￫ A year ago we received a message from interstellar space. For the second time.
It’s not that NASA tried to keep it secret, it’s just that they were working on the data up to last month. Now they can say more about the message, which came from 120 times the distance between earth and sun, sent by a transmitter powered by plutonium and having strength equal to that of a fridge light.
Okay, you probably guessed that this was from Voyager 2 and that the email subject was clickbait. A year ago the spacecraft officially left sun’s domain, which is defined by the reach of the “solar wind”, the stream of particles sent out from the sun, before it is pushed back by “interstellar wind”.
Voyager 2 crossed this “heliosphere” six years after Voyager 1, and their combined data can now say a few things about it – like that the edge of the heliosphere ends abruptly instead of fading, and that it is shaped like a blunt bullet (their words, not mine).
What’s next? The two Voyagers will keep texting home for only a few years more, but they are expected to continue orbiting around the galaxy for an extra five billion ones...
￫ If you haven’t happened to hear the following theory already, the first time is always fun: there are several reasons to believe that the molecules which started life on earth might have arrived in meteorites. Seriously, the jury’s still out on this one.
However, a new indication in favour of this theory just showed up; various types of sugars molecules were found in two meteorites (in NWA801 and Murchison, if you have to know). This is admittedly a little avant-garde; especially considering that they included ribose, a main constituent of RNA.
￫ Using the Arecibo radio telescope, 19 more galaxies were found to have a lot less dark matter than expected, adding to the four previously known ones. By the way the weighing was done by seeing how fast hydrogen clouds move in them.
Surprising as it may sound, this is one more indication that dark matter really exists – i.e. that it is actual matter of a form still unknown to us. Other possibilities include theories of gravity that work differently than we think, but then they’ll have to hold for every galaxy, not for every galaxy minus 23 and counting. (Since dark matter has been one of the greatest mysteries in physics for too long a time now and, as you just read, we don’t even know yet if it is matter, then I’d name this one the most important news of this eventful month.)
Of course, now these galaxies also have to be explained, but that’s a different story.
...and one with particles
￫ Sometimes we think we are so cool for knowing everything about the elementary particles. And then quarks arrive.
Actually, quarks usually arrive in threes, as three of them make up the proton and same for neutron, that is practically the nuclei of the atoms in everything. The issue is that the size of the proton is still an open debate, as the three quarks resemble a cloud rather that solid spheres, and that cloud’s extent has been measured with different results through the years.
The size of the proton has been measured by using electrons, which are either thrown at it and bounce away or monitored for how they move around it. The controversy started some years ago, when an experiment used muons instead (colloquially known as the “heavier cousins of electrons”, which makes them the Dudley Dursley of elementary particles). The result was significantly smaller, and it was repeated just a few months ago in a second independent experiment.
Meanwhile, good old electron-using experiments kept getting the larger result. Now, this discrepancy filled several people with hope. The reason is that the only known difference between experimental results and the predictions of the Standard Model, the theory describing particles, also comes from a measurement involving muons: the “muon g-2 measurement” of the distribution of the magnetic field of muons. Unavoidably, people started hoping that the difference in the proton size might also be pointing to the same source of yet unknown physics.
Alas, last month the PRad (Proton Radius) collaboration announced that by improving the experimental techniques by a lot and using electrons, they now get a result very close to that from muons. Still, unlike hope, not all controversy is lost; now the experiment crowds have to find out why all the previous measurements with electrons were consistently different; it might have been just a matter of accuracy but also it might involve some physics factor that was overlooked.
And in case you wonder why size matters so much, then think that the list of properties of the elementary particles is like the most precise zoo we have ever built; if experiments were able to count the number of spots on every jaguar, cat and frog in there, then it’d be weird if they couldn’t tell how many feet penguins have.