I'm a retired designer with infinite curiosity for people, ideas, inventions, discoveries and circumstances and their surprising connections
CONNECTIONS: Blackest Black
I remember several years ago, a friend told me an anecdote. A child – perhaps his son – asks his mother: “Is there a blacker color than black?” To the negative response of the mother, the child persists: “If it existed, I would paint the bathroom in that color and then I would make the sink and tub black to brighten up the room…”
What was at the time a fun and surreal idea is now a reality. It’s called BlackestBlack and it is a substance invented in 2019 by physicists at the Massachusetts Institute of Technology capable of absorbing 99.995% of light, and is the blackest material ever created by man, blacker than any black you have ever seen… literally a black hole.
Someone who had dealt with black (no, I’m not talking about black holes) is the amateur astronomer (he had a medical degree) Heinrich Wilhelm Olbers (1758–1840), another of the usual early geniuses we encounter in the history of science, who at 19, while attending the University of Gottingen, identified a method, still used today, to determine the orbit of comets.
We are here interested in a paradox that bears his name, even if previously formulated by several other astronomers.
Olbers’ paradox, which he described in 1823, establishes that the brightness of the sky conflicts with the theory of a static and infinite universe.
In other words: imagining the universe as an infinite series of concentric spheres with an even number of stars in each sphere, the sky should be as bright as the sun. Looking up, our eye would encounter a star anywhere in the sky. The objection that more distant stars would be less bright is countered by the fact that more distant (and larger) spheres would have more stars. So why is the sky black?
Over time there were several attempts to explain the paradox. Astronomers, physicists, and even the writer Edgar Allan Poe, advanced hypotheses such as that there are vast dark clouds in space or that… the stars end and what we see is the empty space beyond.
The solution to the riddle came with the American astronomer Edwin Powell Hubble (1889 – 1953), but first we need to take a step back.
You have probably noticed a certain physical effect: if a train or a motorcycle passes in front of you, its noise is of higher tone as it approaches and of lower tone as it moves away. The classic iiiiiiiiiiuuuuuuuuuu.
This is called the Doppler effect, from the name of the Austrian physicist Christian Andreas Doppler (1803 – 1853) who enunciated it.
The effect is easy to explain. Imagine a gun approaching and shooting beans toward you (every bean being equivalent to a sound wave). As it approaches, after shooting each bean, it will move toward you before shooting the next one. So, the interval between one bean and the next is shorter than if the gun had been stationary, the beans therefore will arrive at a higher frequency. Substituting sound waves for beans, higher frequency, equals higher sound. Moving away the opposite happens. With each bean, the gun moves away: beans arrive at a lower frequency.
Second concept: light is – for the purposes of our discussion – an emission of waves whose frequencies determin the color spectrum. Starting from the lowest frequency: infra-red (not visible to the human eye), red, yellow, green, blue, purple, ultra-violet (not visible).
Hubble observed that the light of the more distant stars appeared to be redshifted, that is their spectrum was shifted toward a lower frequency, so he obviously inferred that they are receding. Hence: the universe is expanding.
And this provides the most likely explanation for Olbers’ paradox: the most distant stars are also the oldest and have been traveling – in an expanding universe – for billions of years. Their light has thus shifted in the spectrum below the visible threshold, in the microwave region.
His observations on the correlation between the redshift and the distance of the observed galaxies, led to the formulation of Hubble’s law (that galaxies are moving away from the Earth at speeds proportional to their distance: the farther they are, the faster they are moving away from Earth), the subsequent theories on the explosive birth of the universe (Big Bang) and the stomach ache of a well-known physicist.
Albert Einstein in fact, in 1917, formulating the equations underlying his Theory of General Relativity, obtained results that were not compatible with the static universe which was the premise of his studies. Failing to make sense of it all, he had introduced a constant, a number that represents a component of energy that somehow had to be present in nature. Something like: “I get 2 + 2 equals 5, so there must be a 1 somewhere”. When he learned of Hubble’s discovery, he found that in an expanding universe the accounts were balanced without the need for the constant and said that that was the biggest mistake of his life.
Mr. Hubble’s name is passed down among other things by the largest and most technologically advanced space telescope ever built, launched into orbit in 1990 and still fully operational. Above the distortions caused by the Earth’s atmosphere, the telescope sends extremely detailed images offering a view almost to the borders of space and time.
Among other things, forty years after the death of Hubble, the telescope that bears his name, made it possible to accurately determine the rate of expansion of the Universe.
The beginnings had not been very promising for the Hubble telescope. One of the main components, the parabolic mirror that NASA had commissioned from a specialized company, had proved defective and the images were below expectations. Luck would have it that the telescope was designed to be repaired in orbit by astronauts. During five Space Shuttle missions it was possible to replace components and update the software.
In 2019, in addition to the telescope, there were 2,000 artificial satellites orbiting the earth. Practically invisible, but now an integral part of our daily life. Satellites for communications, for navigation, for pollution verification, for the study of continents, for hurricane tracking. Satellites for weather forecasts, for the study of the atmosphere, military satellites and so on.
And scientist say that the increase will be exponential. For example, the American company Space X, set up by Elon Musk, creator of the Tesla electric car, plans to launch 12,000 satellites by 2027. 12,000!
Whatever the pros and cons of this space race, the fact remains that we have to deal with one reality: overcoming gravity is expensive.
Launches of the Space X carriers, currently considered the cheapest on the market, cost $ 133 million per launch, or something like $ 13,000 per kilogram placed into orbit.
It is therefore not surprising that alternatives to current technology are being sought, which is basically based on principles dating back to the first gunpowder rockets invented in China around 1200.
Among the different systems proposed there is the so-called space elevator. The concept, at the moment theoretical, foresees a cable stretched between a point on earth and a satellite placed in a geostationary orbit, that is, orbiting around the earth at a height and a speed that always keep it on the same vertical. The loads would move up and down this cable without the aid of rockets.
The biggest obstacle is obviously the cable itself. It should be at least 37,000 kilometers long and strong enough not to collapse under its own weight.
The only technology that could produce such a cable is that of nanotubes.
In 1985, the American chemist Richard Errett Smalley (1943 – 2005), Nobel Prize for Chemistry in 1996, discovered that, in particular conditions, carbon atoms can arrange themselves to form microscopic hollow cylinders: carbon nanotubes.
Nanotubes exhibit extraordinary physical and chemical characteristics with potential uses in electronics, chemistry and even medicine. A theoretical computer using nanotubes instead of current silicon components would have mind-boggling performance and would break all current miniaturization barriers.
Nanotubes represent the strongest organic material ever made. An ideal nanotube would have a tensile strength 100 times greater than that of an equivalent sized steel bar with 6 times less weight.
So, at least theoretically, they could be used for the space elevator cable.
If, on the other hand, you want a more realistic application, spread a forest of nanotubes, vertically aligned like the hairs of a carpet, on a suitably treated aluminum sheet and you will get a new substance with a particular property: that of absorbing 99.995% of the light. Exactly what the engineers at the Massachusetts Institute of Technology did, naming it BlackestBlack.