The Universe & Dark Matter

Physicists have long theorized that our universe may not be limited to what we can see. By observing gravitational forces on other galaxies, they've hypothesized the existence of "dark matter," which would be invisible to conventional forms of observation.


Pran Nath, the Matthews Distinguished University Professor of physics at Northeastern University, says that "95% of the universe is dark, is invisible to the eye."


"However, we know that the dark universe is there by [its] gravitational pull on stars," he says. Other than its gravity, dark matter has never seemed to have much effect on the visible universe.    READ MORE...

Einstein's Discoveries Lead to Gravitational Laser

Einstein’s work was crucial for the current understanding of gravitational waves and the development of stimulated radiation that culminated in the invention of lasers. Dr Jing Liu, from the University of Chinese Academy of Sciences, has combined the two into an intriguing proposal: it is possible to create the gravitational equivalent of a laser.

Let’s start with the basics. The word laser stands for Light Amplification by Stimulated Emission of Radiation. A laser is made of light all with roughly the same frequency (or, in other words, it is monochrome) and it is coherent, so it can be focused to a tight spot or can be used to create ultrashort pulses. By stimulating a quantum mechanical energy transition, it is possible to get light out all with the same frequency.

Natural lasers exist and they are called masers – with the "m" standing for microwaves. These astrophysical masers come from a bunch of sources, including comets, stellar atmosphere, and even the aurorae of Jupiter. So if light can make a laser, could gravity as well?   READ MORE...

Uniting Gravity, Spacetime, and Quantum Theory

In a groundbreaking announcement, physicists from University College London (UCL) have presented a radical theory that unifies the realms of gravity and quantum mechanics while preserving the classical concept of spacetime, as outlined by Einstein.

This innovative approach, detailed in two simultaneously published papers, challenges over a century of scientific consensus and proposes a revolutionary perspective on the fundamental nature of our universe.

Dichotomy in modern physics
Modern physics rests on two contradictory pillars: quantum theory, which rules the microscopic world, and Einstein’s theory of general relativity, explaining gravity through spacetime curvature. These theories, despite their individual successes, have remained irreconcilable, creating a significant rift in our understanding of the universe.  READ MORE...

Theory Unites Gravity and Quantum Mechanics

A radical theory that consistently unifies gravity and quantum mechanics while preserving Einstein's classical concept of spacetime has been announced in two papers published simultaneously by UCL (University College London) physicists.

Modern physics is founded upon two pillars: quantum theory on the one hand, which governs the smallest particles in the universe, and Einstein's theory of general relativity on the other, which explains gravity through the bending of spacetime. But these two theories are in contradiction with each other and a reconciliation has remained elusive for over a century.

The prevailing assumption has been that Einstein's theory of gravity must be modified, or "quantized," in order to fit within quantum theory. This is the approach of two leading candidates for a quantum theory of gravity, string theory and loop quantum gravity.   READ MORE...

Einstein Was Wrong About Gravity

Einstein's theory of gravity—general relativity—has been very successful for more than a century. However, it has theoretical shortcomings. This is not surprising: the theory predicts its own failure at spacetime singularities inside black holes—and the Big Bang itself.

Unlike physical theories describing the other three fundamental forces in physics—the electromagnetic and the strong and weak nuclear interactions—the general theory of relativity has only been tested in weak gravity.

Deviations of gravity from general relativity are by no means excluded nor tested everywhere in the universe. And, according to theoretical physicists, deviation must happen.

Deviations and quantum mechanics
According to a theory initially proposed by Georges Lemaître and widely accepted by the astronomical community, our universe originated in a Big Bang. 

Other singularities hide inside black holes: Space and time cease to have meaning there, while quantities such as energy density and pressure become infinite. These signal that Einstein's theory is failing there and must be replaced with a more fundamental one.

Naively, spacetime singularities should be resolved by quantum mechanics, which apply at very small scales.

Quantum physics relies on two simple ideas: point particles make no sense; and the Heisenberg uncertainty principle, which states that one can never know the value of certain pairs of quantities with absolute precision—for example, the position and velocity of a particle. 

This is because particles should not be thought of as points but as waves; at small scales they behave as waves of matter.  READ MORE...

Probing Dark Energy

Dark energy illustration. Credit: Visualization by Frank Summers, Space Telescope Science Institute. Simulation by Martin White, UC Berkeley and Lars Hernquist, Harvard University





Could one of the biggest puzzles in astrophysics be solved by reworking Albert Einstein’s theory of gravity? Not yet, according to a new study co-authored by NASA scientists.

