A Cosmological Mystery

Astronomers have discovered a cosmic "ring" that's so enormous, it defies explanation with our best theories of the universe.

Named the Big Ring, the gigantic spiral of galaxies and galaxy clusters is 1.3 billion light-years wide and has a circumference of 4 billion light-years, making it one of the largest objects ever seen.

Because the Big Ring is so far from Earth — 9 billion light-years away — its light is too dim to be viewed with the naked eye. But if it were brighter, it would appear 15 times the size of the full moon in the night sky.  READ MORE...

A Cosmology Mystery

A recent study proposes that the “Hubble tension,” a discrepancy in measurements of the universe’s expansion rate, can be resolved using the alternative MOND theory of gravity. This theory suggests local matter density variations account for the observed discrepancies.

Study by the Universities of Bonn and St. Andrews proposes a new possible explanation for the Hubble tension.

The universe is expanding. How fast it does so is described by the so-called Hubble-Lemaitre constant. But there is a dispute about how big this constant actually is: Different measurement methods provide contradictory values. This so-called “Hubble tension” poses a puzzle for cosmologists. Researchers from the Universities of Bonn and St. Andrews are now proposing a new solution: Using an alternative theory of gravity, the discrepancy in the measured values can be easily explained — the Hubble tension disappears. The study has now been published in the Monthly Notices of the Royal Astronomical Society (MNRAS).
Understanding the Universe’s Expansion

The expansion of the universe causes the galaxies to move away from each other. The speed at which they do this is proportional to the distance between them. For instance, if galaxy A is twice as far away from Earth as galaxy B, its distance from us also grows twice as fast. The US astronomer Edwin Hubble was one of the first to recognize this connection.  READ MORE...

Universe Expansion Could be a Mirage

Astronomers use the light from distant stars, such as the Helix Nebula seen here, to measure the apparent expansion of the universe. New resaerch suggests there may be more to the pictue that we're not seeing. (Image credit: NASA/JPL-Caltech/SSC)



The expansion of the universe could be a mirage, a potentially controversial new study suggests. This rethinking of the cosmos also suggests solutions for the puzzles of dark energy and dark matter, which scientists believe account for around 95% of the universe's total energy and matter but remain shrouded in mystery.


The novel new approach is detailed in a paper published June 2 in the journal Classical and Quantum Gravity, by University of Geneva professor of theoretical physics Lucas Lombriser.


Scientists know the universe is expanding because of redshift, the stretching of light's wavelength towards the redder end of the spectrum as the object emitting it moves away from us. 

Distant galaxies have a higher redshift than those nearer to us, suggesting those galaxies are moving ever further from Earth.

More recently, scientists have found evidence that the universe's expansion isn't fixed, but is actually accelerating faster and faster. This accelerating expansion is captured by a term known as the cosmological constant, or lambda.


The cosmological constant has been a headache for cosmologists because predictions of its value made by particle physics differ from actual observations by 120 orders of magnitude. The cosmological constant has therefore been described as "the worst prediction in the history of physics."

Cosmologists often try to resolve the discrepancy between the different values of lambda by proposing new particles or physical forces but Lombriser tackles it by reconceptualizing what's already there.     READ MORE...

Expansion of Universe Nearing End

The universe is not only expanding, but accelerating that expansion, leading most scientists to anticipate it will keep on growing for a very long time, if not forever. However, a trio of Princeton physicists have challenged this view, presenting a model of the universe in which this expansion is nearly at its end. The universe will start to contract in on itself, they claim, and that could happen surprisingly soon. This is a cosmologist’s “soon”, however, of the order of 100 million years, not something most people would recognize as imminent.

The discovery of acceleration in the expansion of the universe has shaken up cosmology perhaps more than anything else this century. Beforehand the primary debate was whether the universe would expand forever, albeit more slowly, or be dragged back into a “big crunch” as gravity overcame the movement apart.

