astrophysics

The Poetry of Science IV

jhalper — Thu, 26 Feb 2015 07:19:52 +0000

The Poetry of Science IV

Manot Cave cranium

With a skull and Keats, there was little choice but to write about the new online items in rhyme. So with apologies to Shakespeare, Keats and the scientists, as well as the people at SpaceIL, here are today's grab bag of poems. As usual, follow the links.

On a Lone Cranium

Alas poor Yorick – We can only know

Where you lived all those eons ago

Walking, did you take those others in stride;

Human, yet strange, as they strode alongside?

Did your children wander forth,

Searching for a greener North?

Can your skull, a bit of bone,

Tell us where our seeds were sown?

To the Moon

There was a fine crew in Rehovot

That aimed for the Moon with a “space boat”

It’s barely a cart

But they’ve built it quite smart,

For cool science it’s bound to promote

In a Heartbeat

“Two hearts that beat as one,”

Just one beat? Where’s the fun?

Just one cell can beat as twenty

For your heart, love, that is plenty

Oh yes, and we have women PhDs, too. If you're an outstanding female Israeli PhD looking for help with your postdoc, click here.

jhalper Thu, 02/26/2015 - 02:19

Dull paleossiferous twit !
You've popped your poor skull like a zit
Now neither your glia nor seeds of the chia
Can make a great bust out of it

Useful Things

catdynamics — Mon, 02 Feb 2015 23:36:57 +0000

Useful Things

Because I must trim browser tabs, here is a current short list of things that might be useful:

Threebody

ASCL - Astrophysics Source Code Library - Open Source Code
Visible Spectra of the Elements - Except Astatine :-(
Astronomy Simulators - small web simulators for elementary concepts.
Some quite nifty.
From University of Nebraska.
All the Kepler 2 Campaign 0 data - with some tools to play with it

catdynamics Mon, 02/02/2015 - 18:36

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Very nice, especially Threebody; thanks for the heads up.

Flow, Beauty and Mystery (and two new haikus)

jhalper — Tue, 18 Mar 2014 11:52:19 +0000

Flow, Beauty and Mystery (and two new haikus)

Today’s new articles involve flow: the flow of positrons through the Universe and the flow of particles around the tiny cilia of corals. They involve beauty and mystery, as well. The particle flow, imaged in brilliant colors, won first place in the photography category of the 2013 Science/National Science Foundation International Science & Engineering Visualization Challenge.

And positrons – the anti-matter opposites of electrons – have been found in large numbers flowing in near-Earth space. Weizmann Institute research points to an answer to one riddle: Why did a satellite monitoring these positrons find so many of them? But the central mystery of their existence – where do they come from – remains open.

In the spirit of flow, beauty and mystery, here are two new haikus. Follow the links to learn more.

Image: Shapiro, Fernandez, Stocker and Vardi

Winding into waves

Invisible coral flows

Tiny living tides

Anti-electron,

Born of a far cosmic crash

What news do you bring?

jhalper Tue, 03/18/2014 - 07:52

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So You Want To Be An Astrophysicist? Part 1.5: thinking about grad school, redux

catdynamics — Tue, 07 Jan 2014 01:38:34 +0000

So You Want To Be An Astrophysicist? Part 1.5: thinking about grad school, redux

So, now you’re at university, and you’re thinking about heading for grad school …
A seasonal revisit of some old rumblings^*

^*NB: this discussion should not be construed to be anything but hypothetical ramblings, they do not reflect in any way the official position of any academic institution, department or graduate program, especially not the one I am part of!

So You Want To Be An Astrophysicist? Part 1.5: thinking about grad school
Posted by Steinn Sigurðsson on January 16, 2012
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So, now you’re at university, and you’re thinking about heading for grad school …

More re-re-runs from Ye Olde Blogge

The following is horribly UScentric, ’cause that’s where I am right now.
The general principles are broadly applicable, the actual getting into grad school procedure bit in future post will be both US and THEM centric.
Now what?

Caveat: these numbers are somewhat dated, but the shift is not large enough yet for me to bother re-searching them.