The universe is expanding at an accelerating rate, and physicists don’t know why. This phenomenon seems to contradict everything scientists understand about gravity’s effect on the cosmos: It’s as if you threw an apple in the air and instead of coming back down, it continued upward, faster and faster. The cause of the cosmic acceleration, dubbed dark energy, remains a mystery.

A new study marks the latest effort to determine whether this is all simply a misunderstanding: that expectations for how gravity works at the scale of the entire universe are flawed or incomplete. This potential misunderstanding might help researchers explain dark energy. However, the study – one of the most precise tests yet of Albert Einstein’s theory of gravity at cosmic scales – finds that the current understanding still appears to be correct. The study was from the international Dark Energy Survey, using the Victor M. Blanco 4-meter Telescope in Chile.


The results, authored by a group of scientists that includes some from NASA’s Jet Propulsion Laboratory (JPL), were presented Wednesday, August 24, at the International Conference on Particle Physics and Cosmology (COSMO’22) in Rio de Janeiro. 

The work helps set the stage for two upcoming space telescopes that will probe our understanding of gravity with even higher precision than the new study and perhaps finally solve the mystery.  READ MORE...

Laws of Logic

Physicists are translating commonsense principles into strict mathematical constraints on how our universe must have behaved at the beginning of time.  Patterns in the ever-expanding arrangement of galaxies might reveal secrets of the universe’s first moments.

M.C. Escher’s Circle Limit III (1959). M.C. Escher

For over 20 years, physicists have had reason to feel envious of certain fictional fish: specifically, the fish inhabiting the fantastic space of M.C. Escher’s Circle Limit III woodcut, which shrink to points as they approach the circular boundary of their ocean world. If only our universe had the same warped shape, theorists lament, they might have a much easier time understanding it.

Escher’s fish lucked out because their world comes with a cheat sheet — its edge. On the boundary of an Escher-esque ocean, anything complicated happening inside the sea casts a kind of shadow, which can be described in relatively simple terms. In particular, theories addressing the quantum nature of gravity can be reformulated on the edge in well-understood ways. The technique gives researchers a back door for studying otherwise impossibly complicated questions. Physicists have spent decades exploring this tantalizing link.

Inconveniently, the real universe looks more like the Escher world turned inside out. This “de Sitter” space has a positive curvature; it expands continuously everywhere. With no obvious boundary on which to study the straightforward shadow theories, theoretical physicists have been unable to transfer their breakthroughs from the Escher world. orld, the fewer tools we have and the less we understand the rules of the game,” said Daniel Baumann, a cosmologist at the University of Amsterdam.  READ MORE...

A Time Without Time

Eternal inflation is a hypothetical inflationary universe model, which is itself an outgrowth or extension of the Big Bang theory.  According to this theory, the inflationary phase of the universe's expansion lasts forever throughout most of the universe. Because the regions expand exponentially rapidly, most of the volume of the universe at any given time is inflating. Eternal inflation, therefore, produces a hypothetically infinite multiverse, in which only an insignificant fractal volume ends inflation.

The idea of the inflation of the Universe started in the 1970's when a belief developed that within nanoseconds of the BIG BANG, the universe expanded exponentially.

But Stephen Hawking does not agree with that theory and believes that external inflation does not occur.

Eternal inflation emerges because, in the very early universe, the quantum fluctuations in the field that drives inflation are as big as the field’s average value. But Hawking argues that under those conditions one cannot simply carry on with Albert Einstein’s general theory of relativity, but instead must use a maneuver like Maldacena’s to view the entire situation in a space with one less dimension. In that alternative space, things are more tractable, they claim, and the physics does not lead to eternal inflation. Instead, a single, well-behaved universe merges.

In 1997, Argentine-American theorist Juan Maldacena considered a volume of space in which gravity was at work. It’s like saying whatever goes on inside a can of soda can be captured by a theory describing only what’s happening on the can’s surface.

So in Hawking’s through the principle of holography, the very early universe should be described by a theory with just three spatial dimensions and no time.

And, while this author is no theoretical physicist, I wonder quite innocently I would have to say, where does time come from when it finally appears?  And if it does finally appears which we all can agree that it does, then what caused time to be created?  And, can time's creation be attributed to the BIG BANG or to our Creator?