Tag Archives: #einstein

Previously Unknown Letter Reveals Einstein’s Thinking On Bees, Birds and Physics (Physics)

A recently discovered letter written by Albert Einstein discusses a link between physics and biology, seven decades before evidence emerges.

The 1949 letter by the physicist and Nobel laureate discusses bees, birds and whether new physics principles could come from studying animal senses.

It’s a position still being realised within physics to this day, with a growing body of research and understanding of how animals such as birds and bees find their way around.

Now a study led by RMIT University in Melbourne, Australia, discusses how recent discoveries in migratory birds back up Einstein’s thinking 72 years ago.

The previously unpublished letter was shared with researchers by Judith Davys – Einstein had addressed it to her late husband, radar researcher Glyn Davys.

RMIT’s Associate Professor Adrian Dyer has published significant studies into bees and is the lead author of the new paper on Einstein’s letter, published in the Journal of Comparative Physiology A.

Dyer said the letter shows how Einstein envisaged new discoveries could come from studying animals.

“Seven decades after Einstein proposed new physics might come from animal sensory perception, we’re seeing discoveries that push our understanding about navigation and the fundamental principles of physics,” he said.

The letter also proves Einstein met with Nobel laurate Karl von Frisch, who was a leading bee and animal sensory researcher.

In April 1949, von Frisch presented his research on how honeybees navigate more effectively using the polarisation patterns of light scattered from the sky.

The day after Einstein attended von Frisch’s lecture, the two researchers shared a private meeting.

Although this meeting wasn’t formally documented, the recently discovered letter from Einstein provides insight into what they might have talked about.

“It is thinkable that the investigation of the behaviour of migratory birds and carrier pigeons may someday lead to the understanding of some physical process which is not yet known,” Einstein wrote.

Professor Andrew Greentree, a theoretical physicist at RMIT, said Einstein also suggested that for bees to extend our knowledge of physics, new types of behaviour would need to be observed.

“Remarkably, it is clear through his writing that Einstein envisaged new discoveries could come from studying animals’ behaviours,” Greentree said.

More than 70 years since Einstein sent his letter, research is revealing the secrets of how migratory birds navigate while flying thousands of kilometres to arrive at a precise destination.

In 2008, research on thrushes fitted with radio transmitters showed, for the first time, that these birds use a form of magnetic compass as their primary orientation guide during flight.

One theory for the origin of magnetic sense in birds is the use of quantum randomness and entanglement. Both of these physics concepts were first proposed by Einstein.

The letter to Glyn Davys shows the openness of Einstein’s mind to novel possibilities observed in nature and the evidence that he took an interest in von Frish and his bee research.

‘Einstein, von Frisch and the honeybee: a historical letter comes to light’, with Adrian Dyer, Andrew Greentree, Jair Garcia, Elinya Dyer, Scarlett Howard and Fredrich Barth, is published in the Journal of Comparative Physiology A (DOI: 10.1007/s00359-021-01490-6).

Featured image: Letter by Albert Einstein, validated by The Hebrew University of Jerusalem, where Einstein bequeathed his notes, letters and records. © Dyer et al. 2021, J Comp Physiol A / The Hebrew University of Jerusalem


Provided by RMIT University

RUDN University physicist Developed Software Solution To Measure The Black Holes Stability (Astronomy)

Even if a black hole can be described with a mathematical model, it doesn’t mean it exists in reality. Some theoretical models are unstable: though they can be used to run mathematical calculations, from the point of view of physics they make no sense. A physicist from RUDN University developed an approach to finding such instability regions. The work was published in the Physics of the Dark Universe journal.

Even if a black hole can be described with a mathematical model, it doesn’t mean it exists in reality. Some theoretical models are unstable: though they can be used to run mathematical calculations, from the point of view of physics they make no sense. A physicist from RUDN University developed an approach to finding such instability regions. ©RUDN University.

The existence of black holes was first predicted by Einstein’s general theory of relativity. These objects have so strong gravitational pull that nothing, not even light, can escape them. Dense and massive, black holes deform space-time (a physical construct with three spatial and one temporal dimension). Many mathematical models used to describe black holes include corrections to account for such space-time curvatures. The main condition of existence for every black hole model is its stability in cases of minor spatial or temporal changes. Mathematically unstable black holes make no physical sense, as the objects they describe cannot exist in reality. A physicist from RUDN University suggested a method to identify black hole instability parameters in 4D space-time.

