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Science guides

Step-by-step how-tos, head-to-head comparisons and honest roundups — every guide worked through with current figures, then backed by a RECATOOLS calculator or AI-directory entry so you can act on it.

498 guides published 17 topic areas Latest guide Oct 2026

Tagged Statistics · 10 guides

All 498 Developer Tools 68 AI & ML 63 Finance 52 Home & Living 46 Chinese Culture 43 Science 40

Old black-and-white family photographs spread across the open pages of worn albums

Science 6 min

An X chromosome comes from fewer ancestors than a family tree allows

A man's X chromosome can come only from his mother's side, while a woman's comes from both parents, so the ancestors who...

Nadia Rahim

Pub. 15 Oct

Rows of labelled donated blood bags hanging in a blood bank

Science 6 min

Rare blood-group variants allow most of the child blood types a chart forbids

The textbook ABO rule forbids at least one child blood type for every pairing of parent types except A with B. Rare inhe...

Nadia Rahim

Pub. 8 Oct

A calligraphy brush on an ink stone in front of practice characters

Science 5 min

When yi (一) and bu (不) change tone, and why pinyin usually doesn't show it

一 is said yí before a fourth tone and yì before the others; 不 becomes bú only before a fourth tone; and a third tone r...

Nadia Rahim

Pub. 23 Sep

Old family photographs laid on a family register book

Science 7 min

How many ancestors did you have a thousand years ago?

Doubling every generation gives you about a trillion ancestors a thousand years back, more people than have ever lived....

Nadia Rahim

Pub. 21 Sep

Close-up of the objective lenses on a laboratory microscope

Science 7 min

Why your DNA ancestry estimate is vaguer if you are Asian

A result full of "Broadly" labels is telling you something real, but not about your ancestry. One company's own document...

Nadia Rahim

Pub. 31 Aug

A rendered DNA double helix in amber tones against a black background

Science 5 min

When a DNA match could be your grandparent or your half-sibling

A match sharing around 1,700 centimorgans could be a grandparent, an aunt or uncle, or a half-sibling. The averages for...

Nadia Rahim

Pub. 31 Aug

A white cup of cappuccino dusted with chocolate sits on a saucer on a round metal tray, a spoon and a small biscuit beside it, with a person's folded arms resting on the wooden table behind, out of focus.

Science 7 min

What Actually Decides When Caffeine Wears Off

Coffee at four, still awake at midnight? The usual answer is that a substance is gone after ten half-lives — a tidy numb...

Nadia Rahim

Pub. 15 Aug

Laser-cut wooden tiles engraved with element symbols and numbers lie scattered across a pale table, with a few already slotted into the empty squares of a wooden periodic-table grid at the right.

Science 6 min

Why Isn't the Periodic Table Sorted by Weight?

The periodic table is not ordered by weight. Walk our own 118-element data from hydrogen to oganesson and the weight fal...

Nadia Rahim

Pub. 15 Aug

Gloved hands closing a vernier caliper around a length of timber, with its scale in view.

Science 9 min

Significant Figures: The Digits Your Calculator Invents

We audited our own science calculators against the precision their inputs actually justify. Across 768 multiplications a...

Nadia Rahim

Pub. 13 Aug

Rows of young seedlings in small peat pots on a sunlit sill, lit from behind.

Science 5 min

What a Punnett Square Cannot Tell You

The square says three-to-one, and the lesson usually adds that in a family of four, three children will show the trait a...

Nadia Rahim

Pub. 12 Aug