「重力の単位ガルはガリレオにちなむ/en」の版間の差分

2026年10月29日 (木) 19:34時点における最新版

#0023 Science & nature

Fact rank

S

Raised from the expected A to S: the origin, the size and the legal scope were all confirmed in primary sources (GSI's explanation and the text of the law)

Wow rank

B

Mildly interesting that the "gal" heard in earthquake news is also a unit of gravity

Usefulness

—

A fact worth knowing for its own sake

Verification: Supported by evidence

Posted by: Mamechi editors ・ Verified: 2026-10-29 ・ Method: AI + human ・ On Wikipedia?: Already on Wikipedia

AI verification reports the evidence it found; it does not guarantee that a claim is true.

The unit of gravitational acceleration, the gal (Gal), is named after Galileo Galilei; 1 gal is 1 cm/s², and Earth's gravity is about 980 gal. Under Japanese law the gal is a special unit that may be used only for measuring gravitational acceleration and the acceleration of earthquake shaking.

Why

It was named after Galileo, who discovered the law of falling bodies and studied how things accelerate as they fall (GSI).

Evidence

Primary Explanation by GSI. Geodesy and geophysics express gravitational acceleration in Gal (0.01 m/s²), named after Galileo Galilei, who discovered the law of falling bodies. Earth's gravitational acceleration is 9.8 m/s² (980 Gal). GSI's absolute gravity measurements go down to 1 microgal link

Primary Cabinet Order on Units of Measurement (e-Gov), Appended Table 6. The gal (one hundredth of a metre per second squared) and the milligal (one thousandth of a gal) may be used only for "measurement of gravitational acceleration or vibration acceleration relating to earthquakes" link

Notes and limits

The gal is not an SI unit. Surface gravity ranges from about 976 to 983 gal with latitude and elevation; 980 is a rounded value (standard gravity is 980.665 gal). The "gal" of earthquake shaking is the same unit, which is easy to confuse with gravity itself. The origin and legal status are also in the Japanese Wikipedia article on the gal.

Derivations

Derived from: 体重計の数字は緯度が高いほど大きく出る

Derived facts: —

@@ 2行目: / 2行目: @@
 {{豆知識
 |番号=0023
+|投稿者=まめち編集部
 |本文=The unit of gravitational acceleration, the gal (Gal), is named after Galileo Galilei; 1 gal is 1 cm/s², and Earth's gravity is about 980 gal. Under Japanese law the gal is a special unit that may be used only for measuring gravitational acceleration and the acceleration of earthquake shaking.
+|なぜ=It was named after Galileo, who discovered the law of falling bodies and studied how things accelerate as they fall (GSI).
 |ジャンル=科学・自然
 |ファクト度=S