Each cohort in the US is about 4+ million people, about 4000 of those major in physics, in round numbers.
Since participation in the further education in the US is almost 50%, that is 4000 out of about 2 million, or 0.2% of undergraduates (specifically, about 1.2 million bachelors degrees are awarded each year, with physics major 0.34% of those, near historic lows, trend has flattened after many years of decline, and may even be showing some secular rise
(see APS jobs in physics stats).
For what it is worth, about 1200-1500 PhDs in physics are currently awarded each year, almost half to non-US students, so about 1/6 to 1/7 of physics undergrads end up doing a PhD, in physics. The “rule of thirds” you’d infer from the raw numbers (# PhDs = 1/3 # BSc) is surprisingly robust at each step.

The number of astronomy undergraduates is much smaller still, since not a lot of universities (61 according to this article by Cabanela and Partridge in AER) have a separate astronomy department, or a separate major (so a lot of people who become astronomers or astrophysicists start as physics majors, or have an astronomy minor).

The number of astronomy PhDs is fluctuating around 120 each year, with significant Poisson noise, as one might expect.

There are 25-30 major research universities which dominate the astronomy PhD production, so classes are small, and the intake is fought over hard.
Having said that, current astronomy undergraduate production is about 400 per year, and has grown significantly (AIP stats summarises). A lot of those are double majors with physics. Naively then about 1/2 of undergrads go on to PhDs, but after you allow for the foreign intake, it is more like 1/4 – 1/5, since some also go into graduate school in physics (and of course other fields, but I am not considering those now).

So, the good news is that if you’re in the major, you have a high prior probability of going to grad school. You just have to pass the classes, get good grades, not go broke, survive the insanity of university, enjoy life, and take the GRE exam, the only exam stupider than the SATs…

So, what should you do. First, take all the math classes you can handle, especially if your interest is astrophysics; take calculus of course, through ODE, PDE, Complex Analysis, and some course covering spectral methods (Fourier and Laplace transforms etc). Better know what a Bessel function is when you get to grad school, and know immediately where to start on solutions to second order differential equations. Take also probability theory and statistics, linear algebra, numerical analysis, and computational techniques. If you can stand it, differential geometry, topology, functional analysis, and some advanced classes never hurt anyone.
I know I keep hammering on this point, but the primary limit on career paths within astrophysics is inadequate math preparation – too many students take minimal load of math classes and skip mathematics that is “not relevant” and then find years later that they did need if after all but they don’t have the time, inclination or energy to go back and learn on their own.
Did I mention statistics? I’m increasingly convinced that a good survey of applied statistics is the single best thing any student can learn, especially if leavened with some probability theory.

Then take physics. You don’t have to take all of it, but would it hurt to do so?

Solid state physics, wave theory, optics and quantum field theory all show up somewhere in astrophysics (all of physics does, that is why astrophysics is the greatest sub-field in physics! ;-) oh, and take relativity if you’re at one of the few places it is offered.

What else. Well, the prereqs and college mandated hoops of course.

Don’t burn yourself out, but given a choice, wouldn’t you rather take a gen ed class on something that is interesting (to you).

Funky minors sound fun and macho, but they can destroy a GPA, a graduation schedule and enthusiasm – approach with care.

Then think about what you like to do when you finally get there? Like to build things? Add labs and engineering classes (especially electronic and optics).
Like data? Then add more statistics and computing classes.
Like to think? Go buy a ruled pad and nice black ink pen (no pencils, this isn’t kindergarten).

So, you did that, aced all the classes, are student president, captain of some NCAA team, and still have time to party.
Now what.

Well, a long time ago, there was a rule of thumb: the odds of an incoming undergraduate in physics/astronomy getting a faculty position at a research university is about the same as the odds of an NCAA division 1 football player making the NFL.
But the earning potential is different (not as much as you’d think, lifetime average!).
And in both cases, it is not a bad career move, even if you don’t make it all the way, the alternate career paths can be sweet. Oh, and in both cases, where you go to school matters a lot, for your average odds. But remember, there is always a Jerry Rice!

