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Archive for the ‘Science’ Category

A favourite XKCD:

Made out of Meat

Here’s a few idle, Friday afternoon thoughts. I study distant galaxies. I use mathematical models of the laws of nature (and a supercomputer) to try to predict the properties of light emitted by and scattered through swirling vortices of matter, each containing a thousand trillion trillion trillion tons of stars, gas and dark matter, almost a trillion trillion kilometers away. My discipline – cosmology – has taken as its object of study the universe as a whole. And we’re doing pretty well, thanks for asking. I’d like to think that I am an evidence collecting, theory discovering, model investigating, equation solving (with a little help from my computer) machine.

And then I hear a talk from a biologist. I am reminded that I’m a fighting, fleeing, feeding, and reproducing machine. The lump of stuff in my head was produced by causes that “see” survival and reproduction. My brain is the control centre of a biological organism, and there seems to be precious little overlap between survival, reproduction and astrophysical ability. (Unless my astrophysical brain has made me so attractive to the ladies that it significantly increases my chances of reproduction. I’ll ask my wife.) An accurate mental picture of the world, formed using mostly reliable senses and the ability to reason logically, creatively and flexibly, seems useful to survival. But to use a brain to do cosmology? Really? (If you haven’t read Terry Bisson’s wonderful short essay “They’re made out of meat“, then do it now: “Thinking meat! You’re asking me to believe in thinking meat!”.)

A parable. Suppose I call Toyota customer services.

Me: Hi there. I own a 1993 Toyota Camry. I have a question.

Toyota: Certainly, sir. Is the car running well, getting you from A to B in comfort?

Me: Sure. It’s doing all that nicely. I was thinking about using it to drive to the moon.

Toyota: … Right … Wouldn’t recommend that, Mr Barnes. No … uh … not really in the user manual, I’m afraid. Not what it’s made for.

Suppose I find a customer support label on the back of my brain.

Me: Hi there. I own and operate one of your brains. I have a question.

Support: Certainly, sir. Is it operating your body, correctly? Are you getting enough food? Have you found a mate?

Me: Sure. It’s doing all that nicely. I was thinking about using it to do theoretical physics, discover the fundamental laws of the universe and use them to understand the structure and evolution of the universe and all its contents.

Support: … Right … Wouldn’t recommend that, Mr Barnes. No … uh … not really in the user manual, I’m afraid. Not what it’s made for.

Let’s be clear about the point I’m making here. I don’t doubt that physicists in general and cosmologists in particular have discovered true facts about the universe. It’s just a tad amazing that we can do that sort of things with our brains. (We use computers and telescopes as well, of course, but they too are the products of human brains). To extend the analogy, it’s as if I find myself standing on the moon, wondering how I got there. And as I look around, all I can see is a 1993 Toyota Camry. It’s not that I doubt where I am; I’m wondering how I got here in that! I’m not asking: how do I know that our investigation of the universe is successful? I’m asking: why is our investigation of the universe successful? How does fighting/fleeing/feeding/reproducing machine manage to do theoretical physics?

Perhaps the boring answer is the right one: we do it bit by bit. If we view science as extended and refined common sense, then maybe we can understand how a brain “made for” understanding local terrestrial environments is able to understand the universe. We don’t directly grasp the universe, of course. We rely on mental pictures and analogies. Mathematical models of the universe are perhaps analogies with equations. Having a mental picture of the world is useful. Just add curiosity and get practicing.

It seems like the same problem arises for mathematics – how does a brain manage to investigate such abstract ideas as those of pure mathematics? The same answer suggests itself: abstract thinking is useful. Just add curiosity and get practicing.

The universe is easy

We seem to need another ingredient in this explanation. That a brain can do theoretical physics and cosmology suggests not only that it is a remarkably adaptable, programmable thing, but also that the universe is an easier problem than we might have expected. A great example of this is the so-called cosmological principle. (I discuss this in more detail in my Australian Physics article here.)

That the universe is rationally analysable at all, that there is order and reason waiting for us in the mathematical structure of the universe, is a remarkable fact. The intellectual problem we are presented with in nature is, in a very real and precise sense, solvable.  It is one thing that the universe exemplifies such beautiful mathematics as Lagrangian dynamics; it is another, a fortiori, that the Lagrangians that describe our universe display numerous and deep symmetries. The universe is a complicated place, and the mathematics that describes it must be complicated at some level. The remarkable thing is that the complication is on top; there is simplicity underneath. To be more precise, the laws of nature are simple, their solutions can be complicated. Newton’s law of gravitation is simple, but for even three bodies, its solution cannot be written down analytically.

