Student solves a 100-year-old physics enigma

(This article is courtesy of physics.org)    

 

Student solves a 100-year-old physics enigma

EPFL's student solves a 100-year-old physics enigma
The bubble not rising upward Credit: EPFL

An EPFL Bachelor’s student has solved a mystery that has puzzled scientists for 100 years. He discovered why gas bubbles in narrow vertical tubes seem to remain stuck instead of rising upward. According to his research and observations, an ultra-thin film of liquid forms around the bubble, preventing it from rising freely. And he found that, in fact, the bubbles are not stuck at all—they are just moving very, very slowly.

Air bubbles in a glass of water float freely up to the surface, and the mechanisms behind this are easily explained by the basic laws of science. However, the same laws of science cannot explain why air bubbles in a tube a few millimeters thick don’t rise the same way.

Physicists first observed this phenomenon nearly a century ago, but couldn’t come up with an explanation—in theory, the bubbles shouldn’t encounter any resistance unless the fluid is in motion; thus a stuck bubble should encounter no resistance.

Back in the 1960s, a scientist named Bretherton developed a formula based on the bubbles’ shape to explain this phenomenon. Other researchers have since postulated that the bubble doesn’t rise due to a thin film of liquid that forms between the bubbles and the tube wall. But these theories cannot fully explain why the bubbles don’t rise upward.

While a Bachelor’s student at the Engineering Mechanics of Soft Interfaces laboratory (EMSI) within EPFL’s School of Engineering, Wassim Dhaouadi was able to not only view the thin film of liquid, but also measure it and describe its properties—something that had never been done before. His findings showed that the bubbles weren’t stuck, as scientists previously thought, but actually moving upwards extremely slowly. Dhaouadi’s research, which was published recently in Physical Review Fluids, marked the first time that experimental evidence was provided to test earlier theories.

Dhaouadi and EMSI lab head, John Kolinski, used an optical interference method to measure the film, which they found to be only a few dozen nanometers (1 x 10-9 meters) thick. The method involved directing light onto an air bubble inside a narrow tube and analyzing the reflected light intensity. Using the interference of the light reflected from the tube’s inner wall and from the bubble’s surface, they precisely measured the film’s thickness.

Dhaouadi also discovered that the film changes shape if heat is applied to the bubble and returns to its original shape once the heat is removed. “This discovery disproves the most recent theories that the film would drain to zero thickness,” says John Kolinski.

These measurements also show that the bubbles are actually moving, albeit too slowly to be seen by the human eye. “Because the film between the bubble and the tube is so thin, it creates a strong resistance to flow, drastically slowing the bubbles’ rise,” according to Kolinski.

These findings relate to fundamental research but could be used to study fluid mechanics on a nanometric scale, especially for biological systems.

Dhaouadi joined the lab as a summer research assistant during his Bachelor. He made rapid progress, and continued the work of his own volition. “He essentially participated out of his interest in the research, and wound up publishing a paper from his work that brings to rest a centuries-old puzzle,” says Kolinski.

“I was happy to carry a research project early in my curriculum. It is a new way of thinking and learning and was quite different from a Homework set where you know there is a solution, although it may be hard to find. At first, We did not know if there would even be a solution to this problem.,” says Dhaouadi, who is now completing a Master’s degree at ETH Zurich. Kolinski adds: “Wassim made an exceptional discovery at our lab. We were happy to have him working with us.”


Explore further

When bubbles bounce back


More information: Dhaouadi, Wassim and Kolinski, John M., Bretherton’s Buoyant Bubble, Physical Review Fluids, 2019, DOI: 10.1103/PhysRevFluids.4.123601

A ‘no-brainer Nobel Prize’: Hungarian scientists may have found a fifth force of nature

(THIS ARTICLE IS COURTESY OF CNN)

 

A ‘no-brainer Nobel Prize’: Hungarian scientists may have found a fifth force of nature

Physicist Attila Krasznahorkay, right, works with a fellow researcher at the Institute for Nuclear Research at the Hungarian Academy of Sciences.