“For a model to be considered feasible, a black hole described by it has to remain stable in case of minor space-time fluctuations. One of the most promising approaches to developing alternative gravity theories includes adding corrections to Einstein’s equation, including the fourth-order Gauss-Bonnet correction and the Lovelock correction that provides a higher level of generalization,” said Roman Konoplya, a researcher at the Educational and Research Institute of Gravitation and Cosmology, RUDN University.

The physicist studied stability in the Einstein-Gauss-Bonnet theory in which a black hole is described by Einstein’s equation with a fourth additional component. Previously, he had focused on a different mathematical description of a black hole, the so-called Lovelock theory, that describes a black hole as a sum of an infinite number of components. The instability region turned out to be closely associated with the values of the so-called coupling constants: numerical coefficients by which the corrections to Einstein’s equation are multiplied.

According to the physicist, the Einstein-Gauss-Bonnet model does not provide for the existence of small black holes, because if coupling constants are relatively big compared to other parameters (such as the radius of a black hole), the model almost always turns out to be unstable. The stability region is much bigger if the coupling constant has a negative value. Based on these calculations, he and his team developed a program to calculate black hole stability based on any of its parameters.

“Our approach helps test black hole models for stability. We made the code publicly available so that any of our colleagues could use it to calculate instability regions for models with an unspecified set of parameters,” added Roman Konoplya.

References: R.A.Konoplya, A.Zhidenko et al., “(In)stability of black holes in the 4D Einstein–Gauss–Bonnet and Einstein–Lovelock gravities”, Physics of the Dark Universe, Volume 30, December 2020, 100697 https://doi.org/10.1016/j.dark.2020.100697

Provided by RUDN University

Einstein’s Theory of Relativity, Critical For GPS, Seen In Distant Stars (Astronomy)

What do Albert Einstein, the Global Positioning System (GPS), and a pair of stars 200,000 trillion miles from Earth have in common?

The answer is an effect from Einstein’s General Theory of Relativity called the “gravitational redshift,” where light is shifted to redder colors because of gravity. Using NASA’s Chandra X-ray Observatory, astronomers have discovered the phenomenon in two stars orbiting each other in our galaxy about 29,000 light-years (200,000 trillion miles) away from Earth. While these stars are very distant, gravitational redshifts have tangible impacts on modern life, as scientists and engineers must take them into account to enable accurate positions for GPS.

Image credit: NASA/CXC/M. Weiss

While scientists have found incontrovertible evidence of gravitational redshifts in our solar system, it has been challenging to observe them in more distant objects across space. The new Chandra results provide convincing evidence for gravitational redshift effects at play in a new cosmic setting.

The intriguing system known as 4U 1916-053 contains two stars in a remarkably close orbit. One is the core of a star that has had its outer layers stripped away, leaving a star that is much denser than the Sun. The other is a neutron star, an even denser object created when a massive star collapses in a supernova explosion. The neutron star (grey) is shown in this artist’s impression at the center of a disk of hot gas pulled away from its companion (white star on left).

These two compact stars are only about 215,000 miles apart, roughly the distance between the Earth and the Moon. While the Moon orbits our planet once a month, the dense companion star in 4U 1916-053 whips around the neutron star and completes a full orbit in only 50 minutes. 

In the new work on 4U 1916-053, the team analyzed X-ray spectra — that is, the amounts of X-rays at different wavelengths — from Chandra. They found the characteristic signature of the absorption of X-ray light by iron and silicon in the spectra. In three separate observations with Chandra, the data show a sharp drop in the detected amount of X-rays close to the wavelengths where the iron or silicon atoms are expected to absorb the X-rays. One of the spectra showing absorption by iron is included in the main graphic, and an additional graphic shows a spectrum with absorption by silicon.

However, the wavelengths of these characteristic signatures of iron and silicon were shifted to longer, or redder wavelengths compared to the laboratory values found here on Earth (shown with the dashed line). The researchers found that the shift of the absorption features was the same in each of the three Chandra observations, and that it was too large to be explained by motion away from us. Instead they concluded it was caused by gravitational redshift. 

