Tag: gravity

MIT’s Chilling Experiment That Could Prove Gravity Is Quantum

MIT researchers have found a bold new way to approach one of science’s biggest mysteries: is gravity truly a quantum force?

By chilling a tiny mirror to near absolute zero using lasers — a method traditionally used in atomic physics — they’ve opened a new experimental window into the intersection of quantum mechanics and gravity. This fusion of cutting-edge cooling and classical tools might finally let scientists observe whether gravity behaves like other quantum forces, a question that has puzzled physicists for decades.

The Gravity Puzzle: Is It Quantum?

One of the most profound open questions in modern physics is: “Is gravity quantum?”

While the other fundamental forces—electromagnetic, weak nuclear, and strong nuclear—have been successfully described by quantum theory, gravity still stands apart. So far, scientists haven’t been able to create a consistent quantum theory of gravity, leaving a major gap in our understanding of the universe.

“Theoretical physicists have proposed many possible scenarios, from gravity being inherently classical to fully quantum, but the debate remains unresolved because we’ve never had a clear way to test gravity’s quantum nature in the lab,” says Dongchel Shin, a PhD candidate in the MIT Department of Mechanical Engineering (MechE). “The key to answering this lies in preparing mechanical systems that are massive enough to feel gravity, yet quiet enough — quantum enough — to reveal how gravity interacts with them.”

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Forget Radio Telescopes—Aliens Could Be Using Gravitational Waves to Communicate

One of the most exciting breakthroughs in astronomy over the past decade was the detection of gravitational waves. Since the days of Galileo Galilei, astronomy was about the detection of electromagnetic signals with telescopes. As it turns out, the main constituents of the Universe are not observable in that way.

Our current data indicates that 85% of the matter in the Universe is invisible electromagnetically, constituting dark matter. In addition, 70% of the energy budget of the Universe is dark energy. Cosmologists infer these constituents because they affect visible matter gravitationally. Can we build a detector of near-Earth objects that would sense the gravitational signal of passing dark objects?

If dark matter is made of asteroid-mass objects, like primordial black holes, our telescopes would not notice them even when they pass near Earth. In a recent paper, I showed that the LIGO-Virgo-KAGRA gravitational wave observatories could detect a dark object if it moves close to the speed of light and its mass is larger than a hundred million tons. Such an object would cross the radius of the Earth within two hundredths of a second and produce a gravitational tidal signal in the frequency band of LIGO-Virgo-KAGRA. Needless to say, no such object was detected so far.

Within a decade, the LISA space observatory will expand gravitational wave detection to the frequency range between milli- and micro-Hertz and a smaller spacetime strain. This will usher in a new era of sensitivity to dark near-Earth objects in the asteroid mass range. It could also open the door to the detection of Unidentified Anomalous Phenomena (UAP) gravitationally, which the Galileo Project observatories are attempting to detect electromagnetically. Pulsar Timing Arrays(PTAs) probe a frequency range of a few nano-Hertz, but so-far they were only sensitive to the cumulative gravitational wave background at these frequencies – which constitute the noise floor for the detection of individual sources.

Gravitational wave detectors are the most exciting telescopes of the next millennium as they will open the door for detecting objects that we had never noticed before. As I showed in another recent paper, it is impossible to block or dissipate gravitational wave signals. They offer the optimal communication method, detectable through Earth or the Sun.

It is conceivable that extraterrestrial technological civilizations communicate in gravitational signals, and our failure to notice them so far is because traditional SETI relied on seeking electromagnetic signals with traditional telescopes. If so, the silence that triggered Fermi’s question: “Where is everybody?” stems from our blindness to gravitational signals at the appropriate frequency.

Aliens would choose a communication channel that does not interfere with the frequencies of the loudest natural sources of gravitational waves in the cosmos. These are black hole binaries of stellar mass – to which LIGO-Virgo-KAGRA is tuned, as well as supermassive black hole pairs – to which LISA and PTAs are tuned. In that case, gravitational-SETI will need to develop sensitivity in other frequency bands.

The main challenge in producing detectable gravitational signals is the requirement to move large masses at high speeds. To within an order of magnitude, the gravitational wave strain is of order the gravitational potential produced by the transmitter divided by the speed of light squared times the square of the characteristic speed by which its mass moves in units of the speed of light. For context, the gravitational wave strain produced by the nearest stellar binary, Alpha-Centauri A & B – as the two stars orbit each other every 80 years, is only of order 10^{-24} and extremely challenging to detect.