(CNN)Essentially the entirety of physics centers on four forces that control our known, visible universe, governing everything from the production of heat in the sun to the way your laptop works. They are gravity, electromagnetism, the weak nuclear force, and the strong force.

New research may be leading us closer to one more.
Scientists at the Institute for Nuclear Research at the Hungarian Academy of Sciences (Atomki) have posted findings showing what could be an example of that fifth force at work.
The scientists were closely watching how an excited helium atom emitted light as it decayed. The particles split at an unusual angle, 115 degrees, which couldn’t be explained by known physics.
The study’s lead scientist, Attila Krasznahorkay, told CNN that this was the second time his team had detected a new particle, which they call X17, because they calculated its mass at 17 megaelectronvolts.
“X17 could be a particle, which connects our visible world with the dark matter,” he said in an email.
Jonathan Feng, a professor of physics and astronomy at the University of California, Irvine, told CNN he’s been following the Hungarian team’s work for years, and believes their research is shaping up to be a game changer.
If these results can be replicated, “this would be a no-brainer Nobel Prize,” he said.

Hungarian scientists are building on 2016 results

Three years ago, the Hungarian researchers published a similar paper in Physical Review Letters, one of the most prestigious journals in physics.
The nuclear physics experimental team had been studying another isotope, beryllium-8, as it decays down to a ground state. They saw electrons and positrons splitting off from the atom at unusual angles.
Those findings, which showed particles coming off beryllium-8 at around a 140-degree angle, were strange and new.
“We introduced such a new particle, which nobody saw before, and which existence could not be understood by the widely accepted ‘Standard Model’ of particle physics, so it faced scrutiny,” Krasznahorkay said in an email.
The findings by Krasznahorkay’s team didn’t get much attention at first, but they raised Feng’s eyebrows. He said he “didn’t want to leave potentially revolutionary results just sitting on the table.”

A physicist in California developed a theory to explain the unusual results

In short, it could change physics as we know it, or it could have just been a simple lab error.
“Some people said they screwed up,” Feng said.
But he believed the Hungarians were for real. His research group published a paper on the heels of the Hungarians’ 2016 work, laying out a theory to observe what Krasznahorkay’s experimental team had seen.
They referred to this unseen fifth force in action as a “photophobic force,” meaning that it was as though the particles were “afraid of light.”
Meanwhile, nuclear physicists around the world set to work looking for errors in the Hungarians’ work, and have come up empty-handed over the past few years.
“Some very well-known nuclear physicists have done that exercise,” Feng said.
The numbers seemed to add up, and no one could find ways their equipment was calibrated incorrectly.
And Feng said his own team was comparing the Hungarian experiments with “with every other experiment that’s been done in the history of physics.”
The only way to explain X17 was a hitherto undetected “fifth force.”

The findings point toward the Holy Grail of physics

To move their breakthrough idea from 2016 forward, the Hungarians would need to repeat the results again. That’s exactly what their 2019 results do.
Feng says there was only a one in a trillion chance that the results were caused by anything other than the X17 particle, and this new fifth force.
He added that if another research group could repeat these results with a third type of atom in addition to beryllium and helium, “that would blow the cover off this thing.”
Experimental research groups have already been reaching out to him hungry to do that.
More sightings of the fifth force could lead to scientists settling on a specific name for it, understanding its workings more deeply, and developing practical applications for how to harness its power.
They’re leading us closer to what’s considered the Holy Grail in physics, which Albert Einstein had aimed at but never achieved. Physicists hope to create a “unified field theory,” which would coherently explain all cosmic forces from the formation of galaxies down to the quirks of quarks.
But the universe isn’t giving up its secrets easily.
“There’s no reason to stop at the fifth,” Feng said. “There could be a sixth, seventh, and eighth force.”