So, end of your junior year, if you can still stand the field, you need to start seriously working on grad school applications, and planning for the GREs. More later…

catdynamics Mon, 01/06/2014 - 20:38

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Physical Benefits

jhalper — Sun, 13 Oct 2013 03:47:35 +0000

Physical Benefits

Of the four new articles online on our website, three happen, purely by accident, to be on physics research. The three are very different, and yet each is an illustration of the ways that basic physics research changes our world – in small and large, practical and enlightening ways. And each is situated at a different intersection between the technological and the theoretical – a technological breakthrough that resulted from a successful attempt to provide proof for a theoretical construct, new inventions based on elementary physical principles of light, and a theory substantiated through a large array of advanced particle detectors.

Take the work of Dr. Shahal Ilani. Ilani and his research team created something that had been predicted back in 1934 by Eugene Wigner: an electron crystal. In an electron, or Wigner crystal, individual electrons are held in a fixed configuration by mutual repulsion. Clearly, there are no practical uses, yet, for electron crystals (Ilani’s first, proof-of-concept, crystal consisted of two electrons). One creates them for their own sake – to prove the prediction, and thus a fundamental precept of quantum physics.

The challenge was to produce a system so inert that the electrons would only interact with one another; not with any other part of the system. And that has led to a very practical invention. Ilani and his team managed to create their original tiny electron crystals in ultrapure carbon nanotubes. But scaling up the nanotubes to make larger electron crystals was problematic: Adding length increased the probability that electron-attracting defects would be introduced. So Ilani and his team developed a whole new method for producing flawless carbon nanotubes; these are likely to have a number of immediate applications.

A system for creating ultrapure nanotubes. Image: Dr. Shahal Ilani

Dr. Dan Oron’s research, in contrast, is eminently practical: He, too, builds nanocrystals, but these are tiny rod-shaped crystals about 50 nanometers long that can absorb two low-energy photons and emit a high-energy one in their place. This neat trick may enable the design of solar collectors that could make use of a much broader range of the light spectrum.

Oron’s research has also led him into biological imaging: A microscopy method he developed uses femtosecond (a millionth of a billionth of a second) laser pulses that start out long and shorten as they penetrate living tissue. He and his colleagues then used these pulses to image excited neurons within mouse brains.

But if you look closely at Oron’s work, the advanced technology also illuminates some basic light physics. For example, the nanorods make use of the dual nature of light. They absorb light as individual photons, but are tuned to the wavelength of the light: The radius of each rod is set to a particular wavelength (color). The microscopy, as well, depends, among other things, on a precise understanding of the way that light scatters from a surface.

Nanocrystals seen under an electron microscope. Image: Dr. Dan Oron

The third article concerns a phenomenon that has no foreseeable practical application: high-energy neutrinos that come from the far reaches of space, passing straight through the earth on their way. Prof. Eli Waxman is a theoretical physicist who, together with the late Prof. John Bahcall, had developed a theory proposing that such cosmic neutrinos originate near certain young black holes, as well as suggesting an upper limit to the number of particles that could be detected. That number is very small because, even though billions of them are passing through at any one instant, only rarely do they interact with matter. Though it did not take 80 years (as it did with the Wigner crystal) for technology to catch up to the theory, several decades did intervene between the original idea and the detection of neutrinos that appear to support Waxman and Bahcall’s model.

That technology is quite impressive – not least in size and scope. This is the IceCube experiment, based on some 5,000 detectors buried in a several-kilometer cubic array under the Antarctic ice. It takes an array that large (and isolated from other sources of radiation) to detect a mere handful of neutrinos.

Because these neutrinos have traveled straight from their source to the earth, they carry information about how they were produced – a sort of telescope that can peek into the insides of stars. They can thus give us clues as to the very workings of the universe – in other words, basic physics at its finest.

IceCube detector array

jhalper Sat, 10/12/2013 - 23:47

Outer Planets’ Stormy Weather: All on the Surface

jhalper — Thu, 16 May 2013 09:54:43 +0000

Outer Planets’ Stormy Weather: All on the Surface

Have you complained about the weather recently? On the gas giants at the edges of our solar system, Uranus and Neptune, hurricane-like storm systems as big around as Earth blow 1000 km/h winds for years on end.

