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Physicists make progress towards developing an extremely accurate ‘nuclear’ clock

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Scientists have made significant progress in developing a novel clock that relies on minute changes in energy within an atomic nucleus. Conceptually, a nuclear clock has the potential to surpass the precision of the world’s most accurate timekeeping devices, referred to as optical clocks, while also being less susceptible to disruptions.

Additionally, a nuclear chronometer could enable physicists to investigate the fundamental forces of nature using novel approaches. “We will have the capability to investigate situations involving dark matter and fundamental physics that are presently unattainable through alternative means,” states Elina Fuchs, a theoretical physicist at CERN, the particle-physics laboratory in Europe located near Geneva, Switzerland.

The highly anticipated discovery, achieved through a partnership between the Vienna University of Technology and Germany’s national metrology institute, the PTB, in Braunschweig, utilized an ultraviolet laser to induce a transition in the energy levels of a nucleus of the radioactive element thorium-229. The frequency of light that is absorbed and emitted by the nucleus serves as the mechanism for the clock’s ticking. The researchers disseminated their findings in the scientific journal Physical Review Letters on the 29th of April.

“This is significant,” states Adriana Pálffy-Buß, a theoretical physicist affiliated with the University of Würzburg in Germany. Using a laser to drive the transition is a crucial step that signifies the ability to construct a clock.”The achievement represents the combined efforts of numerous scientific organizations over a period of almost fifty years,” states Olga Kocharovskaya, a physicist affiliated with Texas A&M University in College Station.

Exactly on time
So well do optical clocks keep time that they only go off by one second every 30 billion years. To change an electron’s energy state around an atom like strontium, they need a certain frequency of visible light. This frequency controls how fast they tick.

But a nuclear clock would work better. To make the transition more energetic, the protons and neutrons in the nucleus would be raised to a higher energy level. This would use a slightly higher frequency of radiation, which would allow time to be cut even more precisely, making the clock more accurate. A clock like this would also be much more stable than an optical clock, since particles in the nucleus are not as affected by outside fields or temperature as electrons are.

But it has been hard to find a material with the right nucleus. Most nuclei have big energy changes that need a lot more than the push of a tabletop laser. Scientists found out in the 1970s that thorium-229 is different because its first energy state is very close to its ground state. In 2003, physicists suggested using thorium-229 as the building block of a super-stable clock. But they had to find the exact energy of the transition and the laser frequency that went with it, which could not have been predicted with any degree of accuracy using theory. The numbers have been narrowed down in a number of different ways since then.

To see the change, scientists put radioactive thorium atoms into calcium fluoride crystals that were only a few millimeters wide. They used a custom-built laser to scan the expected area and finally found the right frequency: about 2 petahertz (1015 oscillations per second). They were able to identify this frequency by observing the photons released by the nuclei as they returned to a lower-energy state. Thorsten Schumm, an atomic physicist at the Vienna University of Technology and co-author, remembers writing “found it” in big red letters in his lab book at a meeting the next day to talk about the signal that looked promising. He says, “It was very clear.”

The team was 800 times more accurate than the next best attempt when they found the frequency. According to co-author and PTB physicist Ekkehard Peik, since then, a team at the University of California, Los Angeles, has used the same frequency to achieve the same result. He calls it “a very nice confirmation.”

Help with basic physics
Scientists will have to greatly lower the laser’s resolution in order to make the system work as a real clock. This is so that it can reliably stimulate the nucleus at just the right frequency, according to Peik. “Building such a laser remains a big challenge,” says Kocharovskaya. “But there are little doubts that it will be possible in the near future.”

The group says that a thorium-based nuclear clock might be about 10 times more accurate than the best optical clocks if everything goes as planned. “This will be a better clock because it will be more resistant to changes in the outside world,” says Schumm. The clock might be smaller and easier to carry around if the nuclei are in a solid crystal instead of an optical system.

