The International Fusion Energy Project (ITER) fusion reactor, consisting of 19 massive coils looped into multiple toroidal magnets, was originally slated to begin its first full test in 2020. Now scientists say it will fire in 2039 at the earliest.

This means that fusion power, of which ITER's tokamak is at the forefront, is very unlikely to arrive in time to be a solution for the climate crisis.

"Certainly, the delay of ITER is not going in the right direction," Pietro Barabaschi, ITER's director general, said at a news conference on Wednesday (July 3). "In terms of the impact of nuclear fusion on the problems humanity faces now, we should not wait for nuclear fusion to resolve them. This is not prudent."

The world's largest nuclear fusion reactor is the product of collaboration between 35 countries — including every state in the European Union, Russia, China, India and the U.S. — ITER contains the world's most powerful magnet, making it capable of producing a magnetic field 280,000 times as strong as the one shielding Earth.

The reactor's impressive design comes with an equally hefty price-tag. Originally slated to cost around $5 billion and fire up in 2020, it has now suffered multiple delays and its budget swelled beyond $22 billion, with an additional $5 billion proposed to cover additional costs. These unforeseen expenses and delays are behind the most recent, 15-year delay.

Related: Nuclear fusion reactor in UK sets new world record for energy output

Scientists have been trying to harness the power of nuclear fusion — the process by which stars burn — for more than 70 years. By fusing hydrogen atoms to make helium under extremely high pressures and temperatures, main-sequence stars convert matter into light and heat, generating enormous amounts of energy without producing greenhouse gases or long-lasting radioactive waste.

But replicating the conditions found inside the hearts of stars is no simple task. The most common design for fusion reactors, the tokamak, works by superheating plasma (one of the four states of matter, consisting of positive ions and negatively charged free electrons) before trapping it inside a donut-shaped reactor chamber with powerful magnetic fields.

Keeping the turbulent and superheated coils of plasma in place long enough for nuclear fusion to happen, however, has been challenging. Soviet scientist Natan Yavlinsky designed the first tokamak in 1958, but no one has since managed to create a reactor that is able to put out more energy than it takes in.

One of the main stumbling blocks is handling a plasma that's hot enough to fuse. Fusion reactors require very high temperatures (many times hotter than the sun) because they have to operate at much lower pressures than is found inside the cores of stars.

The core of the actual sun, for example, reaches temperatures of around 27 million Fahrenheit (15 million Celsius) but has pressures roughly equal to 340 billion times the air pressure at sea level on Earth.

Cooking plasma to these temperatures is the relatively easy part, but finding a way to corral it so that it doesn't burn through the reactor or derail the fusion reaction is technically tricky. This is usually done either with lasers or magnetic fields.

In this excerpt from her new book "Vector: A Surprising Story of Space, Time, and Mathematical Transformation", mathematician Robyn Arianrhod explores the 4,000-year evolution of the language of mathematics — from complex descriptions to the symbolic form we know today.

Learning to think symbolically

Algebra has been part of mathematics since records began nearly 4,000 years ago, but not always in the symbolic form we learn today. In fact, for most of those four millennia it was written entirely in words and numerals — although works such as Euclid’s famous 300 B.C.E. textbook "Elements" also included geometric diagrams, to help prove such things as Pythagoras's theorem, and to show how to expand squares that we would write today as (a+b)^2.

So "algebra" was communicated in cumbersome word problems or increasingly complicated diagrams — although geometry did have its advantages. For instance, it's the easiest way to prove Pythagoras's theorem. In figure 1.1, I've given an algebraic adaptation of such a proof, although the ancients simply rearranged the diagram to show visually that the shaded area is equal to the sum of the areas of the squares on the adjacent sides of the triangle — a pretty clever approach!

It took a long time for algebra to emerge from arithmetic and geometry as a separate subject. It didn't even get its name until medieval times, and that was thanks to the ninth-­century Persian mathematician Muhammed ibn-­Mūsā (al-­)Khwārizmī… He studied at Caliph al-­Ma’mūn’s pioneering Baghdad-­based university, or "House of Wisdom," when the great Arabic translation movement was at its height: Greek, Indian, and other ancient manuscripts were being collected from all corners of the burgeoning Islamic empire and translated into Arabic.

Imperialism is rarely ethical and often violent, but it can ultimately lead to cultural cross-­fertilization, and in this case the visionary translation movement was so important that by the 12th century, Europeans were learning Arabic in order to translate these manuscripts into Latin — including Ptolemy’s "Almagest" and Euclid’s "Elements," along with new Arabic works such as those of al-­Khwārizmī. The name "algebra” famously comes from the first word in the title of his book "Al-Jabr wa’l muqābalah" — which means something like "The Compendious Book on Calculation by Completion and Balancing."

Judging from the problems al-­Khwārizmī included, an example of what he meant by "Completion" is "completing the square," the method you might have learned in school to solve quadratic equations...

Al-­Khwārizmī didn't write equations in the symbolic form we use today, either. In fact, to modern eyes his book is more arithmetical than algebraic, and one of its important impacts in Europe, when it was translated into Latin, was the popularization of the Hindu-­Arabic decimal system of numeration that eventually evolved into our modern one.

