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Imaginary numbers might seem like unicorns and goblins interesting but irrelevant to reality.

But for describing matter at its roots, imaginary numbers turn out to be essential. They seem to be woven into the fabric of quantum mechanics, the math describing the realm of molecules, atoms and subatomic particles. A theory obeying the rules of quantum physics needs imaginary numbers to describe the real world, two new experiments suggest.

Imaginary numbers result from taking the square root of a negative number. They often pop up in equations as a mathematical tool to make calculations easier. But everything we can actually measure about the world is described by real numbers, the normal, nonimaginary figures were used to (SN: 5/8/18). Thats true in quantum physics too. Although imaginary numbers appear in the inner workings of the theory, all possible measurements generate real numbers.

Quantum theorys prominent use of complex numbers sums of imaginary and real numbers was disconcerting to its founders, including physicist Erwin Schrdinger. From the early days of quantum theory, complex numbers were treated more as a mathematical convenience than a fundamental building block, says physicist Jingyun Fan of the Southern University of Science and Technology in Shenzhen, China.

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Some physicists have attempted to build quantum theory using real numbers only, avoiding the imaginary realm with versions called real quantum mechanics. But without an experimental test of such theories, the question remained whether imaginary numbers were truly necessary in quantum physics, or just a useful computational tool.

A type of experiment known as a Bell test resolved a different quantum quandary, proving that quantum mechanics really requires strange quantum linkages between particles called entanglement (SN: 8/28/15). We started thinking about whether an experiment of this sort could also refute real quantum mechanics, says theoretical physicist Miguel Navascus of the Institute for Quantum Optics and Quantum Information Vienna. He and colleagues laid out a plan for an experiment in a paper posted online at arXiv.org in January 2021 and published December 15 in Nature.

In this plan, researchers would send pairs of entangled particles from two different sources to three different people, named according to conventional physics lingo as Alice, Bob and Charlie. Alice receives one particle, and can measure it using various settings that she chooses. Charlie does the same. Bob receives two particles and performs a special type of measurement to entangle the particles that Alice and Charlie receive. A real quantum theory, with no imaginary numbers, would predict different results than standard quantum physics, allowing the experiment to distinguish which one is correct.

Fan and colleagues performed such an experiment using photons, or particles of light, they report in a paper to be published in Physical Review Letters. By studying how Alice, Charlie and Bobs results compare across many measurements, Fan, Navascus and colleagues show that the data could be described only by a quantum theory with complex numbers.

Another team of physicists conducted an experiment based on the same concept using a quantum computer made with superconductors, materials which conduct electricity without resistance. Those researchers, too, found that quantum physics requires complex numbers, they report in another paper to be published in Physical Review Letters. We are curious about why complex numbers are necessary and play a fundamental role in quantum mechanics, says quantum physicist Chao-Yang Lu of the University of Science and Technology of China in Hefei, a coauthor of the study.

But the results dont rule out all theories that eschew imaginary numbers, notes theoretical physicist Jerry Finkelstein of Lawrence Berkeley National Laboratory in California, who was not involved with the new studies. The study eliminated certain theories based on real numbers, namely those that still follow the conventions of quantum mechanics. Its still possible to explain the results without imaginary numbers by using a theory that breaks standard quantum rules. But those theories run into other conceptual issues, making them ugly, he says. But if youre willing to put up with the ugliness, then you can have a real quantum theory.

Despite the caveat, other physicists agree that the quandaries raised by the new findings are compelling. I find it intriguing when you ask questions about why is quantum mechanics the way it is, says physicist Krister Shalm of the National Institute of Standards and Technology in Boulder, Colo. Asking whether quantum theory could be simpler or if it contains anything unnecessary, these are very interesting and thought-provoking questions.

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Quantum physics requires imaginary numbers to explain reality - Science News Magazine

Mathematical equations offer unique windows into the world. They make sense of reality and help us see things that haven't been previously noticed. So its no surprise that new developments in math have often gone hand in hand with advancements in our understanding of the universe. Here, we take a look at nine equations from history that have revolutionized how we look at everything from tiny particles to the vast cosmos.

One of the first major trigonometric rules that people learn in school is the relationship between the sides of a right triangle: the length of each of the two shorter sides squared and added together equals the length of the longest side squared. This is usually written as a^2 + b^2 = c^2, and it has been known for at least 3,700 years, since the time of the ancient Babylonians.

