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There is a gravitational monster at the heart of our galaxy. Known as Sagittarius A*, it is a supermassive black hole with a mass of more than four million Suns. Long-term observations of the stars closely orbiting Sag A* place it at about 4.3 solar masses, give or take 100,000 or so. Observations of light near its horizon by the Event Horizon Telescope pin the mass down to 4.297 solar masses, give or take about 10,000. Those results are astoundingly precise given how difficult the mass is to measure, but suppose we could determine the mass of our galaxy’s black hole to within a single solar mass. That might be possible with gravitational wave astronomy.

Gravitational wave astronomy is still in its infancy. Presently, our gravitational wave observatories are only sensitive enough to detect the mergers of stellar-mass black holes and neutron stars within the Milky Way. We aren’t able to detect the mergers of supermassive black holes, nor the gravitational waves when a star is consumed by a supermassive black hole. But in the not-too-distant future, we will have space-based gravitational observatories such as LISA. They will be orders of magnitude more sensitive than what we currently have. And as a recent study shows, these new observatories should be sensitive enough to give us ultra-precise measurements of a black hole’s mass and rotation.

The idea behind this work is to focus on brown dwarfs. These objects straddle the mass range between planets and stars. Too large to be a planet, but too small to ignite core fusion like a star. Brown dwarfs have masses between 13 and 78 Jupiters and tend to be roughly the size of our Jovian neighbor. They aren’t quite as common as red dwarf stars, but should be fairly common within the center of our galaxy. That means some brown dwarfs should approach very close to Sag A*. Some of them will surely be gravitationally trapped by the black hole, slowly spiraling ever closer to its event horizon and oblivion. These are the ones the article focuses upon.

The gravitational chirp of a black hole merger. Credit: LIGO

Even the largest brown dwarfs have less than a hundredth the mass of the Sun. They are like specks of dust compared to Sag A*. This means the gravitational dance between a brown dwarf and black hole is an example of an extremely large mass-ratio inspiral (XMRI). The gravitational waves produced by this dance would be small perturbations of the black hole, and as such would be critically dependent on the precise mass and spin of the black hole.

To show just how precise those measurements might be, the team looked at the estimated statistics for brown dwarfs near Sag A* as well as the strength of their gravitational signals. They found that within a typical range of mass and orbital eccentricity, an observatory such as LISA should be able to observe about 20 inspiraling brown dwarfs. This would allow us to determine the mass of Sag A* to better than one part in a million and its spin to one part in 10,000. Those estimates are at the best-case end of what is likely, but it shows that as gravitational wave astronomy improves, we are going to make some outstanding observations.

Reference: Vázquez-Aceves, Verónica, Yiren Lin, and Alejandro Torres-Orjuela. “SgrA* spin and mass estimates through the detection of multiple extremely large mass-ratio inspirals.” arXiv preprint arXiv:2412.20738 (2024).

The post Here's How We Could Measure the Mass of SgrA* to Within One Solar Mass appeared first on Universe Today.

Diamond, often celebrated for its unmatched hardness and transparency, has emerged as an exceptional material for high-power electronics and next-generation quantum optics. Diamond can be engineered to be as electrically conductive as a metal, by introducing impurities such as the element boron. Researchers have now discovered another interesting property in diamonds with added boron, known as boron-doped diamonds. Their findings could pave the way for new types of biomedical and quantum optical devices -- faster, more efficient, and capable of processing information in ways that classical technologies cannot.

Diamond, often celebrated for its unmatched hardness and transparency, has emerged as an exceptional material for high-power electronics and next-generation quantum optics. Diamond can be engineered to be as electrically conductive as a metal, by introducing impurities such as the element boron. Researchers have now discovered another interesting property in diamonds with added boron, known as boron-doped diamonds. Their findings could pave the way for new types of biomedical and quantum optical devices -- faster, more efficient, and capable of processing information in ways that classical technologies cannot.