Yet Al-­Khwārizmī is often called the "father of algebra." He may have used words rather than symbols, and the problems he included may have been simple — his purpose, he tells us, was to teach students how to solve basic problems in "cases of inheritance, legacies, partitions, lawsuits and trade, and in all their dealings with one another, or where the measuring of lands, the digging of canals, geometrical computation, and other objects of various sorts and kinds are concerned."

But he systematically set out word-­form linear and quadratic equations, with algorithmic methods for solving them — that is, for finding the "unknown numbers," our modern x's and y's. In fact, the English word "algorithm” — meaning a set of rules for performing a calculation or other operation — comes from "algorismi,” an early Latinized attempt at Al-­Khwārizmī.

…

The beauty of symbolic equations is that it's much easier to see these general patterns when you can see a problem at a glance. Compare this:

Take the square of the unknown number,
then add the unknown number to itself
and take the sum away from the square;
now let the total be eight.

with this:

x^2–2x=8

And there's more: The earliest mathematicians solved each equation separately, but it's easier if you can see that whatever method works for the equation x^2–2x=8 will also work for any equation of the same form, x^2–ax=b. Eventually, ancient mathematicians did begin to recognize this, but progress was relatively slow because they had to keep all these patterns in their heads, or in long, convoluted sentences, and it was easy to lose track.

The first to publish any equation in a transparent, recognizably modern symbolic form were [Thomas] Harriot's executors in 1631, and then [René] Descartes in an appendix to his 1637 "Discourse on Method." (There were a few earlier attempts, but the symbolism — more properly called abbreviation — was tortured and idiosyncratic.) Even the +, −, =, and × signs we take for granted only came into widespread use in the 17th century. Which means that the earlier algebraists we know of — the ancient Mesopotamians, Egyptians, Chinese, and Greeks, the medieval Indians, Persians, and Arabs, as well as the early modern Europeans — all had expressed their equations mostly in words or pictorial word images.

Related: 9 equations that changed the world

It is a singular skill to think symbolically, as this long history shows. Take the word problem I gave above: it is an example of algorithmic thinking. But symbolic thinking is algorithmic and more, for its symbols sometimes contain the seeds of a new kind of creativity — a new kind of far-­reaching yet economical thought.

A classic case is Albert Einstein’s E=mc^2. Einstein did not set out to find the connection between energy and matter. Rather, he simply wanted to calculate the kinetic energy of a moving electron according to his new theory of relativity, so that his theoretical prediction could be tested experimentally.

A few months later, however, 26-­year-­old Einstein began to realize the significance of his equation. He wrote it up in his fifth groundbreaking paper of 1905, his annus mirabilis, but it would take him two more years to tease out the full, dramatic implications of this symbolic relationship. To realize that this wasn’t just a calculation about a particular form of energy and a particular type of matter, it was general: if a body gains (or loses) energy, it also gains (or loses) mass. This bizarre idea is alien to all our commonsense experience — but there it was, hidden in the symbols of his equation. It took experimental physicists decades to experimentally confirm this astonishing mathematical prediction.

A much simpler and earlier example is the sequence of powers x, x^2, x^3 and so on. The first "power" is 1, so x is really x^1 , where the 1 was traditionally linked geometrically to a 1-­D line. The next two, x^2 and x^3, are pronounced "x squared" and "x cubed" by analogy with the area of a square and the volume of a cube. These names highlight the way that early mathematicians thought geometrically rather than algebraically, because of the tangible nature of geometry. By contrast, symbolic algebra is abstract: you have to give it meaning, even if it is simply the display of an interesting pattern such as x, x^2, x^3, x^4,... But this flexibility is algebra's great strength. You can write down as many (finite) higher powers as you like, without having to visualize them as physical objects.

This may sound obvious today, but it took three and a half thousand years for mathematicians to move from solving quadratic equations — "quadratic" derives from the Latin for "square," so quadratic equations are those whose highest power is x^2 (the unknown multiplied by itself, as the ancients put it) — to solving "cubic" and higher equations. These higher-degree equations are much more difficult, of course; but part of the reason solutions didn't come easily was that algebra was tied to words and concrete images for such a very long time.

For instance, I mentioned Al-­Khwārizmī’s "completing the square" in order to solve a quadratic equation. It's actually a 4,000-­year-­old problem, dating back (as far as the historical record shows) to cuneiform tablets made by mathematicians living, like Al-Khwārizmī, in the region of modern-­day Iraq. These ancient Mesopotamians solved quadratic equations by literally completing a square.

Here is a typical teaching problem of the time: "Add 20 of my length to the area of my square, [to get] 21. How square is my square?" This type of problem, and the algorithm for solving it, is similar to those taught today — except that four millennia ago, the method was worked out entirely geometrically. First, draw a square of arbitrary side x (in modern notation); then add to it a rectangle of dimensions 20 [by] x. Now split this additional rectangle into two equal smaller ones and arrange them beside and below the original square. Finally, complete this new, larger square, as in figure 1.2.

The Mesopotamians had practical problems in mind when they developed this method, at least initially. Living in a land where water was at a premium, their tablets contain many problems relating to canal and reservoir excavations, the capacity of cisterns, the construction and repair of dams and levees, and administrative accounts relating to these tasks — and to solve these problems, these ancient mathematicians had to solve equations relating to areas and volumes.