Help with basic physics
Scientists will have to greatly lower the laser’s resolution in order to make the system work as a real clock. This is so that it can reliably stimulate the nucleus at just the right frequency, according to Peik. “Building such a laser remains a big challenge,” says Kocharovskaya. “But there are little doubts that it will be possible in the near future.”

The group says that a thorium-based nuclear clock might be about 10 times more accurate than the best optical clocks if everything goes as planned. “This will be a better clock because it will be more resistant to changes in the outside world,” says Schumm. The clock might be smaller and easier to carry around if the nuclei are in a solid crystal instead of an optical system.

Very accurate optical clocks have made it possible for scientists to do things like measure differences in clock speeds to look into Earth’s gravitational field. Kocharovskaya says that these methods “could get a major boost.”

On a deeper level, physics could also use some help. Says Fuchs that a nuclear clock would be 10,000 times more aware of changes in fundamental constants, like the strength of the strong nuclear and electromagnetic forces. This means they could find possible types of dark matter, an invisible substance that physicists believe makes up 85% of the universe’s matter and is thought to cause tiny changes in the strength of these forces.

Fuchs says, “It’s possible that there’s very “light” dark matter that moves around, which could make these fundamental constants move.” She says that nuclear clocks might be able to pick up on that wiggle because these forces control the energy of their transition, and any change in their strength would change the tick in a way that can be measured. She also says that nuclear clocks could find out if the masses of some particles change over time. Fuchs and her colleagues are already working on their first paper, which is based on the measurement of frequency. She says, “This is pretty exciting for us.”

As Editor here at GeekReply, I'm a big fan of all things Geeky. Most of my contributions to the site are technology related, but I'm also a big fan of video games. My genres of choice include RPGs, MMOs, Grand Strategy, and Simulation. If I'm not chasing after the latest gear on my MMO of choice, I'm here at GeekReply reporting on the latest in Geek culture.

Physics

What are the consequences of flying over an earthquake?

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Have you ever pondered the potential consequences of being aboard a commercial flight at a significant altitude when a colossal earthquake occurs? Presumably, you would be in an altered state of consciousness that would hinder your ability to perceive and comprehend any sensory experiences, correct? The answer to that question is contingent upon several factors.

Seismic activity and atmospheric conditions
Although it may appear improbable, an earthquake can potentially lead to several consequences that could pose challenges for a flight, depending on the circumstances. However, it is important to first examine the connection between the atmosphere and the earth before delving into that topic.

Attila Komjathy, a scientist at NASA’s Jet Propulsion Laboratory (JPL) of the California Institute of Technology, explained on NASA’s website that when the ground shakes, it generates small atmospheric waves that can travel all the way up to the ionosphere. This is a region known as the exosphere, which can reach a distance of up to 1,000 kilometers (600 miles) from the Earth’s surface.

Consequently, an earthquake has the potential to induce certain atmospheric disruptions, but is this sufficient to disrupt the operation of an aircraft? Simply put, the answer is no. However, if we delve deeper into the matter, the answer remains a resounding no, but with some intriguing nuances.

Earthquakes emit seismic waves, which manifest as pressure waves (P waves) and shear waves (S waves). S waves are restricted to propagating through solid media, such as the ground, while P waves have the ability to transmit through different types of media, including liquids and gases. Consequently, they have the ability to enter the atmosphere. When sound is transformed into soundwaves, they often have a frequency below 20 hertz, which is the minimum level for human hearing. Consequently, these soundwaves, known as infrasound, are usually inaudible.

Nevertheless, as these waves propagate through the air, their intensity diminishes. This phenomenon is known as attenuation, and it essentially refers to the decrease in sound intensity as the distance between the source and the listener increases. It is also a phenomenon that diminishes the intensity of sunlight as it passes through different layers of the atmosphere or other substances, such as the ocean.

Consequently, an aircraft traversing an earthquake, regardless of its intensity, would remain unaffected by the seismic vibrations beneath. Once the P waves have propagated through the rock and subsequently the air, their intensity will have significantly decreased, rendering them overshadowed by the plane’s own noise and movement.

