Science News July 26 (Patreon)

[This is a transcript with links to references.]

Welcome everyone to this week’s science news. Today we’ll talk about Einstein, who was right again, metals that heal, a new type of stellar object, a quantum drum, how conscious awareness comes about, maybe, a better way to tell apart alien signals from boring human signals, a hot spot on the moon, illegal trade of hazardous chemicals, and of course, the telephone will ring.

Physicists in Germany tested Einstein’s Principle of Equivalence at unprecedented precision, and confirmed that Einstein was right, yet again.

You might have heard that there are two different types of masses. No, I don’t mean fat and muscles, this is physics. I mean inertial and gravitational masses. The inertial mass is what resists acceleration, the gravitational mass is what makes a body attractive. No, I don’t mean fat and muscles.

Einstein’s theory of general relativity is based on the idea that those two types of masses are exactly the same. This leads to the conclusion that in a gravitational field in vacuum everything falls with the same acceleration, regardless of what it’s made of.

But what if I told you. What if I told you there aren’t just two different masses, but 15. Ok, that was a joke. We physicists are so funny, aren’t we. But I’m not joking when I say that strictly speaking there are 3, rather than two, different types of masses.

That’s because there are two different types of gravitational masses. The one is the mass that creates a gravitational field. It’s called the “active gravitational mass”. The other one is the mass that reacts to the gravitational field of another body. That one is called the “passive gravitational mass”.

Now, in Einstein’s theory of general relativity, all three masses are assumed to be the same. But it’s really just an assumption. That inertial mass is equal to gravitational mass has been tested very precisely, but that the two types of gravitational mass are the same, not so much.

But there’s a clever way to test this which is using the moon. That’s because the moon has more aluminium on one side and more iron on the other.If their ratio of active to passive gravitational mass was not the same, that would slightly shift the centre of the passive gravitational mass. As a result, the orbit of the moon would be somewhat different.

The orbit of the moon has been very precisely measured though and that allows physicists to put bounds on the difference between those two masses.Physicists already did this 1986, but in the new paper they did it again with more data, and showed that passive and active gravitational masses are equal to approximately 14 decimal places.

You might find this a rather academic study because certainly no one doubts Einstein. But it’s not that simple. The issue is that Einstein’s theories don’t account for quantum effects, but we know that matter does have quantum effects. So strictly speaking we don’t know how Einstein’s principle of equivalence even works. Physicists have come up with no less than 4 options, and measurements like this are not so much trying to confirm an already well-confirmed theory as actually trying to figure out how it works in regimes we haven’t tested.

So just because Einstein was right again doesn’t mean there’s nothing left to do.

Hello?

Hi Rishi,

They did what? Train an artificial intelligence to come up with the best English swear word.  Alright, I’ll bite. What is it?

Ber? Honestly, to me it sounds a little sheepish.

Right, so instead of bleeping we could be sheeping. That’s *ing ingenious.

Ah, if an AI deduced it, I am sure Berlin will understand, thanks for calling.

Scientists at Sandia National Laboratories have discovered evidence that metals can self-heal cracks.

The group set out to use an electron microscope to better understand how fatigue cracks spread through platinum in a vacuum. They were surprised to instead see a crack re-fuse – before re-growing along a different path. The healing process appeared to be similar to cold-welding, which has been previously observed in other precious metals, and is used the production of microelectronic devices. These findings confirm an idea put forward by one of the paper’s authors in 2013  that when cracking takes more stress than healing microstructures will tend to promote healing. It’s like, you know, sometimes you make up with your boyfriend because it’s easier than moving out.

Such fatigue cracks account for over 90 percent of in-service failures, when machines break, so this is pretty amazing. You may think it’s starting to look like every cloud has a silver lining – and some of them are self-healing. But not so fast.

As they write in the paper “Stress equilibrium suggests that if local compressive stresses promote crack healing in one area, there must also be areas in which tensile stresses enhance crack opening.”

In other words, if you can heal cracks in one place, you make some in another place. So unfortunately this doesn’t explain why, when the repairman finally shows up, the washing machine is suddenly working again.

Next we have a discovery by researchers who aren’t sure what they discovered.

