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They hold the keys to new physics. If only we could understand them.
Somehow, neutrinos went from just another random particle to becoming tiny monsters that require multi-billion-dollar facilities to understand. And there’s just enough mystery surrounding them that we feel compelled to build those facilities since neutrinos might just tear apart the entire particle physics community at the seams.
It started out innocently enough. Nobody asked for or predicted the existence of neutrinos, but there they were in our early particle experiments. Occasionally, heavy atomic nuclei spontaneously—and for no good reason—transform themselves, with either a neutron converting into a proton or vice-versa. As a result of this process, known as beta decay, the nucleus also emits an electron or its antimatter partner, the positron.
There was just one small problem: Nothing added up. The electrons never came out of the nucleus with the same energy; it was a little different every time. Some physicists argued that our conceptions of the conservation of energy only held on average, but that didn’t feel so good to say out loud, so others argued that perhaps there was another, hidden particle participating in the transformations. Something, they argued, had to sap energy away from the electron in a random way to explain this.
Eventually, that little particle got a name, the neutrino, an Italian-ish word meaning “little neutral one.” //
All this is… fine. Aside from the burning mystery of the existence of particle generations in the first place, it would be a bit greedy for one neutrino to participate in all possible reactions. So it has to share the job with two other generations. It seemed odd, but it all worked.
And then we discovered that neutrinos had mass, and the whole thing blew up. //
Nazgutek Ars Scholae Palatinae
23y
866
That was a fun read. I feel like I've climbed a single Dunning-Kruger step and now I feel like I know that I know less about the universe than I did before reading this article! //
NameRedacted Ars Praetorian
7y
445
Subscriptor
karadoc said:
such that relative to you the neutrino's direction of motion would then be reversed (compared to before you overtook it)... so then I'd expect that to be a right-handed neutrino from the point of view of that speedy observer.
I may be very wrong here, but I think that the entire point of chirality is that you can’t just reverse it by changing your perspective.NameRedacted Ars Praetorian
7y
445
Subscriptor
karadoc said:
such that relative to you the neutrino's direction of motion would then be reversed (compared to before you overtook it)... so then I'd expect that to be a right-handed neutrino from the point of view of that speedy observer.
I may be very wrong here, but I think that the entire point of chirality is that you can’t just reverse it by changing your perspective. //
NameRedacted Ars Praetorian
7y
445
Subscriptor
Back when I first graduated with my engineering degree, I really wanted to go back and get a PHD in physics because I loved QM so much.
Every time I read one of these articles, I’m glad I didn’t. Don’t get me wrong, this stuff is exciting: but I don’t think I could handle how much the universe “wants” to perplex us.
I have little doubt that the physics world will need to completely change everything to figure out all four of the big “mysteries”: Neutrinos, Dark Matter, Dark Energy, and the Hubble Constant. I also have little doubt that the solution will be complex, expensive, and be an advancement on the level of QM (I.e. atomic energy and semiconductors).
I hope I’m alive for when it happens, but *$&@ am I ever glad I haven’t spent my career trying to sort it out. //
Simk Smack-Fu Master, in training
4y
56
Subscriptor++
I really enjoyed that article! I'm none the wiser for having read it, but that seems fitting for the subject matter. //
neil_w Ars Praetorian
13y
464
Well, the properties of neutrinos don’t line up like this. They’re weird. When we see an electron-neutrino in an experiment, we’re not seeing a single particle with a single set of properties. Instead we’re seeing a composite particle—a trio of particles that exist in a quantum superposition with each other that all work together to give the appearance of an electron-neutrino.
For a moment I considered just closing the browser tab after reading this paragraph.
This was a very good article, trying to explain the nearly unexplainable. Hat tip to the physicists who are able to grasp it all. //
dmsilev Ars Praefectus
14y
5,375
Subscriptor
The sum of all three neutrino masses cannot be more than around 0.1 eV/c2
The absolute value of the square of the difference between m2 and m1 is 0.000074 eV/c2
The absolute value of the square of the difference between m2 and m3 is 0.00251 eV/c2
One thing which the article didn't mention is that there's an additional question hiding in these constraints. Usually, mass scales with family; the electron is lighter than the muon is lighter than the tau, and similarly for the quarks. We assume that that's the case for neutrinos as well, that m1 (the major constituent of electron neutrinos) is less than m2 is less than m3. That's called the "normal hierarchy" solution. However, the data doesn't prove that. There's also an "inverted hierarchy" fully consistent with the data which swaps the ordering. And we can't tell which one is correct. The only reason for the somewhat prejudicial names "normal" and "inverted" is the sense of elegance that the laws of physics should be somewhat consistent.
Scientists carried out a survey of five million distant solar systems with the help of 'neural network' algorithms and it took an interesting turn when they found nearly 60 stars surrounded by what appeared as "giant alien power plants."
