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换算的数学与历史背景。

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Fundamentals

The metric system explained — and why it works

A short tour of the metric (SI) system, its base units, prefixes, and why it has conquered most of the world.

6 min Data

Decimal vs binary prefixes (KB vs KiB, MB vs MiB)

Why a "1 TB" drive is not 1,024 GB, and what the IEC binary prefixes fixed in 1998.

5 min Temperature

Temperature scales explained — and why the conversion is affine

Celsius, Fahrenheit, Kelvin, Rankine, Réaumur. The first three are common; the last two are special-purpose.

5 min Fuel Economy

Why fuel-economy conversion is reciprocal, not linear

MPG and L/100km measure the same thing, but the conversion passes through an inverse. Here is why.

4 min Length

Length units beyond the metre — light-years, ångströms, and nautical miles

Why some length units live in physics and astronomy, not in everyday conversation.

4 min Energy

Energy units vs power — why BTU/hour and watt are different

Watt is a power unit, watt-hour is an energy unit. The h matters.

4 min Fundamentals

The 7 SI base units — what they are and how they are defined

A quick reference to the seven base units of the International System of Units.

5 min Pressure

Pressure units — psi, bar, atm, pascal, torr

Why every industry has its own pressure unit and how to translate between them.

4 min