How does this connect with General Relativity and GPS? As predicted by Einstein’s theory, clocks under the force of gravity run at a slower rate than clocks viewed from a distant region experiencing weaker gravity. This means that clocks on Earth observed from orbiting satellites run at a slower rate. To have the high precision needed for GPS, this effect needs to be taken into account or there will be small differences in time that would add up quickly, calculating inaccurate positions.

All types of light, including X-rays, are also affected by gravity. An analogy is that of a person running up an escalator that is going down. As they do this, the person loses more energy than if the escalator was stationary or going up. The force of gravity has a similar effect on light, where a loss in energy gives a lower frequency. Because light in a vacuum always travels at the same speed, the loss of energy and lower frequency means that the light, including the signatures of iron and silicon, shift to longer wavelengths.

This is the first strong evidence for absorption signatures being shifted to longer wavelengths by gravity in a pair of stars that has either a neutron star or black hole. Strong evidence for gravitational redshifts in absorption has previously been observed from the surface of white dwarfs, with wavelength shifts typically only about 15% of that for 4U 1916-053.

Scientists say it is likely that a gaseous atmosphere blanketing the disk near the neutron star (shown in blue) absorbed the X-rays, producing these results. The size of the shift in the spectra allowed the team to calculate how far this atmosphere is away from the neutron star, using General Relativity and assuming a standard mass for the neutron star. They found that the atmosphere is located 1,500 miles from the neutron star, about half the distance from Los Angeles to New York and equivalent to only 0.7% of the distance from the neutron star to the companion. It likely extends over several hundred miles from the neutron star.

In two of the three spectra there is also evidence for absorption signatures that have been shifted to even redder wavelengths, corresponding to a distance of only 0.04% of the distance from the neutron star to the companion. However, these signatures are detected with less confidence than the ones further away from the neutron star.

Scientists have been awarded further Chandra observation time in the upcoming year to study this system in more detail.

A paper describing these results was published in the August 10th, 2020 issue of The Astrophysical Journal Letter and also appears online. The authors of the paper are Nicolas Trueba and Jon Miller (University of Michigan in Ann Arbor), Andrew Fabian (University of Cambridge, UK), J. Kaastra (Netherlands Institute for Space Research), T. Kallman (NASA Goddard Space Flight Center in Greenbelt, Maryland), A. Lohfink (Montana State University), D. Proga (University of Nevada, Las Vegas), John Raymond (Center for Astrophysics | Harvard & Smithsonian), Christopher Reynolds (University of Cambridge), and M. Reynolds and A. Zoghbi (University of Michigan).

NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s CXC controls science and flight operations from Cambridge and Burlington, Massachusetts.

References: Nicolas Trueba, J.M. Miller, A.C. Fabian, J. Kaastra, T. Kallman, A. Lohfink, D. Proga, J. Raymond, C. Reynolds, M. Reynolds, A. Zoghbi, “A Redshifted Inner Disk Atmosphere and Transient Absorbers in the Ultra-Compact Neutron Star X-ray Binary 4U 1916-053”, ArXiv, pp. 1-15, 2020. DOI: 10.3847/2041-8213/aba9de arXiv:2008.01083

Provided by University Of Michigan

Timekeeping Theory Combines Quantum Clocks And Einstein’s Relativity (Physics)

A phenomenon of quantum mechanics known as superposition can impact timekeeping in high-precision clocks, according to a theoretical study from Dartmouth College, Saint Anselm College and Santa Clara University.

Quantum mechanics allows for a clock to move as if it were simultaneously traveling at two different speeds. New research finds that this leads to a correction in atomic clocks known as “quantum time dilation.” Credit: Petra Korlevic.

Research describing the effect shows that superposition—the ability of an atom to exist in more than one state at the same time—leads to a correction in atomic clocks known as “quantum time dilation.”

The research, published in the journal Nature Communications, takes into account quantum effects beyond Albert Einstein’s theory of relativity to make a new prediction about the nature of time.

“Whenever we have developed better clocks, we’ve learned something new about the world,” said Alexander Smith, an assistant professor of physics at Saint Anselm College and adjunct assistant professor at Dartmouth College, who led the research as a junior fellow in Dartmouth’s Society of Fellows. “Quantum time dilation is a consequence of both quantum mechanics and Einstein’s relativity, and thus offers a new possibility to test fundamental physics at their intersection.”