Nearly 3,000 years later, Al-­Khwārizmī, too, focused on similar practical problems, and he used a similar geometrical method of completing the square — and so did other mathematicians right up to the 17th century.

Using computer simulations of stellar evolution, researchers found that dark matter particles captured by these stars' gravity may frequently collide with and "annihilate" each other inside the star, transforming into ordinary particles while releasing a significant amount of energy. 

This additional energy source could maintain the star's stability and potentially make it immortal, even after its regular supply of nuclear fuel has run dry, the researchers suggest.

"Stars burn hydrogen in nuclear fusion," lead study author Isabelle John, a doctoral candidate in astroparticle physics at Stockholm University, told Live Science via email. "The outward pressure from this balances out the inward pressure from the gravitational forces, and keeps the stars in a stable equilibrium." 

However, many stars spotted near the Milky Way's central black hole seem to be far younger than theories of stellar evolution predict. To investigate this mystery, the researchers tested whether the stars could be drawing energy from the plentiful supply of dark matter thought to exist at the galactic center. 

"Our simulations show that if stars can collect large amounts of dark matter, which annihilates inside the star, this can provide a similar outward pressure, making the star stable due to dark matter annihilation rather than nuclear fusion — so stars can use dark matter as a fuel instead of hydrogen," John said. "The important difference is that stars use up their hydrogen, which will eventually cause them to die. On the other hand, stars can collect dark matter continuously."

The study, published to the preprint server arXiv in May, has not been peer reviewed yet.

Stars defying theory

Stellar evolution is a well-studied subject. Relationships among a star's age, luminosity, size and temperature have been derived with high precision both with theory and astronomical data. However, recent observations have shown that the properties of stars near the center of the Milky Way defy the generally accepted theory of stellar evolution.

Related: Baby stars that defy explanation are 'swarming like bees' around Milky Way's supermassive black hole

"The innermost stars of our Galaxy, the S-cluster stars, show a series of properties that [are] not found anywhere else: It is not clear how they got so close to the center, where the environment is thought to be rather hostile to star formation," John explained. "They also seem to be much younger than what would be expected if the stars had moved there from somewhere else. Additionally, it seems like there are unexpectedly many heavy stars."

These strange properties of the S-cluster stars could be explained by the presence of an additional source of energy within them. For instance, this extra energy source could allow the star to burn hydrogen — the usual energy source — at a lower rate, causing it to age more slowly and appear younger than it actually is.

In their recent study, John, along with Tim Linden of Stockholm University and Rebecca K. Leane of the SLAC National Accelerator Laboratory at Stanford University, suggested that this source could be the annihilation of dark matter particles. This explanation aligns with the fact that greater amounts of dark matter are believed to lurk at the galaxy's center, right where the oddball stars were observed. 

"Throughout most of the Milky Way, the dark matter density is not high enough to affect stars," John said. "But at the Galactic Center, the amount of dark matter is very high, potentially many billion times higher than on Earth."

Virtual annihilation

To test their hypothesis, the researchers conducted a computer simulation of the life cycle of a star surrounded by a dark matter cloud with a density matching that of the galactic center. They assumed dark matter consists of weakly interacting massive particles, one of the primary candidates for dark matter components.

Since dark matter particles have not yet been found in laboratory experiments, the strength of their interaction with ordinary matter and the rate at which they annihilate each other are not known. But the study showed that for certain values of these quantities, the dark-matter-based mechanism of energy production perfectly explained the observed properties of the S-cluster stars.

However, to confirm their explanation, the authors believe that more stars need to be discovered near the galactic center. Additionally, more precise measurements of the parameters of known stars must be conducted to reliably compare observations with theoretical predictions. Hopefully, such observations will be possible in the near future using the Very Large Telescope in Chile or the Keck Observatory in Hawaii, the researchers said.

"More precise observations of the S-cluster stars will provide us with more information about these stars and ongoing processes," John said. "This will show if the observations are consistent with our simulations, or if other explanations of their unusual properties become more favorable."

A wealth of astrophysical and cosmological evidence points to the existence of dark matter, from the inexplicable rotation curves of certain galaxies to the growth of the largest structures in the universe. Attempts to explain this wide variety of observations with alternative formulations of gravity have failed, so the vast majority of astronomers think dark matter is some unknown form of matter that only rarely interacts with light or with normal matter.

But that is a very broad idea that encompasses a lot of possibilities. Dark matter may be made of massive particles, but searches for those kinds of particles have largely turned up empty. So an intriguing alternative is that dark matter is exceptionally light, either in the form of theoretical particles known as "axions" or as an exotic form of photon that carries a bit of mass.

With that incredible lightness — millions of times lighter than the lightest known particles — dark matter could act in very strange ways. In particular, instead of appearing as individual point-like bullets, the dark matter would behave more like large waves that slosh around the cosmos.

In a recent study published to the preprint server arXiv, physicists explored models of ultralight dark matter that wasn't entirely dark, allowing it to interact extremely rarely with normal matter. Most of the time, these interactions barely registered, producing nothing detectable. But in rare cases, the dark matter and normal matter interacted enough to produce a sizable amount of radio waves.

