Fig. 1: A hydrogen atom consists of a tiny proton “orbited” by an electron.
There’s been a lot of reporting recently on a puzzle in particle physics that I haven’t previously written about. There have been two attempts, a preliminary one in 2010 and a more detailed one reported just this month, to measure the size of a proton by studying the properties of an exotic atom, called “muonic hydrogen”. Similar to hydrogen, which consists of a proton orbited by an electron (Figure 1), this atom consists of a proton and a short-lived heavy cousin of the electron, called the muon (Figure 2). A muon, as far as we have ever been able to tell, is just like an electron in all respects except that it is heavier; more precisely, the electromagnetic force and the strong and weak nuclear force treat electrons and muons in exactly the same way. Only the first two of these forces should play a role in atoms (and neither gravity nor any force due to the Higgs field should matter either). So because we have confirmed our understanding of ordinary hydrogen with very high precision, we believe we also understand muonic hydrogen very well also. But something’s amiss. (more…)
The meaning of the title of Clara Moskowitz’s new article for the public, “Dark Matter Mystery May Soon Be Solved“, all lies in the word “may”. It may. It may not.
According to the article, “the answer to this cosmic mystery could come within the next three or four years, scientists say.”
I have to admit that this kind of phraseology, which one often sees in the press in reports about science, drives me a bit nuts. Which scientists? How many of them? You can’t tell from this line whether this is something that a group of three or four mavericks are claiming, or whether it is conventional wisdom shared by most of the community. And “the answer… could come…”? Interpreted literally it is content-free: yes, the answer could come in the next few years, or not — but you don’t need any scientists to tell you that. If one interprets it more optimistically — that it is intended to imply that the answer will very likelycome within the next three or four years — then I think it is far from clear what fraction of the experts will agree with that statement.
Rather than debate the claim, let’s start with the physics. What will determine how long it takes to discover what dark matter is made from? (more…)
Just ask the Nobel Prize committee: is quantum physics some sort of speculative new science? (A smart educated woman asked me, just a week ago, `What do you think about that quantum physics stuff?’, as though it were in the same category as theories of consciousness, speculations about the origin of life, and string theory.) No way: it’s all over your computers and cell phones; it’s in many modern light bulbs; it’s the laser that reads the prices at the grocery store and your ticket at a concert; it’s the heart of the best timepieces and the eyes of the best microscopes; it’s what makes solids solid and liquids flow, and powers chemical reactions and radioactivity; it’s probably playing a big role in biology that we’re just starting to understand; and it’s sunshine and moonlight and the glowing auroras borealis and australis. It’s the foundation and fabric of your world.
And though it may be bizarre, it is by no means abstract. Maybe in the early 1930s one could still say it was abstract; but already for many decades particle physicists have passively observed individual particles, one at a time, behaving in quantum mechanical ways. Today scientists can control individual quantum objects, things whose behavior can only be predicted by accepting the odd rules and counter-intuitive implications of our quantum world. In particular, physicists have learned to capture and manipulate individual photons (particles of light), atoms, and ions (atoms with an electron removed or added, to make them electrically charged — see the Figure below.) It is for their work advancing these capabilities, making possible new classes of experiments and opening up the potential for new technologies, that Serge Haroche and David Wineland have won the Nobel Prize for 2012. Read about it here (brief press release or summary for non-technical readers)… using your preferred quantum-mechanical device.
Light emitted from three individual ions of Beryllium, trapped and held in place for an extended period of time. (National Institute of Standards and Technology image gallery.)
The promised follow-up article on the workshop last week in Waterloo, Canada will have to wait til Monday; I had too many scientific activities and chores to take care of today, and I want to make sure the article, which is a bit complicated, is nevertheless clear. But in the meantime, let’s celebrate Martian Curiosity!
