Blogs / Cosmic Variance

Welcome to this week’s installment of the From Eternity to Here book club. This week we’re tackling two chapters at once: Chapter Four, “Time is Personal,” and Chapter Five, “Time is Flexible.” That’s just because these chapters are relatively short; next time we’ll return to one chapter per week.

Excerpt:

Starting from a single event in Newtonian spacetime, we were able to define a surface of constant time that spread uniquely throughout the universe, splitting the set of all events into the past and the future (plus “simultaneous” events precisely on the surface). In relativity we can’t do that. Instead, the light cone associated with an event divides spacetime into the past of that event (events inside the past light cone), the future of that event (inside the future light cone), the light cone itself, and a bunch of points outside the light cone that are neither in the past nor the future.

It’s that last bit that really gets people. In our reflexively Newtonian way of thinking about the world, we insist that some far away event either happened in the past, the future, or at the same time as some event on our own world line. In relativity, for spacelike separated events (outside one another’s light cones), the answer is “none of the above.” We could choose to draw some surfaces that sliced through spacetime, and label them “surfaces of constant time,” if we really wanted to. That would be taking advantage of the definition of time as a coordinate on spacetime, as discussed in Chapter One. But the result reflects our personal choice, not a real feature of the universe. In relativity, the concept of “simultaneous faraway events” does not make sense.

These two chapters take on a task that is part of the responsibility of any good book on modern cosmology or gravity: explaining Einstein’s theory of relativity. Both special relativity and general relativity, hence two chapters. In retrospect they are pretty short, so an argument could be made that I should have just combined them into a single chapter.

The special challenge of these chapters is precisely that many readers — but not all — will already have read numerous other popular-level expositions of relativity. But you have to do it. Fortunately, my favorite way of talking about relativity is a little bit different from the standard one, and lines up well with the overarching goal of understanding the meaning of “time.” In particular, I try to make the point that the secret to relativity is to think locally — to compare things happening right next to each other in spacetime, not events that are widely separated. You’re allowed to compare separated events, of course, but the answers are necessarily dependent on arbitrary choices of coordinates, and that leads to endless confusion. So you won’t read a lot about “length contraction” or “time dilation,” but you will read a lot about the actual amount of time measured along a trajectory.

Unfortunately, a search for vivid examples of the maxim “freely-falling paths through spacetime experience the longest amount of proper time” led me directly to the most embarrassing mistake in the book. (At least, “most embarrassing mistake so far uncovered.”) Sordid details below the fold!

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This is an idea that has been bouncing around for a while, but is now apparently seen in experiments: real-world photosynthesis taking advantage of quantum mechanics. (Story in Wired, via @symmetrymag. Here’s the Nature paper on which it’s all based.)

The idea is both simple and awesome: you want to transport energy through an “antenna protein” in a plant cell to the “reaction-center proteins” where it is chemically converted into something useful for the rest of the plant. Obviously you’d like to transport that energy in the most efficient way possible, but you’re in a warm and wet environment where losses are to be expected. But the plants somehow manage the nearly impossible, of sending the energy with nearly perfect efficiency through the judicious use of quantum mechanics.

We can think about this in terms of Feynman’s way of talking about quantum mechanics: rather than a particle taking a unique path between two points, as in classical mechanics, a quantum particle takes every possible path, with simple paths getting a bit more weight than complicated ones. In the case of the protein, different paths for the energy might be more or less efficient at any particular moment, but this bit of quantum trickery allows the energy to find the best possible route at any one time. Imagine at rush hour, if your car could take every possible route from your home to the office, and the time it officially took would be whatever turned out to be the shortest path. How awesome would that be?

The reason you can’t do that is that your car is a giant macroscopic object that can’t really be in two places at once, even though the world is governed by quantum mechanics at a deep level. And the reason for that is decoherence — even if you tried to put your car into a superposition of “take the freeway” and “take the local roads,” it is constantly interacting with the outside world, which “collapses the wave function” and keeps your car looking extremely classical.

Proteins in plants aren’t as big as cars, but they’re still made of a very large number of atoms, and they’re constantly bumping into other molecules around them. That’s why it’s amazing that they can actually maintain quantum coherence long enough to pull off this energy-transport trick. Previous studies had hinted at the possibility, but only by cooling the proteins down and shielding them from external jiggling. This new work happens at room temperature in the context of marine algae, so it seems to indicate that it can happen in real environments.

One step closer to building my teleportation machine. Get to work, quantum engineers!