Among the 60 stars, seven of them - which were M-dwarf stars and ranged between 60 per cent and 8 per cent the size of the Sun - were seen releasing high infrared 'heat signatures,' as per the astronomers. //
While these structures are named for Freeman Dyson, a physicist and mathematician who proposed the building of a Dyson sphere to contain and capture all of a star's energy output, the concept actually goes back to a 1937 novel, Star Maker, by author Olaf Stapledon.
But as far as this study actually having detected such structures? Color me skeptical. //
What isn't said is what other explanations might cause these mid-infrared emissions; while I'm a biologist and not a cosmologist, it seems to me that a G-sequence star like our sun, were it to be surrounded by a cloud (or clouds) of gas or dust, may well also emit such an IR signature. And that's a lot more likely than an alien civilization that would by necessity be thousands, or millions of years ahead of us, technologically. //
Cliff-Hanger
3 hours ago
Ward, I'm a little disappointed. Dyson structures mentioned and not one bad pun about vacuum cleaners sucking the energy out of the stars.
Simultaneity Ain't what It Used to Be
One of the most fundamental deductions Albert Einstein made from the finite speed of light in his theory of special relativity is the relativity of simultaneity—because light takes a finite time to traverse a distance in space, it is not possible to define simultaneity with respect to a universal clock shared by all observers. In fact, purely due to their locations in space, two observers may disagree about the order in which two spatially separated events occurred. It is only because the speed of light is so great compared to distances we are familiar with in everyday life that this effect seems unfamiliar to us. Note that the relativity of simultaneity can be purely due to the finite speed of light; while it is usually discussed in conjunction with special relativity and moving observers, it can be observed in situations where none of the other relativistic effects are present. The following animation demonstrates the effect. //
... by extracting transmissions from the LM from those originating in mission control onto separate tracks with the Audacity audio editor, I was then able to time-shift transmissions originating from the Earth by the light delay of 1.2865 seconds to reproduce what Buzz Aldrin and Neil Armstrong heard through their headphones in the cabin of the Eagle lunar module on the surface in Mare Tranquillitatis. During the landing phase, an on-board tape recorder in the lunar module captured the voices of Armstrong and Aldrin even when they were not transmitting on the air to ground link. From this noisy source, I have restored the few remarks by Armstrong which were only heard within the cabin. This is, then, the lunar touchdown as heard by the astronauts who performed it.
Now it's obvious what happened to Armstrong's post-landing transmission! Right before he began the call, Duke's message, sent a second and a quarter earlier, arrived at the Moon. While, from an earthly perspective, this was spoken well before Armstrong said “Houston”, on the Moon this message “stepped on” the start of Armstrong's transmission (especially considering human reaction time), and caused him to pause before continuing with his message. Note also that on the Earth-based recording, Duke's response occurs almost immediately after the end of Armstrong's transmission, but on the Moon, the astronauts had to wait for the pokey photons to make it from the home planet to their high gain antenna on its distant satellite.
There are about 200 billion stars in our Milky Way galaxy. Over the next million years our descendents will spread among the stars in an exponential explosion of life, remaking the galaxy as surely as life has remolded Earth in its own image. //
Imagine the variety of worlds and wealth of living species flourishing upon them! Water worlds, desert planets, mountains that reach above the sky—every habitat imagined in science fiction will become real, and many more yet to spring from the imagination of world-makers born half a million years from now.
Terranova is a highly premature anticipation of this exhilarating milestone in the endless adventure of life and intelligence. Every day around 11 a.m. Universal Time a new planet is created using random parameters, and an image of it, as seen from the bridge from your approaching starship, is produced.
“If they existed, they would be here”, said Fermi. So where are they? Nowhere in evidence. Intelligent beings with technologies advanced millions of years beyond our own, spread to the far ends of the galaxy, should not be difficult to detect. We already possess the means to detect even primitive technological civilisations like our own at a distance of hundreds of light years.
If they existed, they—the first intelligent species to expand outward among the stars—would be here. And since we look around and see nobody but ourselves, then it is only reasonable to conclude, “We are here, so we are them.”
Here are two options for future humans to keep us in the habitable zone.
One last reflection to stress the importance of our Moon, which keeps the tilt of the Earth stable and limits the amount of wobble along the planetary axis. https://www.universetoday.com/164878/we-owe-our-lives-to-the-moon/
With every shift in the tilt, the seasons would radically change. Instead of regular, predictable changes year after year, we would experience ages with endless summers, or ages with violent but short winters, or anything in between. The rhythm of the seasons provides a pulse for life, which has the freedom to grow and evolve without trying to overcome great climactic shifts caused by a changing axis.
Luna acts as a great gravitational counterweight, stabilizing the motion of the Earth. By providing a source of gravity external to our planet, the Earth’s interior is free to shift and reconfigure as it pleases – the Moon steadies our hand and keeps us upright.
Our planet is endowed with extravagantly rich mineral ore deposits. How did we get them and why is it significant? It turns out that the source of these deposits is not indigenous; rather, large asteroid/comet strikes over the past 2 billion years produced Earth’s richest metal ore deposits.