How can we ensure that life-saving drugs or genetic therapies reach their intended target cells without causing harmful side effects? Researchers have taken an important step to answer this question. They have developed a method that, for the first time, enables the precise detection of nanocarriers -- tiny transport vehicles -- throughout the entire mouse body at a single-cell level.

AI applications like ChatGPT are based on artificial neural networks that, in many respects, imitate the nerve cells in our brains. They are trained with vast quantities of data on high-performance computers, gobbling up massive amounts of energy in the process. Spiking neurons, which are much less energy-intensive, could be one solution to this problem. In the past, however, the normal techniques used to train them only worked with significant limitations. A recent study has now presented a possible new answer to this dilemma, potentially paving the way for new AI methods that are much more energy-efficient.

Carbon fiber-reinforced polymers (CFRPs) are used in the aerospace, automotive, and sports equipment industries. However, their recycling remains a major problem. In a recent study, researchers demonstrated a novel direct discharge electrical pulse method for the efficient, effective, and environmentally friendly separation of CFRPs to recover high-quality carbon fibers. This work is expected to pave the way for a more sustainable world.

Engineers have demonstrated a well-known quantum thought experiment in the real world. Their findings deliver a new and more robust way to perform quantum computations and they have important implications for error correction, one of the biggest obstacles standing between them and a working quantum computer.

Engineers have demonstrated a well-known quantum thought experiment in the real world. Their findings deliver a new and more robust way to perform quantum computations and they have important implications for error correction, one of the biggest obstacles standing between them and a working quantum computer.

Scientists are working to produce plant-based cheese with all the characteristics of real cheese, but with better health benefits. To create a cheesy product with the same texture as the real thing, they looked at a variety of physical attributes such as the melting, stretching, and oil-release upon grilling and heating and studied isolates from three proteins and how they interacted with the oil and with the starch matrix of the cheese alternative. Using a blend of sunflower and coconut oil decreased the saturated fat content of the cheese, creating a healthy and sustainable alternative to dairy cheeses and other plant-based cheeses.

Using advanced imaging techniques and precise microfluidics control to stretch out curly DNA into a straight line, new research demonstrates techniques for stretching and immobilizing DNA with minimum thermal fluctuation to enable detailed analysis. A team at Nagoya University experimented with ways to uncurl a DNA molecule using pressure applied to liquid flowing in a channel, with the pressure flow providing shear force that uncurled the DNA molecule. They found that controlling the flow velocity of the liquid helps fine-tune the shear force applied and allows precise adjustments of the stretch ratio of the DNA.

In recent years, more than 60 countries have developed strategies to stimulate the market ramp-up of hydrogen, particularly in the industrial sector. However, in 2023, less than ten percent of the originally announced green hydrogen production was realized, shows a new study. The main reason: hydrogen remains expensive and there is little willingness to pay the cost.

Are humans or machines better at recognizing speech? A new study shows that in noisy conditions, current automatic speech recognition (ASR) systems achieve remarkable accuracy and sometimes even surpass human performance. However, the systems need to be trained on an incredible amount of data, while humans acquire comparable skills in less time.

Water droplets under freezing conditions do not spontaneously detach from surfaces as they do at room temperature due to stronger droplet-surface interaction and lack of an energy transformation pathway. Since accumulated droplets or ice have to be removed manually or with mechanical equipment, which is costly and inefficient, preventing droplet accretion on surfaces is both scientifically intriguing and practically important. Researchers have now invented a ground-breaking self-powered mechanism of freezing droplet ejection that allows droplets to shoot themselves away, paving the way for cost-efficient and promising technological applications.

Regulars at this site will surely know of Robert Lang, physicist and origami master (art website here) whom I met a while back at the Kent Presents meetings. We became friendly and thereafter he contributed both wildlife photos and origami photos to this website (see all his posts here).

I was scheduled to meet Robert and his wife Diane today after the meetings and get a tour of their home and studio (she’s an author), thereafter then sallying forth to dinner. I hadn’t seen Robert in years, and had never met Diane, so I was looking forward to visiting their digs and to seeing some of the famous origami.