Acceleration, and the Dark Energy used to explain it, appeared to end the possibility the universe would ever contract again, but a minority of physicists aren't ready to let the idea go. Professor Paul Steinhardt, in particular, has proposed “bouncing” models of the universe. Now Steinhardt and co-authors claim in Proceedings of the National Academy of Sciences that the turning point from expansion to contraction could be close without us being able to tell.

The authors do not assert certainty. They refer to three models of Dark Energy's nature. One of these would see the universe continue to expand faster and faster forever, while a second would see it slow at an unpredictable point, probably far in the future.  READ MORE...

Lost in Spacetime

Einstein’s forgotten twisted universe

There’s a kind of inevitability about the fact that, if you write a regular newsletter about fundamental physics, you’ll regularly find yourself banging on about Albert Einstein. As much as it comes with the job, I also make no apology for it: he is a towering figure in the history of not just fundamental physics, but science generally.

A point that historians of science sometimes make about his most monumental achievement, the general theory of relativity, is that, pretty much uniquely, it was a theory that didn’t have to be. When you look at the origins of something like Charles Darwin’s theory of evolution by natural selection, for example – not to diminish his magisterial accomplishment in any way – you’ll find that other people had been scratching around similar ideas surrounding the origin and change of species for some time as a response to the burgeoning fossil record, among other discoveries.


Even Einstein’s special relativity, the precursor to general relativity that first introduced the idea of warping space and time, responded to a clear need (first distinctly identified with the advent of James Clerk Maxwell’s laws of electromagnetism in the 1860s) to explain why the speed of light appeared to be an absolute constant.

When Einstein presented general relativity to the world in 1915, there was nothing like that. We had a perfectly good working theory of gravity, the one developed by Isaac Newton more than two centuries earlier. True, there was a tiny problem in that it couldn’t explain some small wobbles in the orbit of Mercury, but they weren’t of the size that demanded we tear up our whole understanding of space, time, matter and the relationship between them. But pretty much everything we know (and don’t know) about the wider universe today stems from general relativity: the expanding big bang universe and the standard model of cosmology, dark matter and energy, black holes, gravitational waves, you name it.

So why am I banging on about this? Principally because, boy, do we need a new idea in cosmology now – and in a weird twist of history, it might just be Einstein who supplies it. I’m talking about an intriguing feature by astrophysicist Paul M. Sutter in the magazine last month . It deals with perhaps general relativity’s greatest (perceived, at least) weakness – the way it doesn’t mesh with other bits of physics, which are all explained by quantum theory these days. The mismatch exercised Einstein a great deal, and he spent much of his later years engaged in a fruitless quest to unify all of physics.  READ MORE...

Multiple Universes

If the multiverse exists, there could be another you somewhere out there, doing exactly what you're doing now. (Image credit: Getty Images)

The multiverse is a hypothetical group of multiple universes. Together, these universes comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. The different universes within the multiverse are called "parallel universes", "other universes", "alternate universes", or "many worlds".  SOURCE:  Wikipedia

Multiverse Theory 

...suggests that our universe, with all its hundreds of billions of galaxies and almost countless stars, spanning tens of billions of light-years, may not be the only one. Instead, there may be an entirely different universe, distantly separated from ours — and another, and another. Indeed, there may be an infinity of universes, all with their own laws of physics, their own collections of stars and galaxies (if stars and galaxies can exist in those universes), and maybe even their own intelligent civilizations.

It could be that our universe is just one member of a much grander, much larger multitude of universes: a multiverse.

The concept of the multiverse arises in a few areas of physics (and philosophy), but the most prominent example comes from something called inflation theory. Inflation theory describes a hypothetical event that occurred when our universe was very young — less than a second old. In an incredibly brief amount of time, the universe underwent a period of rapid expansion, "inflating" to become many orders of magnitude larger than its previous size, according to NASA.