Using the Murchison Widefield Array, a low-frequency radio telescope in Western Australia, a group of astronomers found an unusual pattern of pulsing radio emission. The signal varies in brightness by two orders of magnitude, lasts between 30 and 300 seconds, and recurs every 20 minutes or so.

Naturally, they named it GPM J1839–10  and asked their mom if they could keep it.

It’s the second such object they have found. They reported the first one last year, but it stopped pulsing soon afterwards. This one however, they found in the data archives going back more than three decades, so it’s been around for some while.

This pattern with the long pauses doesn’t fit any known stellar object. It could fit a slowly rotating neutron star, known as a magnetar,  which sometimes show such pauses, but those usually emit much more X-rays. It’s too bright to be a white dwarf or brown dwarf binary, and an interaction between a star and an exoplanet wouldn’t generate enough energy. Actually, if it’s pulsing that slowly it shouldn’t emit any radio waves.

So they don’t know what they’ve discovered, but at least now they have two of whatever it is, guess that’s progress of sorts.

Scientists from the University of Copenhagen have developed a quantum drum. It’s a super sensitive measurement device for force and acceleration, and they say it might one day go into your smartphone.

This quantum drum is an example of a quantum sensor. It’s a super thin membrane, just 15 nanometres thick, made of a type of crystal. If you accelerate it, it vibrates, and that can be used to measure the acceleration. We just saw in recent news episode why that is interesting. If you can measure acceleration very precisely you can calculate exactly which path you are going, without the need for a GPS receiver.

The problem with these quantum sensors is that normally they have to be cooled with big devices to near absolute zero and most people don’t like it when their thumbs freeze to the phone.

In the new paper now they used laser cooling from room temperature. Laser cooling means basically that you target each piece of the membrane with a laser and give it just the right kick so that it remains still. Basically, if you can use the laser to quiet the membrane sufficiently, then you can tell other disturbances. The researchers say that this device could not just measure acceleration and forces but also temperature and detect traces of gasses very accurately.

Though I think it’s somewhat of a stretch to say that it’ll soon be in your smartphone, and you don’t need a quantum sensor to detect that stretch.

A group of American scientists has used newly released historical weather data to estimate the radioactive fallout of US nuclear weapons tests.

Their results suggest that fallout went much further than the government acknowledged, ultimately spreading to the entire United States, except Alaska and Hawaii. Radioactive compounds also didn’t stop at the border to Canada. Fallout from the first bomb, Trinity,  that was detonated in the New Mexico desert in July 1945 went as far as Crawford Lake near Toronto. I’m all for sharing research results, but maybe not quite as literally.

That seems pretty important. But why did it take 78 years to find out? It’s because to do the calculation you need good weather data, and good weather data from the 1940s is hard to come by. But in March this year, the ECMWF released global weather data dating back to the 1940s for altitudes up to 10 kilometers. This dramatically improved the accuracy for the nuclear fallout estimate.

To paraphrase Oppenheimer: Bomb first, questions later.  Luckily there was a “later”, and it seems that the time has come for questions. The new findings might be used to update legislation that compensates people exposed to fallout, notably those who lived near nuclear test sites or downwind from the Trinity test. Census data show that at the time half a million people lived within a two hundred and forty kilometre radius of the Trinity test site, so that’s a lot of people who might now come and ask for money.

Also brings new meaning to New Mexico’s state motto, “Crescit eundo – it grows as it goes.”

A team of neuroscientists claims to have measured how we become consciously aware of something that we see. They say that their finding agrees with two leading theories of consciousness, that should be competitors.

Brain studies usually work with functional magnetic resonance imaging, that tells you which parts of the brain are active. The problem is that this imaging method is slow. It tells you what parts of the brain are active, but it isn’t particularly useful if you want to know in which sequence a signal is processed.

One can instead measure brain activity from electrical signals. This is often done on people who have electrodes implanted into their head for medical purposes. Such studies have found that if we look at images, then there are surges of activity in certain brain regions, but these peaks fade away within fractions of seconds whereas conscious awareness often lasts longer. Well, sometimes anyway. So that doesn’t seem to have much to do with consciousness.

For the new study now, they looked at the brain activity of 10 patients who have electrodes in their brains for treating epilepsy. They showed them images and measured the brain response. They found that after the initial spike went away, there was a longer lasting signal in parts of the brain that is responsible for digesting visual information. The researchers claim that this part of the brain holds the perception, and that another part of the brain can then use it.

