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How Lasers and Wi-Fi Were Born – Thanks to Cosmology

by Wilson da Silva 4 months ago in Humanity · updated 11 days ago

Truly revolutionary technologies come from the most unlikely places, like cosmology, which gave us lasers, GPS and even Wi-Fi.

WHERE DO WE come from? How did we get here? They are questions which have been asked as long as there have been people. And answering them has given us not only valuable insights, but created great technologies along the way.

In fact, it wasn’t until the 20th century that cosmology — the study of the origin and development of the universe — improved much on what the Ancient Greeks knew 2,300 years before: Earth is a sphere; most stars are unchanging in position, but some celestial objects, dubbed ‘planets’ (from the Greek word for ‘wanderer’), followed strange but predictable paths in the night sky; and these planets are much closer to us. Even the idea that Earth circled the sun was first proposed in 300 BC by the Hellenistic author Aristarchus of Samos, well before Nicolaus Copernicus returned to it in 1514.

But the real revolution in modern cosmology began in 1687, when English mathematician Isaac Newton published his hugely influential book Philosophiæ Naturalis Principia Mathematica. His laws of motion and universal gravitation applied not only to falling apples, but to how planets move in the sky. It was then that astrophysics was truly born, and our modern technological world began to take shape.

Sir Isaac Newton’s own first edition copy of his ‘Philosophiae Naturalis Principia Mathematica’ with his handwritten corrections for the second edition (Trinity College, Cambridge)

His mathematical explanations for mass, force and motion ushered in a mechanical view of the physical world that made possible the construction of bridges, the draining of canals and the calculation missile trajectories, dominating our understanding of the physical world. They’re still used every day.

Still, right into the 20th century, the Milky Way galaxy — the bright swathe of stars easily seen on a clear night — was thought to be our entire universe. That assumption began crumbling as larger and larger telescopes were built from the 1860s onwards, but it took until the 20th century for astronomers to suspect the Milky Way was just one of many ‘island universes’, or galaxies.

And then it got really strange.

In a paper published in the German physics journal Annalen der Physik in 1905, Albert Einstein had proposed his theory of special relativity, along with the now famous equation, E=mc2. In the paper, entitled “Does the Inertia of a Body Depend Upon Its Energy Content?”, he expanded on Newton’s laws of motion so that they applied to objects moving at high speed, and then explained why light was unaffected by these laws: why it was that, if a car travels at 80 kilometres per hour, its headlight beams do not travel at the speed of light plus 80 km/h.

He postulated that the speed of light is the same for all observers, and set the speed of light in vacuum — 299,792,458 metres per second — as a universal constant; the maximum speed at which all energy, matter and information in the universe can travel.

Albert Einstein, the renowned German theoretical physicist, became an American citizen in 1940 (Piqsels)

ton’s model, gravity had been ascribed to an ‘unknown force’ produced by immense objects which act on the mass of other objects. Einstein argued that gravity actually arose as a property of space and time: the greater the mass of an object — such as a moon or a sun — the more it distorted, or bent, the very fabric of space.

And because relativity links mass with energy, and energy with momentum, this curvature of space-time — the gravitational effect — was directly related to the energy and momentum of whatever matter and radiation was present.

While at first it sounded bizarre, the theory did neatly account for several strange effects unexplained by Newton’s law, such as anomalies in the orbits of Mercury and other planets. But if true, it would also mean the universe was not static and unchanging as scholars had believed for thousands of years — something Einstein himself worried about. If he was right, where was the evidence for this?

Astronomer Edwin Hubble guiding Mount Wilson’s 100-inch telescope in 1924 (Carnegie Observatories)

Einstein didn’t need to wait long. In 1929, American astronomer Edwin Hubble astounded the world in a paper in Proceedings of the National Academy of Sciences entitled “A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae”, wherein he showed conclusively that the further away astronomical objects are, the faster they appear to be travelling away from us. He had long resisted the conclusion, but could not dismiss the data. The only possible explanation was that the universe was expanding and, hence, changing — just as Einstein had relunctabtly predicted.

