101 Things Everyone Should Know at Least Once in Their Life

Nobody hands you a manual at 18.

You pick things up in pieces (from a parent, a rough week, a stranger on the internet) and some of those pieces turn out to be wrong. Others you never get at all. That’s how smart people end up carrying a credit card balance while their savings sit in a drawer.

This list collects 101 things worth knowing at least once. There are ten chapters, from money to history, plus a few oddities at the end. I checked the claims against sources as I went, and three famous ones (lightning, honey and neutron stars) turned out shakier than the internet admits. You’ll see the fixes flagged as we go.

Ready? Let’s start where it hurts most: your wallet.

Money Rules Nobody Taught You in School

What should everyone know about money? Three things carry most of the weight: let compound interest work for you, kill high-interest debt before you invest, and keep three to six months of expenses in cash. Get those right and the rest is detail.

1. Compound interest is the strongest force in personal finance. Use the Rule of 72: divide 72 by your annual return to estimate how many years it takes to double your money.
2. Pay off high-interest debt first. Credit card rates often hit 20% or more, which beats nearly any investment you’ll find.
3. Build an emergency fund. Aim for three to six months of essential expenses in an account you can reach fast.
4. Inflation quietly eats cash. Money sitting idle loses buying power every single year.
5. Low-cost index funds beat most actively managed funds over the long haul. Fees do most of the damage.
6. Fees compound too. A 1% annual fee can swallow a huge slice of your returns over decades.
7. Automate your saving. Pay yourself first, before the money has a chance to get spent.
8. Watch for lifestyle creep. A raise vanishes the moment your spending climbs to match it.
9. Use credit cards only if you pay the full balance. Carry one and the card starts working against you.
10. Guaranteed high returns signal a scam. If it sounds too good to be true, it is.

Scammers who chase your savings usually reach you through your phone or inbox first, which brings us to your devices.

Tech Habits That Keep You Off the Hacked List

How do you stay safe online? Use a password manager with a unique password for every account, switch on two-factor authentication, and back up your files three ways. Install updates, too. Most attacks don’t need a genius; they need you to skip the boring stuff.

11. Use a password manager and a unique password for every account.
12. Turn on two-factor authentication, ideally through an authenticator app or passkey rather than SMS texts.
13. Follow the 3-2-1 backup rule: three copies, two types of storage, one off-site or in the cloud.
14. Install software updates. Most of them are security patches in disguise.
15. Phishing runs on urgency. Check the sender, skip the link in the panicky message, and go to the site directly.
16. “The cloud” is just somebody else’s computer. Know where your data actually lives.
17. If a service is free, you’re often the product. Your data or your attention is what’s being sold.
18. AI can be confidently wrong. Verify the claims, numbers and citations that matter.
19. Restarting really does fix a lot. It clears out temporary glitches.
20. Public Wi-Fi is mostly fine for HTTPS sites, but fake hotspots exist. Skip banking on networks you don’t know.

Your gadgets aren’t the only things that need regular maintenance. You do, too.

Small Health Habits With Outsized Payoffs

What health basics matter most? Sleep seven to nine hours, move a little every day, wash your hands properly, wear sunscreen, and know your blood pressure, cholesterol and blood sugar. None of it is glamorous. All of it has decades of evidence behind it. (General information only, not medical advice.)

21. Adults need roughly 7–9 hours of sleep. It shapes your mood, immunity and memory.
22. Wash your hands with soap for about 20 seconds. It’s one of the cheapest health interventions around.
23. Daily movement beats perfection. Even moderate walking is linked to lower mortality.
24. Learn basic CPR. Hands-only compressions at 100–120 per minute can save a life.
25. Know your local emergency number and your address, so you can say both clearly under stress.
26. Wear SPF 30+ sunscreen daily if you’re outdoors. It’s your best anti-aging and skin cancer defense. Boring, I know.
27. Pale-yellow urine is a decent hydration check.
28. Food beats supplements for most people. Supplements fill specific gaps, not general ones.
29. Antibiotics don’t work on viruses. Misusing them drives antibiotic resistance.
30. Know your numbers and your family history (blood pressure, cholesterol, blood sugar) and get regular checkups.

Joking aside, if you only act on one item in this whole article, make it CPR. Everything else is nice to have. That one’s a life.

Taking care of your body is the easy half. Your head is where things get strange.

Your Brain’s Little Glitches (and How to Outsmart Them)

Why does our thinking go wrong so predictably? Because brains run on shortcuts. We favor evidence that agrees with us, feel losses more than gains, and cling to the first number we hear. Knowing the shortcuts won’t make you immune, but it gives you a fighting chance to catch them.

