Joss Bland-Hawthorn has tweeted that Prof. Richard Hunstead passed away last night. When I started my undergraduate studies at Sydney University, Dick was one of the organisers of the Talented Student Program. He bore with a smile my barrage of naive questions about the universe and cosmology, and directed me towards a project on the origin of wiggles in the cosmic microwave background. His enthusiasm was catching and I was hooked; almost 20 years later, I’m still researching cosmology.


I always found Dick to be friendly and approachable, as an undergrad, as a PhD student trying to work out how Australian astronomy worked, and as a postdoc. He had a wealth of knowledge and was highly respected. In the last few years, he gave a generous endowment to the Sydney Institute for Astronomy.

Rest in peace.

Dear Rod,

Next year will mark 20 years since I graduated from Coffs Harbour Christian Community High School. I’m sure you’d count me as a success story – I went from Macksville to Cambridge, and a career as a research astrophysicist.

It is with some frustration that I read your recent comments regarding climate change. Firstly, you may want to think about the effect on your students of dismissing Ms Thunberg as a “little girl” (she is 16) and as having “mental problems” (she has Asperger’s syndrome). My recollection is that you treated my classmates and me as young adults, capable and responsible. You would not have been so dismissive if Greta was in one of your classes.

Secondly, you refer to “the predictions of a little girl and false prophets.” You are referring, I presume, to the weight of scientific evidence accumulated by thousands of scientists across the world for decades. I would be happy to bring you up to date. For example, since the beginning of the industrial revolution, the amount of carbon dioxide in the atmosphere has increased by 45%. Carbon dioxide accounts for 10-20% of our atmosphere’s ability to trap heat. Over the last century, sea levels have risen, and the Earth has gotten warmer. These are not prophecies; these are measurements. They are not made by teenagers. They are not made by lone, extreme voices speaking outside their area of expertise, like Paul Ehrlich. They are made by people like me who have dedicated their careers to the study of the natural world. Maybe everything will be fine, but that is far from obvious.

Finally, you seem to imply that climate change will not be a problem because the “world’s future is in the hands of God.” Indeed it is. But God’s plan, for better or worse, was to give humans responsibility for “the fish of the sea and the birds of the air and over every living creature that moves on the ground.” The Bible gives instructions on caring for the land (Lev. 25), and warnings about disobeying those instructions: “you shall sow your seed in vain.” God did not promise to prevent the North American dustbowls of the 1930’s, the tragedy of the Aral Sea, or continuing famines around the world. Our actions have consequences; there is no promise in the Bible that we will be rescued from every effect of our own greed and stupidity.

Yes, the climate change movement contains attention seekers and doomsayers. So does the church. We are also warned about those who cry, “Peace, peace, when there is no peace.” (Jer. 6:14) And yes, scientists have been wrong about all sorts of things in the past. But “some scientists have been wrong in the past, so I’m sure it will turn out that they’re wrong about everything now” is a very risky prophecy. The search for truth and right action needs something between denial and alarm. In the words of Chesterton, we need to hate the world enough to want to change it, and yet love it enough to think it worth changing.

As usual, I’ll be holidaying in Macksville again at the end of the year. I’d be happy to catch up for a chat any time.


Luke Barnes

A YouTube video has been brought to my attention, which seems to show physicist Roger Penrose refuting the idea that the entropy of the universe is fine-tuned for life. The crucial section starts at 16:05. The video is jarringly edited: we aren’t shown what the interviewer actually asked before this section. The longer, complete interview is linked to, but I haven’t watched it.

Penrose: “It’s a gross course tuning. The entropy in the gravitational field is ridiculously small compared with the entropy in matter. There’s nothing fine-tuned about it – it’s just huge.”

[Abrupt cut]

Interviewer: People had argued that there are these constants that are fine-tuned for life, and he said “look at the entropy. That could be much much higher and life would still be here, so that’s not fine-tuned for life.

Penrose: I absolutely agree with that. The entropy in the gravitational field could have been far larger without disturbing life, as far as I can see.

Penrose’s comments are completely correct. My problem is not with Penrose, but with the editors of the video. They rely on an ambiguity regarding the term “fine-tuned for life.”