Related: There may be a 'dark mirror' universe within ours where atoms failed to form, new study suggests

This would occur when the dark matter encountered a plasma and when the frequency of dark matter waves lined up with the frequency of plasma waves. When this happened, a resonance would occur, amplifying the interaction and producing radiation in the form of radio waves, the team’s models suggested.

The universe is no stranger to plasmas — all stars spew plasma into space in the form of stellar wind — so theorists had already explored the production of radio waves due to dark matter interacting with environments such as the solar corona or the interstellar medium. But in this new research, the scientists discovered an interaction point much closer to home: our planet's ionosphere.

Earth's ionosphere is the thin, hot layer of the upper atmosphere, and it consists of a loose collection of ionized (charged) particles — a plasma. It naturally has waves sloshing through it, and the researchers discovered that those waves can interact with waves of hypothetical dark matter that might be washing over Earth.

The radio waves produced by this interaction would be barely detectable. But the researchers found that by using a carefully tuned radio antenna to search for a specific frequency of radio waves over the course of a year, they might be able to detect these waves.

This idea is especially promising because Earth's ionosphere offers several advantages over other sources of dark-matter-produced radio waves. For one, the ionosphere naturally reflects many radio waves from deeper space, making it relatively devoid of contaminating signals. Second, the ionosphere is right above us, easy to access, and already the subject of constant monitoring and study.

It's a long shot. This form of dark matter is highly theoretical, and it would take years, if not decades, to perfect the observation technique to search for these radio waves. But if it works, it would be a gold mine, allowing us to study one of the most mysterious elements in the universe right on our cosmic doorstep.

The three-body problem describes a system containing three bodies that exert gravitational forces on one another. While it may sound simple, it's a notoriously tricky problem and "the first real worry of Newton," Billy Quarles, a planetary dynamicist at Valdosta State University in Georgia, told Live Science.

In a system of only two bodies, like a planet and a star, calculating how they'll move around each other is fairly straightforward: Most of the time, those two objects will orbit roughly in a circle around their center of mass, and they'll come back to where they started each time. But add a third body, like another star, and things get a lot more complicated. The third body attracts the two orbiting each other, pulling them out of their predictable paths.

The motion of the three bodies depends on their starting state — their positions, velocities and masses. If even one of those variables changes, the resulting motion could be completely different. 

"I think of it as if you're walking on a mountain ridge," Shane Ross, an applied mathematician at Virginia Tech, told Live Science. "With one small change, you could either fall to the right or you could fall to the left. Those are two very close initial positions, and they could lead to very different states."  

There aren't enough constraints on the motions of the bodies to solve the three-body problem with equations, Ross said. 

Related: Cosmic 'superbubbles' might be throwing entire galaxies into chaos, theoretical study hints

But some solutions to the three-body problem have been found. For example, if the starting conditions are just right, three bodies of equal mass could chase one another in a figure-eight pattern. Such tidy solutions are the exception, however, when it comes to real systems in space.

Certain conditions can make the three-body problem easier to parse. Consider Tatooine, Luke Skywalker's fictional home world from "Star Wars" — a single planet orbiting two suns. Those two stars and the planet make up a three-body system. But if the planet is far enough away and orbiting both stars together, it's possible to simplify the problem. 

"When it's the Tatooine case, as long as you're far enough away from the central binary, then you think of this object as just being a really fat star," Quarles said. The planet doesn't exert much force on the stars because it's so much less massive, so the system becomes similar to the more easily solvable two-body problem. So far, scientists have found more than a dozen Tatooine-like exoplanets, Quarles told Live Science.

But often, the orbits of the three bodies never truly stabilize, and the three-body problem gets "solved" with a bang. The gravitational forces could cause two of the three bodies to collide, or they could fling one of the bodies out of the system forever — a possible source of "rogue planets" that don't orbit any star, Quarles said. In fact, three-body chaos may be so common in space that scientists estimate there may be 20 times as many rogue planets as there are stars in our galaxy.

When all else fails, scientists can use computers to approximate the motions of bodies in an individual three-body system. That makes it possible to predict the motion of a rocket launched into orbit around Earth, or to predict the fate of a planet in a system with multiple stars.

With all this tumult, you might wonder if anything could survive on a planet like the one featured in Netflix's "3 Body Problem," which — spoiler alert — is trapped in a chaotic orbit around three stars in the Alpha Centauri system, our solar system's nearest neighbor. 

"I don't think in that type of situation, that's a stable environment for life to evolve," Ross said. That's one aspect of the show that remains firmly in the realm of science fiction.

Einstein discovered that the universe has a "speed limit." 

His special theory of relativity, which explains the relationship between mass, time and space, suggests that as an object approaches the speed of light, its mass and energy become infinite, as Space.com explains. That means that it's impossible for an object to travel faster than light.

He argued that space and time are interwoven. 

While Einstein didn't invent the concept of space-time, which was first proposed by German mathematician Hermann Minkowski, his special theory of relativity showed that space and time grow and shrink relative to one another in order to keep the speed of light constant for the observer. Based on his theory, when we travel through space, time moves a tiny bit slower. At incredible speeds, like the speed of light, time stands still.

He won the Nobel Prize for his explanation of the photoelectric effect. 

The photoelectric effect is the observation that metal plates eject electrons when hit by beams of high-energy light. The photoelectric effect can't be explained by classical physics, which saw light as a wave. Einstein proposed that we view light as both a particle and a wave — with the frequency of the wave determining the energy of the particle and vice versa. 