First, a big congratulations to the NASA folks! Very impressive, and fantastically cool. I was a huge fan of the Spirit and Opportunity rovers, especially of their 3D photography. Looking at those photos on a big screen, through red/green 3D glasses. brought me to sweeping Martian vistas and deep Martian craters — as vivid and as close as I’ll ever see them. It was amazing stuff, and I look forward to more from the new rover.
Professor Richard Muller of UC Berkeley isn’t the first scientist to be converted to the idea that humans are causing a change in the climate through carbon dioxide emissions. Nor is he, by a long shot, the most expert among them. But he’s one of the most famous, now, because he was also a loud skeptic not long in the past. He’s described the reasons for his conversion, based on a scientific study that he organized and helped lead, in a recent op-ed post in the New York Times. It’s a little self-serving at best, but makes for interesting reading. (more…)
A distant topic, yet not distant at all. Science, as a process, creates trustworthy knowledge; it has proven this over and over, and much of our economy is based upon it. But scientists? As individuals, they are just as human as anyone else: they make mistakes, harbor biases, believe things without much evidence, overstate their cases, and do all sorts of problematic things. Some are a lot more reliable than others, and often the unreliable ones are the ones who take their scientific case to the media (the reliable ones often not seeing the need to do so). Consequently, media stories on science are on average somewhat less reliable than the ones scientists produce and read.
Multiple arguments against the arsenic-incorporating bacterium result have been made from the beginning. Now two new papers (#1, #2) have hit Science magazine, and the press. Both argue (among other things) that the bacterium in question is still dependent on phosphorous and that there is no sign of arsenic in its DNA.
Which is all to say that reproducibility lies at the core of scientific research. It is the process of confirmation and cross-checking of a result that allows a media story that begins “Scientists say…” to be transformed into a textbook that begins “Science says…” When you read a story in the press, you should always look for the key indications that multiple and separate groups of scientists agree on the result — not necessarily that there is broad consensus, but at least that the scientists making the claim aren’t entirely out on their own. [For the recent discovery of the Higgs particle, we have two different experiments making the claim.] If those indications are missing, I’d advise you to file the result under “unconfirmed,” and not to bet on it.
[UPDATE: in the comments below, Dennis Overbye (the article’s author) explains what his wording was intended to imply, and that his article contains no error, just wording that was perhaps a little too simple. I have also replied, with a request for much greater clarity in future, and explaining why I feel this is such an important issue.]
Although a lot of the article is pretty good (though I can’t vouch for its accuracy in describing what’s going on inside the experiments) it does contain a HUGE conceptual and factual error that is vastly misleading. [According to the author Dennis Overbye, this is not an error, but phraseology that is perhaps not entirely clear; see his comment below.] Here’s what it says about the Higgs particle:
“The new data will show whether [the hint in the December data] was a fluke or whether they are really on the road to discovering the long-lost [Higgs] boson, physicists say. They are racing to make a deadline to report the results at the International Conference on High Energy Physics, or Ichep, in Melbourne, Australia, starting July 4.
This, all agree, is the boson’s last stand. If the December signal fades, it probably means that the Higgs boson, at least as physicists have envisioned it for the past 40 years, does not exist, and that theorists have to go back to their drawing boards.”
This is misinformation — completely wrong — and in the interest of its readers, I do hope the Times would publish a correction. [Again, I refer you to Overbye’s comment.]
This is NOT “the boson’s last stand”, and NOBODY agrees that it is the case. What everyone agrees (with one caveat about heavier Higgs particles that actually haven’t been ruled out yet) is that it is the last stand of the Standard Model Higgs particle. The Standard Model Higgs particle is only the SIMPLEST possible type of Higgs particle. Read about this form of Higgs particle here, if you like.
Let me say that again. There is a big difference between ruling out the Standard Model Higgs particle and ruling out all possible forms of the Higgs particle.
