Science News March 8 (Patreon)

[This is a transcript with references.]

Welcome everyone to this week’s science news. Today we’ll talk about a new LHC anomaly, wakefield acceleration, nuclear fusion progress, how to look around corners in augmented reality, the largest magnetic fields we’ve ever seen, engineers who have designed better wood, birds that change their colour, metamaterials that guide robots, and of course, the telephone will ring.

We just put to rest an LHC anomaly in January but now we have a new one. The CMS collaboration just put out an analysis of the data collected in the previous LHC run from 2016 to 2018, proton-proton collisions at 13 TeV.

They looked at collisions that produce a pair of an electron and a muon. In a small energy range of around 146 GeV they found more of those pairs than expected from the predictions of the standard model. In this figure, the green band is the expected range.

Particle physicists quantify the statistical significance of a signal with multiples of sigma, where sigma is one standard deviation. The more sigma away from the expectation, the higher the statistical significance. This signal is currently at 2 point 8 sigma. That’s well below the discovery threshold in particle physics which is at 5 sigma.

We have seen far bigger anomalies come and go in particle physics, so it’s too early to get excited, but what does it mean? First of all, it means that we’re going to see a lot of papers proposing explanations for this anomaly in the coming months. And then, other LHC experiments will see if they find a similar anomaly in their data. And then there’s the question whether it’ll also show up in the new data.

What could it be? Well, this is particle physics, so the most obvious thing it could be is some kind of new particle that decays into an electron and a muon. For example, the red line in this figure is a fit with a new Higgs-like particle that has a mass of 146 GeV. Since the evidence is presently at best so-so, maybe we should for now call it the Higgs-so-son.

A team at the University of Michigan has figured out how to push a laser into the extreme ultraviolet by amplifying it in the wake of an electron beam.

The idea is called “wakesurfing”. I hope we all agree that physics has the coolest words. Wakesurfing was first proposed in 1979 as a way to accelerate charged particles. The idea indeed works pretty much like if you’re actually surfing in the wake of a motorboat.

You create a plasma from some gas, usually a noble gas. You shoot a laser beam into the plasma. The laser displaces some of the electrons from the nuclei and creates a rapidly moving distortion in the plasma. It’s moving at almost the speed of light and has an electric field in it. Then you can inject other particles into the wake of that plasma disturbance. They get dragged along and accelerate.  

In 1989, another group of researchers pointed out that this also works for other laser beams. For this you use one laser to create the plasma wake, and then you shoot another laser into the wake. You don’t actually accelerate the second laser beam, but you increase its energy. So, the idea has been around for some while, but up to now they couldn’t get it to work efficiently.

In the new paper they now suggest to use an electron beam to create the wake that amplifies the laser. This was not an experiment. So far, it’s a mathematical model with a computer simulation. You can see here how it would work.

If you focus on the flying-saucer-like object on the right, that’s an animation of the frequency of the laser’s electric field. You can see that it rises to more than 40 times the original. For a quadrillionth of a second, it even got to a 50-fold increase. This corresponds to about 10 trillion watts and is about as much as the total power generation in the whole world.

Isn’t that what we all want? Being world-famous for a quadrillionth of a second?

This is a representation of the 3D simulation. Look at the red and blue shapes in the midst of the larger coloured disks. They represent the electric field amplitude of the laser. You can see that the amplitude grows 10-fold. The researchers hope that they can soon experimentally realize this idea.
 
Wakefield acceleration is also a big hope for particle physics. At the moment, particle colliders are huge. The Large Hadron Collider at CERN, which is currently the largest particle collider in the world, needs a 27-kilometer ring of superconducting magnets, plus other structures, to accelerate protons. Wakefield acceleration could dramatically shrink the size of particle colliders, and with that also the cost.

CERN has a research program for wake-field acceleration that has made big progress in the past decade. The energies they can reach aren’t yet high enough to go beyond the LHC. But if they shrink them down to handheld devices, maybe we’ll finally get real lightsabres, so stay tuned.

A private California-based company, TAE Technologies, and Japan’s National Institute for Fusion Science  have made a breakthroughin hydrogen-boron fusion.