Einstein transformed the way physicists view light.

Before Einstein's special theory of relativity, physicists thought that light traveled through a substance called "the luminiferous ether." Throughout the late 19th century, scientists ran experiments to try to prove its existence.

Einstein's fascination with physics was lifelong.

Beginning at age 5, Einstein became captivated by the invisible forces that moved the needle of his compass, according to the American Physical Society. That led to a lifelong quest to explain those invisible forces.

At the age of 12, he taught himself geometry. 

To study, he read out of a textbook, which he dubbed his "holy geometry book" and "second miracle" (the first being his compass needle). 

He wasn't well-liked by his teachers.

One of the instructors at the Luitpold-Gymnasium in Munich, where Einstein received much of his early education, told the young Einstein that nothing good would ever come of his life. 

Einstein played the violin.

At 5 years old, his mother signed him up for lessons. At first, he didn't enjoy playing at all, according to the American Nuclear Society. But after discovering Mozart, he developed a love for the hobby and played into his old age.

He wrote his first scientific paper at the age of 16.

Titled "On the Investigation of the State of the Ether in a Magnetic Field," the essay asked how magnetic fields impact "ether," the theoretical substance that at the time was believed to transmit electromagnetic waves. 

After university, Einstein was rejected from every academic position he applied for.

Eventually, he settled for a job evaluating patent claims for the Swiss government, according to the American Institute of Physics. He described the job, which gave him the time and energy to focus on solving the physics problems that underlie our world, as "a kind of salvation."

He helped convince the physics world that atoms exist. 

Einstein was interested in the problem of Brownian motion, the observation that if you put tiny objects (like pollen) in water, they appear to jump around erratically. Einstein proposed that invisible particles were colliding with the pollen, causing it to move, and came up with a formula describing this phenomenon. In 1908, French physicist Jean Baptiste Perrin tested and confirmed Einstein's theory, swaying the physics world to accept the existence of atoms, according to the American Physical Society. 

Einstein was a pacifist.

At 16, he left Germany to escape mandatory military service. Later, he was one of only four German intellectuals to openly declare their opposition to German participation in World War I, calling nationalism "the measles of the human race." 

Einstein's theories of relativity challenged the view that the universe was static.

His equations predicted a dynamic universe, one that was expanding or contracting. Flummoxed by this finding, Einstein assumed there was a flaw in his equations and introduced a "cosmological constant" which allowed for a universe that didn't change size. When Edwin Hubble confirmed that the universe is, indeed, expanding, Einstein called the cosmological constant "his greatest mistake."

Four of Einstein's most notable papers were all published in one year. 

In 1905, dubbed his "year of miracles," Einstein published his explanation of the photoelectric effect, his theory on Brownian motion, and two papers on his general theory of relativity. 

He was friends with Charlie Chaplin.

Chaplin even invited Einstein and his wife, Elsa Einstein, as his guests of honor at the premier of his 1931 film "City Lights." There, Chaplin famously told Einstein: "The people applaud me because everybody understands me, and they applaud you because no one understands you."

Einstein believed in God.

However, he didn't believe in a personal god that answered prayers. Instead, he thought that God revealed himself through the "harmony" of the universe. "He [God] does not play dice," he famously wrote. 

Einstein was a target for the Nazis.

They sponsored conferences and book burnings against Einstein and labeled his theories "Jewish physics." In 1933, Einstein fled Germany to escape Nazi death threats, settling first in Britain and then eventually in Princeton, New Jersey.

His work enabled the development of the atomic bomb.

The equation E = mc2 provided the theoretical basis for the weapon's potential — but didn't explain how to build one. 

At the start of World War II, he wrote to then-President Franklin D. Roosevelt, warning of possible German nuclear weapons research.

He urged the president to initiate development of an atomic bomb — but later regretted doing so, according to the American History of Natural History. In an interview with Newsweek, he said: "Had I known that the Germans would not succeed in developing an atomic bomb, I would have done nothing."

Later, he opposed the use of atomic weapons. 

After the bombing of Hiroshima and Nagasaki, he formed the Emergency Committee of Atomic Scientists, an organization that educated Americans about the dangers of atomic weapons.

Einstein was a member of the National Association for the Advancement of Colored People (NAACP). 

He saw parallels between the experience of Black Americans and his experience as a Jew living in Nazi Germany. In a 1946 commencement speech delivered at the historically black college Lincoln University, Einstein decried segregation and called it "a disease of white people," Smithsonian magazine reported.

The FBI kept a 1,400-page dossier on Einstein.

His pacifist stance and left-leaning politics made him suspicious in the eyes of the agency as a potentially "extreme radical," National Geographic reported. This was especially true during the McCarthy era, when many people were accused of communism or blacklisted from work. 

Einstein was asked to be the president of Israel. 

However, when he was offered the position in 1952, he was already near the end of his life, according to the American Museum of Natural History. Due to his poor health and lack of experience "dealing properly with people," he declined.

He did not believe that black holes could exist. 

In a 1939 article, he laid out a series of arguments trying to prove that black holes — objects with such high gravity that even light can't escape them — are impossible, Scientific American reported. Ironically, It's Einstein's general theory of relativity that shows us black holes do, in fact, exist. 

