The availability heuristic: we overestimate the probability of events we can easily recall (plane crashes, shark attacks) and underestimate common risks (car accidents, heart disease). Media exposure literally distorts risk perception. Knowing this does not fully fix it.

Every pop song you love probably uses I-V-vi-IV (C-G-Am-F in C major). The circle of fifths explains why: these chords share the most common tones. Once you see it, you hear it everywhere. Ignorance was bliss.

Before worrying about growth, make sure your unit economics work. If it costs $50 to acquire a customer who generates $30 in lifetime value, scaling just means losing money faster. CAC < LTV is the most important inequality in business.

The Baroque, in 3 pages (PDF). 📄

Growth-rates reference (PDF) — tap expand to read. 📄

The only universal principle in strength training: progressively increase the demand. More weight, more reps, more sets, shorter rest, better ROM, or slower tempo all count. The body adapts to exactly what you ask of it. Nothing more.

Static stretching before exercise does NOT prevent injuries. Meta-analyses consistently show this. Dynamic warmups (leg swings, arm circles, bodyweight squats) prepare muscles better. Save static stretching for after.

Best framework for industry analysis after 40+ years. Supplier power, buyer power, threat of substitutes, threat of new entrants, competitive rivalry. Most startup pitches only address rivalry. The other four forces kill more companies.

$e^{i\pi} + 1 = 0$. Five fundamental constants connected by three basic operations. Feynman called it "the most remarkable formula in mathematics." What makes it deep is not the beauty. It falls out naturally from the Taylor series of $e^x$ when you plug in $ix$. Beauty as a consequence, not a goal.

"She was sad" vs "She traced the rim of her cold coffee, untouched for an hour, and watched the rain streak patterns on the window that looked like the tears she wouldn't let fall." Same emotion. Completely different impact.

Salt meat 45+ minutes before cooking (moisture gets drawn out, then reabsorbed with flavor) or right before (surface only). Salting 5-15 minutes before is the worst window. Moisture on the surface prevents browning.

"It was a bright cold day in April, and the clocks were striking thirteen." Orwell tells you EVERYTHING about his world in one sentence. Try this: write a first line that tells the reader something is wrong without stating it explicitly. Post yours below.

The Maillard reaction needs amino acids + reducing sugars + heat above 140°C. Caramelization is a different process (sugars only, higher temp). This is why you need a DRY surface and HIGH heat for a good sear. Moisture keeps the temperature at 100°C. No browning.

Read the entire passage FIRST without looking at questions. Write a one sentence summary. Then tackle each question. It feels slower but you stop re-reading everything four times. Saved me about 40% of my CARS time.

Fast loop: atmosphere ↔ biosphere (years to decades). Slow loop: atmosphere ↔ lithosphere (millions of years). Fossil fuels short-circuit the slow loop. We are releasing carbon that took millions of years to store in just decades. That is the whole problem.

If the main clause expresses Wishes, Emotions, Impersonal expressions, Recommendations, Doubt, or Denial (WEIRD), use subjunctive. Quiero que vengas. Es importante que estudies. This covers 80% of cases. You are welcome.

Sartre: existence precedes essence. You are not born with a purpose, you create it. Sounds liberating until you realize you cannot blame your nature, upbringing, or circumstances. You are "condemned to be free." Camus took it further: the universe is absurd, and the proper response is to embrace it anyway.

Hot take: $\tau = r \times F$ (torque) deserves more love. It bridges rotational and linear mechanics, and once you see a seesaw problem through that lens, angular momentum clicks immediately. Try it on your next problem set.

Hot take: Dijkstra is over-taught and Bellman-Ford is under-taught. Yes, Dijkstra is faster. But Bellman-Ford handles negative edges and the relaxation concept is foundational for understanding DP on graphs. Your move, textbooks.

90% of the mechanics mistakes I see in this group vanish if you draw the FBD first. No shortcuts, no 'I can see it in my head'. Forces you don't draw are forces you'll forget.

Not about saving cute animals. Ecosystem services (pollination, water purification, soil fertility, disease regulation) depend on species interactions. Lose the keystone species and the network collapses. See: wolves in Yellowstone.

Biggest jump of my prep (124→128): after every paragraph write a 5-word main-point note in the margin. It forces active reading and gives you a map to answer from. Highlighting is passive; it feels productive and isn't.