Guide

What if ... the glass was suddenly really half empty?

19/6/2025

Translation: machine translated

I've never asked myself physics questions like this before. Nevertheless, I love Randall Munroe's answers, which are scientifically sound and decorated with comics. After all, they only lead to doom in the subjunctive.

Physics is divisive. I'm not thinking of atoms, but of school classes. On the one hand, there are the few who have everything figured out and are excited to discover the world and its connections. On the other, the many who break out in a cold sweat at the mere sight of formulae and endure the lessons. Physics came into my life in the form of a man in white with a crown of hair, a syllabus and lots of chalk. Initially motivated, I was soon more interested in looking out of the window.

Now, decades later, I sometimes regret that. Because everything is physics. And physics can be anything. Even downright funny! Randall Munroe proves this with his books. I really like the man because he swapped a career at NASA for stick figures and scientific answers to absurd questions. No matter what your relationship to science is - they are absolutely worth reading.

Non-fiction

What if? 2 - Was wäre wenn?

German, Randall Munroe, 2022

Reference books

What if? Was wäre wenn?

German, Randall Munroe, 2020

Non-fiction

HOW TO - Wie man's hinkriegt

German, Randall Munroe, 2019

Non-fiction

What if? 2 - Was wäre wenn?

Reference books

What if? Was wäre wenn?

Non-fiction

HOW TO - Wie man's hinkriegt

Munroe is the creator of the webcomic xkcd and not only has a talent for getting to the heart of things with just a few strokes. He also throws himself into the absurd questions of his audience with holy seriousness. In his search for answers, he thinks them through so consistently that even as a seventh-grader I would have been interested. The physical deductions are just as apt as Munroe's humour. After all, anything goes in the subjunctive - and the human brain has reserved a large area for absurd knowledge. Three examples of why the disclaimer «do not try any of this at home» should only be taken seriously to a limited extent. What if ...

... the earth suddenly stopped rotating?

The important point here is that the atmosphere would maintain its speed. The short answer (pretty much everyone would die) is unsurprising. Rather Munroe's realisation that only then does it get interesting. Unfortunately, not for the 85 per cent of the world's population who live between the northern and southern 42nd parallel and would be wiped out by a gigantic storm and its consequences, which he reveals one by one. At the start of the disaster, there would perhaps be a few people left at a research station at the South Pole - who could then search for Munroe's video explanation on YouTube. Spoiler: It's not getting any better any time soon.

Shortly summarised: Further inconveniences would be the days and nights, each six months long, leading to new convection storms on the day side and freezing cold on the night side. Until the good old moon comes to the rescue: It still orbits the earth in this model. While in reality it moves 3.8 centimetres away from the Earth every year, it would now slowly come closer to the stationary Earth until it starts to rotate again. All's well that ends well, but everything is broken.

... a glass would really be half empty?

One tends to see the opportunities, the other always sees the risks - and we all know the glass question that literally separates the pessimists from the optimists. One thing is certain: both contain the word «Mist». And crap happens quickly when Munroe reaches for the pen to replace the air in the glass with a vacuum. The world doesn't end here. But the physicist prefers to hide under the table while the Optis and Pessis argue.

Most people could probably at least agree on which half of the glass is full and which is empty. Munroe also takes this question to the extreme and shows that broken glass does not usually bring happiness. At least not if the optimist is too close to the glass.

... everyone would point a laser pointer at the moon?

Would it change colour and glow green or red (humanity would still have to agree on the colour)? Of course, the quick answer is not enough for Munroe. Some of the light would arrive, but even billions of these things wouldn't be able to do anything against the sunlight. How boring. More power is needed. What if the world's population were to use the focussed light from searchlights or IMAX projectors with 30,000 watt lamps? After all, that would bring the first small successes. And it's just the prelude to the big, apocalyptic cinema in Munroe's head.

With billions of military megawatt lasers, the brightness of the sun could finally be achieved. With the planet's remaining oil reserves and even more power, we could outshine it for two minutes and make the moon glow. A complete success, which is only the preliminary stage for finally turning the Earth's satellite into a lump of plasma. It's admirable how much energy Munroe puts into his thought experiments.

He has found so many fans with his comics over the years that an asteroid was named after him. How fitting. For me, his books are a great mixture of nonsense and knowledge that the world doesn't need at first glance. At second glance, they help us to understand connections and see things with different eyes.

It turns out that trying to answer a silly question thoroughly can lead you to some pretty interesting places.

Randall Munroe

How nice that he takes people like me with him. Not only do I now know how many printers I would need to print out all the Wikipedia updates. But also how to make knowledge stick better.

Header image: Screenshot Youtube/@xkcd_whatif

24 people like this article

Michael Restin

Senior Editor

Michael.Restin@digitecgalaxus.ch

Simple writer and dad of two who likes to be on the move, wading through everyday family life. Juggling several balls, I'll occasionally drop one. It could be a ball, or a remark. Or both.

Guide

Practical solutions for everyday problems with technology, household hacks and much more.

Show all

These articles might also interest you

Guide
Magic Words: What to Say to Get Your Way
by Anna Sandner
Background information
First world problems: when children don’t know what to wish for
by Michael Restin
Background information
My residual love for analogue
by Reto Hunziker