He did believe in the possibility of wormholes.

In a 1935 paper published in the journal Physics Reviews, Einstein and physicist Nathan Rosen proposed that near objects of enormous mass, space-time might curve inward like a rubber tube, creating a tunnel between two different regions. If they exist, these objects would enable travel across vast distances of time and space, Space.com reported.

Einstein didn't wear socks. 

Black holes weren't the only holes this physicist vehemently disagreed with. Because socks invariably develop holes, he disliked them to such an extent that he refused to wear them, according to the American Nuclear Society.

Einstein's brain was stolen.

After his death in 1955, pathologist Thomas Harvey dissected and stole Einstein's brain during an autopsy. Harvey, who wanted to discover the anatomical secrets of genius, eventually received permission from Einstein's son to use the brain for scientific research.

Research on Einstein's brain found extra folding. 

The human brain's wrinkled surface gives it a much larger surface area than a smooth brain and is an important part of advanced cognition. Einstein's brain had extra folding in its gray matter, the site of conscious thinking, especially in the frontal lobe, where abstract thought and planning occurs.

He loved sailing. 

However, the physicist was terrible at it — so terrible, in fact, that his neighbors frequently had to rescue him when is boat invariably capsized, according to the American Nuclear Society.

His birthday is Pi Day. 

March 14 is a special date because written numerically, it matches the first three digits of mathematical constant pi: 3.14. However, that's not the only reason it's significant. It's also the birthday of Einstein, who was born in 1879.

Einstein invented a refrigerator. 

The contraption, which he developed alongside colleague Leo Szilard, didn't require motors or coolant. Instead, it used boiling butane to suck energy from a compartment, lowering the temperature inside, Live Science previously reported.

Einstein's ultimate goal was to describe the workings of the entire universe — from subatomic particles to the farthest reaches of space — in one theory. 

He called the concept "The Grand Unified Theory." He never realized this dream, but physicists are still working to find it.

In his new book "CHARGE: Why Does Gravity Rule?", theoretical physicist Frank Close explores the fundamental forces that govern our world, posing questions along the way that seek to explain how the delicate balance of positive and negative charges paved the way for gravity to shape our universe.

In this except, he explains how magnetism, the most tangible fundamental forces, was discovered, where it comes from and how it got its name.   

The force within

Magnetism is a manifestation of electricity, and vice versa. Electricity and magnetism were imprinted into our surroundings from the beginning. Five billion years ago when the new-born Earth was a hot plasma of swirling electrical currents, these flows created magnetic fields. As the magma cooled to form what is today the world's solid outer crust, magnetism was locked into minerals containing iron, such as magnetite.

Today, the Earth's liquid core is still a terpsichorean frenzy of electric currents, which generate a magnetic field. This extends into the atmosphere and far beyond, invisible to our normal senses. But in spreading from its source in the molten core to the heavens above, it first permeates the Earth's crust. This is where it leaves a tangible imprint, evidence that there exists a force more powerful than gravity at work within the Earth whose influence extends very far.

Way back in the earliest Precambrian, four billion years ago, as the surface cooled, atomic elements accumulated in the strata. The most stable of these, iron, is today one of the most abundant elements in the crust. Igneous rocks formed from volcanic lava. These rocks have the property that in the presence of a magnetic field, their atoms of iron act like soldiers on parade as they themselves become magnetic. This is exploited in popular demonstrations where the magnetic field of a bar magnet can be made visible.

Small filings of iron are first scattered on the surface of a table and then a magnet is placed carefully among them. Its magnetic field induces magnetism in the iron filings, turning them into thousands of miniature magnets. Each of these duly orients itself in the magnetic field, revealing how the direction of the magnetic force varies from place to place. 

Related: Why do magnets have north and south poles?

The bar magnet is a simple model illustrating what happens for the magnetic Earth itself. Earth's north and south magnetic poles are analogous to those of the bar magnet, our planet's magnetic field extending far into space. There are no iron filings out in space, but there are large amounts of iron ores in the hills, cliffs, and mountains on Earth. In some places, by chance, these magnetic clusters are quite extensive, as on the Isle of Elba and Mount Ida in Asia Minor, where large outcrops retain the magnetic imprint in rocks known historically as lodestone, now named magnetite. 

There are legends how thousands of years ago in ancient Greece, a shepherd wearing leather shoes held in place by iron nails stumbled — literally — across magnetite when the powerful magnetism gripped the nails in his footwear. Whether or not a shepherd named Magnes discovered the eponymous rock, and if so whether it was in Magnesia, north of Athens, or on Mount Ida in Asia Minor, or even another Mount Ida in Crete, it is very likely that such experiences, if less dramatic than in the story, would have happened on various occasions. 

Certainly, the power of magnetism would have been apparent ever since the Iron Age. Lightning is a flash of electric current which generates intense magnetic fields and magnetizes ferrous rocks. Smelting to retrieve the pure iron metal from these sources would have revealed their magnetic attraction. So, the phenomenon has probably been known for some 3,000 years. Like the discovery of fire, that of magnetism probably arose in several places independently, all inspired by the natural magnetization of iron in rocks. 

