exchemist

Oh now that is interesting. I had thought Dark Matter was said not to take part in EM interactions. But if WIMPs can have a magnetic moment that clearly can't be right. So we have two possible mechanisms now: momentum transfer via the Weak Interaction, or via a magnetic interaction. But I would have thought if these things have a magnetic moment they might be subject to EM absorption and emission via magnetic dipole interactions with EM radiation. So they would not be 100% dark! Although.....thinking aloud here......unless there was something to create space quantisation, i.e. so that the energy of the state depended on spin orientation, I suppose there would be no absorption or emission.

A collision must imply a force of repulsion, surely? These are QM entities, after all, not billiard balls.

Would the Weak interaction produce a force of mutual repulsion then?

I know next to nothing about the physics proposed for WIMPs (if they exist). But if they are not subject to the EM interaction, in what sense can a WIMP "collide" with an atom of Xe? Something to do with the Strong Force? Or something else? And why would this create a cascade of electrons?

It’s a question of accuracy rather than sensibilities. As we have learned more about the early Middle Ages we have come to recognise a lot more was going on than c.18th and c.19th historians thought, raised as they were on the notion of the Roman empire as some kind of golden age. Details in the link I provided.

No historian speaks any longer about the Dark Ages. We now know they were far from “dark” in terms of culture and civilisation: https://en.wikipedia.org/wiki/Dark_Ages_(historiography)

The geology of the British Isles is like a Rubik’s Cube. It takes many twists and moves to unscramble it over geological time. The Tornquist Sea closed about half a billion years ago and there was plenty going on before that. Scotland is particularly nightmarishly complex.

Exactly what my question would be.

Well yes I can agree this describes a particular attitude within Dutch society, but not that it is the official policy of the Netherlands. If the author asserts it is the latter, I would take issue with that, on the basis of my own experience of living there. The elephant in the room is indeed Islam, but I suggest it is a particularly assertive form of what has come to be known as political Islam, which seems to be relatively recent movement within some branches of the religion. I can quite understand the society coming into conflict with that, as the whole point of it is to challenge the culture, mores and behaviour of the host society.

This reading of the Netherlands is incorrect. It indeed considers itself a secular state, as does France, but in neither case do they consider that merely following a religion makes somebody “non-integrated”. What might make someone non-integrated would be not speaking Dutch and not accepting or tolerating the laws and conventions of the Dutch.

Yes, I don't think V=iR is just a definition. While it is true that ohms can be defined as volts per amp and so on, the relation also means something physical: that there is a thing called resistance in a circuit, which impedes current flow in a way that follows an algebraic rule, and that if you double the voltage you will double the current, and so on. So a number of important concepts are embedded in that equation.

Yes, I wondered about that but decided against. The problem with it is it is only half the equation. The full version is E² = (mc²)² + p²c².

In science? I might vote for E=hν, on the basis that it is self-evidently very simple and is probably the most important relation for anyone who wants to understand anything about light and quantum theory. But then F=ma in mechanics is equally simple and fundamental to understanding. I'm not even sure there is any one simplest, though. Perhaps the question is a bit like asking what is the best cheese in the world. 😊

I suppose post-revolutionary France was the first example of a consciously secular state, though it did not try to make its citizens give up personal religious belief. Communist Russia under Lenin and Stalin was probably the first state to teach children atheism and try to stamp out religion. It didn't work of course.

Well, no culture can be preserved unchanged in aspic, especially in the modern world with its IT interconnections and ease of international travel. But I simply do not buy this notion of some new culture taking over, at a national level. There is no evidence that national institutions, laws, education etc are being radically changed by some new culture. I do acknowledge there are places whose character has changed due to the natural tendency of immigrants to form ghettos. But elevating that to a national takeover is getting it out of proportion. Where I sympathise is that I do think there should be more of an expectation for incomers to fit in. Perhaps there is a role for the planning system and local law enforcement here, and maybe an induction process for people acquiring citizenship, as they have in the Netherlands: https://www.government.nl/themes/migration-and-travel/integration-in-the-netherlands/civic-integration-in-the-netherlands

I was impressed with the ingenuity of the Gateshead millennium bridge when I visited Newcastle a couple of years ago. I took me a moment to work out why the footway was curved and how it operated. Unlike the one in Bristol, this one is operated fairly frequently I think. Pretty shocking that the seals failed without warning on the Bristol bridge. Did they leave it for years without operating it?

Well, fairly obviously, people tend not to welcome military conquest. By the way, the Copts were not “replaced”. The indigenous people became Arabised, that is converted to Arab culture, language and religion. Today’s Copts are the Christian remnant of the previous Byzantine culture. But none of this is relevant to present day immigration to Britain.