The 1st Sun Details from NASA’s Parker Solar Probe Are Out. And They’re Hot!

(THIS ARTICLE IS COURTESY OF SPACE.COM)

 

The 1st Sun Details from NASA’s Parker Solar Probe Are Out. And They’re Hot!

An artist's depiction of NASA's Parker Solar Probe gathering data about the sun.

An artist’s depiction of NASA’s Parker Solar Probe gathering data about the sun.
(Image: © Johns Hopkins University Applied Physics Laboratory)

Want to see the sun in a whole new way?

Now you can do just that by looking through a host of science data newly made available to the public. That information was gathered by NASA’s Parker Solar Probe during its first two close passes of the sun. The flybys brought the spacecraft closer to the sun than any previous vehicle had gone, offering scientists an incredible opportunity to learn more about our star.

“Parker Solar Probe is crossing new frontiers of space exploration, giving us so much new information about the sun,” Nour E. Raouafi, Parker Solar Probe project scientist at the Johns Hopkins University Applied Physics Laboratory, said in a statement. “Releasing this data to the public will allow them not only to contribute to the success of the mission along with the scientific community, but also to raise the opportunity for new discoveries to the next level.”

Related: NASA’s Parker Solar Probe Mission to the Sun in Pictures

Parker Solar Probe launched in August 2018 for a seven-year mission that is targeting the constant stream of highly charged plasma leaving the sun, called the solar wind, and the star’s outer atmosphere, called the corona. Studying these phenomena requires getting incredibly close to the sun; the spacecraft primarily gathers data while within about 23 million miles (37 million kilometers) of our star.

Onboard are four science experiments: Fields Experiment, which studies electric and magnetic fields; Integrated Science Investigation of the Sun, which measures high-energy charged particles in the solar wind and corona; Wide-Field Imager for Solar Probe, which images the solar wind and other structures; and Solar Wind Electrons Alphas and Protons Investigation, which measures different types of particles in the solar wind.

Data gathered by a Parker Solar Probe instrument, the Wide-Field Imager for Solar Probe, in November 2018, during the spacecraft’s first solar flyby.

(Image credit: NASA/Naval Research Laboratory/Parker Solar Probe)

And now, you too can pore through data gathered by those instruments during the first two flybys: Oct. 31-Nov. 12, 2018, and March 30-April 19, 2019. During the second flyby, mission engineers were able to increase the amount of data the spacecraft sent home, thanks to better data-return rates than expected. There is no central hub for the data, but NASA has provided a list of websites to explore.

According to the same NASA statement, the first full-fledged science results from the mission should be published later this year.

Parker Solar Probe has also already made its third flyby of the sun; the spacecraft’s next closest approach is on Jan. 29, 2020.

Email Meghan Bartels at [email protected] or follow her @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.

What Is the Universe Made of?

(THIS ARTICLE IS COURTESY OF LIVE SCIENCE)

 

What Is the Universe Made of?

Image of galaxy cluster Abell 2744 shows dark matter locations

In this image of galaxy cluster Abell 2744, a blue overlay shows the location of dark matter, which makes up about 75% of the cluster’s mass.
(Image: © NASA/ESA/ESO/CXC, and D. Coe (STScI)/J. Merten (Heidelberg/Bologna))

The universe is filled with billions of galaxies and trillions of stars, along with nearly uncountable numbers of planets, moons, asteroids, comets and clouds of dust and gas – all swirling in the vastness of space.

But if we zoom in, what are the building blocks of these celestial bodies, and where did they come from?

Hydrogen is the most common element found in the universe, followed by helium; together, they make up nearly all ordinary matter. But this accounts for only a tiny slice of the universe — about 5%. All the rest is made of stuff that can’t be seen and can only be detected indirectly. [From Big Bang to Present: Snapshots of Our Universe Through Time]

Mostly hydrogen

It all started with a Big Bang, about 13.8 billion years ago, when ultra-hot and densely packed matter suddenly and rapidly expanded in all directions at once. Milliseconds later, the newborn universe was a heaving mass of neutrons, protons, electrons, photons and other subatomic particles, roiling at about 100 billion degrees Kelvin, according to NASA.