Not finding the Standard Model Higgs particle — in Phase 1 of the Higgs search — just means that Phase 2 of the Higgs search has to involve a wider set of search strategies. The two phases of the Higgs search was one of the main topics of my Cosmic Variance guest-post article and of this slightly more detailed article (both articles a bit out of date now as far as the data, but the basic point about the two phases still holds). And in fact I pointed out in a related article, linking to some scientific lectures I gave on the topic, that it will take ten years to be confident there is no Higgs particle of any type. I’m not telling you anything radical; ask any theorist in the field who has worked on Higgs physics and they will tell you the same thing.
So to say that “theorists will have to go back to their drawing boards” if the Higgs does not show up by December 2012 is badly mistaken. There are hundreds of theory papers, going back decades, on versions of the Higgs particle (or particles) that would not show up by December 2012. Here are some examples of such papers by well-known authors: http://arxiv.org/abs/hep-ph/0009158 ; http://arxiv.org/abs/hep-ph/0608310 ; http://arxiv.org/abs/1012.1316; there are plenty of such papers from the 1990s and even the 1980s. Heck, I even wrote some myself.
One other minor error, caused by out-of-date information: the discrepancy between the masses of the possible Higgs signal seen at ATLAS and at CMS (which made the statistical combination of the two data sets unstable to small shifts) did indeed shift when the CMS data was reanalyzed in March. The shift went in the “right direction”, eliminating the discrepancy and increasing confidence in the consistency of the ATLAS and CMS results. On the other hand, the significance of the signal seen at ATLAS and CMS went down in March, too. A complicated story; but these details won’t matter in the long run.
Of course, all of this may be moot, if more evidence for the Higgs shows up at the ICHEP conference in July. But please, NY Times, get your facts straight on this very important point, which lies at the heart of the LHC program! No discovery of the Higgs particle in 2012 absolutely will not mean that we know there is no Higgs particle at all. It just means we would give up on the simplest version of the Higgs (which would be great news!), and that the Higgs search would move on to Phase 2.
Simplified diagram of how the Higgs search proceeds at the LHC; 2012 will be the transition point between Phase 1 and possible branches of Phase 2.
First, I’m participating in a panel discussion today (Thursday June 7th) on the transition that has seen me add science writer and popularizer to my resume’. Here’s the link… free tickets required, click here for details and tickets. Sponsored by SoNYC (Science online New York City), panel discussion entitled “Reaching out of the Ivory Tower”, about the experiences of scientists who are reaching out to the public. Panelists: Ethan Perlstein, Sarah Weisberg, Matt Strassler, Jeanne Garbarino. Location and time: Weiss 305, Rockefeller University, East 66th and York Ave. New York, NY, 7:00 PM. Presenting science to the public in a digestible but honest form is something I feel is important, and I’ll have a few words to say about why I chose to do it now and why via a website and blog. And then I guess the floor will be open to questions, so come on by and ask one!
Reminder: again in New York, Saturday June 16th at 2pm, I’ll be giving a lecture (click here for details): THE EINSTEIN OBSESSION: SCIENCE, MYTH AND PUBLIC PERCEPTION.
Next: I hope you all enjoyed seeing Venus in transit across the Sun Tuesday, in whatever method you chose. If you missed it live, there are of course opportunities to see films of the event — and they’ll save you time, since they’re all speeded up so that the hours pass in a minute or so. Nice views of Venus are complemented by several good-sized sunspots that are roughly the size of the Earth. Venus, you may recall, is the same size as the Earth, but as it was only a third as far away as the Sun yesterday, it appeared three times larger in radius (10 times larger in surface radius) than those sunspots. I managed to see it with the naked eye (with eclipse glasses), but just barely… so tiny! (By the way, if you missed my article on how a transit of Venus was used to obtain the first high-precision measurement of the distance to the sun, here’s the link.)
Here’s one of my own best shots, which I show you not because you can’t find better shots on the internet but because I have learned that most people do not realize you can get such nice views of the sun with so little work.
