Physics
esiegel | September 18, 2013"A cosmic mystery of immense proportions, once seemingly on the verge of solution, has deepened and left astronomers and astrophysicists more baffled than ever. The crux ... is that the vast majority of the mass of the universe seems to be missing." -William J. Broad
It was in the 1930s, looking at dense clusters of galaxies (like Coma, below), that Fritz Zwicky first noticed that the mass in the Universe didn't add up.
Image credit: Adam Block / Mount Lemmon SkyCenter / University of Arizona.
We knew how gravity worked, so it was pretty straightforward -- based on how the galaxies within…
drorzel | September 18, 2013One of the chapters of the book-in-progress talks about neutrino detection, drawing heavily on a forthcoming book I was sent for blurb/review purposes (about which more later). One of the little quirks of the book is that the author regularly referred to physicists trying to "trap" neutrinos. It took me a while to realize that he just meant "detect"-- coming from the AMO community, I naturally assume that "trap" means "localize to a small-ish region of space for a long-ish period of time." That is, after all, what I spent my Ph.D. work doing-- trapping cold atoms.
SteelyKid had a rough…
drorzel | September 17, 2013Element: Ytterbium (Yb)
Atomic Number: 70
Mass: Seven "stable" isotopes, from 168 to 176 amu. Two of those are nominally radioactive, with half-lives vastly in excess of the age of the universe.
Laser cooling wavelength: 399 nm and 556 nm.
Doppler cooling limit: 690 μK in the UV and 4.4 μK in the green.
Chemical classification: A rare earth/ lanthanide, one of the hard to distinguish metals in the little island that floats off toward the bottom of the usual presentation of the periodic table, because it's too hard to wedge them in between barium and hafnium. Yet another greyish metal.
Other…
drorzel | September 13, 2013I've finished a first pass through all the regular chapters of the book-in-progress (in addition to those in in this progress report, there's one more in Section 1 about antiques, and three more in Section 4, two about statistics and one about teamwork). I'm starting to do section-level proofreading, looking at blocks of chapters together.
This isn't a step I had to go through with my previous books, for several reasons. One is just that the smaller set of responsibilities I had then made it easier to find contiguous blocks of writing time-- SteelyKid was born after book 1, and The Pip after…
drorzel | September 12, 2013Over at NPR, Adam Frank has an ode to the use of chalk for teaching science, including a bit of warm fuzzy nostalgia:
I have powerful memories of tracking through derivations presented in class when I was a student. When done well, they pinned my attention down. The act of copying what was appearing on the board was a kind of meditation. You had to stay awake and aware, like a man walking across a frozen pond. Let your mind wander for a moment and BAM! You were lost. You couldn't see how the professor had gotten from one step to the next. But keep your focus and you'd be rewarded with that…
esiegel | September 11, 2013"Like all animals, human beings have always taken what they want from nature. But we are the rogue species. We are unique in our ability to use resources on a scale and at a speed that our fellow species can't." -Edward Burtynsky
It's really a romantic notion when you think about it: the heavens, the Milky Way, is lined with hundreds of billions of stars, each with their own unique and varied solar systems.
Image credit: 湖北直行便 of AstroArts, via http://www.astroarts.jp/photo-gallery/photo/13870.html.
But beyond that -- in addition to the stars -- there are hundreds of billions of planets…
drorzel | September 10, 2013A couple of months back, TED put out a call for auditions for a chance to speak at one of their events. They asked for a one-minute video, and I said "What the hell, I can do that. I need an 'elevator pitch' version of the book-in-progress anyway." This is the result:
So, if you've got a couple of minutes to spare (one minute for the video, plus the better part of a minute for miscellaneous buffering/ network nonsense), check it out. That's as compact a statement of the core argument as I have.
And it was apparently pretty good, because now I get to put together a six-minute version to do…
drorzel | September 9, 2013While I was away for the weekend, intending to mostly ignore the Internet, Steve Maier tweeted:
#FantasyFootball ?
What if #FantasyPhysics existed--who would be your picks?
This, of course, ended up sucking up a huge amount of mental energy for the rest of the weekend, because it's such perfect blog fodder. If I'd had a laptop with me, I might've ended up staying up late writing it up, but instead, I'm skipping the second half of a horror-show game between my Giants and the hated Cowboys to write it on Sunday night...
So. Fantasy physics. For those not up on their pop culture, this is a…
esiegel | September 6, 2013"Education is an admirable thing, but it is well to remember from time to time that nothing worth knowing can be taught." -Oscar Wilde
As many of you know, last weekend I launched a suggestion box here on the site, and I've been overwhelmed by the response: about fifty of you have sent something in to me in the first less-than-a-week of this alone!
Image credit: Thao Nelson of http://mycredo.wordpress.com/.
So, let's start answering them! There are more than enough excellent questions and suggestions to keep me busy for a long time, but with the new academic year starting up, one of them…
esiegel | September 5, 2013"One sees qualities at a distance and defects at close range." -Victor Hugo
A couple of weeks ago we took a look at the most distant galaxy (so far) in the known Universe, a galaxy so far away that it takes exclusively infrared observations from our most power space telescopes (Hubble and Spitzer) in order to detect it. What's perhaps even more remarkable is that the light we do detect from it -- the light we detected in the infrared -- was actually emitted in the Ultraviolet part of the spectrum!