The problem was that their home and studio were in Altadena, California, near Los Angeles, so you can guess what I’m going to say next.

The home and studio are no more, taken down by wildfire. But I’ll let Robert tell the tale. His words, printed with permission, are indented below, and are supplemented with narrated videos (there are even subtitles).  This is the story of a family who lived through the fire but lost everything—except for the most important things: their lives and their animals.

Note that they actually lost two houses, as they had just bought another down the street.

Late Tuesday afternoon, we heard about the Eaton Fire, which started over in Eaton Canyon, about 2 miles to our east and several ridges over. The initial reports were that the wind was driving the fire to the east (away from us), so we were hopeful. At about 6:30 pm, though, my neighbor texted the neighborhood group that he saw a glow over the ridge to our east, and I headed up to my studio to see. By 7:30 pm I saw the fire crest that ridge and we received the “evacuate NOW” notice, so I threw as much as I could grab into my car and headed down, while my wife did the same from our home (with the dogs, tortoises, snake, and tarantula that live with us).

We spent the next few hours driving and parking to try to watch things from a distance. Surprisingly, the evacuation zone ended just to the west of our neighborhood, so after a while, I started making my way to the edge of the zone, staying out of the way of the many emergency vehicles, and presently found a spot from which I could walk to the edge of the canyon that separated me from my studio. From there, I could see the studio; I could also see that the entire multi-thousand-foot mountainside above it was in sheets of flame. The wind was blasting through the canyons, driving 50-foot plumes of flame and embers horizontally. About 1:30 am, I saw a flare-up right at the studio, and within about 10 minutes, it was engulfed. I also realized about that time that the fire would likely take down the telephone poles (and thus, potentially live wires) along my route, so I beat a hasty retreat to my car, and before long, the authorities announced that our area was now evacuation zone. We drove down the hill to Pasadena, found a quiet neighborhood out of the smoke (and, we hoped, the path of the fire), and spent a fitful rest of the night in our cars, awaiting what the morning would bring.

In the morning, my wife stayed with the animals and I drove up the hill to see what became of our house. Major roads were blocked off, but I wove through the neighborhoods, dodging still-burning homes (though the worst was past), downed wires, downed trees, and random debris, until I could get up to my neighborhood. It was a zone of total devastation: nearly all homes burned–and definitely mine. (Actually, both of ours; we had just moved down the street, so both our old house–just moved out of–and the new house–just moved into–were leveled.) I made my way up to my studio at the top of the hill, passing street after street of nothing but smoldering ruins. When I made it up, I found something incredible: the row of houses below my studio had entirely survived! I texted their owners the good news. I could see, though, that my studio had not; I parked (debris blocked my driveway), walked up, and surveyed the destruction, took a few videos and pictures for records, then high-tailed it down the hill.

Right now, the estimates are that 7000 structures were damaged or destroyed. It looks like about 2/3 of Altadena is gone. There’s a lot of snark on the internets about the rich people/celebrities/influencers in Pacific Palisades losing their houses. I haven’t seen similar snark about Altadena, which is a mixed-class, mixed-race community. There are turn-of-the-century buildings, craftsman houses, bungalows, tiny starter homes, and yes, a few mansions left over from the days when it was the summer playground of the rich. My wife grew up here; her father built their house himself in the 40s after clearing the orange groves from the parcel he bought. On the main drag downtown, the local hardware store was where you ran into your neighbors; Fox’s Restaurant had been a local landmark since 1955. All that is gone.

Ironically, I had recently returned from a business trip to Dresden, Germany, which was (famously) fire-bombed and leveled in WWII. They rebuilt. So will we. But it will be a long road to recovery.

*****************

Here a Cal Fire map of fire damage. The damaged area covers about 2/3 of Altadena. My home and studio is in the top middle of the burned civilized area, just to the left of the vertical black bar on the map.

This map is an understatement; I know some of the areas shown in gray actually burned.

