Posts Tagged ‘universe’

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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I’ve invited cosmology questions before, but I wanted to renew the call. I’ve got a Q&A article on cosmology coming out soon, so ask away!

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Every now and then, a paper appears on astroph that has us thinking – is this serious? Or is this an imagination gone a tad wild? (Or is it April 1st?) For example, a friend at the IoA once wrote a proposal (for a graduate course) aiming to find extrasolar planets through bioluminescence. Rarely has an observing proposal been so entertaining.

So it was this week when this paper appeared on astroph. The proposal is as follows: “Genomic complexity” estimates that life on earth began 10 billion years ago (give or take three billion years). This is older than the solar system. A slight problem, perhaps. Suppose, perchance, that life didn’t develop on Earth. Suppose that, long before the solar system was formed, a planet was ejected from another planetary system. En route, this wandering planet (or rogue planet) forms life deep underground, shielded from cosmic rays, lethal radiation and freezing temperatures on the planet surface and warmed by radioactivity of the planet core.

Now suppose that the planet wanders into our solar system. The planet is most likely on an unbound orbit, and thus this will not be a long visit. (The paper estimates this number at around 43 years). But, bathed in the radiation of the sun and the solar wind, the surface of the planet may be stirred up enough to throw rocky shards off the guest planet. Should one of these shards reach a newly-formed Earth, and carry with it life-forms, then we would receive a population of organisms with a few billions of years of evolution behind them – they would be older than the Earth itself. (more…)

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I’ve just about finished by series of responses to various views on the fine-tuning of the universe for intelligent life that I have encountered. Here I will respond to the work of Hector Avalos, who is professor of Religious Studies at Iowa State University. In 1998, he wrote an article for Mercury Magazine entitled “Heavenly Conflicts: the Bible and Astronomy.” While most of the article pertains to the cosmology of the Bible and it’s (shock horror) apparent contradiction with modern cosmology, he spends five paragraphs near the end discussing the anthropic principle. He writes:

Attempts to relate the Bible to astronomy are often intertwined with the search for the meaning and purpose of human life. In particular, discussions by John A. Wheeler, John Barrow and other cosmologists concerning the so-called anthropic principle – the idea that the physical constants of the universe are finely tuned for human existence – have attracted interest. The anthropic principle would assert, for example, that if the charge of the electron were other than what it is or the weights of the proton and neutron were different, then human existence would not be. But do these precise quantities necessarily indicate that human beings were part of some intelligent purpose?

The primary assumption of the anthropic principle, which is really a new version of the older “divine design” or teleological argument, seems to be that the “quantity of intelligent purpose” for an entity is directly proportional to the quantity of physico-chemical conditions necessary to create that entity. But the same line of reasoning leads to odd conclusions about many non-human entitles.

… let’s use the symbol P to designate the entire set of physico-chemical conditions necessary to produce a human being … Making a computer requires not only all the pre-existing conditions that enable humans to exist but also human beings themselves. In more symbolic terms, making a computer requires P + human beings, whereas only P is needed to make human beings. By the same logic, garbage cans and toxic pollution produced by human beings would be more purposed than human beings. So measuring the divine purpose of an entity by the number of pre-existing conditions required to make that entity is futile.

This response to the fine-tuning of the universe is confused on many levels. (more…)

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[Edit, 4/2/2012: I’ve written a more complete critique of Stenger’s book The Fallacy of Fine-Tuning: Why the Universe Is Not Designed for Us. It’s posted on Arxiv. In particular, the program MonkeyGod is critiqued in Appendix B; most of the points raised below remain valid.]

This post is the second critiquing Victor Stenger’s take on the fine-tuning of the universe for intelligent life. Here are some more of Stenger’s claims. (The quotes below are an amalgam of the articles on this page.)

I think it is safe to conclude that the conditions for the appearance of a universe with life are not so improbable as the those authors, enamored by the anthropic principle, would have you think … [T]here could be many ways to produce a universe old enough to have some form of life.

How does Stenger reach this conclusion?

I have written a program, MonkeyGod … I have studied how the minimum lifetime of a typical star depends on three parameters: the masses of the proton and electron and the strength of the electromagnetic force. (The strong interaction strength does not enter into this calculation.) Varying these parameters by ten orders of magnitude around their present values, I find that over half of the stars will have lifetimes exceeding a billion years, allowing sufficient time for some kind of life to evolve. Long stellar lifetime is not the only requirement for life, but it certainly is not an unusual property of universes. (more…)

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[Edit, 4/2/2012: I’ve written a more complete critique of Stenger’s book The Fallacy of Fine-Tuning: Why the Universe Is Not Designed for Us. It’s posted on on Arxiv.]

This post is part of a series that responds to internet articles on the fine tuning of the universe. Here I will respond to Prof. Victor Stenger, who is a particle physicist at the University of Hawaii and known for his defence of atheism. Stenger, according to Wikipedia, is currently writing a book on fine-tuning. Here I will respond to a point he made in a debate with Dr. William Lane Craig.

Stenger proposes the following counterexample to the claim that interesting conclusions can be drawn from the improbability of the fine-tuning of the constants/initial conditions/laws of nature:

Low probability events happen every day.  What’s the probability that my distinguished opponent exists?  You have to calculate the probability that a particular sperm united with a particular egg, then multiply that by the probability that his parents met, and then repeat that calculation for his grandparents and all his ancestors going back to the beginning of life on Earth. Even if you stop the calculation with Adam and Eve, you are going to get a fantastically small number. To use words that Dr Craig has used before, “Improbability is multiplied by improbability by improbability until our minds are reeling in incomprehensible numbers.” Well, Dr Craig has a mind-reeling, incomprehensibly low probability – a priori probability – for existing.  Yet here he is before us today. (more…)

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Today, more on the work of William Lane Craig on the fine-tuning of the universe for intelligent life. The issue today is whether the laws/constants/initial conditions of the universe are, in some way, necessary. We think that the probability of a randomly chosen universe (with its laws, constants and initial conditions) being life-supporting is vanishingly small. We reach this conclusion by altering the laws/constants/initial conditions and predicting the outcome.

But perhaps when we have a deeper understanding of the laws of nature, we’ll realise that these constants couldn’t have been different. Or at least, we’ll realise that many of them are related, and thus cannot be altered independently. This would significantly reduce the probability of “getting the universe right”, as there are fewer dials to be tuned.

Let’s have a look at Craig’s response to this argument: (more…)

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