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Archive for the ‘The Universe’ Category

I’ve been a bit quiet around here, lately. Travel is my excuse. I’m currently in Cambridge, collaborating with a few colleagues on a project. I’ll be back in Sydney next week, so if you’re near Epping on Friday 4th July 2014, why not come along to hear me speak at the Astronomical Society of NSW:

“What Happened at the Big Bang?”

Friday 4th July 2014 – 8:00pm
Topic: What happened at the Big Bang?
Speaker: Dr Luke Barnes, University of Sydney
Venue: Epping Creative Centre – 26 Stanley Road, Epping

Abstract:
Was the big bang the beginning of the universe? Does the big bang represent the beginning of time itself? This is an age-old question, and has been remarkably informed by modern cosmology.

I will answer this question once and for all.

I will follow the theorems, evidence and hints that lead us back in time. In particular, I will discuss the expansion of the space, the physics of the very early universe, the recent BICEP2 results and cosmic inflation, the effect of quantum physics, and the reason (or one of them) why Stephen Hawking is famous.

Biography:
Dr Luke A. Barnes is a postdoctoral researcher at the Sydney Institute for Astronomy. After undergraduate studies at the University of Sydney, Dr. Barnes earned a scholarship to complete a PhD at the University of Cambridge. He worked as a researcher at the Swiss Federal Institute of Technology (ETH), before returning to Sydney in 2011. He has published papers on galaxy formation and cosmology, and recently has taken an interest in the fine-tuning of the universe for intelligent life. He blogs at letterstonature.wordpress.com.

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The Conversation has published an article of mine, co-authored with Geraint Lewis, titled “Have cosmologists lost their minds in the multiverse?“. It’s a quick introduction to the multiverse in light of the recent BICEP2 results. Comments welcome!

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Front Cover of Australian PhysicsMy article “Cosmology Q & A” has been published! It appeared in the magazine Australian Physics, 51 (2014) 42-6 and is reproduced here with permission. After a brief overview of modern cosmology, it (tries to) answer the following questions:

  1. Is space expanding, or are galaxies just moving away from us?
  2. Is everything getting bigger?
  3. Ordinary matter and radiation cause the expansion of the universe to decelerate. But our universe is accelerating! How? What is the universe made of?
  4. Dark Energy? Is that like Dark Matter?
  5. How big is the universe?
  6. How big is the universe really?
  7. If the universe were finite, could I see the back of my own head?
  8. Is space expanding faster than the speed of light?
  9. Are there galaxies moving away from us at more than the speed of light?
  10. Light from distant galaxies is observed to be redshifted. Is this because the expansion of space stretches the wavelength, or because is it a Doppler shift due to the recession of the galaxy?
  11. Does the universe have zero total energy?
  12. Energy is not conserved!? Shouldn’t that send shivers up the spine of any physicist?
  13. The very universe, we are told, began in thermal equilibrium. How did equilibrium establish itself so quickly?
  14. How does the initially smooth universe we see in the CMB become today’s universe of stars and galaxies?

As before, further questions in the comments are always welcome.

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More on the upcoming Carroll vs. Craig dialogue (previously, one, two, three). I have some leftover business from my previous post on the contingency argument for the existence of God. It concerns the question why is there something something rather than nothing?, a question I’ve discussed on a few previous occasions.

The Question

The question “why is there something something rather than nothing?” is not an argument, obviously. It’s a question. It’s relationship to the cosmological argument for the existence for God is as an entree, a taster. It’s supposed to get you thinking about existence.

Imagine two parties. At one is everything that actually exists (or has existed) – the “actual” party. At the other, everything that could exist – the “possible” party. Horses are at both parties, unicorns only the possible party. Why? Because of something at the actual party, in this case the evolutionary ancestors of the horse. When something moves from possible to actual, it’s because of an invitation from the actual party. Those in the possible party can’t crash the actual party. They don’t exist, and so don’t have any causal powers, so can’t make anything actually happen.

So this actual party – did everyone get their invitation off someone else? Is there an infinite regress of inviters? It can’t form a loop – I invite you and you invite me – because that’s just crashing the party. Could there be a party where everyone must be invited by someone who’s already there? Why is anyone at the party? Why does anything exist?

Not the Question

Aside: The question is not: “something came from nothing. How could that happen?”, to which the answer is supposedly: because God can make something out of nothing. That confuses the contingency argument with the Kalam argument. The question is “Why is there something rather than nothing?”. The answer is: God is a necessary being, so it is not possible for there to be nothing. God must exist.

Nothing, Naturally

Carroll discusses the question “why is there something rather than nothing?” in this blog post. Amongst other things, he discusses the claim that “nothingness is uniquely natural”, so that we need some special reason why something exists. He argues that we have no basis for such a conclusion, as our intuitions for naturalness and simplicity are based on our experience in this world, and so don’t automatically apply to the universe itself.