Voyager II image of Neptune, showing storm features. Image: NASA

But wait…What exactly constitutes weather on a giant gas planet? Here on planet Earth, there is a clearly delineated gas layer enveloping the solid/liquid layer we call home. Our weather arises from our planet’s rotation and the solar heating of its surfaces. On a rapidly-rotating gas planet (a day on Neptune is 16 hours long), which receives little warmth from the sun, how do storms arise? Is the whole planet a swirling, turbulent mass, or is the weather confined to an outer layer, like on Earth?

We now have, if not an exact answer, an upper limit for the thickness of weather systems on those planets. And it turns out that they are surprisingly Earth-like (frigid 1000 km/h winds aside): The winds blow in an atmospheric layer that is no more – and probably less – than 1000 km thick. That is much less than one percent of the mass of these planets.

The researchers who calculated this limit – at the Weizmann Institute, Tel Aviv University and the University of Arizona – used slight variations in the gravitational field – gravity maps of the planets – to work out the depth of the weather. On Earth, large masses like mountains slightly increase the planet’s gravitational pull on nearby objects. On gas planets, wind-driven variations in the gas density are what create rises and dips in the gravitational map. By calculating the theoretical gravitational fields on idealized planets of the same size, but lacking winds, and comparing these with the observed gravity, the team was able to ascertain the contribution of wind to the overall pattern.

According to lead author Dr. Yohai Kaspi, having a better grasp of what is occurring on the planets’ surfaces will give us clues to the events taking place deeper within the planets, as well as information leading to theories about their formation and possibly even hints as to the makeup of the many largish exoplanets that have been detected in recent years. Kaspi is on the scientific team of NASA’s Juno mission to Jupiter, and is planning to apply this method sometime around 2016, when the spacecraft will be taking detailed measurements of that planet’s gravity.

jhalper Thu, 05/16/2013 - 05:54

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outer planet strorm systems

NASA Astrophysics Roadmap: The Next 30 Years

catdynamics — Thu, 09 May 2013 06:42:32 +0000

NASA Astrophysics Roadmap: The Next 30 Years

What are Origami Nanosat Telescopes? How about Kinetic Inductance Detectors?
More importantly, what should we do with them?

NASA's Astrophysics is doing a Roadmap exercise, with the stated intent to look at science goals, technology and capabilities up to 30 years out!

White papers were solicited a few weeks ago, and about 100 were received and are archived online, about 3/4 on science and 1/4 on technology.

There was originally supposed to be a workshop for presentation of selected white papers, but in the world of sequestration that was not feasible, so instead there was a two day online townhall meeting, run over Adobe Connect

Much of my time this week was spent keeping half an ear on the roadmap presentations, for a while in parallel with trying to follow the concurrent first part of the Astrobiology Roadmap web chat!

There were typically just under a 100 participants online at any given time, many of which were the Roadmap Team Members

Several things struck me about the presentations: one is that the technology talks were incredibly interesting, and suggested not only that we are about to get lets of fun new toys, but that for many areas of astrophysics we are approaching perfect detectors - a phrase I first heard quoted about modern radio receivers.

Our detector technology is asymptoting to reaching quantum limits in efficiency across all wavebands and modes of detection.
Further, as with the Planck mission, for some observations we are approaching the point where we will observe all there is to detect - improved equipment will not give more or better signal.

What struck me about the science presentations, is that they tended to be narrow, focused on narrow science goals in small subfields, and they were all about old stuff - stuff we've been thinking about or trying to do for at least a decade, for the most part.

I also did not see the word "exoplanet" in any of the presentation titles. Of the white papers selected for online presentation, that is.
Maybe we're about to get a new division in NASA's Science Mission Directorate?

But that is details, the real question is what DO we want to be doing 30 years from now, and in the time leading up to then?

Well, everything!

Seriously, we ought to be monitoring the whole sky at all wavelengths, synoptically, as a matter of routine, thirty years from now.
We know we can have the technological capabilities, we know how it could be done, and the cost is finite.
The cost is actually trivially small on the scale of the world economies over that same time.

I don't think we are really arguing over that, the discussion is really about priorities, what to start first, what order to do things in, and how quickly to proceed.
This is important mostly because with current funding constraints we can't move ahead on all fronts, so some fields will be left for later. Which means firing a lot of the current researchers and giving up existing capabilities, on our way to the bright and glorious future.
Bummer.

