January 2008

I went to see Lawrence Krauss‘s lecture at the National Academy of Sciences last Thursday night (a Smithsonian Associates lecture). He actually gave two talks, with questions and a break in-between. Professor Krauss is a very engaging speaker, and I quite enjoyed the evening. As usual I videotaped the lecture (this proved useful as I didn’t have to take notes; upon viewing again over the weekend a lot more was able to sink in).

After the talk he signed books (picture at left is Prof. Krauss inscribing my copy of Hiding in the Mirror). He thanked me again for taking and letting Scientific American use pictures from a previous lecture.

I will attempt to summarize the lecture(s):

Part One: “Our Miserable Future” dealt with the sobering thought that the universe will eventually end. Probably. Really.

A major part of cosmology in the 20th century involved trying to determine the geometry of the universe. It is either Closed, Open, or Flat. An Open universe will basically expand forever, while a Closed universe will stop expanding and eventually collapse back in on itself. A Flat universe is right on the border between the two – the expansion will slow over time, but never quite stop.

So, how much “stuff” is there in the universe? Is there enough to make it stop expanding? One way of determining the amount of matter present is via an effect called gravitational lensing. If you look at a certain cluster of galaxies some 2Gly (billion light years) away, you can also detect what turn out to be multiple images of another cluster some 2 Gly behind it. The multiple images form due to gravity from the nearer cluster acting like a lens on the light from the farther one. You can do the math to determine how much matter must be in the nearer cluster to get this effect. It turns out that most of the required matter is not visible – hence, “Dark Matter“.

Based on such indirect evidence, it appears that within 95% certainty there is only about 30% of the amount of matter needed to stop an expansion. So, we are in an Open universe.

But, studies used to measure the geometry of the universe directly (via the Cosmic Microwave Background) show that the universe is actually Flat. How do you reconcile these two very different observations? Well, that’s where “Dark Energy” comes in. We only detect about 30 percent of the mass needed to be a Flat universe (via lensing, etc.) so how to we make up the other 70%? We put energy in empty space. This Dark Energy (in empty space) is gravitationally repulsive.

Scientists looked at the light from a bunch of bright supernovae, and found they were accelerating away from us. Doing the math, they calculated how much energy they have to have in empty space to be “repulsing” the supernovae away from us. It was exactly the needed 70%.

So, the Universe is:

  • 70% Dark Energy
  • 25% Dark Matter
  • 5% The rest (galaxies, stars, planets, humans).

In other words, we are truly insignificant in the universe. :) Also, the nature of Dark Energy will ultimately determine the fate of the universe. That’s the rub – we have no idea what this “Dark Energy” actually is.

The rest of the first part dealt with the concept that a lot of the universe has already disappeared to us, i.e., objects we could have seen 5 billion years ago have already accelerated (and thus redshifted) away from us to such an extent that we can’t detect them. Finally Professor Krauss talked about the ability (or lack thereof) of life (as consciousness) to live forever in an expanding universe:

If Quantum Mechanics ultimately governs a universe starved of energy consciousness will end for any eternally expanding universe. We need Infinite time to determine the Ultimate fate of the universe (and the future of life within it), but we only have a Finite time left.

Part Two of the lecture primarily dealt with the Anthropic Principle, which basically states that the only universe we can see is the one that supports life. In other words the universe is the way it is because we are here. This in a nutshell attempts to answer questions such as:

  • Why are we (life) happening just *now* in the timeline of the universe, when the density of matter just happens to be about 30% of the energy density of empty space?
  • Why is gravity the weakest force in nature?
  • Why is a proton 2000 times heavier than an electron?
  • Why are there 3 generations of elementary particles?


Because if any of these were different, life would not exist (to observe it).

Supposedly String theorists are particularly enamored of this idea, with their “string landscape” that postulates something like 10^500 different universes. One of them is bound to be this one.

Professor Krauss lists some fundamental Anthropic Problems:

  • It is an idea based on ignorance (“We don’t know why”).
  • You never know which variables are anthropically selected.
  • It is never compelling, only suggestive, and
  • It has been wrong before.