However, most versions of the cosmological argument don’t explicitly appeal to the naturalness of nothing. Carroll, following Grunbaum, discusses Swinburne. In Grunbaum’s paper “Why is There a World AT ALL, Rather Than Just Nothing?”, he quotes Swinburne: “It remains to me, as to so many who have thought about the matter, a source of extreme puzzlement that there should exist anything at all” (pg. 336). I think, however, they’ve missed the point of what Swinburne is saying. (I say this with some trepidation. Grunbaum is a professional philosopher, and something of a legend. Fools rush in …) (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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On February 21-22 (2014), Sean Carroll and William Lane Craig will debate at the Greer-Heard Forum, at the New Orleans Baptist Theological Seminary. The topic is “God and Cosmology: The Existence of God in Light of Contemporary Cosmology”. For a number of reasons, I have high hopes for this one. Here’s why.

I (mostly) like the format

We start with a dialogue between the two parties, for 1.5 hours. As a spectator, I prefer the debate format. While a dialogue sounds like a friendly chat rather than a confrontation, in practice it unfairly unfavors the rude and the loud. We are at the mercy of the disciplinary skill of the moderator. However, this one shouldn’t be too bad. Craig will let his opponent talk, and I get the same impression from Carroll.

Given the list of things I’d like them to discuss, as I’ll discuss in future posts, I’m hoping that each party gets an opening statement of at least 20 minutes. They both have a lot to say about this topic, and need the time to present their case thoroughly.

The next day we’re back with 4 speakers, each with an hour that includes responses from Carroll and Craig. That’s a very interesting arrangement and I’m keen to see how it works in practice. The day rounds out with concluding comments from the two debaters.

Good choice of debaters

I’ve listened to a number of William Lane Craig’s debates and the best ones are usually against other philosophers, for this reason. The topic is God, or at least something closely related to the almighty. In any argument for or against the existence of God, at least one of the premises must be metaphysical. So against, say, a scientist, Craig can absorb a lot of the scientific expertise of his opponent and focus on the (often unstated) philosophical assumptions behind their remarks. The debate moves to matters philosophical, which gives Craig the home advantage. Some of Craig’s opponents know less than nothing about philosophy; what they think they know about philosophy is wrong. On the other hand, Craig knows enough of the science that is relevant to his arguments to be able to defend the scientific premises against a philosopher.

Carroll has an undergraduate philosophy minor and as a grad student in astrophysics at Harvard, sat in on courses with John Rawls and Robert Nozick. His blog posts and articles show a familiarity with and respect for philosophical issues. Carroll is close to the ideal opponent for this debate, as he should be able to hold his own on matters philosophical, whilst holding a substantial advantage on matters cosmological.

Good Choice of Respondents

I’m guessing that Craig will defend three of his usual five arguments – the Kalam cosmological argument from the beginning of the universe, the contingency argument, and the design argument from the fine-tuning of the universe for intelligent life. The contingency argument doesn’t rely on any particular scientific theories, so Craig doesn’t need any particular backup on that front. For the Kalam cosmological argument, his scientific case for the premise “the universe has a beginning” has been provided in recent times by James Sinclair. In particular, Craig’s most sophisticated defence of the argument in recent times is in the The Blackwell Companion to Natural Theology, which was co-written with Sinclair. Sinclair is a Warfare Analyst with a masters in cosmology, so his credentials are slightly unorthodox.

Also writing in the The Blackwell Companion to Natural Theology is Robin Collins, a philosopher with a background in physics. He has specialised in the argument from the fine-tuning of the universe for intelligent life. So that gives Craig his backup for his third argument.

Carroll has two philosophers in tow. Alex Rosenberg is a philosopher at Duke University who Craig has debated before, and whose book “The Atheist’s Guide to Reality” was praised by both sides of the debate as seeing rather clearly the consequences of atheism. Tim Maudlin is a philosopher of science at New York University. His book “Philosophy of Physics: Space and Time” is marvellous. He also seems to have taken an interest in the fine-tuning of the universe for intelligent life. (I have a few reservations about his opinions on that topic.)

That’s an interesting line up. I’d gladly hear any of them speak on the topic at hand; all four of them in a row with responses from Carroll and Craig is very promising.

My advice

I think this debate could be uniquely insightful on this important topic. Craig has said an awful lot about cosmology in recent years, and no one has really pressed him on the details. They’ve mostly (though not unreasonably) appealed to cosmological authorities. (For the love of Pete, nobody read out an email from Alex Vilenkin. More on that soon.) Carroll has said a lot about the implications of cosmology for theism, and there are some philosophical niceties to be examined there as well. Stay tuned for parts two, three, and four.