Super Bowl Sunday is, of course, the great American holiday. Past years have seen inspirational performances by Joe Namath, Joe Montana, and Janet Jackson. This year pits the New Orleans Saints against the Indianapolis Colts. New Orleans, of course, is known as a city of saintly behavior, while Indianapolis’s claim to fame involves horsepower in some tangential way.

When faced with contests of ritualized violence, we like to look for the science. So check out this video of Saints quarterback Drew Brees participating in a rigorous laboratory experiment by throwing the ol’ pigskin at an archery target. Joking aside, that is some pretty sick accuracy there.

Impressive that a human arm beats a bow and arrow for accuracy (although it’s not completely clear that the distances and conditions were perfectly analogous). All in the wobble, apparently. But if I were defending my castle from the barbarian hordes or something, I’d still prefer archers over some guys throwing footballs.

From Eternity to Here addresses the problem of the arrow of time — why is the past different from the future? But Chapter Six is all about time travel, and in particular the interesting version in which you travel backwards in time. Whether it’s possible, what rules it would have to obey, and so on. And now — even though I’m sure there aren’t more than two or three of you out there who haven’t purchased the book already — you can get a sneak peek of part of that chapter. It’s going to be the cover story in the March issue of Discover, and the story is already available online.

And here’s a bit of multimedia bonus: to get the cool exploding-clock image, the intrepid editors worked with Biwa Studios to film high-speed video of exploding clocks, and you can see the whole videos online. They run the events forwards and backwards, just in case your personal arrow of time needs to be calibrated.

One may ask, why is there a chapter about time travel in a book about time’s arrow? Just couldn’t resist the temptation to talk about everything related to “time”? In fact there is a deeper reason. In the real world, the laws of physics may or may not allow for closed timelike curves — physicist-speak for time machines. (Probably not, but we’re not as sure as we could be.) But apart from the difficulty in constructing them, time machines boggle our minds by offering up logical paradoxes — what’s to prevent you from traveling into the past and killing your parents before they met? There is a consistent way to handle these paradoxes, simply by insisting that they never happen. (And we’re still hopeful that the folks at Lost adhere to this principle, regardless of the surface interpretation of last night’s Season Six premiere.)

The reason why that’s hard to swallow is because we can’t imagine anything that stops us from killing our parents, once we grant the existence of time machines. We conceptualize the past and future very differently — the past is settled once and for all, while we can still make choices about what happens in the future. That, of course, is the arrow of time. At the heart of what bothers us about time-travel paradoxes is the difficulty of establishing a uniform arrow of time in a universe where time loops back on itself.

Of course the easy, and probably correct, way out is to simply believe that time machines don’t and can’t exist. But disentangling the demands of logic from the demands of common sense is always a rewarding exercise in its own right.

Every year, not long after the state of the union address, the administration unveils its budget request to Congress. Then comes the long authorization and appropriations process; in an election year I’d bet that they try hard to have it done before November. The Obama administration’s request came out yesterday, and so it’s time to take a look at how science may fare next year.

Jeffrey Mervis at ScienceInsider over at the AAAS has a nice article summarizing the general picture for science in the budget, including an 8% increase for the National Science Foundation and a smaller 3% boost to the National Institutes of Health. The Office of Science and Technology Policy (headed by the president’s science advisor) has a set of fact sheets on science policy. Check out the one on doubling the science budget – the administration is on track for doing just that by 2017. Will Congress support that?

But, being funded by it, I always start first with the DOE Office of Science. The DOE has a summary document with budget highlights; for the Office of Science the most succinct table shows the breakdown by program and year (click on it for a bigger version):

Overall, the OS is looking at a 4.4% increase over FY2009, not including the stimulus bump in 2009, listed in the column called “recovery”. In a year when the administration wants to freeze discretionary spending, that is not bad for science. It’s clearly coming from savings elsewhere, meaning someone’s program got cut, and those people (and their congressional representatives) will be fighting like crazy to restore it.

Within the OS there are winners and losers as well. Basic Energy Sciences, which covers a host of research in condensed matter including nanotechnology, materials, and multipurpose facilities such as the large light sources, gets the lion’s share of the OS budget, and are slated for a 12% increase. I think this reflects the administration’s desire to foster research in areas that could lead in the near to medium term to new sources of energy. That increase, though, along with increases for advanced computing and bio/environment research, has to come from the other programs in OS, and it appears that fusion energy (-10%) and a line titled “Congressionally Directed Projects” . Now what on earth is that?