In the early 1900s, Albert Einstein presented a revolutionary picture of space and time by showing that the time experienced by a clock depends on how fast it is moving—as the speed of a clock increases, the rate at which it ticks decreases. This was a radical departure from Sir Isaac Newton’s absolute notion of time.

Quantum mechanics, the theory of motion governing the atomic realm, allows for a clock to move as if it were simultaneously traveling at two different speeds: a quantum “superposition” of speeds. The research paper takes this possibility into account and provides a probabilistic theory of timekeeping, which led to the prediction of quantum time dilation.

To develop the new theory, the team combined modern techniques from quantum information science with a theory developed in the 1980s that explains how time might emerge out of a quantum theory of gravity.

“Physicists have sought to accommodate the dynamical nature of time in quantum theory for decades,” said Mehdi Ahmadi, a lecturer at Santa Clara University who co-authored the study. “In our work, we predict corrections to relativistic time dilation which stem from the fact that the clocks used to measure this effect are quantum mechanical in nature.”

In the same way that carbon dating relies on decaying atoms to determine the age of organic objects, the lifetime of an excited atom acts as a clock. If such an atom moves in a superposition of different speeds, then its lifetime will either increase or decrease depending on the nature of the superposition relative to an atom moving at a definite speed.

The correction to the atom’s lifetime is so small that it would be impossible to measure in terms that make sense at the human scale. But the ability to account for this effect could enable a test of quantum time dilation using the most advanced atomic clocks.

Just as the utility of quantum mechanics for medical imaging, computing, and microscopy, might have been difficult to predict when that theory was being developed in the early 1900s, it is too early to imagine the full practical implications of quantum time dilation.

References: Smith, A.R.H., Ahmadi, M. Quantum clocks observe classical and quantum time dilation. Nat Commun 11, 5360 (2020). https://doi.org/10.1038/s41467-020-18264-4 link: http://dx.doi.org/10.1038/s41467-020-18264-4

Provided by Dartmouth College

Symmetry and the Laws of Nature (Quantum)

Not until the 17th century did humans seriously think of the possibility that a body of laws exists that would explain all the observed physical reality. Galileo Galilei, René Descartes, and in particular Isaac Newton demonstrated for the first time that a handful of mathematical laws can explain a wealth of phenomena, ranging from falling apples and ocean tides to the motion of the planets. In the 19th century, Michael Faraday and James Clerk Maxwell were able to do the same for electricity and magnetism.

The Hubble Ultra Deep Field. Almost 10,000 galaxies. Looking back to when the universe was less than a billion years old.Source: Credit: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team/Public Domain

Then the 20th century witnessed the birth of not one but two scientific revolutions. First, Einstein’s theories of Special Relativity and General Relativity inextricably linked the concepts of space and time, and suggested that gravity is not some mysterious force that acts across distance, but rather a manifestation of the warping of the fabric of space-time by masses, a bit like a trampoline sagging under the weight of a person standing on it. Second, Quantum Mechanics asserted that we can only determine the probabilities of outcomes of experiments, not the outcomes themselves. To paraphrase Einstein, God does appear to play dice with the world.

With every step along this path of a deeper understanding of the universe, the role of symmetry as the foundation for the laws of nature has become increasingly appreciated. A symmetry of the laws means that when we observe phenomena from different points of view, we discover that they are governed precisely by the same laws. For example, the law of gravity takes precisely the same form whether we are here on Earth, on the Moon, or in a galaxy ten billion light-years away. This is an example of symmetry under translation. If the laws of physics were not symmetric under translation (that is, they were changing from place to place), it would have been impossible to understand the cosmos.

The laws of physics are also symmetric under rotations. That is, physics has no preferred direction in space. We discover the same laws whether we determine directions with respect to the north, south, or the nearest Starbucks.

A simple example can help clarify the difference between a symmetry of shapes and a symmetry of the laws. The ancient Greeks believed that the orbits of the planets are circular, because circles were considered perfect, being symmetric under rotation by any angle about an axis passing through the circle’s center and being perpendicular to the circle’s area. When astronomer Johannes Kepler discovered that the orbits are in fact ellipses, even Galileo didn’t believe it, since circles seemed more elegant. Newton later showed that elliptical orbits were a natural product of his universal law of gravitation. The fact that his law was symmetric under rotation simply meant that the orbits could have any orientation in space, not that the shape of the orbit had to be circular.

