Category Archives: Cosmology

Of Two Time Indices

In the appendix to a paper I am currently co-authoring, I recently wrote the following within a parenthetical excursus:

When talking of dynamical systems, our probability assignments really carry two time indices: one for the time our betting odds are chosen, and the other for the time the bet concerns.

A parenthesis in an appendix is already a pretty superfluous thing. Treating this as the jumping-off point for further discussion merits the degree of obscurity which only a lengthy post on a low-traffic blog can afford.

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Currently Reading

Random fun items currently floating up through the arXivotubes include the following. Exercise: find the shortest science-fiction story which can connect all these e-prints, visiting each node only once.

Robert H. Brandenberger, “String Gas Cosmology” (arXiv:0808.0746).

String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the current standard paradigm of cosmology, the inflationary universe scenario. Here, the current status of string gas cosmology is reviewed.

Dimitri Skliros, Mark Hindmarsh, “Large Radius Hagedorn Regime in String Gas Cosmology” (arXiv:0712.1254, to be published in Phys. Rev. D).
Continue reading Currently Reading

The Dark Universe

Digging through my drafts pile to find something to post that doesn’t require too much extra writing, I found that I hadn’t yet released this item into the tubes. After The Halting Oracle and The Leech Lattice comes the third volume in our saga of good fantasy-novel titles, Lambda and The Dark Universe.

A few weeks back, Edward Kolb gave a series of talks at CERN on dark matter and dark energy, and how they fit into the standard “ΛCDM” model of the Universe. The abstract is as follows:

According to the standard cosmological model, 95% of the present mass density of the universe is dark: roughly 70% of the total in the form of dark energy and 25% in the form of dark matter. In a series of four lectures, I will begin by presenting a brief review of cosmology, and then I will review the observational evidence for dark matter and dark energy. I will discuss some of the proposals for dark matter and dark energy, and connect them to high-energy physics. I will also present an overview of an observational program to quantify the properties of dark energy.

Kolb’s presentations are, I found, entertaining and informative. At least, I laughed at his jokes — take that as you will. Much of the technical content can also be found in written form in, e.g., Cliff Burgess’ “Lectures on Cosmic Inflation and its Potential Stringy Realizations” (2007).

(Tip o’ the fedora to Jester.)

UPDATE (5 March): the newest figures, from the five-year WMAP results, are that the Universe is 72.1% dark energy, 23.3% dark matter, and 4.62% — everything else.

Science Illiteracy of the Day

BPSDBToday’s installment of “We’re so ignorant about basic science you couldn’t make up the crap we say if you tried” comes from Y-Origins Connection, a magazine which uses “dramatic photos and contemporary graphics” to explain “both sides of the intelligent design debate,” namely the creationist side and the creationists’ view of the scientists’ side. This comes from their website, right up top:

Quantum mechanics has revealed that our material world is based upon an invisible world of subatomic particles that is totally non-material. And over 95% of our universe consists of dark matter and energy that is beyond scientific observation. Also, scientists are openly discussing dimensions beyond ours where walking through walls and teleportation could be realities. The dilemma for materialists is that these areas are beyond the purview of science.

They managed to pack at least one kind of wrong in each sentence. I’m impressed. The overall theme seems to be taking discoveries of science and claiming them to be beyond science. When that well of inspiration runs dry, they take bits of overheard science jargon (hep talk like “extra dimensions” or “quantum teleportation,” let’s say) and throw them together without regard to their meaning. Truly they are strong in the art of nonsense-fu.

Physics from Open Yale Courses

Yale has started putting course material online in a systematic way, following in the grand tradition of MIT’s OpenCourseWare. Among the handful they’ve uploaded so far, the two which catch my eye the most strongly are Fundamentals of Physics and Frontiers and Controversies in Astrophysics. These classes come with Quicktime video of the lectures, and all material is licensed under Creative Commons BY-NC-SA.

Hat tip: Peter Suber.

Teh Burning Stupid: Relativity Edition

To put the “moral” at the beginning, let’s summarize. If you want to raise my blood pressure, one good way to do it is to write a completely wrong, back-to-front absurd tirade against all of twentieth-century physics. Anyone can slip a few errors into an essay, or even a few “fundamental” errors, but if you want the brass ring, you need at the very least to misrepresent the special theory of relativity, the general theory of relativity, quantum mechanics, the use of mathematics in physics and the scientific method. Bonus points if you confuse general relativity with quantum physics; a woop-woop-woop special prize for taking a non-true assertion and calling it a “fundamental premise” of quantum mechanics; and an extra cherry on top if you take three famous observations which support general relativity, lie about two of them and forget the third.