The Greek mathematician Pythagoras is credited with writing down the version of the equation used today, according to the University of St. Andrews in Scotland. Along with finding use in construction, navigation, mapmaking and other important processes, the Pythagorean theorem helped expand the very concept of numbers. In the fifth century B.C., the mathematician Hippasus of Metapontum noticed that an isosceles right triangle whose two base sides are 1 unit in length will have a hypotenuse that is the square root of 2, which is an irrational number. (Until that point, no one in recorded history had come across such numbers.) For his discovery, Hippasus is said to have been cast into the sea, because the followers of Pythagoras (including Hippasus) were so disturbed by the possibility of numbers that went on forever after a decimal point without repeating, according to an article from the University of Cambridge.

British luminary Sir Isaac Newton is credited with a large number of world-shattering findings. Among them is his second law of motion, which states that force is equal to the mass of an object times its acceleration, usually written asF=ma. An extension of this law, combined with Newton's other observations, led him, in 1687, to describe what is now called his law of universal gravitation. It is usually written as F= G (m1* m2) / r^2, where m1 and m2 are the masses of two objects and r is the distance between them. G is a fundamental constant whose value has to be discovered through experimentation. These concepts have been used to understand many physical systems since, including the motion of planets in the solar system and the means to travel between them using rockets.

Using Newton's relatively new laws, 18th-century scientists began analyzing everything around them. In 1743, French polymath Jean-Baptiste le Rond d'Alembert derived an equation describing the vibrations of an oscillating string or the movement of a wave, according to a paper published in 2020 in the journal Advances in Historical Studies. The equation can be written as follows:

1/v^2 * ^2y/t^2= ^2y/x^2

In this equation, v is the velocity of a wave, and the other parts describe the displacement of the wave in one direction. Extended to two or more dimensions, the wave equation allows researchers to predict the movement of water, seismic and sound waves and is the basis for things like the Schrdinger equationof quantum physics, which underpins many modern computer-based gadgets.

Even if you haven't heard of the French baron Jean-Baptiste Joseph Fourier, his work has affected your life. That's because the mathematical equations he wrote down in 1822 have allowed researchers to break down complex and messy data into combinations of simple waves that are much easier to analyze. The Fourier transform, as it's known, was a radical notion in its time, with many scientists refusing to believe that intricate systems could be reduced to such elegant simplicity, according to an article in Yale Scientific. But Fourier transforms are the workhorses in many modern fields of science, including data processing, image analysis, optics, communication, astronomy and engineering.

Electricity and magnetism were still new concepts in the 1800s, when scholars investigated how to capture and harness these strange forces. Scottish scientist James Clerk Maxwell greatly boosted our understanding of both phenomena in 1864, when he published a list of 20 equations describing how electricity and magnetism functioned and were interrelated. Later honed to four, Maxwell's equations are now taught to first-year physics students in college and provide a basis for everything electronic in our modern technological world.

No list of transformational equations could be complete without the most famous equation of all. First stated by Albert Einstein in 1905 as part of his groundbreaking theory of special relativity, E = mc^2 showed that matter and energy were two aspects of one thing. In the equation, Estands for energy,mrepresents mass andcis the constant speed of light. The notions contained within such a simple statement are still hard for many people to wrap their minds around, but without E = mc^2, we wouldn't understand how stars or the universe worked or know to build gigantic particle accelerators like the Large Hadron Collider to probe the nature of the subatomic world.

It seems like hubris to think you can create a set of equations that define the entire cosmos, but that's just what Russian physicist Alexander Friedmanndid in the 1920s. Using Einstein's theories of relativity, Freidmann showed that the characteristics of an expanding universe could be expressed from the Big Bang onward using two equations.

They combine all the important aspects of the cosmos, including its curvature, how much matter and energy it contains, and how fast it's expanding, as well as a number of important constants, like the speed of light, the gravitational constant and the Hubble constant, which captures the accelerating expansion of the universe. Einstein famously didn't like the idea of an expanding or contracting universe, which his theory of general relativity suggested would happen due to the effects of gravity. He tried to add a variable into the result denoted by the Greek letter lambda that acted counter to gravity to make the cosmos static. While he later called it his greatest mistake, decades afterwards the idea was dusted off and shown to exist in the form of the mysterious substance dark energy, which is driving an accelerated expansion of the universe.