For magnetic rocks are ubiquitous. By the sixteenth century travellers recorded the best examples, from East India and the Chinese coast: "Very massive and weighty, [the stone] will draw or lift up the just weight of itself in iron or steel" [Robert Norman, The Newe Attractive, 1581]. As knowledge of the phenomenon spread from Greek myth to Latin, and on to English, the names morphed into 'Magnes rock' or 'magnet'. 

© [Oxford University Press]

Extract from CHARGE: Why Does Gravity Rule? by Frank Close, published by Oxford University Press, available in hardback and eBook formats 

The images — taken during just 24 hours of observation — show twinkling galaxy clusters, colorful wisps of gas clouds and one of the largest-known spiral galaxies in unprecedented levels of detail. 

By capturing thousands of images like these for the next six years, the space telescope will catalog a third of the entire night sky and image more than a billion galaxies that are up to 10 billion years old, according to ESA.

"This space telescope intends to tackle the biggest open questions in cosmology," Valeria Pettorino,  a Euclid project scientist, said in a statement. "And these early observations clearly demonstrate that Euclid is more than up to the task."

Launched into orbit on July 1, 2023, Euclid was designed to compile wide-lens images to help scientists hunt for two of the universe's most mysterious components: dark matter and dark energy.

Related: Mysterious 'Green Monster' lurking in James Webb photo of supernova remnant is finally explained

Researchers think dark matter and dark energy together make up about 95% of the universe, but they do not interact with light so can't be detected directly. Instead, scientists study these mysterious components by observing the way they interact with the visible universe around them: Dark matter can be seen by observing its gravitational warping effects on galaxies; and dark energy in the force propelling the universe's runaway expansion.

By collecting images across its enormous field of view, Euclid will help scientists to detect the telltale clues of warped matter by creating two maps — one of the gravitational lensing of galaxies that could reveal dark matter, and the other of matter shock waves called baryon acoustic oscillations that can measure dark energy.

But besides having immense scientific value, Euclid's images are also stunning. Here's our guide to the five released on Thursday (May 23).

Abell 2390 and Abell 2764

Euclid's first image is of the galaxy cluster Abell 2390, a gigantic grouping of 50,000 galaxies located inside the Pegasus constellation 2.7 billion light-years from Earth. The image features  "intracluster light" from stars ripped out of their parent galaxies and beaming as lone lanterns in interstellar space. By measuring the warping of light around immense galaxies such as this, Euclid can help reveal the quantity and distribution of invisible dark matter across the universe.

Another image, of the galaxy cluster Abell 2764 that's located 1 billion light-years from Earth in the Phoenix constellation, shows hundreds of galaxies held within a halo of dark matter, with some galaxies spiraling around each other.

Messier 78

This stunning image of the star nursery Messier 78, located 1,300 light-years away within the constellation Orion, shows stars forming between vibrant tendrils of gas and dust. More than 300,000 new objects were revealed by Euclid's powerful infrared eye in this image, including baby stars and ejected rogue planets.

NGC 6744

This image shows the massive spiral galaxy NGC 6744, situated 30 million light-years away within the Local Group — the super-group of more than 20 tight-knit galaxies to which the Milky Way belongs. Euclid's image captured a previously undetected dwarf galaxy orbiting its larger neighbor. By studying this region, scientists hope to understand how stars form within galaxies and discover the role that spiral structures play in this process. 

The Dorado Group

The final image showcases the Dorado Group, a collection of galaxies 62 million light-years away in the constellation Dorado. These sparring galaxies are locked in a complex dance, at the end of which they will collide with each other and merge. 

The five images are part of Euclid's early release observations, and they will be joined by many more images in the coming years. 

"They give just a hint of what Euclid can do," Pettorino said. "We are looking forward to six more years of data to come!"

It should come as no surprise that accomplishing this exercise is no easy feat — even in a small stunt plane or fighter jet — and it takes a skilled pilot to execute it. But is it possible to do a barrel roll in something larger, like a commercial airliner?

Richard P. Anderson — a pilot, professor of aerospace engineering and director of the Eagle Flight Research Center at Embry-Riddle Aeronautical University in Florida — said it is, and even knows people who have proof of doing them.

"I know people on their own with videotapes [doing barrel rolls]," Anderson told Live Science. 

Perhaps the most famous pilot ever to accomplish one in a commercial plane was Alvin Melvin "Tex" Johnston, a test pilot for Boeing. In the summer of 1955, Johnston took a four-engine Boeing 367-80 (also known as the Dash 80) out for a spin — literally.

Related: What happens when a plane makes an emergency landing?

To impress Boeing executives watching from a yacht on Lake Washington near Seattle, the "maverick pilot" did two barrel rolls, along with a chandelle, a stunt in which a pilot combines a 180-degree turn with a climb, according to the Los Angeles Times. That Monday, Johnston's boss called him into his office and asked him what he was doing. Johnston reportedly replied, "Selling airplanes," according to Plane & Pilot Magazine.

So how did he successfully execute a barrel roll in such a large aircraft? Anderson said the size of the plane doesn't matter as much as the pilot's ability to temper the amount of g-forces placed on the aircraft during the roll.

"The physics are the same regardless of the size of the airplane," Anderson said. "In a barrel roll, the pilot is trying to keep the g-loading on the airplane near 1 g. In other words, pretty close to what we feel here on Earth."

