Field
Physics & Chemistry
Matter, energy, the cosmos and chemical phenomena.
3 Ideas · 9 questions
Physics studies matter, energy, space and time, from tiny bubbles to the whole universe. Some of its best questions start with something everyone can see. Why is the sky dark at night? Why can sound in water make light?
The pieces here begin with such a question and follow the reasoning step by step. They say what physicists have measured, what they still debate, and where a popular story goes further than the evidence.
Start with Olbers’ paradox. The dark night sky turns out to tell us that the universe has a finite age. Sonoluminescence shows a small and strange effect that is still not fully explained. The fine-tuned universe asks why the constants of nature seem to allow life, and why physicists and philosophers answer that question so differently.
Start here
The best first reads in this field, in this order.
IdeaIntro
Why Is the Night Sky Dark? Olbers' Paradox, Explained
For four hundred years a dark night sky was one of the hardest puzzles in astronomy. You learn why that darkness is a real surprise, which simple fact about time explains it, and why the most common explanations fail. You also pick up a habit for testing claims: ask what you should already see if they were true.
6 min read≈ 1,350 words3 questions
IdeaIntermediate
What Is Sonoluminescence?
Play a loud, very high tone into a flask of water, and a tiny point of light can appear in the dark. You learn how sound turns into light during one cycle of a single bubble and why a small shrimp does the same in the sea. You also learn what physicists still cannot explain about it.
7 min read≈ 1,500 words3 questions
IdeaIntermediate
Why Does the Universe Seem Fine-Tuned for Life?
When hydrogen fuses into helium inside the Sun, about 0.7 percent of its mass turns into energy. You learn why physicists say life depends on numbers like this one, and how the anthropic principle, the multiverse and the idea of a designer each try to explain it. You also learn the strongest doubts about the whole argument, and a habit of thought that helps far beyond physics.
7 min read≈ 1,520 words3 questions