31. Confirmation bias: we hunt for evidence that backs up what we already believe.
32. Hedonic adaptation: we get used to upgrades fast, so more stuff rarely buys lasting happiness.
33. Sunk cost fallacy: what you’ve already spent shouldn’t steer what you do next. Ask what’s best from here.
34. Memory is reconstructive, not a recording. Vivid memories can still be wrong.
35. The spotlight effect: people notice your flaws and slip-ups far less than you imagine.
36. Habits run on cue, routine, reward. Change the cue or the reward and the habit shifts.
37. Loss aversion: losing $100 stings more than gaining $100 feels good, and that skews decisions.
38. Anchoring: the first number you see sways your judgment, especially in negotiations and shopping.
39. Name the emotion. Saying “I feel anxious” turns the volume down; psychologists call it affect labeling.
40. Social comparison feeds unhappiness. You’re setting your behind-the-scenes against everyone else’s highlight reel.

Good thinking needs good tools, and science is the best toolkit we’ve ever built.

Science Basics That Win Arguments

What science basics should everyone know? Correlation isn’t causation, a scientific theory is a tested explanation rather than a hunch, and good science changes its mind when the evidence changes. Those three ideas help you size up almost any claim you’ll ever hear.

41. Correlation isn’t causation. Two things moving together doesn’t mean one pushes the other.
42. Seasons come from Earth’s tilt, not its distance from the Sun.
43. A scientific “theory” is a well-tested explanation, not a guess.
44. Vaccines train your immune system by showing it a harmless version of a threat.
45. Sunlight takes about 8 minutes to reach us, so you always see the Sun as it was a few minutes ago.
46. Atoms are mostly empty space. It’s a handy picture, though the “empty” part is really full of electron clouds and fields.
47. Energy can’t be created or destroyed, only transformed.
48. Humans are about 99.9% genetically identical. The exact figure shifts with how researchers count, but the point stands: we’re far more alike than different.
49. Iron and other heavy elements were forged in stars and stellar explosions. Much of the gold likely comes from colliding neutron stars. You’re literally made of star material.
50. Good science changes its mind when evidence changes. That’s a feature, not a flaw.

Science also gave us the internet, and the internet came with a whole new set of ways to get fooled.

How to Not Get Fooled Online

How do you avoid being fooled online? Check what other sources say about a site before you trust it, treat outrage as a warning sign, and remember that a padlock only means the connection is encrypted. Slow down, open a second tab, and verify before you share.

51. Practice lateral reading. To judge a source, open new tabs and see what others say about it.
52. Nothing online is truly deleted. Screenshots and archives exist.
53. Reverse image search (Google Lens, TinEye) quickly exposes fake or recycled photos.
54. Algorithms chase engagement, not truth or your wellbeing.
55. The padlock means encrypted, not trustworthy. Scam sites use HTTPS too.
56. Your digital footprint is searchable by employers, schools and strangers.
57. Incognito mode doesn’t make you anonymous. It only hides history on your own device.
58. If content makes you furious, pause before sharing. Outrage is the fuel of misinformation.
59. Check whether your email’s been in a breach at haveibeenpwned.com.
60. Don’t overshare: location, travel plans, documents, kids’ details.

Once you’re harder to fool, you’ve got more attention to spend. Here’s how to spend it well.

Get More Done Without Burning Out

How do you get more done? Sort tasks by urgency and importance, protect blocks of time for real work, and quit multitasking. Then lower the barrier to starting, because five minutes is usually enough to get moving. Momentum handles the rest.

61. The Eisenhower Matrix: sort tasks by urgent versus important, then focus on the important-but-not-urgent pile.
62. Two-minute rule: if it takes under two minutes, do it now.
63. Multitasking is mostly task-switching, and it drags down quality and speed. Do one thing at a time.
64. Parkinson’s Law: work swells to fill the time you give it, so set deadlines.
65. Time-block your calendar for important work, not only meetings.
66. Done beats perfect. Ship a good version, then improve it.
67. Manage energy, not just time. Save the hard stuff for your peak hours.
68. Write it down. Your brain is for thinking, not storing to-do lists.
69. Learn to say no. Every yes costs time somewhere else.
70. Start for just five minutes. Motivation often follows action, not the other way around.

Got your calendar under control? Good. Now go somewhere.

Travel Smarter Before You Pack

What should you sort out before traveling? Check your passport validity, buy travel insurance, and carry copies of your documents. Many countries want six months of passport validity beyond your travel dates, and a medical emergency abroad can cost a fortune. Do these early and the trip itself gets easier.