That consciousness works in this way, like a spotlight that shines on some things and not others, is called the “global workspace theory” of consciousness.

The competing theory is integrated information theory, IIT for short, which has it that consciousness comes about from the overall connectivity of the brain, nothing with spotlights and so on. But the researchers say that their finding also support IIT, because according to this theory the neural activity in specific visual processing regions at the back of the brain should remain stable as long as the visual experience continues, and that was also the case.

When the pixies asked “Where is my mind” they probably didn’t think they’d actually get an answer, but here we are.

Researchers at the University of California at Berkeley have developed a new algorithm to distinguish signal from noise as humanity waits for a call from ET.

The tool was developed as part of the Breakthrough Listen initiative of the SETI Research Center’s quest for alien signals. Breakthrough Listen is a 100 million dollar project dedicated to searching for signs of intelligent life beyond Earth the largest ever such project. If they actually find an alien signal this will go down in history as the most expensive long-distance call ever.

The new search tool is a script that filters narrowband radio transmissions so we can tell that they’ve passed through outer space. They think that when a signal travels through outer space, then it interacts with the interstellar medium, and that produces characteristic changes  in amplitude that wouldn’t happen if the signal came from earth. Or from one of those satellites that no one in particular is shooting into orbit. They checked this with radio signals that they knew came from Earth, and the filter worked as desired.

But, as always in signal detection, any filter has its downside. In this case, it reduces the risk of false alarms in exchange for a greater risk of missing the real signal. For example, a signal coming from Proxima Centauri, the closest planetary system to earth, to be mislabelled as earthly interference because it hasn’t travelled through enough space. Sorry aliens from Proxima Centauri, you're just not alien enough for us.

ET, if you’re listening, we don’t want much. “Hello what’s up” will do. But if you could throw in the meaning of life, that’d be great!

A group of astrophysicists has re-examined a hotspot on the moon. And no, I don’t mean that the man in the moon now has wi-fi, I mean there is quite literally a hot spot on the moon.

We have known of this hotspot since 1998, when NASA send the Lunar Prospector to orbit around the moon for 18 months. It scanned the moon’s surface with a gamma-ray spectrometer. It found a place on the far side of the moon, that’s the side that faces away from us, which emitted a lot of gamma rays.

But saying that it’s hot is a weird way to put it. The spot is ten degrees warmer than its surroundings at night, but that’s still something like minus 170 degrees Celsius , so not exactly what normal people would call warm. The thing is though, it’s radioactive.

In 2009, NASA’s Lunar Reconnaissance Orbiter was able to snag some higher-resolution pictures of the spot. Those showed that it looked like a volcano of granitic origin that probably ceased erupting more than 3 billion years ago. This was really surprising at the time, because scientists had thought that volcanic activity on the moon had basaltic lava, instead of the heavier, granitic type.

Now, researchers have confirmed that this hot spot is indeed the product of granitic volcanism. Using data collected by microwave instruments aboard China’s Chang’e-1 and Chang’e-2 spacecraft in 2007 and 2010, researchers from Arizona’s Planetary Science Institute re-examined the geothermal activity at the hot spot. They say it’s indeed almost certainly a relic of a volcanic system, and a fairly large one, with roughly 50 kilometres in diameter.

Maybe when we settle on the moon, we can use the hotspot to generate power. And then the man in the moon will finally get his wifi.

According to a new study just published in Nature Sustainability, illegal trade of hazardous chemical is thriving.

The Rotterdam Convention from 1998 is an international treaty which regulates hazardous chemicals. It controls 54 different chemicals and groups of chemicals, and says how they can be used, handled, and traded. Or rather, how they cannot be used, handled, and traded. The convention has been signed by one hundred sixty one of the world’s roughly two hundred countries, but that doesn’t include the U.S.

The new study examined 46 of the 54 chemicals regulated by the convention. They found that from 2004 to 2019, 64 point 5 million tons of those chemicals were traded globally, 27 point 5 million tons of them illegally. They also found that several toxic pesticides are still being traded despite being banned by the Stockholm Convention in 2004.

I wonder how this works in practice. Are there stores on the dark web where you put asbestos into a cart and go to checkout? If you buy two tons of DDT, do you get a toxic comment for free? I have so many questions.