I was intrigued to read this report in the Guardian: https://www.theguardian.com/science/2026/aug/12/astronomy-discovery-new-cosmic-object-black-hole-star The Nature paper on which this is based is here: https://www.nature.com/articles/s41586-026-10846-4 It seems there are a lot of these mysterious LRDs in deep space images taken by the James Webb telescope. Now a team has made a detailed spectroscopic analysis of one of these, at a redshift corresponding to 660m yrs after the Big Bang, so very early in the life of the cosmos. Apparently the red comes from (redshifted) Balmer emission of hydrogen, which has a very sharp cutoff, known as the Balmer Break or Balmer Jump. This I gather occurs at the ionisation limit of the Balmer series (transitions to or from the n=2 shell to higher quantum levels). I had not heard of this before, but I suppose it makes sense that while atoms in high excited states can drop down to n=2 to give a series of emission lines, once the atom is ionised, recombination of the ion with a free electron (of varying kinetic energy) can occur at any energy so the intensity at any given wavelength will be far lower, hence the Balmer break. This Balmer break seems to be a standard effect seen in the spectra of stars, but what is unusual in this case is that it is so pronounced. It also seems to be accompanied in the spectral signature of this object by Hβ (n=2 <->3 and and Hγ (n=2<->4) lines in absorption, i.e. there is gas in front of the emitter that must be already in the n=2 1st excited state. All this they say is consistent with a black hole at the centre of a hydrogen cloud hot and dense enough to populate the n=2 atomic level. They speculate that this and the other LRDs may be black holes in the early universe in a stage of rapid growth, ingesting gas clouds. They call these objects black hole stars, because of their emission. They would seem to be a new type of astronomical object. At least, that is my imperfect understanding of it. Corrections and comments welcome.

No more than the people of Ukraine appreciate invasion by the Russians, I imagine.

Surely all you have done here is to define "totalising", when applied to an ideology? There are plenty of political and religious ideologies that do not do this, but then you would presumably not call them "totalising". So then toleration of good faith disagreement in "totalising ideologies" is impossible, by virtue of your own definition. But there are quite a few of them around, it is true, from exclusivist religious sects to political movements. I think it is a form of tribalism. You have to be either with them 100%, or against them, in which latter case you are designated as the enemy. One sees this among football supporters, for instance. The demand for allegiance to an "in group" of some kind seems to be quite deeply embedded in human nature, which can all too easily lead to intolerance of those who are in some way different.

If you don’t want racist political parties to succeed, you have to be able to understand what drives people towards them. In my opinion, the culture issue is real enough in places like London’s East End or Leicester, without invoking racism at all. Though obviously it will tend to breed racism. (I’m disappointed to hear of your wife’s experience, especially in a fairly prosperous suburb of Southwest London.)

On the assimilation point I think that's a 2 way process. The host community comes to accept and see benefits from the incomers' culture, while the incomers adapt to the ways of the host country to some degree and fit in better. You see this in things like the proliferation of different styles of food, different style of music, and even respect for different attitudes to alcohol. I see a lot of mixed race couples in London, too, presumably growing from being at school and college together and getting comfortable with one another. My son has Muslim friends from school and university and has just returned from a camping trip with an Indian physicist (doing a PhD in string theory). For people of my generation this would have been very unusual, though we did have some Jewish friends.

Yes. Remember, that’s what Brexit was all about. Although culturally, Europeans are obviously far closer so easy to assimilate.

It is not skin colour, but cultural: the language, the script, e.g. on the shop fronts, the dress, the mosques. You are right of course. We have had a Chinese area in Soho for decades. It has become an accepted part of the London scene and where everyone goes for good Chinese food. But these things take time, for the previous inhabitants to adjust, move out or die, and for the incomers to start to smooth off the rough edges by adapting to some degree to the ways of the new host country. Islam is particularly tricky right now as there happens to be a movement towards more rigid observance of its cultural codes, notably the way women are allowed to dress. So rather than becoming integrated, some muslim communities appear ever more intent on being alien. (One has a bit of that in Stamford Hill with Ashkenazi Jews, but that's on a very small scale by comparison). But there you go. Britain had an empire, got rich on the backs of the colonised peoples, taught everyone English..... and now, surprise surprise, the previously colonised people come to Britain! One can hardly argue it is unfair.

Intellectually yes of course you are right. East London has always had its waves of minorities. In the late c.19th it was full of Jews. But they gradually assimilated, became more prosperous and moved to north London, spreading out and diluting themselves as they did so. Now the better off Jews are in Golders Green and St. John's Wood and the poorer ones in Stamford Hill. The Bangladeshis have taken their place. (Tower Hamlets council is now riddled with Bangaldeshi-style political manipulation, intimidation and corruption:https://www.standard.co.uk/news/politics/lutfur-rahman-tower-hamlets-mayor-aspire-b1205024.html) On a larger scale we have the Midlands city of Leicester. This dynamic pie chart shows the radical change in ethnicity since 1961: https://en.wikipedia.org/wiki/Demographics_of_Leicester#/media/File:Ethnic_demography_of_Leicester_from_1961_to_2021.gif I do think we need to be aware of the emotional effect of radical change on the people directly affected when neighbourhoods change so rapidly over the course of a generation. I am sure this is one of the chief sources of support for these new far-right parties. As for what the prescription is to deal with it, I think there is not much to be done apart from controlling further immigration and then waiting for time to assimilate the minority communities. They will gradually adopt the "western" way of life of their adopted country (which has its attractions for Muslim and Hindu women especially!) and intermarriage. But there will be many bumps in the road.