To complete the maneuver, the pilot must do the roll while also pitching the plane's nose up and then letting the nose fall downward — all while flying the aircraft at cruising speed, which is roughly 550 to 600 mph (885 to 965 km/h), as if it’s soaring through a barrel, according to Flying magazine. 

"The only real limiting thing about doing a barrel roll is how fast the airplane rolls," Anderson said. "In a barrel roll, what you do is pull the nose up, and as you do the roll, you let the nose fall, which allows you to keep this low-stress environment. As the nose falls as you roll, what you have to do is be able to get the airplane all the way around in its roll prior to the nose pointing too far down. As long as the airplane has a reasonable roll rate, the physics say that any size airplane can do it."

David Haglund, a veteran pilot for the U.S. Air Force and a docent at The Museum of Flight near Seattle, added that the amount of airspace available to complete the roll is also important, especially in a large airplane versus a small Cessna.

"Before performing this maneuver, a pilot would consider the airspace available," Haglund told Live Science in an email. "In an airliner, a barrel roll would require a block of altitude 2,000 feet [600 meters] above and below the level flight altitude (4,000 feet total) [12,000 m] to be on the safe side."

But although it's physically possible, some manufacturers have built a limitation into large, modern-day aircraft, perhaps to dissuade any future Tex Johnstons from performing similar acrobatic feats, especially with passengers on board.

"The Airbus doesn't give the pilot the ability to roll beyond 60 degrees of bank without disabling part of the auto-flight system that governs the plane's operating envelope," said Haglund, who has experience flying A330 and A350 models.

For nearly a century, scientists have known that the universe is expanding. But in recent decades, physicists have found that different types of measurements of the expansion rate — called the Hubble parameter — produce puzzling inconsistencies.

To resolve this paradox, a new study suggests incorporating quantum effects into one prominent theory used to determine the expansion rate.

"We tried to resolve and explain the mismatch between the values of the Hubble parameter from two different prominent types of observations," study co-author P.K. Suresh, a professor of physics at the University of Hyderabad in India, told Live Science via email.

An expanding problem

The universe's expansion was first identified by Edwin Hubble in 1929. His observations with the largest telescope of that time revealed that galaxies farther from us appear to move away at faster speeds. Although Hubble initially overestimated the expansion rate, subsequent measurements have refined our understanding, establishing the current Hubble parameter as highly reliable.

Later in the 20th century, astrophysicists introduced a novel technique to gauge the expansion rate by examining the cosmic microwave background, the pervasive "afterglow" of the Big Bang.

However, a serious problem arose with these two types of measurements. Specifically, the newer method produced a Hubble parameter value almost 10% lower than the one deduced from the astronomical observations of distant cosmic objects. Such discrepancies between different measurements, called the Hubble tension, signal potential flaws in our understanding of the universe's evolution.

Related: Newfound 'glitch' in Einstein's relativity could rewrite the rules of the universe, study suggests

In a study published in the journal Classical and Quantum Gravity, Suresh and his colleague from the University of Hyderabad, B. Anupama, proposed a solution to align these disparate results. They underscored that physicists infer the Hubble parameter indirectly, employing our universe's evolutionary model based on Einstein's theory of general relativity.

The team argued for revising this theory to incorporate quantum effects. These effects, intrinsic to fundamental interactions, encompass random field fluctuations and the spontaneous creation of particles from the vacuum of space.

Despite scientists' ability to integrate quantum effects into theories of other fields, quantum gravity remains elusive, making detailed calculations extremely difficult or even impossible. To make matters worse, experimental studies of these effects require reaching temperatures or energies many orders of magnitude higher than those achievable in a lab.

Acknowledging these challenges, Suresh and Anupama focused on broad quantum-gravity effects common to many proposed theories.

"Our equation doesn't need to account for everything, but that does not prevent us from testing quantum gravity or its effects experimentally," Suresh said.

Their theoretical exploration revealed that accounting for quantum effects when describing the gravitational interactions in the earliest stage of the universe's expansion, called cosmic inflation, could indeed alter the theory's predictions regarding the properties of the microwave background at present, making the two types of Hubble parameter measurements consistent.

Of course, final conclusions can be drawn only when a full-fledged theory of quantum gravity is known, but even the preliminary findings are encouraging. Moreover, the link between the cosmic microwave background and quantum gravitational effects opens the way to experimentally studying these effects in the near future, the team said.

"Quantum gravity is supposed to play a role in the dynamics of the early universe; thus its effect can be observed through measurements of the properties of the cosmic microwave background," Suresh said.

"Some of the future missions devoted to studying this electromagnetic background are highly probable and promising to test quantum gravity. … It provides a promising suggestion to resolve and validate the inflationary models of cosmology in conjunction with quantum gravity."

Additionally, the authors posit that quantum gravitational phenomena in the early universe might have shaped the properties of gravitational waves emitted during that period. Detecting these waves with future gravitational-wave observatories could further illuminate quantum gravitational characteristics.

"Gravitational waves from various astrophysical sources have only been observed so far, but gravitational waves from the early universe have not yet been detected," Suresh said. "Hopefully, our work will help in identifying the correct inflationary model and detecting the primordial gravitational waves with quantum gravity features."