In physics’s search for the ultimate laws of nature, many physicists wouldn’t accept a proposed fundamental theory unless it were simple, elegant, and beautiful. Paul Dirac went so far as to say that “it is more important to have beauty in one’s equations than to have them fit experiment”. It follows that physics cannot explain why the laws of nature are simple, elegant, and beautiful. Now there’s a thought for the weekend.

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Next month, I’ll be in Minnesota at the St. Thomas Summer Seminars in Philosophy of Religion and Philosophical Theology, presenting the science of fine-tuning to a bunch of philosophers. I presented similar lectures back in 2011 – they’re on YouTube. I’ve got a new section this time on Bayesian approaches to the multiverse and naturalism. I found a few guinea pigs to test it out on, so if you’re in Sydney on Saturday then come along. Here’s the details:

Title: Fine-tuning and Naturalism

Abstract: Christopher Hitchens stated that “At some point, we [the New Atheists] are all asked which is the best argument you come up against from the other side. I think every one of us picks the fine-tuning one as the most intriguing.” After introducing the fine-tuning of the universe for intelligent life, I will consider what it means for naturalism, the multiverse, and science’s quest for the ultimate laws of nature.

Time: Saturday 30th of May 2015, 4pm.

Address: St Philips Anglican Church, 402 Port Hacking Rd Sth Caringbah

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If you’re in Sydney on Monday (18th May, 2015), then come along to The Royal pub in Darlington to see A Pint of Science! It’s an international science festival, with similar events in 9 countries. I’ll be speaking on:

Universes, one after the other)
Cosmologists are considering the idea that our universe is just one of a vast ensemble. I’ll give two reasons to take that incredulous look off your face, and two reasons to put that incredulous look right back again.

You’ll also hear “Quantum origin of galaxies, stars and life”, by Archil Kobakhidze (theoretical particle physicist), and Quantum Technologies of the Future by David Reilly (quantum physicist).

And, naturally, beer. All welcome!

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It’s been a while, but I’ve finally gotten around to jotting down a few thoughts about the Sean Carroll vs. William Lane Craig debate. I previewed the debate here (part one, two, three, four). I thoroughly enjoyed the debate. Future posts will discuss a few of the philosophical questions raised by the debate, but I’ll briefly discuss some of the science in this point. (I didn’t manage to record my talk a few weeks ago, but this post summarises it.)

Firstly, I want to refer you to the much greater expertise of Aron Wall of UC Santa Barbara. I’ll list them all because they’re great.

(I’m on the “astrophysics” end of cosmology. The beginning of the universe probes the “particle and plasma and quantum gravity and beyond” end of cosmology. I know the field, but not as well as someone like Wall or Carroll.)

No one expects the beginning of the universe!

Regarding the scientific question of the beginning of the universe, here is how I see the state of play. Cosmologists don’t try to put a beginning into their models. For the longest time, even theists who believed that the universe had a beginning acknowledged that the universe shows no sign of such a beginning. We see cycles in nature – the stars go round, the sun goes round, the planets go round, the seasons go around, generations come and go. “There is nothing new under the sun”, says the Teacher in Ecclesiastes. Aristotle argued that the universe is eternal. Aquinas argued that we cannot know that the world had a beginning from the appearance of the universe, but only by revelation.

So when a cosmic beginning first raised its head in cosmology, it was a shock to the system. Interestingly, theists didn’t immediately jump on the beginning as an argument for God. Lemaître, one of the fathers of the Big Bang theory and a priest, said:

“As far as I can see, such a theory [big bang] remains entirely outside any metaphysical or religious question.”

In 1951, Pope Pius XII declared that Lemaître’s theory provided a scientific validation for existence of God and Catholicism. However, Lemaître resented the Pope’s proclamation. He persuaded the Pope to stop making proclamations about cosmology.

The philosophical defence of the argument from the beginning of the universe to God (the Kalam cosmological argument) starts essentially with Craig himself in 1979, half a century after the Big Bang theory is born.

In fact, the more immediate response came from atheist cosmologists, who were keen to remove the beginning. Fred Hoyle devised the steady state theory to try to remove the beginning from cosmology, noting that:

“… big bang theory requires a recent origin of the Universe that openly invites the concept of creation”. His steady-state theory was attacked “because we were touching on issues that threatened the theological culture on which western civilisation was founded.” (quoted in Holder).

Tipping the Scales

But what of the beginning in the Big Bang model? Singularities in general relativity weren’t taken seriously at first. Einstein never believed in the singularities in black holes. Singularities were believed to be the result of an unphysical assumption of perfect spherical symmetry. In Newtonian gravity, a perfectly spherical, pressure-free static sphere will collapse to a singularity of infinite density. However, this is avoided by the slightest perturbation of the sphere, or by the presence of pressure. A realistic Newtonian ball of gas won’t form a singularity, and the same was assumed of Einstein’s theory of gravity (General Relativity).