71. Many countries require six months of passport validity past your travel dates. Check early.
72. Keep digital and paper copies of your passport, visas and insurance.
73. Buy travel insurance. Medical emergencies abroad can be ruinously expensive.
74. Use a no-foreign-fee card, and when asked, pay in the local currency rather than your home currency.
75. Learn ten phrases: hello, thanks, please, how much, where is. Effort earns goodwill.
76. Download offline maps and get an eSIM or local SIM before you need one.
77. Pack light. Carry-on only saves money, time and lost-luggage stress.
78. Know the local scams (fake taxis, “free” bracelets, overly helpful strangers) before you go.
79. Check visa and vaccine requirements well ahead of time.
80. Stay flexible with dates. Moving a day or two can cut flight prices noticeably.

Travel is really just history you can touch, so let’s look back for a minute.

History Lessons Worth Remembering

What history is worth knowing? Mostly the big shifts: Rome’s two endings, the printing press, the Industrial Revolution, and the pandemics and near-misses that shaped modern life. History also scrambles your sense of time. Cleopatra lived closer to the Moon landing than to the building of the Great Pyramid.

81. Cleopatra lived closer in time to the Moon landing than to the building of the Great Pyramid.
82. The Western Roman Empire fell in 476 CE. The Eastern (Byzantine) Empire lasted until 1453.
83. The printing press (1440s) spread knowledge faster than anything before it and reshaped religion, science and politics.
84. World War II was the deadliest conflict in history, with roughly 70–85 million deaths.
85. Most of human history was extreme poverty. Living standards only climbed sharply after the Industrial Revolution.
86. The 1918 flu killed an estimated 50 million people, though estimates vary widely and some run far higher.
87. In 1983, Soviet officer Stanislav Petrov judged a missile alert to be a false alarm, and he may well have prevented nuclear war.
88. Smallpox killed hundreds of millions before vaccination wiped it out. It was declared eradicated in 1980.
89. Writing was invented independently in several places, including Mesopotamia, China and Mesoamerica.
90. “History is written by the victors” is only half true. Survivors, archaeologists and later scholars often rewrite the story.

We’ll finish with the fun stuff. These last eleven facts sound made up. Most of them aren’t.

Eleven Facts That Sound Fake (Mostly Aren’t)

What are the most surprising facts everyone should know? Octopuses have three hearts, a day on Venus outlasts its year, and sharks are older than trees. A few popular “fun facts” need small corrections, though, and I’ve fixed those below.

91. Honey keeps for an absurdly long time, because its low moisture and acidity stop most microbes. Correction: the popular claim that edible honey was found in Egyptian tombs is unproven. Smithsonian Magazine repeated it in 2013, but beekeepers who traced the story say no tomb honey has ever been confidently identified, let alone eaten. Sealed honey lasting decades is solid; the pharaoh’s snack is the shaky part.
92. A day on Venus is longer than its year. The planet takes about 243 Earth days to spin once and about 225 to orbit the Sun.
93. Octopuses have three hearts and blue blood.
94. Sharks are older than trees. They’ve been around for over 400 million years.
95. Bananas are slightly radioactive thanks to potassium-40. Harmlessly so.
96. There are more possible chess games than atoms in the observable universe.
97. A teaspoon of neutron star material weighs somewhere between 10 million and several billion tons, depending on which source you trust and how big your spoon is. Either way, it’s absurdly heavy.
98. Lightning flashes roughly 40 times a second worldwide, not the classic 100. Correction: the 100-per-second figure traces to a 1925 estimate. NASA satellite data found about 37 flashes a second, though ground strikes versus cloud flashes get counted differently, so treat any single number loosely.
99. Scotland’s national animal is the unicorn.
100. Wombats produce cube-shaped poop.
101. The Eiffel Tower can grow about 15 cm taller in summer as the iron expands in the heat.

The Cheat Sheet: Numbers Worth Memorizing

Which numbers are worth memorizing? Eight of them cover most of the practical advice above: sleep, savings, CPR, sunscreen, handwashing, backups, passports, and the Rule of 72. Screenshot the table, stick it on the fridge, and you’ve kept the highlights without rereading all 101.

Where to Start (You Don’t Need All 101)

Which of the 101 should you do first? Pick three: turn on two-factor authentication, set up an automatic transfer to savings, and learn hands-only CPR. Each takes under an hour, and each protects something you can’t easily replace.

Honestly, nobody absorbs 101 things in one sitting. Bookmark this page, work through a chapter a week, and send the CPR item to someone you love. Facts shift now and then (see lightning), so treat this list as a living one.

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