Most people are familiar with the 0s and 1s that make up computer bits. But this critical concept wouldn't have become popular without the pioneering work of American mathematician and engineer Claude Shannon. In an important 1948 paper, Shannon laid out an equation showing the maximum efficiency at which information could be transmitted, often given as C = B * 2log(1+S/N). In the formula, C is the achievable capacity of a particular information channel, B is the bandwidth of the line, S is the average signal power and N is the average noise power. (The S over N gives the famous signal-to-noise ratio of the system.) The output of the equation is in units of bits per second. In the 1948 paper, Shannon credits the idea of the bit to mathematician John W. Tukey as a shorthand for the phrase binary digit.

Very simple things can sometimes generate unimaginably complex results. This truism might not seem all that radical, but it took until the mid-20th century for scientists to fully appreciate the idea's weight. When the field of chaos theory took off during that time, researchers began to get a handle on the ways that systems with just a few parts that fed back on themselves might produce random and unpredictable behavior. Australian physicist, mathematician and ecologist Robert May wrote a paper, published in the journal Nature in 1976, titled "Simple mathematical models with very complicated dynamics," which popularized the equation xn+1 = k * xn(1 xn).

Xn represents some quantity in a system at the present time that feeds back on itself through the part designated by (1 xn). K is a constant, and xn+1 shows the system at the next moment in time. Though quite straightforward, different values of k will produce wildly divergent results, including some with complex and chaotic behavior. May's map has been used to explain population dynamics in ecological systems and to generate random numbers for computer programming.

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9 equations that changed the world - Livescience.com

The sensory experience of growing productive crops can also help mitigate the psychological effects of long-term space travel. Theres a certain emotional connection to food that doesnt come from a dehydrated space pantry. Spencer says the team cracked open the door of the APH every day to observe their vegetable companions with all the tenderness of home gardeners. When harvest day came, they batted their bounty around the ISS, taking selfies and delighting in watching the fruits pirouetting around the spacecraft. Even when the sharp heat of that first bite made them scrunch up their faces, the astronauts still reveled in the chilies, which they ate with fajita beef and rehydrated tomatoes and artichokes.

We were thinking no heat, so that [the peppers] wouldnt be dangerous, but maybe the astronauts need a little spice in their life, says Paul Bosland, who along with his colleagues at the Chile Pepper Institute genetically engineered the Espaola Improved chili pepper seeds grown in Plant Habitat-04. (They are the new extraterrestrial pride of New Mexico.)

Working with NASA, Bosland cultivated a variety that could accommodate both the nutritional needs of astronauts as well as the logistics of growing a plant in space. Boslands crosses are designed with Mars in mind: Bred to be early-maturing, compact, efficient under low light, resilient in low-pressure environments, and to pack three times the Vitamin C of an orange to prevent scurvy.

Every aspect of the plants growth cycle was mechanized. Seeds were planted along with a specially-developed fertilizer in a soil-less, arselite clay medium, and each quadrant was equipped with salt-absorbing wicks that protected the seedlings from scorching due to the saline residue of the fertilizer. Once they germinated, the astronauts thinned the plants until only four remained. The 180-plus sensors controlled every aspect of their growth conditions, including adjusting the colors of the lights to stunt their growth and keep them at a manageable two-foot height.

Despite the highly-controlled growing environment, microgravity affected the plants in some unforeseen ways. Without a gravitational tug, the flowers and their pollen-laden stamen grew facing upward. Ironically, that thwarted how the APH was supposed to pollinate themby using fans that pulsed soft bursts of air meant to mobilize pollen, the way a breeze would. Instead, astronauts had to fill in as knock-off bees, manually pollinating them one plant at a time.

Microgravity also posed challenges to watering. As demonstrated by the Canadian Space Agency, water behaves differently in microgravity than on Earth. Unable to fall, flow, or ascend, water creates an aqueous layer enveloping the surface of whatever it clings to. But clingy water can suffocate a plants roots; as Bosland notes, chili peppers dont like their feet wet.

This was one of the challenges APH engineer and Kennedy Space Center research scientist Oscar Monje had to solve. The system recycled water in a closed loop; the entire experiment used approximately the same amount of water as an office water cooler. Moisture sensors regulated the exact amount that adhered to a roots surface. Then any water unabsorbed by the plant would evaporate after humidity sensors created the arid environment peppers crave. Its not a technology thats ready to roll out on say, the moon or Mars. The APH uses a watering system thats not sustainable for crop production right now. But its good enough for conducting space biology experiments, Monje says.

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Growing Peppers on the ISS Is Just the Start of Space Farming - newsconcerns