Every bit of matter that makes up all the known elements in the periodic table — and every object in the universe, from black holes to massive stars to specks of space dust — was created during the Big Bang, said Neta Bahcall, a professor of astronomy in the Department of Astrophysical Sciences at Princeton University in New Jersey.

“We don’t even know the laws of physics that would have existed in such a hot, dense environment,” Bahcall told Live Science.

About 100 seconds after the Big Bang, the temperature dropped to a still-seething 1 billion degrees Kelvin. By roughly 380,000 years later, the universe had cooled enough for protons and neutrons to come together and form lithium, helium and the hydrogen isotope deuterium, while free electrons were trapped to form neutral atoms.

Because there were so many protons zipping around in the early universe, hydrogen — the lightest element, with just one proton and one neutron — became the most abundant element, making up nearly 95% percent of the universe’s atoms. Close to 5% of the universe’s atoms are helium, according to NASA. Then, about 200 million years after the Big Bang, the first stars formed and produced the rest of the elements, which make up a fraction of the remaining 1% of all ordinary matter in the universe.

Unseen particles

Something else was created during the Big Bang: dark matter. “But we can’t say what form it took, because we haven’t detected those particles,” Bahcall told Live Science.

Dark matter can’t be observed directly — yet — but its fingerprints are preserved in the universe’s first light, or the cosmic microwave background radiation (CMB), as tiny fluctuations in radiation, Bahcall said. Scientists first proposed the existence of dark matter in the 1930’s, theorizing that dark matter’s unseen pull must be what held together fast-moving galaxy clusters. Decades later, in the 1970’s, American astronomer Vera Rubin found more indirect evidence of dark matter in the faster-than-expected rotation rates of stars.

Based on Rubin’s findings, astrophysicists calculated that dark matter — even though it couldn’t be seen or measured — must make up a significant portion of the universe. But about 20 years ago, scientists discovered that the universe held something even stranger than dark matter; dark energy, which is thought to be significantly more abundant than either matter or dark matter. [Gallery: Dark Matter Throughout the Universe]

Hubble Space Telescope Image

Captured in 2014 by the Hubble Space Telescope, this picture of the evolving universe is among Hubble’s most colorful deep-space images.

(Image credit: NASA/ESA)

An irresistible force

The discovery of dark energy came about because scientists wondered if there was enough dark matter in the universe to cause expansion to sputter out or reverse direction, causing the universe to collapse inward on itself.

Lo and behold, when a team of researchers investigated this in the late 1990s, they found that not only was the universe not collapsing in on itself, it was expanding outward at an ever faster rate. The group determined that an unknown force — dubbed dark energy — was pushing against the universe in the apparent void of space and accelerating its momentum; the scientists’ findings earned physicists Adam Riess, Brian Schmidt and Saul Perlmutter the Nobel Prize in Physics in 2011.

Models of the force required to explain the universe’s accelerating expansion rate suggest that dark energy must make up between 70% and 75% of the universe. Dark matter, meanwhile, accounts for about 20% to 25%, while so-called ordinary matter — the stuff we can actually see — is estimated to make up less than 5% of the universe, Bahcall said.

Considering that dark energy makes up about three-quarters of the universe, understanding it is arguably the biggest challenge facing scientists today, astrophysicist Mario Livio, then with the Space Telescope Science Institute at Johns Hopkins University in Baltimore, Maryland, told Live Science sister site Space.com in 2018.

“While dark energy has not played a huge role in the evolution of the universe in the past, it will play the dominant role in the evolution in the future,” Livio said. “The fate of the universe depends on the nature of dark energy.”