It meant that, in the far future, galaxies would spread farther and farther apart; it also meant that, in the distant past, the universe must have been smaller and denser, eventually congregating at one single, unimaginably hot and impossibly compressed point. Did time itself have a beginning?

This is the origin of Big Bang theory. Over the next 50 years, countless observations by astronomers have confirmed this seemingly fantastical notion. Parallel advances in the physics of the small — the atoms and the subatomic particles that constitute all things — helped build a solid framework of evidence around this view of how the cosmos arose.

Slices of the universe at different times in its history; today, at 4 billion and 11 billion years ago. The faster the galaxies moves away from us, the more of its light is shifted to the red end of the spectrum as its wavelengths get longer (NASA/ESA/M. Kornmesser)

After the initial expansion, about 13.7 billion years ago, the universe cooled sufficiently to allow the superheated energy of the Big Bang to condense into various subatomic particles, eventually forming protons, neutrons and electrons. From this morass came the simple elements of hydrogen, helium and lithium. Gigantic clouds of these elements coalesced as gravity took hold, forming stars which ignited with heat and light, eventually forming galaxies as the stars clumped together.

Inside stars, clouds of gas — compressed by the titanic crush of gas columns above them — created all the heavier elements: carbon, iron, silicon, lead and so on. Some of the stars eventually died in cataclysmic explosions known as supernovae, expelling these heavier elements inside them into space, where gravity again brought them together, forming planets and moons. Even the ‘echo of the Big Bang’ was discovered in 1965 — a cosmic background radiation permeating all space, created by the raging oceans of white-hot energy at the dawn of time.

FROM THE 1960s on, astronomers tried to answer the question: would the universe continue to expand forever or collapse back in a Big Crunch?

They didn’t get far. Observations began to indicate that there wasn’t enough visible matter in the universe to account for gravitational forces they could see acting within galaxies and between them. One of the first to recognise this was Ken Freeman, an Australian astrophysicist whose 1970 Astrophysical Journal paper, “On the Disks of Spiral and S0 Galaxies” described how spiral galaxies rotate; it is widely recognised as the start of the paradigm shift that came to be known as ‘dark matter’.

“There must be in these galaxies additional matter which is undetected … its mass must be at least as large as the mass of the detected galaxies, and its distribution must be quite different from the exponential distribution which holds for the optical galaxy,” he wrote. The paper is now one of the most cited single-author papers in astrophysics.

An artist’s impression of the Milky Way with a blue halo indicating the distribution of the dark matter surrounding it (ESO/L. Calçada)

Suddenly, a big portion of the stuff making up the universe was thought to be a strange kind of matter that didn’t emit light or interact with normal matter in any way except via gravity. Evidence for dark matter has since repeatedly turned up in astronomical observations: in the lumpiness of the cosmic background radiation or the velocity dispersion patterns of galaxy clusters, for instance.

Physicists have proposed a number of particles responsible for dark matter. One group is known collectively as weakly interacting massive particles (or WIMPs), another is a new light neutral particle, the axion. Several projects to detect them directly are underway — mostly in deep underground laboratories that reduce the background effect from cosmic rays — in places like old iron and nickel mines the U.S. and Canada and a mountainside in Italy.

As if that wasn’t enough, astronomers were again stunned in 1998 when two international teams — one led by Australian astrophysicist Brian Schmidt and another by American Saul Perlmutter — announced that the expansion of the universe was actually accelerating, rather than slowing as expected. This was a surprise as the defining feature of gravity is that it slows moving objects over time: hence, the universe’s expansion should be slowing in the billions of years since the Big Bang.

Saul Perlmutter and Brian Schmidt, who won the 2011 Nobel Prize in Physics, at a press conference following the ceremony (Nobel Institute)

Einstein’s general theory of relativity did allow gravity to push as well as pull, but most physicists had thought this purely theoretical. Not anymore.