The next 80 years of cosmology sees the scales tipping back and forth, for and against the beginning. (more…)

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As I explained in my last posts (one, two), I’m expecting good things from the upcoming dialogue between Sean Carroll and William Lane Craig. Here, I’ll look at a species of the cosmological argument for the existence of God known as the contingency argument.

Before all that: Sean has linked to my previous post about this debate. Just to be clear, I don’t think Sean needs much advice. I’m really using these posts as an excuse to discuss Carroll’s ideas. He knows the arguments, knows the cosmology, has a clear idea about what naturalism is and how to defend it, and is an excellent public speaker. Carroll’s arguments are interesting and relevant, and Craig’s response won’t be anything as basic as “here’s a Grammar 101 lesson on using terms of negation and indefinite pronouns.”

Long post ahead. The short story: Carroll needs to make clear his objection to the Craig’s version of the principle of sufficient reason. In particular, why think that the universe is an exception (perhaps the only exception) to the general trend that things exist for a reason?

Craig’s Version of the Argument

The cosmological argument for the existence of God has been defended through the ages by a who’s who of thinkers: Plato, Aristotle, Al-Kindi, Ibn Sina, Al-Ghazali, Maimonides, Aquinas, Scotus, Spinoza, Leibnitz, … Of course, it has also been critiqued, most famously by Hume and Kant. The debate continues. Craig’s version of the contingency argument goes like this.

  1. Everything that exists has an explanation of its existence (either in the necessity of its own nature or in an external cause).
  2. If the universe has an explanation of its existence, that explanation is God.
  3. The universe exists.

It follows from these premises that God exists (homework). Note that this argument has nothing to do with whether the universe has a beginning.

Some atheists (Lawrence Krauss in particular) object to the second premise, thinking that God is just crowbarred in, an ad hoc assumption. But premise 2 has its own argument:

4. Since the universe is the totality of space, time, matter and energy (i.e. that’s the sense of universe being used here), the cause of the universe must be spaceless, timeless, and immaterial.
5. The most plausible immaterial kind of thing that could cause a universe is a mind.
6. A spaceless, timeless, and immaterial mind that causes the universe deserves to be called God.

Premise 5, in turn, has its own argument based on the causal effeteness of abstract entities. If you want to go after premise 2, you need to deal with this argument. Krauss didn’t.

Getting slightly ahead of myself, Carroll seems to object to Premise 1. This premise is a version of the infamous Principle of Sufficient Reason (PSR). It is a mild version, applying only to things, not to all (contingent) truths. Craig argues for premise 1, or at least that the universe is not an exception to premise 1, as follows.

  1. It would be arbitrary for the atheist to claim that the universe is the exception to the rule. Merely increasing the size of the object to be explained, even until it becomes the universe itself, does nothing to remove the need for some explanation of its existence.

Alexander Pruss has advanced arguments for a version of the PSR along these lines. (I’m paraphrasing, dangerously).

8. If the universe could exist without explanation, then it would be inexplicable why just anything couldn’t exist without explanation. In other words, why is only the universe an exception to premise 1?
9. Universal principles are simpler than principles that apply to an arbitrary subset. The simplest explanation of fact that contingent things typically have explanations is that all contingent things have explanations.

Carroll’s Case

Let’s consider with what Carroll’s response might be, as gleaned from this reply to an op-ed piece by Paul Davies.

“[A]t first glance, it seems plausible that there could be [an] answer to the question of why the laws of physics take the form they do. But there isn’t. At least, there isn’t any as far as we know, and there’s certainly no reason why there must be. The more mundane “why” questions make sense because they refer to objects and processes that are embedded in larger systems of cause and effect. … The universe (in the sense of “the entire natural world,” not only the physical region observable to us) isn’t like that. It’s not embedded in a bigger structure; it’s all there is. We are lulled into asking “why” questions about the universe by sloppily extending the way we think about local phenomena to the whole shebang. What kind of answers could we possibly be expecting? … [The correct possibility seems to be] that’s just how things are. There is a chain of explanations concerning things that happen in the universe, which ultimately reaches to the fundamental laws of nature and stops. This is a simple hypothesis that fits all the data; until it stops being consistent with what we know about the universe, the burden of proof is on any alternative idea for why the laws take the form they do.”

Let’s break it down. Lurking in the background of this entire discussion is this question: what makes an explanation an ultimate explanation? What is it about this explanation that makes another iteration of “and why?” out-of-bounds? Carroll’s argument seems to be:

10. Chains of explanations have to end somewhere.
11. Once we arrive at a simple explanation that fits all the data, there is nothing to be gained by going any further. Such an explanation should be considered an ultimate “stopping-point” explanation.
12. The fundamental laws of nature are just such an explanation for the physical universe.
13. Thus, we should consider the fundamental laws of nature to be the ultimate explanation of the universe.