Now, I am not a Washington insider by any means, but I don’t recall seeing that designation explicitly in the tables before. I believe, though, that it means projects funded through Congressional earmarks. Are all earmark-funded projects being killed? It certainly appears so…

Within my own field the tea leaves say that the administration is requesting that the Tevatron remain in operation through 2011, support participation in the LHC and work on future upgrades to the experiments, and begin to develop the next big project at Fermilab, so-called “Project X” (which deserves a post all by itself some day). Project X will deliver an ultra-intense beam of protons for neutrino and rare decay experiments, including the Long Baseline Neutrino Experiment proposed for the Deep Underground Science and Engineering Laboratory (DUSEL) in the Homestake Mine in Lead, South Dakota. There is also a substantial appropriation for the Dark Energy Survey; Fermilab is building the camera.

So begins the 2011 budget cycle.

Welcome to this week’s installment of the From Eternity to Here book club. Next up is Chapter Three: “The Beginning and End of Time.” Remember that next week we’re doing two chapters at once, Four and Five.

For those who missed them, here’s the Science Friday discussion, and here’s the Firedoglake book salon with Chad. I should also point to some substantive review/discussions: Wall Street Journal, New Scientist, USA Today, and Overcoming Bias.

Excerpt:

For the most part, people interested in statistical mechanics care about experimental situations in laboratories or kitchens here on Earth. In an experiment, we can control the conditions before us; in particular, we can arrange systems so that the entropy is much lower than it could be, and watch what happens. You don’t need to know anything about cosmology and the wider universe to understand how that works.

But our aims are more grandiose. The arrow of time is much more than a feature of some particular laboratory experiments; it’s a feature of the entire world around us. Conventional statistical mechanics can account for why it’s easy to turn an egg into an omelet, but hard to turn an omelet into an egg. What it can’t account for is why, when we open our refrigerator, we are able to find an egg in the first place. Why are we surrounded by exquisitely ordered objects such as eggs and pianos and science books, rather than by featureless chaos?

This chapter is a fairly straightforward review of the modern understanding of cosmology, with a particular eye on those issues that will become important later in the book. We zip through the expansion, structure formation, and dark energy. There I got to tell a fun personal story of my wager with Brian Schmidt. At least I think it’s fun — including personal stories is not my natural tendency, but at the right moments it can help to humanize all the forbidding science. Hopefully this was one such moment.

A few topics go beyond the standard cosmology summary. I discussed the Steady State theory a bit, because it’s a relevant historical example when we will much later turn to the question of what the universe should look like. I also dwell a bit on vacuum fluctuations and dark energy, because those will pay a crucial role in my personal favorite explanation for the arrow of time. And we close the chapter with a very brief overview of the evolution of entropy. It has to be brief, because we haven’t laid nearly enough groundwork to do the job right. This is a conscious choice, which may or may not work: rather than simply progressing on an absolutely logical path from foundations to conclusions, I felt free to mention points that would be important later, on the theory that they would come as less of a shock if we had established some familiarity. Again, hope that worked.

Tom Levenson, who is an actual writer, advised me to omit “smoking a pipe” from the caption to Figure 7, on the theory that what is shown should not also be told. I left it in anyway. It’s my book!

Last week in Aspen we learned that this week would be when a major decision was reached by CERN at the annual Chamonix meeting as to how to operate the LHC at high energy. Following the magnet quench incident in September 2008, a year-long shutdown ensued for repairs to the magnets, and retrofitting of the rest of the machine for better quench protection circuitry and helium pressure release valves. Not all sectors were warmed up to room temperature for the retrofit last year, but all magnets were trained to go as high as beam energies of 5 TeV (design energy is 7 TeV per beam).

In November and December the LHC commissioning resumed, and it became the world’s highest energy collider on December 8, eventually delivering about 50,000 collisions at 2.36 TeV to CMS and ATLAS before shutting down for Christmas.

But the question facing the LHC managers this week was whether attempting to operate the LHC at 5 TeV on 5 TeV in 2010 was worth the risk to the machine itself. Clearly another disaster of the scale of the one in 2008 would cripple the program for a long time. In the end the decision is to operate the LHC at 3.5 TeV on 3.5 TeV (7 TeV collision energy, 3.5 times that of the Tevatron) and accumulate a substantial amount of physics-quality data: 1 inverse femtobarn, or stop by the end f 2011, whichever comes first. This corresponds to something like ten trillion proton-proton collisions, of which only a small fraction will yield events interesting enough to record for later analysis by the experiments, and of these, only a tiny fraction yielding data relevant for physics.