Nevertheless, airplanes are not exempt from risks during an earthquake. The concerns at hand pertain to navigation and safety, albeit of a distinct nature.

In 2018, a self-proclaimed United States Air Force pilot and aero engineer named Ron Wagner provided a response on Quora to a question inquiring about the impact of earthquakes on an aircraft in flight. Wagner’s response was sufficiently captivating that Forbes subsequently shared it again.

Wagner claims that he piloted an aircraft during an earthquake, causing disruptions to air traffic control. During this occurrence, the earthquake resulted in a loss of electricity at the ground base, which consequently affected the plane’s navigation instruments and its capacity to communicate. The power outage resulted in the loss of radar signals for air traffic control, rendering them unable to determine the location of Wagner’s flight. Nevertheless, these problems were quickly resolved when the emergency power of the ground base was activated.

Although this may sound alarming, it serves as an illustration of potential occurrences. Typically, air traffic control stations possess ample emergency backup generators to handle such situations. In addition, they have meticulously developed contingency plans for system-wide events, which include strategies for addressing potential scenarios such as volcanic eruptions, nuclear fallout, floods, acts of terrorism, and earthquakes.

If you find yourself flying during an earthquake, you can rest assured that there is very little cause for concern. Typically, you will be unaware of the occurrence until you touch down.

All “explainer” articles undergo verification by fact-checkers to ensure their accuracy prior to publication. Information can be updated in the future by modifying, deleting, or adding text, images, and links.

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Medicine and Health

The largest-ever 3D-mapped segment of the human brain remains small enough to fit on a grain of rice

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This vibrant spectrum of cells depicts the most extensive and detailed three-dimensional map ever created of a specific region of the human brain. Although it is the largest, it is still only a cubic millimeter in size, which is approximately equivalent to half a grain of rice. Through this achievement, scientists are now able to observe the complex network of 57,000 cells, linked by 150 million synapses and numerous millimeters of blood vessels, which constitute this particular small area of the human cortex.

Over the past ten years, a partnership between scientists at Harvard University and Google has been dedicated to creating a comprehensive and detailed map of the mouse brain. This represents a significant and crucial advancement in our progress, as it unveils the previously unknown intricacy of a portion of brain matter at the level of synapses.

Senior author Jeff Lichtman stated that the term ‘fragment’ is ironic. His team generated electron microscopy images that serve as the foundation for the new map. “For the majority of individuals, a terabyte is considered to be enormous. However, even a small portion of the human brain, which is minuscule and tiny, still contains thousands of terabytes.”

Using AI algorithms created by Google Research, the imaging from Lichtman’s team at Harvard can be color-coded and reconstructed to unveil unparalleled levels of detail.

It is reasonable to assume that neurons, which are the fundamental nerve cells, would be the most prevalent in the primary organ of the central nervous system, as indicated by their name, correct? However, the team discovered that the number of these cells was actually twice as many as the supporting glial cells, which play a role in maintaining the optimal environment of the brain. The oligodendrocytes, which generate myelin, the crucial insulation surrounding nerve axons, were the most abundant cell type.

The tissue fragment displayed peculiarities such as robust neurons interconnected by 50 or more synapses each, enlarged axons containing what the research team referred to as “unusual material,” and a limited quantity of axons arranged in “extensive whorls.” Due to the fact that the tissue sample was obtained from a patient with epilepsy, it remains uncertain whether these characteristics are associated with the aforementioned condition or not.

Mapping down to this level of detail is crucial because it has the potential to offer future researchers valuable insights into the impact of small-scale connections within brain tissue. These connections may have significant effects on major functions and contribute to the development of diseases.

The scientific field that studies the connections within the brain is referred to as “connectomics.”. Recent advancements in the field include a large-scale global initiative to comprehensively map the intricate connections within the human brain, similar to how we have mapped the human genome. Additionally, the first comprehensive map of an insect brain has been published.

In addition to previous achievements such as last year’s unveiling of a brain cell atlas, scientists can now delve into our intricate network of “little gray cells” with unprecedented depth.