Originally published on Live Science.

Last reversal of the Earth’s magnetic field took twice as long as previously thought

(THIS ARTICLE IS COURTESY OF PHYSICS WORLD)

 

Last reversal of the Earth’s magnetic field took twice as long as previously thought

12 Aug 2019
Geomagnetic field
(Credit: Dormy and Dion)

The last full reversal of the Earth’s geomagnetic field took at least 22,000 years to complete, researchers from the US and Japan have revealed. The finding, which was derived by combining volcanic, sedimentary and ice-core records, suggests that reversals can take several times longer than was previously thought. It also further challenges the notion that a future reversal might be completed within a human lifetime.

The geomagnetic field is produced by the motion of the Earth’s liquid outer core, which acts as a dynamo. Although superficially stable – and presently reliable enough to navigate by – the field does change with time. At present, for example, the magnetic North Pole is in the process of drifting towards Siberia, while the field strength has been decreasing steadily by around 5% for each century since human records began.

Records in the rocks

With magnetically aligned minerals in certain rocks having left us with a record of the magnetic field at the time they were formed, we know that such a weakening can be a precursor to a so-called excursion – in which the magnetic poles shift by up to around 45 degree – or a full blown reversal, in which the field flips and settles upside down. These events, products of growing instabilities in the geodynamo, appear to occur every several hundred thousands years or so.

“Reversals are generated in the deeper parts of the Earth’s interior, but the effects manifest themselves all the way through the Earth,” explains Brad Singer, a geologist at the University of Wisconsin Madison.

Exactly what impact a future reversal might have on human civilization, navigation and communications, however, is unclear. And scientists still don’t understand what causes them, how long a reversal would take, and what the warning signs of one might be.

“Unless you have complete, accurate and high-resolution record of what a field reversal really is like at the surface of the Earth, it’s difficult to even discuss what the mechanics of generating a reversal are,” Singer notes.

Better measurements

To help develop a more accurate picture, Singer and his colleagues took magnetic readings of rock samples from seven lava flows from the Canary Islands, the Caribbean, Chile, Hawaii and Tahiti. They also determined the age of the samples using a newly-enhanced method of potassium-argon radioisotope dating.

“Lava flows are ideal recorders of the magnetic field. They have a lot of iron-bearing minerals and when they cool, they lock in the direction of the field,” says Singer. “But it’s a spotty record. No volcanoes are erupting continuously. So we’re relying on careful field work to identify the right records.”

The team complemented their lava-flow records with two other sources of data on the historic orientation of the geomagnetic field. The first of these were magnetic readings taken from the sea floor, which are less precise than those taken from lava flows – due to variations in sediment rates, weaker magnetization, and biological disruption that can smear the preserved magnetic orientations – but can provide a more continuous record.

Secondly, the researchers took measurements of beryllium deposits across time, as preserved in Antarctic ice cores. Beryllium is produced when cosmos rays hit the atmosphere, which means that periods in which the magnetic field was weaker – and therefore allows more radiation to pass through it – can be identified by increased beryllium in the ice cores.

Combined together, the various records allowed the researchers to piece together the nature of the geomagnetic field over a 70,000-year period centered around the Matuyama-Brunhes reversal – the last time the field completely flipped over, around 784,000 years ago.

Longer reversal

Singer and colleagues found that the final reversal was relatively rapid by geological standards, taking less than 4000 years. However, it was preceded by two individual excursions within a period of instability lasting 18,000 years – more than twice as long as recent research had suggested reversals should take.

“I’ve been working on this problem for 25 years,” said Singer. “And now we have a richer and better-dated record of this last reversal than ever before.”

Andrew Roberts, an earth scientist from the Australian National University who was not involved in the present study, said: “I take these results to indicate that the last magnetic polarity reversal occurred during a prolonged period of time in which Earth’s magnetic field was weak and unstable.”