The story so far:

I might write an actual, non-linkfesty post about this. . . but then again, other corners of the Network are calling to me and reminding me of overdue obligations, so I might leave it to my colleagues.

UPDATE (6 December): gg now has Part 2 out on the blogonets.

UPDATE (16:47 o’clock): Tyler DiPietro dons the asbestos and joins the fun, followed quickly by Mark Chu-Carroll.

UPDATE (9 December): Flavin of the St. Louis Skeptical Society offers an essay.

Sunday Egan

Greg Egan writes,

I wish we had a good word in English that meant only “the shattering majesty of reality”, so atheists could make it abundantly clear that they’re aware of this majesty, but don’t imagine that it’s due to anything that resembles a person in any way. But what atheists absolutely should not do is say “Well, I’m going to use the word ‘God’ to mean ‘the awesomeness of the universe’”. This is helpful for selling lots of tenth-rate pop-science books with “God” in their titles, and for winning the Templeton prize, but even when it’s not plain venal and dishonest it’s linguistically sloppy.

This is why I describe quantum mechanics as Loki playing dice with the Universe. Come on, Loki may be subtle, but he’s not malicious, right?

We can take this one step further. There is a model of the early Universe called string gas cosmology, in which the reason why the Cosmos has three dimensions is essentially the same as the reason why knots can exist in three dimensions but not more or less. (In 2D, there’s not enough “room” for a string to overlap itself, and in 4D or higher, there’s too much room, and a knotted loop can always “slip free”, returning to a simple circle.) I wonder if the Templeton Foundation will pay me for declaring that the Cosmos is the way it is because Aphrodite likes to get tied up in knots?

(Hah! And you thought I was going to quote a passage from Quarantine, didn’t you?)

More on New Scientist

I felt sort of bad saying all that stuff about Wired when the guy who wrote the piece I did like showed up to say “Thanks for the link.” But hey, I’m not going to stop criticizing bad science reporting, nor can I imagine shutting myself up about the practices which I think cause bad science journalism. (Nor do I have the vanity to think that by myself, I’ll make any difference.) I’d feel considerably more uncomfortable if Greg Egan didn’t go and provide a whole new plateful of reasons to be upset with pop science.

Egan has been masochistically plowing through New Scientist ever since the EmDrive incident, when he had found himself “gobsmacked by the level of scientific illiteracy” the magazine had put on display. Now, commenting at The n-Category Café, he gives two additional recent “absurdities.”
Continue reading More on New Scientist

Dangerous Ideas

I must admit that when I hear somebody talking about “dangerous ideas,” one of my eyebrows will — without voluntary intervention on my part — lift upwards, Spock-style. Such talk invariably reminds me of my old film-studies professor, David Thorburn, who said, paraphrasing the acerbic Gerald Graff, “if the self-preening metaphors of peril, subversion and ideological danger in the literary theorists’ account of their work were taken seriously, their insurance costs would match those for firefighters, Grand Prix drivers and war correspondents.”

Still, when Bee at Backreaction says something is interesting, I take a look. Today’s topic is the Edge annual question for 2006, “What is your Dangerous Idea?” Up goes the eyebrow. I don’t want to go near the Susskind/Greene spat about “anthropic” reasoning; frankly, without technical details far beyond the level of an Edge essay, “anthropic” talk rapidly devolves into inanities which resemble the assertion, “Hitler had to lose the war, because otherwise we wouldn’t be sitting around talking about why Hitler lost the war.” Suffice to say that neither Susskind nor Greene mentions NP-complete problems or proton decay.

So, moving on, let’s get to what Bee calls “the more bizarre pieces.” I was particularly drawn to and repelled from (yeah, it was a weird feeling) the essays of Rupert Sheldrake and Rudy Rucker. The latter goes off about “panpsychism,” which sounds like a fantastic opportunity to ramble about quantum mechanics, the inner lives of seashells and the dictionary of Humpty Dumpty, in which words mean exactly what the speaker wants them to mean, reason and usage notwithstanding.

