「体重計の数字は緯度が高いほど大きく出る/en」の版間の差分
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|番号=0012 | |番号=0012 | ||
|本文= | |投稿者=まめち編集部 | ||
|本文=Weighed on the same scale, you read slightly heavier at higher latitudes. | |||
|なぜ=Earth's rotation produces the most centrifugal force at the equator, and the planet bulges there, so gravity at the equator is about 0.5% weaker than at the poles. | |なぜ=Earth's rotation produces the most centrifugal force at the equator, and the planet bulges there, so gravity at the equator is about 0.5% weaker than at the poles. | ||
|ジャンル=科学・自然 | |ジャンル=科学・自然 | ||
2026年10月29日 (木) 19:35時点における最新版
#0012 Science & nature
Fact rank
S
A public agency (the Geospatial Information Authority of Japan) states the figure itself: gravity on the equator is about 0.5% smaller than at the North and South Poles. Consistent with the normal-gravity values in a university lecture and with a calculation from the international gravity formula
Wow rank
S
That your weight changes with where you stand is counter-intuitive, and it can be put in numbers
Usefulness
—
A fact worth knowing for its own sake
Verification: Supported by evidence
AI verification reports the evidence it found; it does not guarantee that a claim is true.
Weighed on the same scale, you read slightly heavier at higher latitudes.
Why
Earth's rotation produces the most centrifugal force at the equator, and the planet bulges there, so gravity at the equator is about 0.5% weaker than at the poles.Evidence
Primary Explanation by the Geospatial Information Authority of Japan. Gravity is the combined force of Earth's attraction and the centrifugal force from its rotation; on the equator it is about 0.5% smaller than at the poles. Gravity in Hokkaido is about 0.15% stronger than in Okinawa, and scales are calibrated with local gravity values link
Secondary Lecture material from the geodesy laboratory, Kyoto University (2017). Because Earth bulges toward the equator and the centrifugal force is largest there, gravity is strongest at the poles and weakest at the equator. Normal gravity is 978.03 Gal (9.780 m/s²) at the equator and 983.22 Gal (9.832 m/s²) at the poles. Checked by calculation with the international gravity formula: 9.804 m/s² in Sapporo (43°N) and 9.780 m/s² at the equator link
Notes and limits
What changes is the scale reading (weight, a force); the body's mass does not change. Spring and load-cell scales show the difference, but a balance (weighing against reference weights) does not. Scales are calibrated to the gravity where they are used, so the difference shows when a scale set up in one place is taken to another latitude. For example, a person who reads 80.0 kg in Sapporo would read about 79.8 kg on the equator and about 80.2 kg at the North Pole (ratio 9.780/9.804 ≈ 0.9975). Within Japan, Naha and Wakkanai differ by about 0.15%, just under 100 g for 60 kg. Gravity also weakens with altitude, so you read slightly lighter on a mountain.
Derivations