In 1915, German mathematical physicist Emmy Noether proved a remarkable theorem that now bears her name. She showed that to every continuous symmetry of the laws of physics there is a corresponding conservation law and vice versa. For example, the symmetry of the laws under translation corresponds to conservation of linear momentum (the product of the mass and the velocity), the symmetry with respect to the passing of time (the laws do not change with time) corresponds to the conservation of energy, and so on. Noether’s theorem therefore demonstrated that two of the pillars of physics, symmetries and conservation laws, are really two manifestations of the same fundamental property.

The symmetries I have described so far had to do with things that don’t change when we change our viewpoint in space and time. Many of the symmetries underlying the subatomic world and the basic forces of nature are associated with changing our perspective on the identity of elementary particles. For example, quantum mechanics allows for electrons to be in states that mix them with another elementary particle called a neutrino. In other words, particles can carry the label “electron,” “neutrino,” or a mixture of both. It turns out that the forces of nature are symmetric (take the same form) under any interchange between electrons, neutrinos, or a mixture of the two, and many other such so-called gauge symmetries exist.

Nobody knows yet whether symmetry is truly the most fundamental concept in the workings of the cosmos, but there is no doubt that symmetry principles have been extremely fruitful in our endeavors to decipher the universe.

References: (1) Livio, M. (2005). The Equation That Couldn’t Be Solved. New York: Simon & Schuster. (2) Livio, M. (2020). Galileo and the Science Deniers. New York: Simon & Schuster.

This article is republished here from Psychology Today under common creative licenses

Einstein’s Theory Of General Relativity Just Got 500 Times Harder To Beat Thanks To The First-Ever Black Hole To Be Caught On Camera (Astronomy)

Albert Einstein’s theory of general relativity proposes that gravity is about matter warping space-time, and it’s stood the test of time for over a century. And, now, observations of the first-ever supermassive black hole to be caught on camera have made it 500 times harder to disprove.

Simulation of M87 black hole showing the motion of plasma as it swirls around the black hole. The bright thin ring that can be seen in blue is the edge of what we call the black hole shadow.University of Arizona

The Event Horizon Telescope’s (EHT) most recent study of the black hole at the center of M87— around 54 million light-years from Earth and 6.5 billion times bigger than our Sun — observed the black hole’s shadow between 2009 to 2017. And it shows that even though it did not change in size, it was a little wobbly.

“Using the gauge we developed, we showed that the measured size of the black hole shadow in M87 tightens the wiggle room for modifications to Einstein’s theory of general relativity by almost a factor of 500 compared to previous tests in the solar system,” explained Feryal Özel, a senior member of the EHT collaboration.

“Many ways to modify general relativity fail at this new and tighter black hole shadow test,” he added.

Einstein’s theory of general relativity survives the extreme

The intense gravity of a black hole curves spacetime, acting like a magnifying glass and causing the black hole shadow to appear larger.

Visualization of the new gauge developed to test the predictions of modified gravity theories against the measurement of the size of the M87 shadow. University of Arizona

The measurement of that visual distortion showed the researchers that the size of the black hole shadow corroborates the predictions of general relativity — a metric theory of gravitation.

According to Einstein, gravity corresponds to changes in the properties of space and time, which in turn changes the straightest-possible paths that objects will naturally follow. Basically, the ‘curvature’ of spacetime is directly related to the energy and momentum of whatever matter and radiation are present.

The supermassive black hole’s ‘wobbly’ shadow proves that Einstein’s theory remains intact even under the most extreme circumstances — a test of gravity along the edge of a supermassive black hole where it’s known to be the strongest.

Black holes exhibit the strongest gravity. University of Arizona

Is there more to a black hole?

The nearly circular shape of the black hole shadow may also lead to a test of the general relativistic no-hair theorem. It states that a black hole is described entirely by its mass, spin, and electrical charge.

This will mean that if two black holes possess the same mass, spin, and electrical charge — they would be considered indistinguishable akin to the identical nature of subatomic particles.

On the other hand, if geometric irregularities are detected, it would potentially indicate the properties that define a black hole extend beyond just its mass, spin, and electrical charge.

