On Earth we never confront the dangerous realms that are routine in the hallways of the night. The largest, brightest, dimmest or most violent regions of space/time lie light-years from our malls. But if we are truly to know our Cosmos and therefore ourselves, we should be aware of these cosmic superlatives.
Anyway, superlatives have become our culture’s fixation – the attention-getting heart of any news story. We can always gain someone’s ear with gossip about the fattest, prettiest, wealthiest, smartest or most egocentric individual whom we’ve encountered; extremes make good “copy.”
When confronting the natural world, our most common superlatives involve temperature. The recent heat wave, where the mercury exceeded 100 degrees for a couple of days in the mid-Hudson Valley, was Topic A everywhere. Off-Earth, however, the signs of heat can be counterintuitive. For stars, or anything that emits its own light, “red-hot” really means cool. In fact, the night’s reddest stars are the only ones tranquil enough to have complex structures like molecules, including water vapor: steam. (Steam, by the way, is totally invisible in space and also here on Earth. It’s that transparent region just beyond the spout of a whistling teapot. The white mist beyond it is where the steam has cooled back into tiny water droplets. That’s not the steam, even if everyone mistakenly thinks otherwise.)
Heat is simply the motion of atoms. At room temperature the gases around you jiggle at just over the speed of sound: 750 miles per hour. When you boil water for tea, you’re simply making the atoms move so fast that they break the bonds that keep them in the liquid state.
Hotter stars that are white like the Sun have a higher level of violence than red ones; the action is way too fast-paced for molecules to endure. The very hottest suns, instantly recognizable by their diamond-blue dazzle, are so frenetic that nothing beyond plain-vanilla hydrogen and helium exists on their surfaces. Color says much, and the universe has conveniently been color-coded for our examination.
There is no ceiling to temperature. A supernova can attain a near-meaningless billion degrees. The lower limit of the temperature scale is much more precisely delineated, because at 459.67 degrees below zero Fahrenheit, all motion stops. Since nothing can move slower than “stopped,” it is impossible for anything to be colder than this: absolute zero. Laboratories have now achieved temperatures to within a few billionths of a degree of absolute zero, making these places colder than anywhere else in the universe. Even the skimpy atoms of space far from any stars are not absolute zero, but are instead bathed in the five-degree (Fahrenheit) toastiness left over from the creation of the current universe.
Like a balky bathroom heater, the sum of all the heat generated by all the stars, supernovae and galaxies does not raise this background temperature of the Cosmos by even one tenth of an additional degree. If we didn’t have the Sun, we’d be toast. It’s our only life-giving source of warmth, and our planet’s greenhouse gases trap in just the right amount to keep us comfy.
Earth’s air-blanket is the key. Our Catskill Mountain 135-degree temperature range from the coldest-ever winter night to that highest heat wave is far more moderate than anyplace that we have ever observed in the universe, with a single exception: the oceans beneath the ice sheets of Jupiter’s mysterious moon Europa – which is why it’s probably teeming with life.