Archive for the Astrohype Category

More from the Dark Energy Survey

Posted in Astrohype, The Universe and Stuff with tags , , , , , , on May 28, 2021 by telescoper

To much media interest the Dark Energy Survey team yesterday released 11 new papers based on the analysis of their 3-year data. You can find the papers together with short descriptions here. There’s even a little video about the Dark Energy Survey here:

The official press release summarizes the results as follows:

Scientists measured that the way matter is distributed throughout the universe is consistent with predictions in the standard cosmological model, the best current model of the universe.

This contrasts a bit with the BBC’s version:

The results are a surprise because they show that it is slightly smoother and more spread out than the current best theories predict.

The observation appears to stray from Einstein’s theory of general relativity – posing a conundrum for researchers.

The reason for this appears to be that the BBC story focusses on the weak lensing paper (found here; I’ll add a link to the arXiv version if and when it appears there). The abstract is here:

The parameter S8 is a (slightly) rescaled version of the more familiar parameter σ8  – which quantifies the matter-density fluctuations on a scale of 8 h-1 Mpc – as defined in the abstract; cosmic shear is particularly sensitive to this parameter.

The key figure showing the alleged “tension” with Planck is here:

The companion paper referred to in the above abstract (found here has an abstract that concludes with the words (my emphasis).

We find a 2.3σ difference between our S8 result and that of Planck (2018), indicating no statistically significant tension, and additionally find our results to be in qualitative agreement with current weak lensing surveys (KiDS-1000 and HSC).

So, although certain people have decided to hype up a statistically insignificant l discrepancy, everything basically fits the standard model…

Do you believe there is intelligent life out there?

Posted in Astrohype, The Universe and Stuff with tags , , on February 15, 2021 by telescoper

Following on from yesterday’s post and inspired by this tweet

I thought I’d try a quick poll on what people think about the existent of intelligent life “out there”. In my experience, and in contrast to the tweet, most astronomers are actually quite open-minded about the possibility of extraterrestrial intelligence. My own view is that while it is entirely possible that there is intelligent life elsewhere in the Universe, scientific belief* should be based on evidence and we simply don’t have any evidence to support the idea. I would therefore say that I don’t “believe” but am agnostic. Sometimes “I don’t know” is the only rational answer.

You might ask me as a cosmologist whether I believe in the Big Bang theory. My answer would be “yes” because I think the evidence supports this description of the Universe. If evidence came along to change my opinion I might believe in it less or not at all. I might also change my mind if a different model came along that fits the observations better.

*In a Bayesian sense I would interpret “refusing to believe” as meaning setting a prior probability of zero, so that no amount of evidence would produce a non-zero posterior probability.

Anyway, setting aside the issue of whether there is even any evidence of intelligent life on Earth here is a poll:

Phosphine on Venus again…

Posted in Astrohype, The Universe and Stuff with tags , , , on February 8, 2021 by telescoper

Remember all the excitement last September about the claimed detection of Phosphine in the atmosphere of Venus? If you do you will remember that the claim has been contested. Now there is another paper on this matter claiming that what was interpreted as a spectral feature due to Phosphine (PH3) could actually be due to Sulphur Dioxide (SO2)). Here is the abstract of the latest paper.

You can find the full paper on the arXiv here.

P.S. I bookmarked the arXiv paper about a week ago but was very busy and forgot about it until now!

Phosphine on Venus, Water on the Moon, and Hype Everywhere

Posted in Astrohype, The Universe and Stuff with tags , , on October 28, 2020 by telescoper

To continue the ongoing saga of Phosphine in the atmosphere of Venus there’s a very strongly worded paper on the arXiv with the following abstract:

It’s one thing to question or refute another group’s result, but there’s no need to be so aggressive about it. The last sentence of the abstract is particularly unnecessary and reprehensible.

Update: the abstract has now been changed.

There has been a lot of reaction on social media from astronomers and others to the perceived “hype” of the initial discovery by the authors. I watched the press conference at the time and I think the authors spoke very sensibly about their work. Of course just because scientists are sensible that’s no reason to suppose the press will also be sensible and there was undoubtedly a great deal of hype about that result. In my experience hype is more likely to be a result of journalists wanting a sensational story and/or institutional press offices wanting to promote their institution that scientists over-egging their own puddings (though that does happen too).

I don’t mind individual scientists or groups of scientists making fools of themselves. It’s the damage to public trust in science that is the real danger here.

The hostile reaction we see in the above paper is an inevitable manifestation of an environment which encourages runaway self-publicity. This is not the only area in which this sort of toxic behaviour happens. I suppose it is mildly reassuring that it’s not only cosmologists that behave in such a way, but is this really what we want astrophysics to be like? I think we’d be better off leaving the petty point-scoring to the politicians.