Hey, “consciousness” is just one tiny part of what living things do, and life is a teensy fraction of what the Universe does. Why not give the rest of the biosphere a little attention and support “panphotosynthesism” instead?
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Egnor, Farrell and Lemaître

I don’t want Science After Sunclipse to become, in Orac’s words, “All Egnor, all the time,” but after my recent intemperate remarks about Egnor’s misguided dualism, I figure I should follow with a link to John Farrell’s rebuttal to Egnor’s cosmology.

Following up on his insistence that science is always seeking to confirm the “design inference,” Egnor says this about Georges Lemaître, the first scientist to conceive of the Horrendous Space Kablooie:

Ironically, we owe much of our modern understanding of the universe to pro-intelligent design astronomers. Georges Lemaître was the astrophysicst who pioneered the Big Bang Theory. Fr. Lemaître (above, with Einstein) was a Belgian Roman Catholic priest, honorary prelate, and a professor of physics and astronomy. He famously described the moment of the Big Bang as “the day without yesterday”, referring to the first day of creation in Genesis, and he was explicit in his belief in the evidence for God’s design in the universe. His Big Bang theory met with considerable opposition because of its religious implications.

Farrell observes, “First, Lemaître was not referring to the day without yesterday as the first day of creation in Genesis. I’m sure it will surprise no one that Mr. Egnor offers no quotes to support his contention.” In fact, Lemaître stated the following at the 1958 Solvay conference:

As far as I can see, such a theory remains entirely outside any metaphysical or religious question. It leaves the materialist free to deny any transcendental Being. He may keep, for the bottom of space-time, the same attitude of mind he has been able to adopt for events occurring in non-singular places in space-time. For the believer, it removes any attempt at familiarity with God, as were Laplace’s chiquenaude or Jean’s finger. It is consonant with the wording of Isaias speaking of the “Hidden God”, hidden even in the beginning of creation. . . . Science has not to surrender in face of the Universe and when Pascal tries to infer the existence of God from the supposed infinitude of Nature, we may think that he is looking in the wrong direction.

Farrell goes on at slightly greater length, but I believe the point has been made.

The Physics of Bronze Age Mythology

Normally, when one sees a book title of the form The Physics of Imaginary Thing X, the implication is that X (Star Trek, superheroes, the Buffyverse, etc.) is being compared to the real world in order to illuminate how the real world works in a fun and memorable way. What would it take for warp drive to work, and how much energy is required to o’erleap a tall building in a single bound? If, as they often are, the movies are horribly wrong, can we use that wrongness to explain what is right?

Plenty of possible titles exist for future works in the same genre, but it looks like Frank Tipler has taken the matzo with his latest:

The Physics of Christianity.
Continue reading The Physics of Bronze Age Mythology

Dark Energy Weirdness

OK, has anybody here heard of Tori Amos? She’s apparently a friend of Neil Gaiman, which is cool, but her Wikipedia article doesn’t cite enough sources for me to figure out what she’s about. Apparently, she’s releasing a music album entitled American Doll Posse; I’d tell you more, but her website requires “the latest flash player.” I did manage to find out that for this album, Amos created five alter egos, four of which are based on Greek goddesses with the fifth being Amos herself. (For the record, the goddesses are Artemis, Persephone, Athena and Aphrodite.) Eris, the patron goddess of the Internet, inspired somebody to write the following on Wikipedia:

On March 23, 2007, toriamos.com released an audio clip from Amos, stating that each of the characters from American Doll Posse has her own online blog. She urged fans to find them, saying “Happy hunting.”

Well, I know where at least one of them is. Pip (Athena) maintains a LiveJournal, on which she writes (this being the point of my odd little story),
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A Quarter of Everything

I have just two quibbles with this New Yorker article on the Large Hadron Collider to which Scott Aaronson directed my attention. First, throughout her informative story, Elizabeth Kolbert consistently abbreviates “Large Hadron Collider” as “L.H.C.” I’ve yet to see anybody in the physics community use the periods when they write “LHC.” Is this some official policy which we, the project’s website and the rest of the Internet just are too lazy to follow? Or are these strange little dots the product of a New Yorker in-house style guide demanding their presence based on some holier-than-Sinai rule about tiny ink specks? If the latter is the case, the foolish prescriptivist responsible needs an introduction to my friend the clue-by-four.

My second and marginally more serious complaint involves the following passage from page five:
Continue reading A Quarter of Everything