Goldfish don’t worry about the water they swim in. People don’t worry about the air they move through. Not too much at least. If you do, you will soon come across dizzying numbers. Like the billion times per second that every atom in a surface is tapped by a nitrogen or oxygen molecule from the air. It doesn’t matter if that atom is in the parquet, in palms, noses, cupboard doors or table tops: every surface is constantly wrapped in a ping-pong match with air molecules.
Almost as special is that the Ancient Greek atomists already suspected this more than two thousand years ago. “Always around the surrounding air whips things,” wrote the Roman philosopher and poet Lucretius in the long poem The rerum kind in which he explained the ideas of those atomists.
Sixteen horsepower
It would then be another seventeen centuries before Otto von Guericke, the brilliant mayor of the Prussian Magdeburg, made that ‘whispering air’ visible. Von Guericke was inspired by Copernicus’ idea that the Earth moves through an otherwise virtually empty space around the Sun. He wanted to simulate and investigate this empty space with a vacuum pump he developed himself. Paradoxically, he then became especially famous when he showed the ‘air pressure’ when approaching that void.
He did this by having two copper hemispheres made that together formed a hollow sphere with a diameter of more than a ruler. If Von Guericke pumped out the cavity in that sphere as much as possible and thereby removed the counter-pressure from the inside, the surrounding air pressed the two halves together. Wall-tight. They could not even pull eight horses apart, as it turned out during a demonstration for Emperor Leopold III. For example, sixteen horsepower lost out against the countless taps with which air molecules pressed the hemispheres against each other.
queuing
Imagine that Von Guericke in his black cloak could have sat down on the symposium with which his distant scientific descendants celebrated the sixtieth anniversary of their Dutch Vacuum Association last month. He would probably have been taken aback by the techniques used by physicists to make spaces as empty as possible these days. They direct the almost-last molecules outwards with systems of paddle wheels, bouncing from blade to blade. Even more sporadically remaining molecules freeze them to extremely cold walls; fix them to sticky walls or bonjour them away with electric fields.
Why all the trouble, the former mayor of Magdeburg might stammer. And would anyone dare to explain the enormous, ultramodern devices from manufacturer ASML with which the chips are made for mobile phones and computers? The tiny structures on those chips are ‘drawn’ on a silicon wafer using gossamer-fine beams of extreme ultraviolet light. But if it’s not used in an almost perfectly empty space, that short-wave ultraviolet light is immediately absorbed. Hence, for example, those vacuum techniques, which would of course be difficult to explain to a seventeenth-century person. But it would probably be good enough for Von Guericke that such an ASML device would soon be in the new European center for chip technology in, yes, his own Magdeburg.
crash tests
And what if Lucretius could also be in the audience? As his robe fluttered around his arms, he might ask about the vacuum in CERN’s particle accelerator near Geneva. In that 27-kilometer accelerator, atoms are chased to almost the speed of light, which only works if no errant air molecules cross their path. So in an almost perfect vacuum. The great thing about this is that the collision tests with the lightning-fast particles (plus data analysis with lightning-fast computer chips) also help to understand that empty space.
That emptiness is nothing, Lucretius would be told. Space is crisscrossed by ghostly neutrinos, pervaded by a Higgs field, may be bursting with invisible dark matter particles, and who knows, maybe even “dark energy” roaming everywhere. Not to mention the particle-antiparticle pairs that constantly bubble up and disappear on the smallest scales. In short, the earth moves against the background of a gigantic not-nothing.
Outside of space and time
What would the faithful Lutheran von Guericke think? And Lucretius who thought the cosmos could do without gods? Perhaps the latter would quote what he once wrote about “the mortal soul” that after death dissolves into nothingness. In that non-being, he wrote, “of course nothing can happen to us who will not be there and disturb our consciousness.” It is outside of space and time and vacuum technology.
I used the translation by Piet Schrijvers (De Rerum Natura)
Margriet van der Heijden is a physicist and professor of science communication at Eindhoven University of Technology.