Another example of hype this week – also involving a paper in Nature Astronomy – was the discovery of water on the Moon (again). The NASA publicity machine pulled out all the stops in advance of this announcement, only for the actual result to be a damp squib. Water is one of the most abundant molecules in space and I’ve lost track of how many times it has been detected on the Moon already. I suppose it is moderately reassuring that hasn’t suddenly disappeared, but from a scientific point of view it’s not all that interesting. I was particularly disappointed when the result turned out to be water, as I had bet on phosphine…

Could it be that the Stratospheric Observatory for Infrared Astronomy (SOFIA) is up for a funding review?

A Question of Phosphine

Posted in Astrohype, The Universe and Stuff with tags , , , on October 21, 2020 by telescoper

Remember all the excitement last month about the claimed detection of phlogiston phosphine in the atmosphere of Venus?

Well, a wet blanket appears to have been thrown over it by a new paper on the arXiv by Snellen et al. Here is the abstract:

The conclusions are very clear, but the paper hasn’t been refereed yet. Let’s see what the authors of the original work have to say. For myself, I think a proper (i.e. Bayesian) analysis of the data is called for…

I should also mention in this context another paper on the arXiv from a few days ago, which uses a null detection to place an upper limit on the phosphine abundance.

Note that one of the authors of this second paper is Jane Greaves, who was on the original discovery paper.

Today’s Big Astronomy Announcement

Posted in Astrohype, Cardiff, The Universe and Stuff with tags , , on September 14, 2020 by telescoper

Rumours have been circulating for a few days about a big astronomical discovery. Here is a video of the announcement:

Sorry, that’s the wrong video.

The actual announcement will take place live at 4pm BST here:

Until a few minutes ago I didn’t have a clue what this was about, but now I do…

Phone ship surprisingly detected in atmosphere of Venus (9)

If you would like to read more about this discovery then you can read the paper in Nature here. Several of the authors are former Cardiff colleagues, including first author Jane Greaves, as well as Annabel Cartwright and my former office mate Emily Drabek-Maunder. Congratulations to them on an exciting result!

P.S. Emily reminded me last night that I was present at the discussion with Jane that started this project, over four years ago. I remember them talking about phosphine but had no idea that it would lead to this!

Finding the Lost Baryons

Posted in Astrohype, The Universe and Stuff with tags , , , , , on June 3, 2020 by telescoper

Taking a break from examination marking I thought I’d post a comment on a recent paper in Nature which you can find on the arXiv here; see also a report here.

The paper, entitled A census of baryons in the Universe from localized fast radio bursts, is an important one which does seem to resolve a longstanding question often called the missing baryon problem. In a nutshell, the problem is that the density of baryons suggested by cosmological considerations – specifically the element abundances produced by Big Bang nucleosynthesis and the cosmic microwave background (CMB) – was, until recently, rather higher than that which has been observed by astrophysical measurements; by `baryonic material’ I mean basically protons and neutrons (whether or not they are in atomic nuclei).

In the framework of the standard cosmological model, The density of baryonic matter (denoted `Ordinary Matter’ in the following figure) contributes only around 5% of the overall mass-energy budget of the Universe:

The first thing to stress is that this paper says nothing about the `Dark Matter’ which, according to the standard model, makes up about 27% of the pie and which cannot be in the form of baryons if the CMB and nucleosynthesis measurements are correct. If it were baryonic it would participate in nuclear reactions and mess up the light element abundances and also interact with photons in such a way as to change the fluctuation spectrum of the cosmic microwave background. Having said that, `dark’ is better adjective to use for hidden baryons than it is for non-baryonic matter, as baryons can absorb light. Non-baryonic matter isn’t really dark, it’s transparent because it doesn’t interact at all with electromagnetic radiation. We are however in the dark about it.

Note that the total density of dark + ordinary matter is about 32%, just what George Ellis and I concluded way back in 1994.

We can be much more certain about baryons actually existing than we can about dark matter because. For one thing, we are made of them. It has, however, been known for ages that the total density of directly visible baryons (ie those associated with stars and galaxies) is much lower than this figure, leading to the conclusion that some of the baryons predicted by cosmologists must be in some invisible form(s). Some, for example, is found by X-ray emissions in dense galaxy clusters, but this component is still inadequate to account for all the missing matter.

It has been suspected for some time that the hidden baryons probably inhabit a diffuse Warm-Hot Component of the Intergalactic Medium which, according to simulations of structure formation, traces its own form of the cosmic web we see in the distribution of galaxies:

The diffuse state and inhomogeneous nature of this intergalactic medium makes it difficult to detect, as explained in the abstract of the paper, but adding a relatively new technique involving fast radio bursts to probe the distribution of matter along the line of sight to the observer, it seems that it has now brought out into the open:

Now the inventory of observed baryons matches the 5% figure we cosmologists always knew it would be, and all is well with the world!