But how this occurs is a complete mystery. One explanation is that this ‘dark energy’ is a property of space itself: that empty space in its very structure encompasses this mysterious energy. Because this energy is a property of space itself, it wouldn’t be diluted as space expands; in fact, as more space is created by the expansion of the universe, more dark energy is created, causing the universe to expand faster and faster.

What cosmologists now know is that 71.4 per cent of the universe is made up of dark energy, and 24 per cent is dark matter. The rest — everything on Earth, all ‘normal’ matter — makes up less than 5 per cent.

WHAT PRACTICAL USE is such knowledge? More than you imagine. The unified description of gravity that arose in Einstein’s 1916 paper unleashed a deluge of technologies, from Google Maps to automatic doors.

Google Maps, like any GPS or satnav device, relies on the network of satellites orbiting Earth to be able to tell where you are in relation to your surroundings at any one time. To do this, a GPS satellite needs meticulous timekeeping — accurate to within 2 nanoseconds (or two thousand-millionths of a second).

Each GPS satellite constantly signals its exact location to sister satellites, then uses onboard atomic clocks to compare signals it receives back, logs the exact time at which each signal was received, then calculates how far that signal has had to travel at the speed of light, to calculate the distance between itself and the other satellites and, therefore, their precise locations in space. When a GPS satellite is thus synchronised with at least two other GPS satellites and your location, it can ‘triangulate’ where you are to an accuracy of up to 30 cm.

An artist’s representation of the GPS satellite constellation (NOAA)

But because all three satellites are spinning around Earth at great speed, they experience time dilation: time passes slightly slower for them than for us on the ground. Hence, the only way to avoid location data from being riddled with errors — making Google Maps useless — is to utilise Einstein’s equations for general relativity to compensate.

Another example is lasers, used in everything from supermarket barcode readers and automatic doors to guided missiles and tooth whitening. It was Einstein’s 1916 discovery of the physical principles behind light that made Light Amplification by Stimulated Emission of Radiation (hence, the word ‘laser’) possible.

A further surprising repercussion of Einstein’s theories was that a stellar object might grow massive enough that even the speed of light was not fast enough to escape its gravitational pull — theoretical objects dubbed ‘black holes’. But they proved devilishly difficult to find.

In 1974, physicist Stephen Hawking suggested that under certain circumstances small black holes might ‘evaporate’ and leak radio signals as they vanished. These signals would be extremely weak, buried in background cosmic noise and probably ‘smeared’.

So, in 1977, Australian physicist and engineer John O’Sullivan, while working at the Dwingeloo Radio Observatory in the Netherlands, co-authored a paper in the Journal of the Optical Society of America entitled “Image Sharpness, Fourier Optics, and Redundant-Spacing Interferometry”. In it, he and colleagues came up with a mathematical tool that might help detect the tiny, smeared signals against a background of intergalactic distortion, hoping to be the first to detect an evaporating black hole.

CSIRO’s John O’Sullivan, searching for black holes, created the technology that gave birth to Wi-Fi (Australian Prime Minister’s Prize for Science)

It was a fabulous invention, but it wasn’t successful at finding small black holes. Six years later, while working in Sydney at Australia’s national science agency, CSIRO , he realised that he could adapt the mathematical technique to unscramble data sent wirelessly over many different frequencies, allowing them to be recombined at a receiver. And so, Wi-Fi was born.

It’s amazing to think how far cosmology has come in a century, and how much it has helped create astonishing advances in technology and living standards that we take for granted. More is known about the cosmos today by the average person than by the best informed scholars who lived in 99 per cent of human history.

And yet, we barely understand just 5 per cent of the physical universe. Whatever the explanation for the puzzling 95 per cent that remains, it will surely lead to important new insights — and, no doubt, bring equally stupendous technological advances.

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Humanity

Wilson da Silva

Wilson da Silva is a science journalist in Sydney | www.wilsondasilva.com | https://bit.ly/3kIF1SO

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