This is the story of the Archimedes palimpsest (hidden writing). Basically, a medieval prayer book was created by taking parchment from several ancient codices (books), scraping off the old text and re-using the parchment to create a new book. One of these ancient manuscripts happened to be a copy (the earliest surviving) of Archimedes Codex C.

The old prayer book/palimpsest was purchased in 1998 at auction for $2 million. The new owner entrusted William Noel, the curator of the Walters Museum in Baltimore with the book in order to unlock it’s secrets. Reviel Netz is a Stanford University classicist, and the two alternate chapters.

I was more interested in the technology used to uncover the Archimedes text than in the text itself. However, the majority of the book concerns the text itself and how it contributes to our understanding of Greek mathematics (geometry, combinatorics, etc.). Turns out that at some point in the last 100 years 4 forged religious paintings were added to the manuscript. These made deciphering the underlying text on these pages especially difficult. Only the last 20 pages or so of this book deals with how they got past this – via high-powered X-rays. This is what initially caught my attention: they used one of the beamlines at the Stanford Linear Accelerator Center (SLAC) to do X-ray absorption studies on the manuscript. This revealed the hidden text via the Fe (iron) in the original Archimedes text’s ink.

In a previous life I actually did some experiments at SLAC using one of the high energy X-ray beam lines [1].

I think Noel is either being tongue-in-cheek (I hope so) or else is actually a new-earth creationist. At one point while discussing parchment (made from sheep skin) he says that sheep skin evolved “or was intelligently designed” with more antibiotic properties on the side facing the outside. In another passage, when discussing dates found in the codex, he says the dates as written were from the “origin of the earth” which “as everyone knows was ~5500 BC”. Again, I hope he was being tongue-in-cheek and doesn’t really believe that the earth is 7,000 years old! But that’s a minor nit and doesn’t detract from the book.

Interestingly (and sadly), as described in the book, most of the damage and deterioration of the Palimpsest took place not in the distant past, but in the 20th century. The book today is very mold damaged, brittle, and some of the pages are actually glued(!) together at the binding. This hinders reading of the underlying text, to say the least.

[1] Biochemistry 35: 12241-12250 (1996)
Structural Investigations on the Coordination Environment of the Active-Site Copper Centers of Recombinant Bifunctional Peptidylglycine alpha-Amidating Enzyme
John S. Boswell, Brian J. Reedy, Raviraj Kulathila, David Merkler, and Ninian J. Blackburn

Sun of SunsThis is book one of Virga. The story takes place inside a planetoid-sized balloon world called Virga. We don’t know much about the outside, but inside Virga is a world of wooden “ships” and swordfights. Some tech does remain (the “suns” are small fusion reactors that give off light for simulated daylight) but most of the story involves intrigue and “naval” battles. Since the people are inside a sphere, there is no gravity unless they create some by spinning their habitats.

Hayden Griffin is a main character, from the nation of Aerie. He is orphaned when Aerie is attacked and taken over by the neighboring nation of Slipstream. Keep in mind that nations are more like city-states, and consist of various wooden habitats all strung together (usually around one of the artificial suns). They all free-float in the world of Virga, and so their absolute position within Virga changes. Hayden’s parents had been trying to build an artificial sun for Aerie when they were attacked. Hayden grows up, and has only revenge on his mind – to kill Admiral Chaison Fanning, who led the expedition that killed his parents.

Venera is the admiral’s scheming wife, and throws a spanner into Hayden’s plans. Eventually Hayden gets a job as Venera’s driver, and they both travel on the admiral’s ship, Rook. Lots of adventures ensue. This is a fun read, once you accept the premise of a balloon world with wooden ships (and just where does all this wood come from?). It would be interesting to learn more about the outside world, but perhaps in a sequel (which is already out). One of the characters – a beautiful armorer, Aubrie – is from the outside. She has made a deal with the admiral to help him with his plan to defeat a neighboring state that is about to invade.

I didn’t particularly like the ending, but then, I’m more of a romantic. I’m not rushing out to read the sequel, but it is in my queue, so I’ll get to it someday.