“This test will be even more powerful once we image the black hole in the center of our own galaxy and in future EHT observations with additional telescopes that are being added to the array,” said Özel.

Provided by University Of Arizona

The Black Hole Firewall Hypothesis Says A Black Hole Would Incinerate You On The Spot (Astronomy)

Most people know that if you fell into a black hole, you’d never get out. You might even know that, in theory, you’d be stretched so much by the extreme gravity that you’d be “spaghettified.” Well, there’s another possibility: the moment you passed the edge of the black hole, you’d be annihilated in a fiery death. Meet the black hole firewall hypothesis.

Black holes are plagued with problems, scientifically speaking. The strange phenomena spring from Einstein’s theory of general relativity, which says that the more massive an object, the more it warps spacetime.

Black holes arise when an object, like the shrinking core of a massive star, packs all of its mass into an infinitely small point that warps spacetime so much that not even light can escape. But if nothing can escape, then information about every particle that enters the black hole is destroyed forever. And quantum mechanics says that’s not possible. The quantum principle that puts a stop to this is called unitarity, which says that information can’t be destroyed.

In the 1970s, theoretical physicists Stephen Hawking and Jacob Bekenstein showed that a black hole’s event horizon, or the border that defines where you can and can’t escape, emits energy known as Hawking radiation. Every bit of Hawking radiation, they said, was emitted in entangled pairs of particles that form near the event horizon (for more on quantum entanglement, check out this article). For every particle in that pair that shoots out as radiation, the other falls into the black hole. Over a long time, all that escaping mass will make the black hole start evaporating into oblivion — not a good sign for unitarity. Hawking and Bekenstein said the information must be escaping as Hawking radiation. No problem!

But hold on a minute. Every entangled pair has one particle that escapes and one particle that falls in, but eventually, that particle that fell in is going to escape, too — and it’ll need an entangled particle to fall in, in turn. That causes a paradox. A particle can only be entangled with one other particle at a time, but for information not to be destroyed, it has to be entangled with more than one particle. What to do?

The only way to resolve this paradox is to assume one of the three fundamental theories at play in this scenario is wrong. The first we already described: the unitarity principle, or the fact that information can’t be destroyed. The second is the equivalence principle, another tenet of general relativity that says there’s no difference between inertial motion and gravity — it’s also the reason you feel heavier climbing in an elevator, and why aviators can refer to their acceleration in terms of the earth’s gravity (or gs). Finally, there’s quantum field theory as a whole, the laws that govern how physics works — even if those laws break down inside the black hole.

There’s no way around it, it seems. One of these principles has to go.

Enter: the black hole firewall. First proposed in 2012 by University of California, Santa Barbara researchers Ahmed Almheiri, Donald Marolf, Joseph Polchinski, and James Sully — often referred to as “AMPS” — the hypothesis says that particles are entangled with more than one other particle, but that entanglement is broken the moment it forms. That would create extreme quantities of energy at the event horizon, creating a curtain of fire that incinerates anything that passes through.

There are a lot of scientists that have big problems with this hypothesis. And yet, no one has disproven it. In 2013, researchers from the University of York published a paper that seemed to fix this issue with entanglement, and in 2016, researchers from the University of Victoria in British Columbia posed a new hypothesis that said yes, you’d burn up when entering a black hole, but just because of your acceleration — no firewall necessary. Even so, the firewall hypothesis still nags at physics — that is, until a more convincing solution comes along.

Einstein’s Special And General Theory Of Relativity (Physics)

Everyone has heard of Albert Einstein’s special theory of relativity. Just imagine the universal explosion of praise that happened when he published this momentous work of science! Then stop imagining. Whatever you’re thinking, it probably went nothing like that.

Fig: Einstein in his office at the university of Berlin, 1920 IMG credit: Wikimedia Commons

When Einstein published his paper on special relativity in 1905, the reception wasn’t exactly warm. His paper talks about “ether,” a theoretical substance that was then accepted as the stuff space is made of, mostly because its existence helped the equations work out. As JSTOR Daily reports, “Einstein argued that space and time were bound up together (something he would elaborate on in his theory of general relativity of 1915, adding gravity to the mix of space/time), a complicated idea that contradicted the long-held belief in something called ether. Einstein’s theory noted there was no experimental confirmation for the substance. There was no proof it existed, other than that the scientific establishment had accepted the concept.”