Carroll’s formula of “simplicity + fits the data” needs a closer look. (more…)

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I don’t know who Rob Sheldon is, but he doesn’t know much about cosmology. He recently was quoted in this post at uncommondescent.com regarding the geometry of the universe. If I lecture cosmology this year, I’ll set this passage as an assignment: find all the mistakes. It gets more wrong than right. I have an article for “Australian Physics” on common questions about cosmology that I’ll post here once it’s out (a fortnight, maybe). In the meantime, I’ll try to clear up a few things.

The discussion of the mathematics of curvature (flat, positive, negative) is about right. It’s when he discusses the universe that things go wrong.

It takes a lot of effort to find any curvature at all, and certainly it is difficult to get good agreement between different types of measurement.

Nope. That’s why it’s called the “concordance model of cosmology” – because the different measurements converge on the same set of cosmological parameters. For example, this plot.

… a “closed” universe that collapses back down to itself …

A common error. In a matter and radiation-only universe, closed implies collapsing. A cosmological constant and/or dark energy changes this: closed vs. open no longer divides collapse vs. expand forever. Here is the plot you’ll need, from John Peacock’s marvellous Cosmological Physics.

… one would like it to have positive curvature to avoid infinities …

Flat and negatively curved universes can be finite. A flat 3-torus, for example, is finite, unbounded and has a flat geometry. Einstein’s general relativity constrains the geometry of the universe but not its topology. (more…)

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As I explained in my last post, I’m expecting good things from the upcoming dialogue between Sean Carroll and William Lane Craig. Before discussing the topic, a few comments about debating.

An awful lot of rubbish has been written about counteracting Craig’s diabolical debating; it’s actually pretty simple. When you speak, make a clear argument for a relevant conclusion. After he speaks, target specific premises of his arguments and explain why you think they are unlikely to be true. That’s it. It sounds simple, and it’s been done very effectively, but so many of Craig’s opponents can’t manage it.

Critics have said that Craig unfairly dictates the flow of the debate, keeping a stranglehold on the topic of his choosing. This doesn’t happen when his opponent keeps him busy. Austin Dacey and Keith Parsons are great examples. Craig won’t ignore your case if you make one, and it’s relevant. Give him something to respond to.

If you fail to make a case, Craig will have read your writings and be prepared to both make your own case for you and critique it. He did this to great effect against Rosenberg. If you fail to address his arguments, he will point this out and repeat them. He is justified in doing so because one often hears the refrain that “I’m an atheist because there’s no evidence for God”. To maintain that there is no evidence, one must be able to explain why the supposed evidence isn’t really evidence at all. As an analogy, one cannot reasonably claim that “there is no evidence that human beings walked on the moon” and not attempt to explain the Apollo 11 photographs and videos.

There is no excuse for debating Craig underprepared. You can listen to a debate from the early 1990’s and get most of his arguments. That said, you are better off reading an article rather than responding to a 20 minute summary. It’s best not to raise objections that he has already addressed in print, or even better, raise them in a way that also addresses his response.

Always go for the argument, never the man. If you’ve shown that Craig is mistaken, then it doesn’t much matter how he convinced himself of such falsehoods. Amateur anthropology/psychology/neuroscience – e.g. any sentence beginning with “human beings have a very strong cognitive bias to believe …” – is a waste of time. Just burn down his arguments; don’t toast marshmallows on the embers. Resist Bulverism!

Remember: critiquing is hard. That someone is wrong doesn’t make it easier. Step 1: understand. Step 2: critique. Here are a few resources. Feel free to add more in the comments.

Kalam Cosmological Argument

Contingency (Leibnizian) Argument

  • I think the most comprehensive presentation of Craig’s version of the argument is in his book “Reasonable Faith”. A shorter (and free) introduction is here.

  • Some of the “Questions of the week” shed more light on the philosophical issues that arise: 132, 190, 248, 329.

  • I recommend Alexander Pruss’ article on the Leibnizian argument in the Blackwell Companion to Natural Theology. Craig calls it “a must”, but be aware that it differs from Craig’s version in both content and style. In particular, Pruss defends a more comprehensive version of the principle of sufficient reason.

Fine-Tuning Argument

  • Again, the book “Reasonable Faith” is the best resource. A slightly older presentation is here.

  • Questions of the weeks that address the argument: 49, 63, 161, 313. In particular, Craig’s response to the multiverse, include the Boltzmann Brain problem: 14, 285.

  • For the scientific details of the argument, Craig relies a lot on the work of Robin Collins. Collins’ best presentation of fine-tuning cases is in this book. He presents the argument itself in the Blackwell Companion to Natural Theology. He has an interesting discussion of the implications of the Boltzmann brain problem in this article.

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