After a one to one-and-a-half year shutdown in 2012 to retrofit the rest of the machine and make other preparations, the LHC will attempt to double the energy, to 14 TeV in the center of mass, in 2013 and accumulate substantial physics data. My best guess is that if the Higgs boson is to be discovered, it will be at high energy with this large sample of 14 TeV data. We might be able to rule it out at 95% confidence in certain mass ranges if it’s not there, but we ought not be able to do that if it is, right? Patience, patience!

Nevertheless, there is no question that in a few weeks, when operated at 7 TeV collision energy, the LHC will become an awesome discovery machine. There are many new physics scenarios in which we will be able to see new phenomena with just a fraction of the full 1 fb^-1 sample. Will nature give up her secrets so readily though? She may not – we may spend this year and the next rediscovering the Standard Model, building up understanding of the detector, and sharpening our analysis tools in order to discover quite subtle effects. No matter what happens, this is the most exciting time in particle physics in decades.

Update: Totally snookered. Via Kieran Healy, the disappointing news that the Habermas account is fake. Yet more evidence that the internet is less than an ideal speech situation.

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I’m not the only person to find it endlessly amusing that Jürgen Habermas, octogenarian theorist of communicative rationality, has taken to Twitter. (The account seems to be legit, but it’s hard to be sure.) This is so over-determined that just last year Lauren Fisher gave a presentation entitled “If Habermas could Twitter.” Well, now we know.

He’s still trying to master the 140-character limit, though. Here’s his latest set of tweets:

Well, yeah. The internet is (in some sense) an egalitarian public sphere, but it raises the danger of fragmentation into self-reinforcing interest groups. Remains to be seen how it will all ultimately play out.

Like any good author, one of my duties is taking to the airwaves to flog my book. A list of upcoming events can be found at Booktour.com, and of course you can always subscribe to the Facebook page or Twitter feed. But I wanted to highlight some stuff coming up over the next two weeks:

• Friday January 29, 12:30 p.m. Pacific: I’ll be appearing on NPR’s Science Friday with Ira Flatow. (That’s today/tomorrow, depending on when you’re reading this.) Listen online, or via your favorite public radio station.
• Saturday January 30, 2:00 p.m. Pacific: From Eternity to Here will be the subject of a Firedoglake Book Salon. I’ll be answering questions online, and our host will be none other than Chad Orzel, who has a book of his own you should check out.
• Saturday February 6, 10:00 a.m. Pacific: Crank up your avatars, I’m giving a talk in Second Life. (And if you don’t already have an avatar, it’s easy to get one. And you can shop for clothes!) Sponsored by MICA, it will be held at the large amphitheater on StellaNova.
• Saturday February 6, 5:00 p.m. Pacific: For everyone here in Los Angeles and environs, I’m doing a good old-fashioned book reading/signing at Skylight Books, an awesome independent bookstore in Los Feliz. 5:00 on Saturday night — what better way to kick off the evening’s festivities?

Hope to see you there, virtually or in person!

Fans of the hit TV series Lost are awaiting the big event next week: the premiere of Season Six on Tuesday night. The show is famous for its mysteries and plot twists, so this year has a special status: it’s the final season, where everything that’s going to be revealed will be revealed. That might not be absolutely everything, but it should be a lot.

Lost has always played with time and narrative — characters’ backstories were told through elaborate flashbacks, lending a richness of nuance to their behavior in the main story. But time travel as a plot device was established as a central theme during Season Five. One happy consequence was the invention of Lost University, through which fans could learn a little about physics and other real-world subjects underlying events in the show.

Naturally, scientifically-minded folks want to know: how respectable is the treatment of time travel, anyway? We are, as always, here to help. My short take: Lost is a TV fantasy, not a documentary, and it doesn’t try all that hard to conform to general relativity or the other known laws of physics. But happily, the most important of the Rules for Time Travelers is very much obeyed: there are no paradoxes. And more interestingly, the spirit of the rules is obeyed, and indeed put to good narrative effect. The potential for time-travel paradoxes helps illuminate issues of free will vs. predestination, a central theme of the show. And what more can you ask for in a time-travel story than that?

Details below the fold, full of spoilers. (Not for the upcoming season, of course.) See also discussions from io9, Popular Mechanics, and Sheril.

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