P. S. I was informed on Twitter after posting this that there was a paper on this topic in Nature a couple of years ago the last sentence of the abstract of which reads:

We conclude that the missing baryons have been found.

What are scientific papers for?

Posted in Astrohype, Open Access with tags , , on May 30, 2020 by telescoper

Writing scientific papers and publishing them in academic journals is an essential part of the activity of a researcher. ‘Publish or perish’ is truer now than ever, and an extensive publication list is essential for anyone wanting to have a career in science.

But what are these papers actually for? What purpose do they serve?

I can think of two main purposes (which aren’t entirely mutually exclusive): one is to disseminate knowledge and ideas; the other is to confer status on the author(s) .

The academic journal began hundreds of years ago with the aim of achieving the former through distribution of articles in print form. Nowadays the distribution of research results is achieved much less expensively largely through online means. Nevertheless, journals still exist (largely, as I see it, to provide editorial input and organise peer review) .

Alongside this there is the practice of using articles as a measure of the ‘quality’ of an author. Papers in certain ‘prestigious’ ‘high impact’ journals are deemed important because they are indicators of status, like epaulettes on a uniform, and bibliometric data, especially citation counts, often seem to be more important than the articles themselves.

I thought it was just me getting cynical in my old age but a number of younger scientists I know have told me that the only reason they can see for writing papers is because you need to do it to get a job. There is no notion of disseminating knowledge just the need to establish priority and elevate oneself in the pecking order. In other words the original purpose of scientific publications has largely been lost.

I thought I’d test this by doing a (totally unscientific) poll here to see how my several readers think about this.

Nearly Time for Timed Assessments

Posted in Astrohype, Covid-19, Maynooth on May 14, 2020 by telescoper

Friday 15th May is the first day of the summer examination period at Maynooth University. I’ve written posts at the start of every examination period I’ve been involved with over the 11 years or so I’ve been blogging but this is definitely the strangest.

Owing to the restrictions imposed by the Irish Government to deal with the Covid-19 emergency, exams in the Department of Theoretical Physics this year will be unsupervised timed assessments, similar to traditional exams but done by remotely by the students and then uploaded to our virtual learning environment, Moodle. I posted about this a few weeks ago here.

The duration of these examinations is the same as usual (2 hours in most cases) and the students should be able to use past examinations to prepare reasonably well for them. The questions, however, have been set in the knowledge that students will have access to notes and textbooks so there there is a lot less ‘bookwork’ in the papers and a greater emphasis on problem solving.

Students have extra time added to scan and upload their answers and have been given detailed instructions on the entire process. Staff across the University have worked very hard to develop this new method of assessment in the short time available and to give as much instruction as possible about the technology needed.

Our overriding concern is to be as fair as possible in giving students to demonstrate what they have learnt. There are contingency plans in case things go wrong and staff will be available for consultation during the assessments in case there are problems. The intention is to ensure as much as possible that no student is penalised for circumstances beyond their control. I honestly think that we have done everything that could have been expected of us in the circumstances to make this new system work.

Nevertheless I don’t mind admitting I’m still a bit apprehensive about the forthcoming tests. A famous General once said that “no plan of battle survives first contact with the enemy*” and some improvisation may be required. Our first examination in Theoretical Physics will not be until Saturday (16th) so at least we will find out what befell Departments in the first wave tomorrow before taking our turn.

At times like this I think the best advice for examiners and examinees alike comes from Douglas Adams.

*In this context the enemy is the technology rather than the students!

Is the Expansion of the Universe Isotropic?

Posted in Astrohype, The Universe and Stuff with tags , , , , , on April 9, 2020 by telescoper

There’s a new paper out that has been making a few waves in cosmology. Here’s the title and abstract:

It’s published in Astronomy & Astrophysics but you can find it on the arXiv here.

Here’s a gratuitous pretty picture showing the distribution of the X-ray clusters used in the analysis.

The discussion in the paper focuses on two possibilities: (i) that the clusters are participating in a large-scale correlated motion; and (ii) that the Expansion of the Universe is not occurring isotropically. The latter option is the one that has attracted the most media attention (presumably because it has the most far-reaching implications). This seems to me to be a very unlikely explanation, however, because anisotropic expansion of the magnitude implied would leave a ~10% signal in the Cosmic Microwave Background which is not observed.

There is, however, a third possibility (admittedly duller than the other two) which is that there is some unknown systematic error in the observations…