Gravitas

Gravitas, an ancient titan of The SI Guard, watches two lead spheres tug on two small ones and twist a hair-thin fibre.

The Physics

G sets the strength of gravity between any two masses. It is measured with torsion balances (Cavendish, 1798) and other lab methods, where the pull between kilogram-scale masses is about 10⁻⁷ N or less.

G = 6.674 30(15) × 10⁻¹¹ m³ kg⁻¹ s⁻²

• G: Newtonian constant of gravitation
• (15): standard uncertainty in the last two digits, 2.2 × 10⁻⁵ relative

Value: CODATA 2018 and CODATA 2022 (NIST, unchanged). G is measured, not fixed by the 2019 SI. It is the least precisely known of the fundamental constants, and the best experiments still disagree by more than their quoted uncertainties.

Honest caveat: Big G is not little g. G is universal; g ≈ 9.81 m/s² is the local acceleration at Earth's surface, which varies by about 0.5% between the equator and the poles. The sticker prints the digits of G; the factor × 10⁻¹¹ in SI units is implied.

On the sticker

Gravitas holds the two glowing spheres of the torsion balance. Printed text: GRAVITAS with the line G = 6.674 30(15). Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.