Sister blog of Physicists of the Caribbean. Shorter, more focused posts specialising in astronomy and data visualisation.

Thursday 13 April 2017

Plato's groupthink


An early example of groupthink ? You could be forgiven for thinking that Plato is here not only describing groupthink, where individuals tend to want to agree with the group because they're part of a group, but supporting it. In context, it's more subtle than that. He's actually suggesting something profoundly, deceptively tautologous - which sounds crazy, but such is the way of Plato.

What he's saying is that people who agree with each other... agree with each other ! That is, when people disagree, it isn't because they think the other person is correct, it's that they think they're wrong... that in that one, specific instant, they think the other person is less intelligent than they are (or is simply mistaken for some other reason). After all, if you thought that both their reasoning and their information was perfect, you could never disagree with them.

So intelligent, knowledgeable people can and do try to outdo each other because they believe the others are mistaken in some specific regard; merely respecting the overall knowledge and intelligence of others in a similar field does not automatically lead to groupthink at all. Indeed, however flawed the academic system is, its system of competitive collaborations is very good at preventing this. It's perfectly possible to agree and disagree with people on different issues. You don't have to think that someone who believes a single different thing to you is inherently and unconditionally stupid.

Yet the wilfully ignorant insist on believing some absurd absolute version of this : we're all desperately trying to agree with each other while simultaneously dismissing external ideas as crackpottery; that we can attack external ideas but not the group's own. Nothing could be further from the truth - the reason a scientific consensus emerges at all is because it's endured a damn good mauling. If your idea can't stand up to that, then you're asking for double standards. And that's not going to happen.

Which is why if you're reading Plato expecting simple, unquestionable conclusions, you're doing it really wrong.

Tuesday 4 April 2017

A 3D spiral from ALMA


A little evening's diversion. A few weeks ago there was this ALMA press release (which I came across again today) about observations of the gas around the star LL Pegasi (). It was already fairly famous from Hubble observations thanks to its remarkably neat spiral pattern. The ALMA observations add velocity information and I wanted to see what this would look like in 3D. Actually I've been wondering about this for a while since there was a similar-ish press release about another sort-of similar object some time ago.

For those who aren't familiar with these types of observations, have a look at the gif in the press release first. There you see the data in a slightly more usual format, as a series of images. Each one shows the gas at some particular velocity along our line of sight. What I've done here is use each image as the slice of a 3D cube - it's fun to look at (maybe even useful) but it doesn't show you the true 3D structure of the object.

The last time something similar like this was doing the rounds I couldn't find the original FITS data I needed to display it. This time I didn't bother. I took the gif, converted it into a sequence of png images, then wrote a Python script to convert the image sequence into a FITS cube and then ran it through FRELLED (what else ? http://www.rhysy.net/frelled-1.html). Oh, and I interpolated extra velocity channels because there weren't very many in the gif (there might be more in the original data, I don't know). So there's a fair amount of extra processing for this one, but probably nothing that would result in any serious differences from the raw data.

What does it all mean ? Haven't got a clue, I just thought it would be nice to look at.

Back from the grave ?

I'd thought that the controversy over NGC 1052-DF2 and DF4 was at least partly settled by now, but this paper would have you believe ot...