Venus in transit, at bottom. Several sunspots dot the central region of the sun’s disk. Photo of projection through binoculars onto white screen. Image has been darkened slightly to sharpen contrast between sun and background. Photo: M. Strassler 2012, all rights reserved.
It’s really quite easy. And though there won’t be any more transits of Venus for us to see, there will be bigger sunspots, transits of Mercury, and solar eclipses to watch over the coming 15 years, so you may as well learn how to do this. You just aim the binoculars, big side toward the sun (as though someone were going to look at the sun — BUT DON’T LET ANYONE LOOK, of course), in the rough direction of the sun, wiggle the binoculars until the shadow of the binoculars becomes as small as it possibly can (which tells you they are aligned with the sun) and at that point the sun will shine through the two sides of the binoculars, giving you two images. Put a lens cover on one of the sides if you want to just get one image. Then let the image project onto something white and smooth that can serve as a screen. By moving the screen forward or back you can get a larger or smaller image; by using the focus on the binoculars you can bring the image of the sun into focus. Works great!
Here’s a picture, taken in a similar way, from the annular eclipse last month — a transit of the moon, even though we don’t usually call it that — taken the same way. I like this shot (though focus is imperfect and it was taken from a funny angle) because where the moon’s shadow touches the sun’s limb you can see a bit of light shining between mountain ranges on the moon!
A few seconds before annularity begins during the annular eclipse of the sun on May 20, 2012. Note, in the region where the moon’s silhouette touches the sun’s limb, a patch of sunlight shining through the mountain ranges on the moon. Light and dark regions at left and right of photo are due to shadows on the projection screen. Photo: M. Strassler 2012, all rights reserved.
Venus, passing between the Sun and the Earth on Tuesday, has now transitioned from an object in the evening sky to one in the morning sky; if you want to see it, large and a very thin crescent through binoculars, you’ll need to get up early, before sunrise. Not yet, though; it will be a few days before Venus is far enough from the Sun to pick out in the dawn sky. For now, you can see Venus via the SOHO satellite, which blots out the sun so what’s nearby can be observed.
A final transition: Ray Bradbury died. Bradbury was one of the 20th century’s great science fiction writers, and I especially enjoyed reading his stories because he didn’t write classic geeky science fiction. His work was much more thoughtful and human than that. I think one could make a case that what made his writing unique was that he didn’t separate science from the rest of life. It’s a good example for the rest of us to follow.
Two interesting claims about dark matter this week, and on the face of it, completely contradictory, but in fact, not obviously so. Before saying one word more, let me repeat my mantra — something that all physicists know but relatively few non-scientists appreciate — most claims of a radical new result turn out to be largely or completely wrong. This is not because physicists are stupid but because doing science at the forefront of knowledge involves using novel techniques that might have unknown pitfalls, and also because a single small mistake can create a fake effect (as we saw most recently with the OPERA neutrino speed measurement.) And because nasty statistical accidents can play tricks on you.
Both claims that I’m about to describe use novel techniques, and their analyses have not been repeated by anyone else. At this point you should understand that both are tentative, and (based on the history of radical claims) the odds are against them. Both might be wrong. That said, both analyses look to me as though they’ve been reasonably well done, and if a mistake has been made, it will require someone far more expert in dark matter studies than I am to point it out.
So let me describe them in turn, to the best of my ability. (more…)
Now, with this backdrop, I would like to ask YOU a question or two. And by “you”, I mean non-scientists. I would like to know how seeing this episode unfold changed (or did not change) your view of science, or physics, or particle physics. Or of science journalism. What’s your perspective on all of this? What surprised you most? What annoyed you or turned you off or excited you? Are you disappointed in or pleased with the scientific process as you saw it unfold? Are you more suspicious of or less suspicious of scientists and/or of science now that you’ve seen this happen? I think these are things that many scientists would be curious to learn.
Granted, since you’re reading this blog, you’re a member of a non-representative sample of the public. But I still think it would be useful to hear what you have to say. So, please. Comment.