Inflation of our universe is thought to have ended about 14 billion years ago, said Heling Deng, a cosmologist at Arizona State University and an expert in multiverse theory. "However, inflation does not end everywhere at the same time," Deng told Live Science in an email. "It is possible that as inflation ends in some region, it continues in others."

Thus, while inflation ended in our universe, there may have been other, much more distant regions where inflation continued — and continues even today. Individual universes can "pinch off" of larger inflating, expanding universes, creating an infinite sea of eternal inflation, filled with numerous individual universes.  READ MORE...

Universe Expanding Faster Than Expected

This image from the Hubble Space Telescope features the spiral galaxy Markarian 1337, which is roughly 120 million light-years away from Earth. In 2006, astronomers saw a certain kind of supernova explode in this galaxy, providing researchers with some of the data nee...IMAGE BY ESA/HUBBLE & NASA, A. RIESS ET AL.

The latest measurements with the Hubble Space Telescope suggest the universe is expanding faster than scientists' models predict—a hint that some unknown ingredient could be at work in the cosmos.

It’s one of the biggest puzzles in modern astronomy: Based on multiple observations of stars and galaxies, the universe seems to be flying apart faster than our best models of the cosmos predict it should. Evidence of this conundrum has been accumulating for years, causing some researchers to call it a looming crisis in cosmology.

Now a group of researchers using the Hubble Space Telescope has compiled a massive new dataset, and they’ve found a-million-to-one odds that the discrepancy is a statistical fluke. In other words, it’s looking even more likely that there’s some fundamental ingredient of the cosmos—or some unexpected effect of the known ingredients—that astronomers have yet to pin down.

“The universe seems to throw a lot of surprises at us, and that’s a good thing, because it helps us learn,” says Adam Riess, an astronomer at Johns Hopkins University who led the latest effort to test the anomaly.

The conundrum is known as the Hubble tension, after astronomer Edwin Hubble. In 1929 he observed that the farther a galaxy is from us, the faster it recedes—an observation that helped pave the way toward our current notion of the universe starting with the big bang and expanding ever since.

Researchers have tried to measure the universe’s current rate of expansion in two primary ways: by measuring distances to nearby stars, and by mapping a faint glow dating back to the infant universe. These dual approaches provide a way to test our understanding of the universe across more than 13 billion years of cosmic history. The research has also uncovered some key cosmic ingredients, such as “dark energy,” the mysterious force thought to be driving the universe’s accelerating expansion.

But these two methods disagree on the universe’s current expansion rate by about 8 percent. That difference might not sound like much, but if this discrepancy is real, it means the universe is now expanding faster than even dark energy can explain—implying some breakdown in our accounting of the cosmos.  READ MORE...

Big Bang Isn't the Beginning

The modern cosmic picture of our universe’s history begins not with a singularity, the Big Bang, 

but rather with a period of cosmic inflation that stretches a flat, uniform universe. The end of 

inflation is the onset of Hot Big Bang., Nicole Rager Fuller/National Science Foundation)

KEY TAKEAWAYS

• The Big Bang teaches us that our expanding, cooling universe used to be younger, denser, and hotter in the past.
• However, extrapolating all the way back to a singularity leads to predictions that disagree with what we observe.
• Instead, cosmic inflation preceded and set up the Big Bang, changing our cosmic origin story forever.

Where did all this come from? In every direction we care to observe, we find stars, galaxies, clouds of gas and dust, tenuous plasmas, and radiation spanning the gamut of wavelengths: from radio to infrared to visible light to gamma rays. No matter where or how we look at the universe, it’s full of matter and energy absolutely everywhere and at all times. 

And yet, it’s only natural to assume that it all came from somewhere. If you want to know the answer to the biggest question of all — the question of our cosmic origins — you have to pose the question to the universe itself, and listen to what it tells you.

