Matt's joined by another of the Podcast's new co-hosts, Chris Carney. We catch up with the marvellous Sarah Cruddas, or do we indeed catch up with two Sarah's one in the mirror universe chatting to Mirror Matt with a beard, almost certainly not!

Apollo 11 astronaut Michael Collins

John Lennon

September 10th

Happy Birthday to Matt and also riding of rockets Mike Mullane, American colonel and astronaut

September 11th

1935 – Gherman Titov, 4th person in space but 2nd to orbit the earth.

1937 – Robert Crippen, still going strong, the pilot of the very first space shuttle, easily the riskiest manned space mission since Gagarin and Titov flights.

Mary Watson Whitney (September 11, 1847 – January 20, 1921)

American astronomer and 22 years the head of the Vassar Observatory. Studied at Harvard as a guest, got her masters from Vassar, studied further in Zurich then came back to the US to teach and then ended up running Vassar Observatory in New York, after being an assistant to another legend Maria Mitchell. 102 scientific papers were published under her guidance. On topics such as variable stars, comets and asteroids.

Chat about Mirror Matter!!

Back on episode 181 we talked about a paper that looked at why stuff exists at all. One of the mysteries of the Universe is why there was a miss-balance of Antimatter and normal matter.

One of the hypotheses that play into this is that mysteriously our universe isn’t quite the same as it should be in the mirror. A very famous experiment by Chien-Shiung Wu showed that the beta decay of cobalt 60 nuclei broke the symmetry of Parity. Something to do with the way electrons came out in a certain direction too often, where you would expect this to be random. The analogy is that the decay was happening differently in a mirror image. ...violating P symmetry.

Now since then, they thought they had saved symmetry by combining it with charge symmetry, in other words, the physics ends up being the same in the mirror if those particles are in fact anti-particles. This is CP symmetry (charge and Parity)

But in 1964 CP was violated by those pesky neutral Kaons. This is actually even more mysterious because everything is so nearly symmetrical.

But time came to the rescue, if you flip the parity, reverse time and make it antimatter you can have your symmetry back. CPT symmetry ...yet to be broken. The implication of CPT symmetry is that a "mirror-image" of our universe — with all objects having their positions reflected through an arbitrary point (corresponding to a parity inversion), all momenta reversed (corresponding to a time inversion) and with all matter replaced by antimatter (corresponding to a charge inversion) — would evolve under exactly our physical laws

Anyway this was all a pointless recap. We were talking about this on 181 because of antimatter and matter balance, ...literally why stuff exists.

But Mirror Matter is NOT AntiMatter. This is something else altogether.

Let’s go back to P Symmetry, all the 4 fundamental forces only particles interactions with the weak force break parity. It’s so fundamental that Tsung Dao Lee and Chen Ning Yang won the Nobel prize, yes Chien-Shiung Wu ran the experiment, but for some reason, she was left off the list.

One proposed way of getting around this bizarre and unsatisfactory part of nature, that messes with the Marie Kwondo in every Physicist, and their constant search for mathematical beauty and tidiness. ...is ...you guessed it Mirror Particles. If every particle has a mirror particle then we end up twice as many fundamental particles ...but we solve the problem.

Mirror particles were discussed by Kobzarev, I.; Okun, L.; Pomeranchuk, I. (1966). "On the possibility of observing mirror particles"

In this paper Okun writes,

There was a flurry of activity in the 60s mostly in Russia, but they may have been very interested in the work of Zwicky that was nudging towards the question of Dark Matter.

It all went quiet in the 1970s everyone was getting jiggy with QCD

There was a bit of a revival in the ’80s, the Russians were still at it and giants of physics such as Sheldon Lee Glashow was writing a paper about mirror particles. It was during this period that the idea that very tiny ordinary electric charges of mirror particles which normally only have a mirror electric charge, appear due to mixing of ordinary and mirror photons, proposed by B Holdom.

The 1990’s was the hay day of the Mirror Particle!!

This was formulated in 1991 by a paper “A model with fundamental improper spacetime symmetries” Foot, R.; Lew, H.; Volkas, R. R.

Robert Foot, from Oz, seems to be the biggest advocate for the theory. He wrote a book Shadowlands: Quest for mirror matter in the universe. But he really pushes the idea that not only would it solve the parity violation but dark matter too!! And a host of the other mysteries of the universe. He also suggests that grains of mirror matter are embedded in the ordinary matter due to the interaction caused by the mixing of ordinary and mirror photons.

Another huge figure in all this is Zurab Berezhiani who forges the connection with dark matter and relating it to the inflation stage of the early universe and seems to have a more strict mirror symmetry than Foot’s

The bullet cluster seems to have pushed the argument in the favour of a mysterious form of dark matter, rather than a modified theory of gravity, causing the extra mass required to keep the faster than they should be stars whizzing off into space. .

The dark matter whose effects can be observed via gravitational lensing is segregated from the shiny matter parts of the clusters. If this dark matter is mirror matter the mirror stars in it must be more prominent compared to mirror gas than ordinary stars compared to ordinary gas.

Gamma-ray bursts may also be caused by collapsing or merging mirror matter stars, according to Zurab and others.

• The mirror matter is aesthetically appealing because it restores the parity symmetry of the world (at least partly).

• It allows explaining neutrino anomalies.

• It explains the missing mass in the Galaxy disk and in some models the Dark matter in general.

• It explains MACHO microlensing events

• For GRBs, it provides the model with the low baryon load

• The available baryon load on the scale of the mass of a small planet is exactly what is needed for fireball models.

• All host galaxies for OT of GRBs are strange ones. This may be an indication for the gravitational interaction of the ordinary galaxy with the mirror one in which it can be immersed.

There are experiments going on all the time to find the mirror particles one I saw jul 2020 was Probing neutron-hidden neutron transitions with the MURMUR experiment, where essentially they are trying to use a nuclear reactor to create neutrons, and the mirror neutrons won’t be blocked by the shielding, but due to the mixing phenomena show up as a very low signal almost in the noise.

Similar to the work of Leah Broussard at Oak ridge and I’ve seen a more recent paper from 2019, but again it was inconclusive. But it caused a lot of fuss in the press as it was billed as Scientist trying to open a portal to a mirror universe.

Wanpeng Tan of University of Notre dame has a great blog called Perfectly Imperfect Mirrors

And this brings me to a very good point about current Particle physics.

What the hell.!!!!

It seems to me that you can expand on the standard model any way you want and then try to come up with an experiment to find your new particles. But I’m beginning to be persuaded that this approach has been an abject failure for quite a long time now. Essentially it’s a form of motivated reasoning and it also seems like quite a wheeze to get a grant. Admittedly you have to understand the physics, but you can literally postulate a random new particle and then get funding to build the machinery to see if it is there. The fact that a theory is falsifiable doesn’t make it scientific. And is this how we want to conduct physics?