The most commonly used fuel for nuclear fusion is deuterium and tritium. Both are heavy isotopes of hydrogen. Deuterium is abundant on earth, but tritium is not. This is one of the major problems for making nuclear fusion commercially relevant.

The company TAE Technologies instead wants to use normal hydrogen and boron as fuel, both of which are abundant on earth. The reaction between them also doesn’t release neutrons, which are a particularly nasty source of radioactivity that one has to deal with when one uses deuterium and tritium.

Using hydrogen and boron is a good idea in principle, but of course there’s a downside, which is that the temperature needed to fuse those two is much higher than that needed for deuterium and tritium fusion. For deuterium and tritium one needs about 100 million Kelvin whereas for hydrogen and boron one needs more than a billion. But the researchers now report they have achieved the world’s first hydrogen-boron fusion in magnetically confined plasma.

The experiments took place at Japan’s Large Helical Device, the world’s second largest stellarator. A stellarator is a device which uses magnetic fields to confine plasma, like a tokamak, but with more complicated magnetic fields.

They injected grains of boron into the middle of the device to create a plasma.And then they fired high-energy protons into the plasma. The boron fused with the protons and created Helium nuclei which they could measure. The team calculates that the method could result in a proton-boron fusion rate of about 10 to the 14 per second.

This sounds good but before you get too excited let me remind you that of course you can do nuclear fusion by accelerating particles and shooting them at a target. The problem is that accelerating these particles takes up a lot more energy than you get out of the fusion. And to generate net energy, the hydrogen-boron approach has a much higher bar to jump than deuterium tritium. So I guess we’ll have to keep on dusting the solar panels for a little longer.

A group of researchers at MIT has developed a new prototype headset for augmented reality that lets you see inside of boxes and around corners. It’s like having x-ray vision, but without the x-rays.

Here’s how it works. The researchers fitted a commercial augmented reality headset, the Microsoft Hololens 2, with an antenna that can read radio signals. That’s because many manufactured goods are already marked with an RFID – a radio frequency identification tag.

Then, the team worked out an algorithm that can find RFID tags in a person’s surroundings and creates a virtual 3D map. It takes into account how humans normally move, for example, we normally don’t walk through walls, and then the headset shows you how to get to the desired item, flashing a holograph to mark the spot.

In more than 230 experiments, the headset was accurate to within a decimetre, more than 95 per cent of the time. The team will present their work at the USENIX Symposium in Boston next month. The researchers say the headset could be useful for people who work in warehouses, by guiding them to specific items. Though I think the major application will be to help people figure out where the scissors have gone this time.

 

Hello.

Hi Elon.

Yes, we do have news from neuroscience this week. Hang on.

Neuroscientists want an emoji for a mouse in a maze.

A come on, I’m sure it’ll be a-mazing. Who doesn’t feel a little mousy every now and then? How’s it going with neuralink by the way.

Elon?

An international team of astrophysicists has for the first time been able to measure the magnetic fields of galaxy clusters, and they did it by using shock waves in the intergalactic medium.

Galaxies in the universe are organized into a web-like pattern of clusters that are linked by filaments and separated by voids. Between galaxies there’s a lot of gas and plasma. When the electrically charged particles in the plasma move around that creates magnetic fields. Cosmologists have long tried to measure those magnetic fields, but it’s difficult because they’re incredibly weak.

The authors of the new paper now had the idea to look for shock waves in the plasma. How do you shock intergalactic plasma? Tell it about that night you were out with Diana? Maybe better not. Shock waves in intergalactic plasma are created for example by the motion of galaxy clusters. These can collide and the collision creates a bow wave. Theoretically, the shock waves force the magnetic fields into order, and that polarizes the emitted radio waves. So one should be able to use the polarization of the radio waves to infer the properties of the magnetic fields that were amplified by the shock waves.

But it’s a weak signal. To tease it out of the measurement, the researchers stacked radio images from 600 thousand pairs of early, massive galaxies, and then averaged them to get a clearer signal of the filaments connecting them.

They used measurements from a large radio telescope in Canada and the Planck satellite. In the end their analysis produced bright ring of polarized light around the galaxy clusters. This is the light from shock waves in the filaments connecting the clusters.