Today, the universe as we see it is expanding, rarifying (getting less dense), and cooling. Although it’s tempting to simply extrapolate forward in time, when things will be even larger, less dense, and cooler, the laws of physics allow us to extrapolate backward just as easily. Long ago, the universe was smaller, denser, and hotter. 

How far back can we take this extrapolation? Mathematically, it’s tempting to go as far as possible: all the way back to infinitesimal sizes and infinite densities and temperatures, or what we know as a singularity. This idea, of a singular beginning to space, time, and the universe, was long known as the Big Bang.

But physically, when we looked closely enough, we found that the universe told a different story. Here’s how we know the Big Bang isn’t the beginning of the universe anymore.  READ MORE...

Wandering Black Holes

Supermassive black holes tend to sit, more or less stationary, at the centers of galaxies. But not all of these awesome cosmic objects stay put; some may be knocked askew, wobbling around galaxies like cosmic nomads.

We call such black holes 'wanderers', and they're largely theoretical, because they are difficult (but not impossible) to observe, and therefore quantify. But a new set of simulations has allowed a team of scientists to work out how many wanderers there should be, and whereabouts - which in turn could help us identify them out there in the Universe.

This could have important implications for our understanding of how supermassive black holes - monsters millions to billions of times the mass of our Sun - form and grow, a process that is shrouded in mystery.

Cosmologists think that supermassive black holes (SMBHs) reside at the nuclei of all - or at least most - galaxies in the Universe. These objects' masses are usually roughly proportional to the mass of the central galactic bulge around them, which suggests that the evolution of the black hole and its galaxy are somehow linked.

But the formation pathways of supermassive black holes are unclear. We know that stellar-mass black holes form from the core collapse of massive stars, but that mechanism doesn't work for black holes over about 55 times the mass of the Sun.

Astronomers think that SMBHs grow via the accretion of stars and gas and dust, and mergers with other black holes (very chunky ones at nuclei of other galaxies, when those galaxies collide).

But cosmological timescales are very different from our human timescales, and the process of two galaxies colliding can take a very long time. This makes the potential window for the merger to be disrupted quite large, and the process could be delayed or even prevented entirely, resulting in these black hole 'wanderers'.  READ MORE

Medieval Islamic Tombs

Thousands of medieval Islamic tombs in eastern Sudan were arranged in hard-to-detect patterns, with sacred "parent" tombs hosting subclusters of emanating burials, according to archaeologists who studied the funerary monuments with a method designed for cosmology.

The team used satellite imagery to identify the locations of more than 10,000 monuments in the Kassala region of eastern Sudan. The monuments include tumuli, which are made of stone and are "relatively simple raised structures, widespread throughout African prehistory and history," and "qubbas," which is a term that referred to Islamic tombs and shrines in the pan-Arab world, a team of researchers wrote in a paper published July 7 in the journal PLOS One.

After the team mapped the funerary monuments, they had trouble interpreting the data, given that few of the monuments had been excavated.

"We faced the challenge of interpreting the creation of the funerary landscape with almost no traditional archaeological data, but [we had] a large enough data set to be able to hypothesize the presence of complex processes both at regional and local scale[s]," Stefano
Costanzo, a doctoral student in archaeology at the University of Naples L'Orientale in Italy and lead author of the journal article, told Live Science.

"To the naked eye, it was clear that the clustered tombs were conditioned by the environment, but deeper meaning may have been implied in their spatial arrangement," Costanzo said. He and other members of the team searched for statistical modeling techniques that could help them detect patterns. Ultimately, they decided on a method called the Neyman-Scott cluster process, which was originally developed to study the spatial patterns of stars and galaxies. As far as the team knows, archaeologists have never used the technique.

"The biggest feature of this model lies in the fact that it can deal with archaeological data sets that [lack excavation data and historical records] but are composed of a very large number of elements, which is the basis to meaningful statistical analyses," Costanzo said.  TO READ ENTIRE ARTICLE, CLICK HERE...