Roberts also notes that it is still possible that the main reversal occurred rapidly. “There have been other prolonged unstable periods, such the Blake and post-Blake events between 120 and 90 thousand years ago, during which the field has been demonstrated to have changed extremely rapidly.”

Gillian Turner, a geophysicist from the Victoria University of Wellington who also was not involved in the study, agrees: “As the accuracy and resolution of dating both volcanic rocks and sedimentary sequences continues to improve, we should expect to see excursion activity associated with successful polarity reversals more and more often.”

The research is described in the journal Science Advances.

New Hubble Data Breaks Scientists’ Understanding of the Universe

(THIS ARTICLE IS COURTESY OF THE SCIENCE NEWS SITE ‘FUTURISM’)

 

New Hubble Data Breaks Scientists’ Understanding of the Universe

A new attempt to find the universe’s age revealed troubling flaws.

Dan Robitzski 7 hours ago

There may be fundamental flaws with our understanding of the universe.

The problem came to light as scientists tried to calculate and measure a value called the Hubble Constant, which represents how rapidly the universe is expanding outward.

The value was first calculated by astronomer Edwin Hubble in the 1920s. But since then, astronomers observing and measuring the universe’s expansion have arrived at different values of the Hubble Constant, none of which seem to agree with one another. The discrepancy calls into question not only our idea of how old the universe is, but also our ability to fundamentally understand the physics that drive its behavior.

“Naturally, questions arise as to whether the discrepancy is coming from some aspect that astronomers don’t yet understand about the stars we’re measuring, or whether our cosmological model of the universe is still incomplete,” University of Chicago astronomer Wendy Freedman said in a NASA press release. “Or maybe both need to be improved upon.”

Freedman is responsible for the latest measurement of the Hubble Constant, which she calculated using a different kind of cosmic landmark from previous experiments.

Her team measured the brightness of red giant stars in distant galaxies. Because these stars reach uniform size and brightness, their distance from Earth can more readily be calculated than some other stars. Freedman’s work, which has been accepted but not yet published by The Astrophysical Journal, found that the universe is expanding at 69.8 kilometers per second per megaparsec, per the press release.

That’s a slower rate of expansion than was calculated in another recent study that focused on a different kind of star but a faster rate than was calculated in yet another study that measured light leftover from the big bang called the Cosmic Microwave Background.

Freedman originally hoped her research would serve as a tie-breaker between those other two studies — but instead it added yet another, possible value for the Hubble Constant for astronomers to reconcile.

“The Hubble constant is the cosmological parameter that sets the absolute scale, size and age of the universe; it is one of the most direct ways we have of quantifying how the universe evolves,” Freedman said in the press release. “The discrepancy that we saw before has not gone away, but this new evidence suggests that the jury is still out on whether there is an immediate and compelling reason to believe that there is something fundamentally flawed in our current model of the universe.”

Further complicating the issue, statistical analysis validates both of those two previous studies, according to a New Scientist article published last week, before Freedman’s study was announced. There’s just a one-in-3.5 million chance that their findings came from random chance.

In the middle of the next decade, NASA hopes to launch the Wide Field Infrared Survey Telescope into orbit, at which point scientists will be able to more precisely measure the distance of celestial objects, per the press release. When that happens, there’s a chance that astronomers will be able to reconcile their various Hubble Constant values.

“The Hubble constant is the biggest problem in cosmology that we have access to right now, and the hope is that this crack in our understanding is going to lead us to some even bigger cracks like dark energy and dark matter,” Duke University astronomer Daniel Scolnic told New Scientist. “We just have to chase the crack.”

READ MORE: NEW HUBBLE CONSTANT MEASUREMENT ADDS TO MYSTERY OF UNIVERSE’S EXPANSION RATE[NASA]

More on the Hubble Constant: Figuring out How Fast the Universe Is Expanding Might Require a New Type of Physics

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NASA/Victor Tangermann