Change is hard. For years after Einstein put his contradiction of ether out into the world, Germany remained the only place it was really taken seriously. In Britain, the idea fell on deaf ears. (Britain was, after all, where the idea of ether originated.) In France, Einstein’s work wasn’t really even considered until after he visited the country in 1910. A few understood it in the U.S. but generally considered it impractical and absurd. What made Germany different? According to scholar Stanley Goldberg, “Many German physicists opposed Einstein’s theory, but it is only in Germany that its opponents understood it. It was the seriousness of the German response, in my view, which ultimately led to the acceptance of relativity, for it insured that the theory would be examined, criticized, and elaborated upon.”

WHAT DOES HIS THEORY ACTUALLY SAY?

Besides denying the existence of ether, Einstein’s special and general theories of relativity helped modern science take a grand leap in its understanding of the universe. Nola Taylor Redd does a wonderful job of summing up both theories: In 1905, Albert Einstein determined that the laws of physics are the same for all non-accelerating observers, and that the speed of light in a vacuum was independent of the motion of all observers. This was the theory of special relativity. It introduced a new framework for all of physics and proposed new concepts of space and time. Einstein then spent 10 years trying to include acceleration in the theory and published his theory of general relativity in 1915. In it, he he worked out the equations for his general theory of relativity, and determined that massive objects causes a distortion in space-time, which is felt as gravity. Imagine setting a large body in the center of a trampoline. The body would press down into the fabric, causing it to dimple. A marble rolled around the edge would spiral inward toward the body, pulled in much the same way that the gravity of a planet pulls at rocks in space.

So, have we got any experimental evidence?? Well friends, although instruments can neither see nor measure space-time, several of the phenomena predicted by its warping have been confirmed.

1) Gravitational lensing: Friends, in this light around a very massive object, such as a black hole, is bent, causing it to act as a lens for the things that lie behind it. Astronomers routinely use this method to study stars and galaxies behind massive objects. Einstein’s Cross, a quasar in the Pegasus constellation, is an excellent example of gravitational lensing. Four images of the quasar appear around the galaxy because the intense gravity of the galaxy bends the light coming from the quasar.

Gravitational lensing can allow scientists to see some pretty cool things, but until recently, what they spotted around the lens has remained fairly static. However, since the light traveling around the lens takes a different path, each traveling over a different amount of time, scientists were able to observe a supernova occur four different times as it was magnified by a massive galaxy. In another interesting observation, NASA’s Kepler telescope spotted a dead star, known as a white dwarf, orbiting a red dwarf in a binary system. Although the white dwarf is more massive, it has a far smaller radius than its companion.

2) Changes in the orbit of Mercury: The orbit of Mercury is shifting very gradually over time, due to the curvature of space-time around the massive sun. In a few billion years, it could even collide with Earth.

3) Frame-dragging of space-time around rotating bodies: The spin of a heavy object, such as Earth, should twist and distort the space-time around it. In 2004, NASA launched the Gravity Probe B GP-B). The precisely calibrated satellite caused the axes of gyroscopes inside to drift very slightly over time, a result that coincided with Einstein’s theory.

4) Gravitational redshift: The electromagnetic radiation of an object is stretched out slightly inside a gravitational field. Think of the sound waves that emanate from a siren on an emergency vehicle; as the vehicle moves toward an observer, sound waves are compressed, but as it moves away, they are stretched out, or redshifted. Known as the Doppler Effect, the same phenomena occurs with waves of light at all frequencies. In 1959, two physicists, Robert Pound and Glen Rebka, shot gamma-rays of radioactive iron up the side of a tower at Harvard University and found them to be minutely less than their natural frequency due to distortions caused by gravity.

5) Gravitational waves: Violent events, such as the collision of two black holes, are thought to be able to create ripples in space-time known as gravitational waves. In 2016, the Laser Interferometer Gravitational Wave Observatory (LIGO) announced that it found evidence of these tell-tale indicators.

In 2014, scientists announced that they had detected gravitational waves left over from the Big Bang using the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope in Antarctica. It is thought that such waves are embedded in the cosmic microwave background. However, further research revealed that their data was contaminated by dust in the line of sight.

