.

Now

Around 1400–1100 BCE.

Why

Page 5 explains how we date the Vedanga Jyotisha — the verses place the winter solstice at the Nakshatra Shravishtha, and the solstice sat there roughly between 1400 and 1100 BCE. That method gives a range of a few centuries, not a single year. Picking 1350 out of the middle of that range implied a precision nobody has. The Scientist File on page 1 already gave the range correctly, so the book was disagreeing with itself.

The letter on page 10 is now unsigned by date, which fits its own opening line: You will never know much about me.

Page 10“The Sun still turns at Shravishtha”

Was

Lagadha’s letter told the reader the Sun still turns at Shravishtha.

Now

The Sun no longer turns where he watched it turn.

Why

This one contradicted the book’s own best piece of reasoning. The solstice has moved off Shravishtha — that shift is exactly how we date his verses. The corrected line keeps what has lasted (the 27 stations, the stick) and admits what has not.

Page 12Aryabhata and the spinning Earth

Was

He wrote down something no book we still have had dared to argue before him.

Now

He wrote down something almost no one was willing to argue.

Why

Greek thinkers had raised the idea of a turning Earth earlier, and those accounts do survive. The Stump the Adult card at the back of the book said so correctly; page 12 did not. What makes Aryabhata remarkable is not that he was first to the thought, but that he built a working astronomy on it and made the numbers answer to it. That is the better story, and it is the true one.

Page 40The Five Wanderers diagram

Was

Headed As they mapped it, with the note that every wanderer laps the Earth.

Now

Headed As we map it today, with every wanderer circling the Sun, and the Sun placed at the centre of the orbit rings.

Why

The diagram uses the lap times we measure now, and the artwork shows a Sun-centred system. Labelling it as the ancient model was simply wrong. What the page teaches — farther out means slower, and Mercury and Venus never stray far from the Sun — was right all along.

Pages 3, 4, 52 and the copyright pageSmaller wording changes

• Page 3 — “A solar year is 366 days” is now “Their solar year was 366 days.” The 366-day year is the Vedanga Jyotisha’s figure, not ours, and page 7 already says a year runs about a quarter-day past 365.
• Page 4 — “After exactly five solar years” loses the “exactly.” The same panel says “back together — nearly,” which is the honest version.
• Page 52 — the description of Jupiter slowing and stopping has been rewritten. Standing on your reference line and coming to a stop against the stars are two different events, and the page merged them.
• Copyright page — the note on sources now says claims are traced to the standard scholarly editions and translations of the Sanskrit works, rather than to the Sanskrit works themselves. The sources listed on page 94 were always accurate; the summary of them overstated.