Image credit: NASA, ESA, Garth Illingworth (University of California, Santa Cruz) and Rychard…
drorzel | September 4, 2013Two chapters of the book-in-progress will be devoted to the development of the modern understanding of the atom. One of these is about the Bohr model, which turned 100 this year, but Bohr's model would not have been possible without an earlier experiment. The actual experiment was done by Ernest Marsden and Hans Geiger, but as is the way of such things, the historical credit mostly accrues to their boss and noted force of nature, Ernest Rutherford. This is the experiment that established the cartoon image of an atom as a solar system, which is utterly unworkable using classical physics, and…
drorzel | September 3, 2013Element: Cesium (Cs)
Atomic Number: 55
Mass: One stable isotope, mass 133 amu.
Laser cooling wavelength: 854nm, but see below.
Doppler cooling limit: 125 μK.
Chemical classification: Yet another alkali metal, column I of the periodic table.
This one isn't greyish, though! It's kind of gold color. Still explodes violently in water, though.
Other properties of interest: The definition of the second in the SI system of units is in terms of the microwave transition between hyperfine ground states in Cs-- 9,192,631,770 oscillations to one second, to be precise. Has a really large scattering…
esiegel | September 2, 2013"We find them smaller and fainter, in constantly increasing numbers, and we know that we are reaching into space, farther and farther, until, with the faintest nebulae that can be detected with the greatest telescopes, we arrive at the frontier of the known universe." -Edwin Powell Hubble
With 110 deep-sky objects scattered throughout the heavens, the Messier Catalogue provides skywatchers across the globe with a number of spectacular targets, from nearby nebulae and clusters to spectacular, distant galaxies. Each Monday, we spotlight a new one right here.
Image credit: Rolando Ligustri,…
esiegel | August 30, 2013"Being told about the effects of climate change is an appeal to our reason and to our desire to bring about change. But to see that Africans are the hardest hit by climate change, even though they generate almost no greenhouse gas, is a glaring injustice, which also triggers anger and outrage over those who seek to ignore it." -Sigmar Gabriel
With all of the scientific issues subject to politicization in this world, there's arguably none that raises such strong emotions as the issue of global warming and climate change. This is the final installment of a three-part series on how one could…
drorzel | August 30, 2013It's been a banner week for blogging advice, between John Scalzi's thoughts on comments and Bee's advice on whether to write a science blog. Both of them are worth a read, and I don't have a great deal to add, but writing the stuff I'm supposed to be writing this morning is like pulling my own teeth, so throwing in a couple of brief remarks is much more enjoyable.
First, Bee's introduction raises an important issue:
I used to think there should really be more scientists blogging. That’s because for me science journalism not so much a source of information but a source of news. It tells me…
esiegel | August 29, 2013"We make the world we live in and shape our own environment." -Orison Swett Marden
If you had never heard of global warming before, how would you figure out whether it's real or not? And if it is real, how would you figure out what humanity's role in it is? To answer this, I've decided to do a three-part series on how you'd go about figuring this out, putting aside all politics, economics, opinion and any other non-scientific factors. If you missed part 1, you can check it out here; today we're going to build on that and talk about what determines the temperature of a planet with an…
drorzel | August 29, 2013Element: Chromium (Cr)
Atomic Number: 24
Mass: Four "stable" isotopes between 50 and 54 amu. Chromium-50 is technically radioactive, with a half-life considerably longer than the age of the universe, so...
Laser cooling wavelength: 425nm, but see below.
Doppler cooling limit: 120 μK.
Chemical classification: Transition metal, smack in the middle of the periodic table. Shiny.
Other properties of interest: Has a fairly large magnetic moment in its ground state, 6 Bohr magnetons, which means it has strong magnetic interactions. For this reason, it's kind of an interesting system to study-- you…
esiegel | August 28, 2013"There is no question that climate change is happening; the only arguable point is what part humans are playing in it." -David Attenborough
It's been a long time since I've written anything on this blog about global warming, climate change, or most Earth-based environmental topics in general. After all, I'm a physicist -- an astrophysicist in particular -- and although I'm well-versed in the physics of the Earth and in science in general, it's not my particular area of expertise.
Image credit: NASA, Johnson Space Center, Apollo 17 crew.
Recently, I've had a number of requests to take a…
drorzel | August 28, 2013I've been revising a chapter on collaboration in science for the book-in-progress, making an analogy to team sports. And it occurred to me as I was trying to find a way to procrastinate, that while science is a highly collaborative endeavor, most of the popular stories that get told about science are not. There's no Hoosiers of science out there.
Now, admittedly, the sample of great pop-culture stories about science period is pretty small. But what does exist mostly concerns individual struggles-- the lone genius who can revolutionize science by just thinking about it in isolation, but who…
drorzel | August 28, 2013Element: Lithium (Li)
Atomic Number: 3
Mass: Two stable isotopes, masses 6 and 7 amu
Laser cooling wavelength: 671 nm
Doppler cooling limit: 140 μK.
Chemical classification: Alkali metal, column I in the periodic table. Yet another greyish metal. We're almost done with alkalis, I promise. Less reactive than any of the others, so the explosions in water aren't very impressive.
Other properties of interest: Lithium-7 is a boson, but has a negative scattering length, meaning that BEC's of lithium-7 tend to implode unless you modify the collisional properties. Lithium-6 is a fermion, and much…