Skyrider

Skyrider, a goggled balloonist, cradles a glowing instrument under the balloon's rigging.

The Physics

In 1912 Victor Hess carried electroscopes up in balloons to 5 350 m (Phys. Z. 13, 1084). Their discharge rate, a measure of ionising radiation, first dipped slightly, then climbed steeply with height. The radiation was coming from above, not from the ground. A flight during a near-total solar eclipse and at night showed no drop, so the Sun was not the source. He shared the 1936 Nobel Prize for cosmic rays.

ionisation rate rises with altitude

• altitude: height above sea level, up to 5 350 m in 1912
• ionisation rate: ions formed per cm³ per second in the electroscope

Cosmic rays are mostly high-energy protons and nuclei from space that shower in the upper atmosphere.

Honest caveat: Near the ground radiation first falls with height, because rock radioactivity fades; the rise wins only above about 1 km.

On the sticker

Skyrider holds a glowing cyan jar-like instrument under balloon rigging at dusk. Printed text: SKYRIDER with the line UP = MORE. Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.