Beyond that, one can argue about when enough is enough - like will the cosmic microwave background measurements be done after the next round? Synoptic surveys are unlikely to be productive for the CMB on decadal time scales...
Then one can argue about details, like cadence for the synoptics, and how deep to go on individual targets. It is likely that high resolution spectroscopy will be capability limited even three decades from now, and probably also really deep imaging. eg we will be limited in target selection for spatially resolved imaging of exoplanets for the foreseeable future, even if we go to arbitrarily large optically perfect mirrors.
As long as there are small numbers of facilities, and steering is limited, targets will outnumber facilities.

I think the distinction here is important - we really ought to be observing everything, true astronomical panopticons.
What we are really talking about is prioritizing the order in which we do things with finite resources, not what we ought to try to do at all.

What is sad is how small the numbers we argue about are. The NSF cuts are based on budget crunches in the tens of millions of dollars per year, while the NASA shortfalls for science to keep going at the pace we're trying to maintain are order a billion dollar per year.

With a little bit more money really astonishing science could be done in the next few decades, but we are reduced to political infighting over a shrinking pot, each subfield hoping to survive long enough to still be there when things get better.

catdynamics Thu, 05/09/2013 - 02:42

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What Everyone Should Know about the Universe on the eve of Planck

esiegel — Wed, 20 Mar 2013 18:25:19 +0000

What Everyone Should Know about the Universe on the eve of Planck

"Scientific discovery and scientific knowledge have been achieved only by those who have gone in pursuit of it without any practical purpose whatsoever in view." -Max Planck

Tomorrow morning, at 8 AM my time, the press conference that cosmologists have spent the past decade waiting for will finally happen, and the Planck satellite -- the most powerful satellite ever to measure the leftover radiation from the Big Bang -- will finally unveil its results about the origin and composition of the Universe.

Image credit: ESA / LFI and HFI Consortia.

They've figured out how to subtract the galactic foreground in all of the seven wavelength-bands where Planck operates to unprecedented sensitivity, and the science is ready to be released! Let's use this opportunity to take a look back on what we know right now, where-and-what the uncertainties are, and what Planck can (or, at the very least, might) teach us about the Universe!

Image credit: Rhys Taylor, Cardiff University.

1.) The Big Bang is safe.

The Big Bang is the idea that the Universe was once in a hot, dense, ionized state and expanded to become our star-and-galaxy-rich cosmos that we live in today. There are three separate cornerstones that lead to this picture: the observed Hubble expansion of the galaxies, whose recession rates increase with increasing distance from us, the observed primordial abundances of the light elements, which are predicted by Big Bang Nucleosynthesis to give us a Universe with about 75-76% hydrogen and 24-25% helium (by mass), and the leftover, nearly uniform blackbody (CMB) radiation at just a few degrees above absolute zero, coming from all directions in space, which marks the leftover glow from the Big Bang itself.

Image credit: Whittle Rodman, University of Virginia.

In the context of General Relativity, our tried-and-true description of gravity in this Universe, only an expanding, cooling Universe in the context of the Big Bang leads to these three predictions simultaneously, and nothing the Planck satellite observes will change that.

Image credit: WMAP Science Team / NASA.

2.) The Universe is mostly dark energy, followed by dark matter, with normal (baryonic) matter making up just a small fraction.

There are three sets of large-scale observations that simultaneously lead to this picture, again in the context of General Relativity.

Image credit: J. Colberg and the VIRGO Consortium.

The observed patterns of large-scale galaxy clustering, combined with the data from ultra-distant distance indicators (like supernovae), and the already known patterns of fluctuations in the microwave background on both large (from WMAP) and small (from the South Pole Telescope and others) scales, all indicate a Universe that's made up of about 71-74% dark energy, 20-24% not-too-hot dark matter, with the remaining 4.6% made up of normal, standard model particles. These standard model particles include everything we've ever observed directly, including protons, neutrons and electrons, photons and neutrinos, and all the exotic, unstable matter we've ever created.

Image credit: Kowalski et al., 2008.