Here’s one way to approach fine-tuning. When we look at the deepest laws of nature that we know, is there is anything noteworthy or rare or interesting or unexpected? Or are these just any old laws? Is there anything about our current deepest laws of nature that might point the way to something deeper still, whether physical or metaphysical? For example, if we discovered that the laws of fundamental particles wrote “made by Brian” on every atom, then we would be suspicious of the claim that these are just any old laws.

To that end, we might want to know: what would just any old universe look like? A systematic and practical way of attacking this question is to vary the fundamental constants and initial conditions of our universe. If I just picked just any old universe from this set, what would it be like? And the answer is: almost certainly dead. Continue Reading »

Western Sydney University is advertising research projects for prospective masters students. You’ll find one from me about our impending collision with the Andromeda Galaxy. (Well, if you can call a few billion years “impending”.)

Will we survive the Andromeda collision?

Supervisors: Luke Barnes (Data Science, Astronomy)
School/Institute: School of Computing, Engineering and Mathematics

The Milky Way’s nearest galactic neighbour – of similar size – is Andromeda, located 2.5 million light years away. We know that Andromeda is moving towards us at about 300 km/s, which means that it will arrive at the Milky Way in about 2-3 billion years. What happens when it arrives?

More details about the project. More details about enrolment.

Reposted from Sydney Observatory:

Verlie Lee passed away on 15th June 2019 in Nambucca Heads and Eungai Creek on the North Coast of NSW at the age of 88. Verlie worked at Sydney Observatory from 1948 to 1954 and she was one of the many ‘hidden figures’ who worked on the Astrographic Catalogue, tides and other charts in observatories during that period. Recently the work many women did behind the scenes in science is being brought to the fore and it is timely to remember Verlie June Maurice’s contribution. I interviewed Verlie Lee on 3 April 2013 and she had many stories of the work and social life at Sydney Observatory which she was keen to share.

Five women star measurers on Observatory Hill in Sydney in front of the rotunda.
Star measurers and computers at Sydney Observatory. Top row left to right: Verlie Maurice, Patricia Lawler. Bottom Row left to right: Margaret Colville, Renae Day, Margaret Browne. Photograph by Winsome Bellamy, 1948.

The Astrographic Catalogue was arguably the most significant astronomy project undertaken in the late nineteenth and early twentieth century in Australia. Sydney, Melbourne and Perth Observatories were part of an international consortium of observatories working together to catalogue the stars using photography. Whilst predominantly men took the photographs of the stars using special ‘astrographic telescopes’, women measured the stars on glass plate negatives, calculated their positions, identified double stars and other irregularities. Verlie was one of 22* women who measured the positions of stars for the Astrographic Catalogue at Sydney Observatory between 1916 and 1963. Continue Reading »

New! With Geraint Lewis, from Cambridge University Press, in Feb 2020:


Free yourself from cosmological tyranny! Everything started in a big bang? Invisible dark matter? Black holes? Why accept such a weird cosmos? For all those who wonder about this bizarre universe, and those who want to overthrow the big bang, this handbook gives you ‘just the facts’: the observations that have shaped these ideas and theories. While the big bang holds the attention of scientists, it isn’t perfect. The authors pull back the curtains, and show how cosmology really works. With this, you will know your enemy, cosmic revolutionary – arm yourself for the scientific arena where ideas must fight for survival! This uniquely-framed tour of modern cosmology gives a deeper understanding of the inner workings of this fascinating field. The portrait painted is realistic and raw, not idealized and airbrushed – it is science in all its messy detail, which doesn’t pretend to have all the answers.

More details here.


Another edition of “How to Use Bayes Theorem Properly 101” (links to previous posts are below). I was listening to a YouTube debate, and one of the speakers offered the following definition of “evidence”:

Evidence is a body of objectively verifiable facts, that are positively indicative of or exclusively concordant with one particular conclusion over any other.

They then demonstrated the many fatal flaws of this definition; for example, there is no such thing as objective verification of facts. Here, I’ll focus on another flaw. Continue Reading »