1818

Aethrioscope

• How cold is the sky?
• If you really want to know,
• you can make an aethrioscope.
• Put a differential thermometer
• in a parabolic metallic cup
• over a tall hollow pedestal.
• Screen one bulb from the sky
• and place the second bulb
• at the focus of the cup.
• When you expose the cup,
• the radiative effect contracts the air
• in the first bulb to pull the mercury up.

Radiative effect

• Without the second law of thermodynamics,
• the radiative effect of a clear sky
• would seem like a special power.
• Euclid thought we see by light
• that emanates from our eyes.
• So the eyes of the evil Doctor Cold
• would bring misery to our intrepid hero
• if he were caught without a cover.

Clear

• X-rays penetrate skin;
• radar cuts through fog or cloud;
• radio through windows and walls.
• Gravity seems like a force and a lens,
• water seems like a force and a lens,
• clear sky seems like a force and a lens.