They also checked their results against the latest simulations of the cosmos and agreed well. The interesting thing about this analysis is that by subtracting the magnetic field from the shock waves they understand better what part of the magnetic field was left over from the early universe, and that’ll certainly come in handy for other studies.

That was about as shocking and polarizing as science news gets.

An international group of material scientists and engineers has figured out how to alter wood to make it suck up carbon dioxide.

But don’t trees already suck up carbon dioxide. Yes. When they’re alive and growing. Those researchers are using wood from trees that have already been chopped down. They scaffold a chemical mixture into the internal structure of the wood so that it continues to absorb carbon dioxide.

Producing the new wood is a two-part process. First, they use some chemicals to strip the wood of its lignin, that’s one of substances its cellular structure is made of. Then they boil the wood in a solution of lye and sodium sulphite, followed by a dip in boiling hydrogen peroxide. Essentially, they bleach it.

You can see here at the bottom of the shot this chalk-white piece of wood that’s been treated. It also shrinks. Then they infuse the stripped wood with some zinc-based compounds, which are known to be good absorbers of carbon dioxide. After that, they dry it out at 80 degrees C.

Why make this effort you may wonder? It’s because wood provides an excellent structure to carry the compounds that absorb carbon dioxide. Wood is biodegradable, renewable, inherently porous and is easy to modify with chemicals. Plus, the structure is strong, even without lignin.

The researchers hope that the new wood could one day be used in place of other construction materials and decrease the carbon dioxide amount in the atmosphere. So maybe I can then carbon-offset the lawn mower by buying more bookshelves.

Hi Rishi,

Yes, I’ve heard you have a tomato shortage.

Just use it as an opportunity to promote original British cuisine. Like spaghetti on toast. Chips on toast. Or, toast on toast! You can survive without those foreign vegetables.

You’re welcome.

A group of American and Peruvian biologists has figured out how the offspring of two pink-throated hummingbirds came out having a golden throat. And it’s got nothing to do with biology, but rather, physics.

When the biologists found the tiny bird in 2013 in the foothills of eastern Peru, they thought it might be a new species of hummingbird. But a DNA analysis revealed that it was the offspring of two known species, each of which had a pink colour. You can see them here in this image. Somehow two pink coloured parent birds had had a gold-coloured baby bird. But how?

Hummingbirds are known for their fabulous iridescent colours. But rather than being the result of pigments, they happen because of the way light scatters off the nanostructures of the feathers. So the biologists went an measured the spectrum of the reflected light

As you can see from these graphs, the spectrum for the hybrid bird, in the middle, is different from that of its parent species. There’s no bump here in the range around 450 nanometres. This is why the colour looks more sharply peaked near yellow.

And if you look at this bottom line of images, that were taken with an electron microscope, then you see that the reason is that the feather nanostructures of the hybrid bird are visibly different from either of its parents species. The parents’ feathers created pink in two slightly different ways and part of that cancelled out when combined.

That’s fascinating. But if you were hummingbird daddy, would you accept this explanation?

A group of Chinese and French computer scientists have developed a wireless indoor system with metamaterials that could be used in hospitals to direct motorized vehicles to patients.

Using robots to help with health care and factory work seems like an obvious idea. But it’s been difficult to make work with optical sensors alone. Optical sensors, like human eyes, can’t see in darkness or through walls or around corners. And as you’ve probably noticed, that sometimes sucks. Moreover, visual information creates privacy issues.

A better way to do it is to use microwaves because those can go through walls, but the problem is that then you need a directional microwave sensor. The innovation of the new study is that they used a metamaterial that acts as a cheap and passive sensor to collect the microwaves at a central location. They use this to create a three-D map and direct the robot.

This video gives a good idea of the system’s capability. The red outline on the left is the microwave image of the man who you see in person on the right. When the man waves his hand, the vehicle moves to the shelf, fetches something, and then finds the man in the corridor.

In their paper they also have an artist’s sketch for the idea which looks like this. I think they should have paid the guy better.

Metamaterials are materials with custom-designed nanoscale structures that can be used to give the material desirable electric, optical, or acoustic properties. It’s a very interesting research area, I talked about this in more detail in a previous video. I’d like to make a joke here but can’t think of anything, so I guess I’ll just make a meta joke.