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I recently read philosopher of science Tim Maudlin’s book Philosophy of Physics: Space and Time and thought it was marvellous, so I was expecting good things when I came to read Maudlin’s article for Aeon Magazine titled “The calibrated cosmos: Is our universe fine-tuned for the existence of life – or does it just look that way from where we’re sitting?“. I’ve got a few comments. Indented quotes below are from Maudlin’s article unless otherwise noted.

In a weekend?

Theories now suggest that the most general structural elements of the universe — the stars and planets, and the galaxies that contain them — are the products of finely calibrated laws and conditions that seem too good to be true. … The details of these sorts of calculations should be taken with a grain of salt. No one could sit down and rigorously work out an entirely new physics in a weekend.

Two few quick things. “Theories” has a ring of “some tentative, fringe ideas” to the lay reader, I suspect. The theories on which one bases fine-tuning calculations are precisely the reigning theories of modern physics. These are not “entirely new physics” but the same equations (general relativity, the standard model of particle physics, stellar structure equations etc.) that have time and again predicted the results of observations, now applied to different scenarios. I think Maudlin has underestimated both the power of order of magnitude calculations in physics,  and the effort that theoretical physicists have put into fine-tuning calculations. For example, Epelbaum and his collaborators, having developed the theory and tools to use supercomputer lattice simulations to investigate the structure of the C12 nucleus, write a few papers (2011, 2012) to describe their methods and show how their cutting-edge model successfully reproduces observations. They then use the same methods to investigate fine-tuning (2013). My review article cites upwards of a hundred papers like this. This is not a back-of-the-envelope operation, not starting from scratch, not entirely new physics, not a weekend hobby. This is theoretical physics.

Telling your likelihood from your posterior

It can be unsettling to contemplate the unlikely nature of your own existence … Even if your parents made a deliberate decision to have a child, the odds of your particular sperm finding your particular egg are one in several billion. … after just two generations, we are up to one chance in 10^27. Carrying on in this way, your chance of existing, given the general state of the universe even a few centuries ago, was almost infinitesimally small. You and I and every other human being are the products of chance, and came into existence against very long odds.

The slogan I want to invoke here is “don’t treat a likelihood as if it were a posterior”. That’s a bit to jargon-y. The likelihood is the probability of what we know, assuming that some theory is true. The posterior is the reverse – the probability of the theory, given what we know. It is the posterior that we really want, since it reflects our situation: the theory is uncertain, the data is known. The likelihood can help us calculate the posterior (using Bayes theorem), but in and of itself, a small likelihood doesn’t mean anything. The calculation Maudlin alludes to above is a likelihood: what is the probability that I would exist, given that the events that lead to my existence came about by chance? The reason that this small likelihood doesn’t imply that the posterior – the probability of my existence by chance, given my existence – is small is that the theory has no comparable rivals. Brendon has explained this point elsewhere. (more…)

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Having had my appetite for the Middle Ages whetted by Edward Grant’s excellent book A History of Natural Philosophy: From the Ancient World to the Nineteenth Century, I recently read Edward Feser’s Aquinas (A Beginner’s Guide). And, on the back of that, his book The Last Superstition. If I ever work out what a formal cause is, I might post a review.

In the meantime, I’ve quite enjoyed some of his blog posts about the philosophical claims of Lawrence Krauss. This is something I’ve blogged about a few times. His most recent post on Krauss contains this marvellous passage.

Krauss asserts:

“[N]othing is a physical concept because it’s the absence of something, and something is a physical concept.”

The trouble with this, of course, is that “something” is not a physical concept. “Something” is what Scholastic philosophers call a transcendental, a notion that applies to every kind of being whatsoever, whether physical or non-physical — to tables and chairs, rocks and trees, animals and people, substances and accidents, numbers, universals, and other abstract objects, souls, angels, and God. Of course, Krauss doesn’t believe in some of these things, but that’s not to the point. Whether or not numbers, universals, souls, angels or God actually exist, none of them would be physical if they existed. But each would still be a “something” if it existed. So the concept of “something” is broader than the concept “physical,” and would remain so even if it turned out that the only things that actually exist are physical.

No atheist philosopher would disagree with me about that much, because it’s really just an obvious conceptual point. But since Krauss and his fans have an extremely tenuous grasp of philosophy — or, indeed, of the obvious — I suppose it is worth adding that even if it were a matter of controversy whether “something” is a physical concept, Krauss’s “argument” here would simply have begged the question against one side of that controversy, rather than refuted it. For obviously, Krauss’s critics would not agree that “something is a physical concept.” Hence, confidently to assert this as a premise intended to convince someone who doesn’t already agree with him is just to commit a textbook fallacy of circular reasoning.

The wood floor guy analogy is pretty awesome, so be sure to have a read.

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