So none of those things will change substantially, although the dark energy/dark matter numbers may shift around a small bit in that range. Although Planck will measure the large scales more accurately and in more wavelengths than WMAP before it, that science has already been done, and Planck will only refine it, not overthrow it. The way it will refine it is extraordinary; while WMAP was limited by the sensitivity of the instruments on it, that's not the case for Planck, according to the ESA:

Planck will provide even more precise measurements with an accuracy set by fundamental astrophysical limits... In other words, it will be impossible to ever take better images of this radiation than those obtained from Planck.

But there are some things that Planck can shed some light on, which have the potential to be extremely exciting!

Image credit: LSST / AURA.

3.) The age, size and expansion rate of the Universe!

Yes, it's true that we often quote that the age of the Universe is 13.7 billion years old, the diameter of the observable Universe is 93 billion light-years across, and the expansion rate -- or the rate that all galaxies (on average) recede away from one another -- is about 71 kilometers/second/Megaparsec. But these numbers are all related to one another, with the age-and-size numbers also dependent on the percentages of dark matter and dark energy.

Image credit: Moresco, Michele et al. JCAP 1207 (2012) 053.

But the expansion rate has a little bit of uncertainty attached to it. It probably couldn't be as low as 60 or as high as 80, but no one would be shocked if it turned out to be 68 km/s/Mpc, or maybe as high as 74 km/s/Mpc. This could mean a Universe as old as maybe 14.2 billion years, or as young as 13.3 billion years, depending on how the dark matter and dark energy parameters adjusted. Half-a-billion years may not be a big deal to you, but when you consider that we've already got stars that push the 13-and-change billion year limit, it's pretty important to astrophysicists that the Universe is at least as old as all the stars in it!

Image credit: Prof. Matt Strassler, 2011.

4.) There are three types of neutrino in the Universe.

We're pretty sure of this one... aren't we? I mean, we've got these huge particle colliders, we've been running them for decades, and we've seen how hordes of them decay. The decay of the Z-boson, for instance, tells us that there are 3.003 ± 0.006 neutrinos species whose mass is less than 4.5 × 10¹⁰ eV. Considering that the heaviest a neutrino is allowed to be is around 0.08 eV, it makes sense to conclude that there are three.

Image credit: Carlo Giunti, via Luca Merlo of http://neutel11.wordpress.com/.

But the cosmic microwave background should also measure the number of neutrino species in an independent way, and would also be sensitive to a bizarre, hypothetical type of neutrino that particle physics wouldn't find conventionally: the sterile neutrino! WMAP, with lousy sensitivity, has claimed to have found about 3.6 ± 0.5 neutrino species, and so while not conclusive, it's suggestive that there could be a new particle (or maybe even 2?) out there! Planck should improve on the WMAP constraints, and this could be interesting.

Image credit: "Cosmic Inflation" by Don Dixon.

5.) How did the Big Bang get started?

According to both the spectrum of density fluctuations imprinted in the CMB and the large-scale-structure of the Universe, and also the best theoretical solution to many open questions in cosmology, the answer to that is cosmological inflation, or a period where spacetime was expanding exponentially fast. At some point, inflation ended, setting up the Big Bang and creating all the matter and energy known to permeate our observable Universe.

Image credit: Ned Wright (+ possibly Will Kinney), via http://ned.ipac.caltech.edu/. (Notes by me.)

Of course, we don't quite understand how all of this happened. As in, there are many models of inflation that could have successfully done this, and we have no way to discriminate between many of them. But the two main classes of models -- models of new inflation and models of chaotic inflation -- have a major difference between them: chaotic models should produce large amounts of long-wavelength gravitational waves, while new inflation should produce almost none. In optimistic models of chaotic inflation, this would cause a polarization of some of the light from the CMB, something that Planck could -- in principle -- pick up. So Planck has the dual potential to either detect primordial gravitational waves and verify not only inflation but a particular model of it, or to disfavor the chaotic inflation scenario in favor of new inflation. (Full disclosure: new inflation has long been my preferred model.)

Image credit: Avi Loeb, 2006.