Five years ago, a team led by Marek Abramowicz published a paper on the possibility that an advanced technological civilization harvests energy from the supermassive (4 million solar-mass) black hole Sagittarius A* at the center of the Milky Way and uses it for communication. They found that a Jupiter-mass structure in the innermost stable circular orbit around the black hole would emit an unambiguous gravitational wave signal that could be observed by LISA.

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SCIENTISTS HAVE SOLVED THIS ANTI-GRAVITY MYSTERY WHILE CONFIRMING NEW FORM OF MAGNETIC LEVITATION

In a groundbreaking discovery, scientists have unraveled an anti-gravity mystery that seemingly defied the norms of classical physics, potentially paving the way for revolutionary advancements in magnetic levitation technology. 

The breakthrough centers on a unique form of magnetic levitation, first demonstrated in 2021 by Turkish scientist Hamdi Ucar, an electronics engineer from Göksal Aeronautics in Turkey. 

Typically, the setup becomes unstable when you try to balance two repelling magnets to counter gravity. However, in a study featured in the journal Symmetry, Ucar revealed that when positioned close to another swiftly rotating magnet, a magnet can both spin and levitate in the air.

In his experiment, Ucar used a Levitron toy with a magnet attached to a motor spinning around 10,000 rpm. When positioned just a few centimeters beneath the swiftly spinning rotor, a second magnet also started to rotate and achieved a stable state of levitation.

Magnetic levitation isn’t a novel concept, with the most familiar example being Maglev trains. However, existing technologies use slow-spinning mechanics or external stabilizers to control the powerful magnetic forces used for lifting and propelling. In contrast, Ucar’s setup relied on high-speed rotation and a unique interaction between the rotating magnets. 

The baffling behavior of the levitating magnets in Ucar’s experiments left researchers perplexed, as it appeared to go against the core principles of physics and the established norms of how magnets interact.

Intrigued by the scientific puzzle, Dr. Rasmus Bjørk and a team of researchers from the Technical University of Denmark embarked on a quest to demystify the unusual phenomenon. 

“Magnets should not hover when they are close together. Usually, they will either attract or repel each other,” Dr. Bjørk explained. “But if you spin one of the magnets, it turns out, you can achieve this hovering. And that is the strange part. The force affecting the magnets should not change just because you rotate one of them, so it seems there is a coupling between the movement and the magnetic force.” 

The researcher’s approach was twofold. The first involved replicating Ucar’s results using off-the-shelf items like neodymium magnets and power tools. In a second, more sophisticated experiment, the scientists used motion-tracking technology to take precise measurements of the 

The findings were revelatory. Experiments showed that as the floater magnet began rotating, it locked in frequency with the rotor magnet, assuming a near-vertical orientation. 

The polar axes of the two magnets, nearly perpendicular to each other, formed a configuration that would typically be unstable. However, in this setup, the spinning magnetic field of the rotor exerted a torque on the floater, locking it in a stable, levitated position.

Through computer modeling that considered the magnetostatic interactions between the two magnets, the research team says they solved the physics-defying anti-gravity mystery and confirmed the discovery of a new form of levitation. 

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The Mystery of the World’s Largest and Deepest Gravity Hole

DEAR INDIAN OCEAN, PLEASE DON’T take offense, but: Why is your gravity hole so big? That question had been baffling scientists ever since the hole was discovered back in 1948. Now a team from the Indian Institute of Science (IISc) thinks they have found the answer: The “hole” in the Indian Ocean is caused by fragments from the sunken floor of another, much older ocean.

In a mysterious part of the Indian Ocean, the pull of gravity is much weaker than anywhere else on Earth. This gravity hole, the world’s largest (and deepest) gravitational anomaly, is officially known as the Indian Ocean Geoid Low (IOGL). (A geoid is a theoretical model of sea levels worldwide, with its irregularities corresponding to variations in the Earth’s gravity.)

There’s nothing mysterious per se about gravitational variation, which corresponds to differences in the density of the subsurface (and submarine) layers of rock. What was unexplained, was the size and amplitude of the anomaly in the Indian Ocean.

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Uneven Gravity Makes You Weigh More in Illinois Than in Indiana

WHAT A WEIRD PLACE THIS planet is. But especially southern Illinois, according to this map of gravity anomalies across three Midwestern states.

Gravity is what made the apple fall from a certain tree (in Woolsthorpe, Lincolnshire), causing Newton to wonder why it fell down straight. But the law of universal gravitation he formulated (and published in 1687) by way of explanation is a lot less uniform than you’d think.

For gravity does vary across the earth, meaning Newton’s apple has a slightly different weight in various other parts of the world and falls at slightly different speeds. That’s due to a combination of four factors.

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