In order to advance this objective and increase the accessibility of these techniques to a wide range of scientists, the Harvard and Google teams have created a set of analytical tools that are openly accessible to the public. “Due to the substantial investment made in this project, it was crucial to present the findings in a manner that allows anyone else to easily access and derive advantages from them,” stated Viren Jain, a member of the Google Research team.

The ultimate objective of this project is to create a comprehensive map of the entire mouse brain. This map will yield approximately 1,000 times more data than what is currently being generated from this 1-cubic-millimeter fragment of the human brain. Therefore, there is still a considerable amount of progress to be made.

The authors acknowledge that approaches to understanding the meaning of neural circuit connectivity data are still in their early stages. However, they consider this petascale dataset as a starting point.

The research findings have been published in the scientific journal Science.

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Medicine and Health

A cutting-edge brain implant has been developed that can accurately translate imagined speech in real time, achieving the highest level of precision to date

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Caltech bioengineers’ new tool has proven to be exceptionally adept at deciphering brain signals related to internal speech. Although it has only been tested in two patients thus far, with further development, this technology has the potential to enable individuals who cannot speak to communicate solely through their thoughts.

BMIs are already achieving remarkable feats. These systems have been utilized to assist paralyzed patients in walking and, in the case of Neuralink’s first experimental subject, enable them to control a computer through a “telepathic” connection.

One of the primary applications of this technology involves facilitating communication. For people who are unable to speak, such as those with neurological conditions or brain injuries, BMIs can give them a voice.

There are some limitations to devices of this kind, like the one that the late Stephen Hawking famously used. One challenge is capturing the natural rhythm of speech, which scientists are actively researching, aided by Pink Floyd. Another limitation is that many speech BMIs rely on users attempting to vocalize words, which may not be feasible for everyone. An optimal solution would involve discovering a method to decipher internal speech, allowing individuals to simply imagine uttering a word. Progress in this field has been made, but it has been quite difficult, and the outcomes have been varied.

Now, the team at Caltech has created a system that can accurately decode internal speech with unprecedented precision.

Microelectrode arrays were surgically inserted into the brains of two male patients who were experiencing tetraplegia, one aged 33 and the other aged 39. The team focused on the primary somatosensory cortex and the supramarginal gyrus (SMG), a brain region that has not been investigated in previous studies on speech BMI.

The interface was trained on a combination of real and made-up words to determine their impact on the system’s effectiveness. The participants were presented with each word either visually or audibly and were subsequently instructed to mentally simulate saying the word for a duration of 1.5 seconds. They were then requested to vocalize the word.

According to first author Sarah Wandelt, this technology would be especially beneficial for individuals who have lost their ability to move. For example, let’s consider a condition such as locked-in syndrome.

Using the BMI, the researchers were able to analyze the real-time activity in the SMG while the participants were contemplating each word. One participant achieved an accuracy of 79 percent, which is comparable to the accuracy of decoding vocalized speech, according to Wandelt and co-author David Bjånes. The other participant, however, only achieved an accuracy of 23 percent.

The technology will require additional refinement and testing on a larger sample size with a broader range of words. However, the study does indicate that the SMG shows promise as a brain region to focus on.

“Although the second participant did not replicate these results, this study holds significance as it is, to my knowledge, the first successful implementation of a real-time speech brain-computer interface using single unit recordings in the SMG,” remarked Blaise Yvert of The Grenoble Institute of Neuroscience, who was not part of the study.

Additionally, the team is interested in exploring whether the BMI can effectively differentiate between different letters of the alphabet. Wandelt and Bjånes propose that decoding individual sound units of speech, known as phonemes, may offer a potential avenue for investigation.

According to Giacomo Ariani, the Associate Editor of the paper, this proof-of-concept study on high-performance decoding of internal speech will undoubtedly capture the attention of researchers who are dedicated to advancing the capabilities of BMIs and other therapeutic devices for individuals who have lost their ability to speak.

The study has been published in the prestigious journal Nature Human Behavior.

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