LIGO spotted the first confirmed gravitational wave on September 14, 2015. The pair of instruments, based out of Louisiana and Washington, had recently been upgraded, and were in the process of being calibrated before they went online. The first detection was so large that, according to LIGO spokesperson Gabriela Gonzalez, it took the team several months of analyzation to convince themselves that it was a real signal and not a glitch.

A second signal was spotted on December 26 of the same year, and a third candidate was mentioned along with it. While the first two signals are almost definitively astrophysical—Gonzalez said there was less than one part in a million of them being something else—the third candidate has only an 85 percent probability of being a gravitational wave.

Together, the two firm detections provide evidence for pairs of black holes spiraling inward and colliding. As time passes, Gonzalez anticipates that more gravitational waves will be detected by LIGO and other upcoming instruments, such as the one planned by India.

Einstein’s theories about space and time have proven to be the most accurate we have so far.


What Would It Be Like To Ride Through A Worm Hole? (Astronomy / Universe)

In “Contact,” Jodie Foster travels through one. So does Matthew McConaughey in “Interstellar,” Spock in the 2009 “Star Trek” film, and pretty much everybody in “Stargate.” Wormholes are ridiculously popular in science fiction, but are they science fact? No one actually knows. There are powerful theories that predict them, but if they do exist, many scientific hurdles stand in the way to riding the wormhole express. That doesn’t mean we can’t imagine what it might be like!

Physicists Albert Einstein and Nathan Rosen first imagined the possibility of a wormhole as a way to avoid a messy detail in physics: the singularity. Singularities are points where the math reaches infinity, like a particle with all of its mass concentrated into an infinitely small point. In a 1935 paper, Einstein and Rosen argued that you could technically avoid a singularity by extending that point into a path that leads to a second location.

To illustrate, if you had a balloon with a dot on either side to each represent a singularity, Einstein and Rosen’s solution would be to push them inward toward each other and connect them, forming a tube-shaped path from one side of the balloon to the other. This was dubbed the Einstein-Rosen Bridge — what most people know as a wormhole.

It wasn’t until 1939 that physicists used Einstein’s theory of relativity to come up with the idea of a black hole, which is essentially a great big singularity. That same math also predicts the existence of a “white hole,” which is a theoretical black hole in reverse — where a black hole has a point where gravity and density reach infinity so that nothing that enters can leave, a white hole has the opposite point where nothing can enter. One popular concept of a wormhole connects a black hole to a white hole. The best part about a wormhole is that those two points could theoretically connect anything to anything, whether that’s two ends of the solar system or two completely separate universes. That would certainly fix all of our problems with faster-than-light travel since that’s not just a problem in physics — it’s an impossibility.

Unfortunately, wormholes aren’t really stable on their own. They open and close so quickly that not even a subatomic particle can make it through. To fix that, you’d need to buttress the wormhole from the inside with exotic matter, which has negative energy density and negative pressure. Even if you could do that, there are still a lot of problems with traveling through a wormhole, not the least of which being that you’d actually have to enter a black hole, which scientists believe would spaghettify your body for eternity (or worse).

But say we live in a sci-fi universe, an alternate reality where physicists have fixed all of these problems and wormholes are an everyday travel method. What would that look like?

You’d begin by free-falling through the outer horizon of a black hole. Once you reached the event horizon, Sandrine Ceurstemont writes for New Scientist TV, you’d see “an infinitely energetic flash of light from the outside world containing an image of the entire history of the universe.” Just your average Tuesday. As you entered the wormhole itself, things would look warped, kind of like an extreme fish-eye lens. The flow of space would turn around and instead of being pulled inward, you’d be pushed outward until you saw another flash of light, this time containing the entire future of the universe. After a third flash of light upon reaching the white hole’s outer horizon, you’d reach your destination.


References: 1) https://physics.aps.org/story/v15/st11 (2) https://www.popularmechanics.com/science/a25800/impossible-physics-of-faster-than-light-travel/ (3) https://www.space.com/20881-wormholes.html (4) https://web.archive.org/web/20120415112903/http://www.newscientist.com/blogs/nstv/2012/03/what-a-trip-through-a-wormhole-would-look-like.html (5) http://physicsbuzz.physicscentral.com/2014/11/what-does-journey-through-wormhole.html