There are other, smaller refinements that could happen, such as a better pinning-down of the epoch of reionization or a more precise measurement of a few cosmological parameters, but these are the five big ones -- confirmation of the first two and potential answers to the last three -- that I'll be waiting on. If you want to watch the NASA announcement live online, it's at 8 AM pacific time on March 21st here, and you can check out the ESA's page here or call in and listen to the teleconference. WMAP redefined the precision to which we understood the Universe when its first data release happened a decade ago, and now Planck has the potential to take us even further in our understanding of the greatest quest of all: the dream of understanding the entire Universe. I can't wait to see what they found!

esiegel Wed, 03/20/2013 - 14:25

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cosmic microwave background

"Foreground subtraction." In my business, the hardest part of any analysis is background subtraction, where the goal is to count a nice chunky peak sitting on top of some more or less uniform (or at least smoothly and slowly varying) baseline.

I can't imagine how to subtract away all of the background "signal" which is sitting on top of the subtle density variations in the CMB, and successfully extract all of those details. If you've already done a posting on this issue, my apologies; if not, it would be very interesting.

What's the point in finding out what happened before the big bang ? Is humanity being unrealistic about the reach of its knowledge ? Are trying to "run before learning to walk ?"

Wow, fascinating article, I somewhat understand some of this (studied Resnick and Halliday years ago). Makes all what most of us earthers argue about (i.e. politics) seem so small in comparison what is happening around us.

Hey EBRecordings,
I would argue that the study of the nature of reality is probably the most noble of pursuits. Those same pursuits, over the last 120 years, have vaulted our technology from steam engines to electric engines and from telegraphs to cell phones. Why ANYONE would question the pursuit of knowledge is as frightening as it is insulting.

Yeah, ya know, that's preety much how I see it.

Hi, a great Planck primer, thanks. Only one request: the figures you include are fascinating, & it would be brilliant to include a (brief) description of what they're showing in the captions.
Thanks for blogging, I often read your articles but haven't commented before.
Becky

"8pm my time"....slow clap. Honestly? We don't know where you live, couldn't you say EST, PST...or something? People live all around the world you know.

Vince#5: Agreed. One need only read the Planck quote in the caption to see the truth in your reasoning. I have always felt that knowledge for its own sake is, not only enough, but paramount and absolutely necessary to the advancement of all mankind. I am always wary, and often frightened, of individuals or groups who ask "why?" when it comes to gaining knowledge. "Why should I care?, Why does it matter?" What's sad is that you cannot win an argument with someone who is ignorant, especially one who chooses that ignorance, with all the facts laid before them. You will never convince them. It is left to the few, the scientists, the entrepreneurs, to DRAG Humanity forward, while the masses benefit from the myriad contributions of science and technology. It is, by and large, a thankless endeavor. The debates go on and on, about how "we" should be spending "our" money and resources. Why build a telescope when we can build more shopping malls? You try to say things like, "where would we be without minds such as Newton and Edison and Curie?" You get a blank stare, or more nonsensical rhetoric. I've since given up. I will speak to children, and other enlightened adults only on such "weird" topics as astronomy and cosmology.
Somewhere, there is an article about yoga-pants being recalled with over 1000 comments. And this article, this type of marvelous, infinitely fascinating topic, has but 6.
I can't think of any more excuses. Nearly half of the planet have access to at least rudimentary scientific facts, and yet only a very, very small percentage of people have any idea about the universe around them, nor do they seem to care. Who can blame the scientists for their eccentricity introvert behavior? Look around you. We have mastered the use of technology (see iPhone users) yet fail to understand the centuries of scientific discovery leading up to the creation the very technology we take for granted. I hate to say it, but it appears to be a losing battle. More and more care less and less about how it all works. You see it every day, and it pains my heart to no end.

Vince, I couldn't agree more; surely the one thing above all others separating us from other animals is the urge to understand the nature of things. We want to know what is going on, not just for its utility, but for its own sake. As Sheldon Glashow said: we are curious creatures.

How do we know the background radiation detected is not from previous lSupernovas in this part of the Milky Way?

Hi Ethan:
"...there are 3.003 ± 0.006 neutrinos species whose mass is less than 4.5 × 10^10 eV."

This exponent seems much too large to me...

"This exponent seems much too large to me…"

You are obviously no astrophysicist.

Indeed, an ERROR BAR of that magnitude isn't, in astrophysics, necessarily a bar to the conclusion being used.