Here are a few of the videos Robert posted on his YouTube site:

Panorama of the fire from the studio:

View of the mountains from the house:

Views of the destroyed house:

Views of the destroyed studio:

From Robert:

Here’s one more image for you: house-by-house fire damage. I’ve annotated where my places were. Not much left of the neighborhood.

[The key to above]: red=burned, black = OK, amber=damaged, green=“affected” (whatever that means).

Distance-wise, the studio and the houses are about a half mile apart by road, less by walking (there’s a trail up the canyon). An easy walk, except for the elevation gain (studio is about 200’ higher in elevation), so I usually drove.

Click to enlarge:  Arrows: studio is at the top, the old house at lower center, and the new house at lower right.  I’m struck by the patchy locations of the houses that survived.

As you can tell from the narration, Robert appears remarkably calm about this, as he was in his email to me about the destruction, which was headed “change of plans.”  I would be wailing with grief! But Robert and I do have one thing in common: a compulsion to document. His is with words and videos, mine involves in putting them on this site.

Best of luck, Robert and Diane, and of course we’re all sorry for your loss.

A range of brainwave-reading devices and other gadgets aim to monitor our nervous systems and intervene to improve our well-being. Do they work?

Two companies, Firefly Aerospace and ispace, are aiming to make the second and third successful private landings on the moon - and both are launching on the same Falcon 9 rocket

A marine crustacean that looks like Darth Vader’s helmet has been recognised as a new species, but it could be under threat from trawling due to its popularity in Vietnamese restaurants

Meanwhile, in Dobrzyn, Hili is the boss cat, of course:

A: Hili, you are not helping me when you lie here.
Hili: I’m supervising. Find somebody else to help you.

Ja: Hili, nie pomagasz mi jak tu leżysz.
Hili: Ja nadzoruję, do pomagania znajdź sobie innych.

Cloud seeding would seem like an easy and obvious way to create rain where none existed before. Is it really that simple?

The problem with debating a flat-Earther is that they didn’t arrive at their conclusions from the weight evidence, so using the evidence isn’t going to work to change their minds.

That said, the evidence for the curved Earth is abundant. Besides the enormous body of photographic documentation, it’s even possible to do the experiment yourself. For example, I recently flew from New York City to Doha, from there to Singapore, then to Brisbane, then to Dallas, then back home. I followed an eastward course for my entire journey, and ended up back where I started. That’s only possible on a globe.

On that journey I got to enjoy plenty of views of the night sky, and one of the most striking features was that the sky was different. On a flat Earth, everyone would get the same view of the sky, but there were stars that I could only see at home and couldn’t on my trip, and vice versa.

And lastly, during a lunar eclipse the shadow of the Earth passes over the Moon. That shadow is always a circle, and only spheres are capable of casting circular shadows 100% of the time, regardless of angle.

But like I said, it’s not about the evidence. People who believe that the Earth is flat think that we are being lied to by scientists and political leaders. Many people don’t trust their society, and especially leaders of that society. And most especially elite leaders of that society. Scientists are indeed elite leaders of the government, academia, and other powerful institutions. By claiming that the Earth is flat, people are really expressing a deep distrust of scientists and science itself.

Distrust in science is a deep, thorny issue. But one way to rebuild trust is to simply listen. I know it sounds counter-intuitive, but studies have shown that people tend to trust other people, not necessarily the facts. So if you encounter a flat-Earth, as I have many times, don’t bother getting in a debate. Instead, change the subject so that you focus on something you find wonderful or extraordinary about the universe or about science. Maybe it’s an exciting new observation, or a clever experimental result, or an example of a real-world impact from scientific learning.

By building bridges based on shared wonder, awe, and curiosity, we can defuse the tension, moving around the flashpoint caused by a triggering proclamation and instead focusing on common ground. That’s the only place where trust can take root. And once trust is established, the question of the geometry of the Earth simply fades into the background.

The post How to Debate a Flat-Earther appeared first on Universe Today.