@SCHWAR_A: That mass would be 45 GeV. What Ethan is saying is that if there were a fourth decay channel for the Z boson that involved neutrinos of less than that mass, our particle accelerators should have seen it. We can't rule out a heavier neutrino (not that there is any compelling argument for a fourth neutrino flavor at least 11 orders of magnitude more massive than the three known). We also can't rule out a neutrino that does not participate in Z boson decay (I'm not sure how that works, either, but IANA particle physicist). The WMAP results suggest that at least one of these two types of neutrinos may exist.

The Planck results apparently leaked out. I have already seen a story from AP that they have measured the age of the Universe at 13.81 billion years. It's not quite 0700 PDT (which, to answer an earlier question, is Ethan's time zone) as I write this.

@Mark

Didn't make it to the end of the article before deciding to complain in the comments section, I see.

The number on the neutrino mass should be about 2 MeV from the Z decay kinematics. What you wrote was half the Z mass, but if the neutrino was very heavy, we could see it in the photon spectrum. (That experiment looks at e+ e- -> Z gamma).

Is there a link to the announcement mentioned to have taken place this morning?

Results are out!

- Universe is 13.8 billion years old.

- DM is 26.8% and DE is 68.3% of the universe, more and less respectively. Normal matter slightly increased at 4.9%.

- Most exciting: Significant asymmetry in temperature across the sky, and a large particularly cold patch. Theorists, start your engines!

*13.82 billion years old

If we didn't encourage exploration at all levels and disciplines, we be stuck in the dull world of thinking the earth is flat and the solar system revolves around the earth. Great job to the satellite builders and scientists, and of course to Max as well.

CB -universal cooling? or universal change? Which is it? Stake out your claim now before Gore gets to it.

"Stake out your claim now before Gore gets to it."

Yeah, the continual whine of the under-achiever in the face of someone who has gotten somewhere and NOT had to prostitute their principles.

Also, Hubble Constant is 67.3 km/s/MPc

I wish the press statements I was reading (from the ESA website, and Nature) included error bars. :(

Wow- good comment on Gore- he;s been wrong a lot.

Ah, you are not only ill-bred, you're an idiot too.

If you want to talk bullshit, do so elsewhere.

Wow- typical insulting liberal. You don't pick on sarcasm to well do you. I didn't know you were the moderator of opinions. Why are liberals always angry when someone has a different opinion? Not very progressive of you.

Typical rightwingnut primadonna.

You insult someone then when someone insults you, you go all prissy and butthurt.

Get over yourself, pal.

You're a waste of carbon and you're merely pissed off that Gore managed to do something with his life and still has his integrity, whereas you've whored yourself out for decades and got nowhere.

And so you slag off others. But they'd better not be mean and slag you off, because that's what liberals do.

Oh, I guess that must mean you, right?

Now, this is a science site, not a rightwingnut gathering place, so piss off back to your sister's house and play that banjo.

" Not very progressive of you."

Hang on, you earlier said:

" typical insulting liberal"

It appears not even YOU believe the bullshit that you spout.

"Why are liberals always angry when someone has a different opinion? "

Yet YOU got angry when I had a different opinion about you than you hold yourself.

I guess rightwingnuts are always unable to follow a thought through more than two words.

Now, if you want to go piss off to your rightwingnut troll feasting ground, put a link and I'll follow you there, but respect the property of Ethan and stop posting rubbish on his site.

Rightwingers like you never respect other people's private property, though, do you.

Not very capitalist of you.

I have always wondered if virtual particles from Zero point energy theory could be part or most of the Dark Matter. I am sure it has been investigated, but I have never seen the results. I assume the current testing will illuminate the dark matter question and I will be watching.

They can't, Henry: they (by dfinition) don't exist long enough for anything else to find out.

Well, not entirely true: there's a version of the maths but that would lead to (IIRC) a difference between measured value and calculated from that their of a factor of 10^100.

Even for astrophysicists, that's a bit high...

Never been to this site before. Enjoyed the article and enjoyed the comments . . . until I got to the intellectual discourse between the rightwingnuts and leftyloonies. Get a life, you guys!

Hey, if I'd turned up here and said:

You know that George Bush Jr fella? He's a fooking idiot, inne?

Then maybe you'd have a point.

As it is, I think an xkcd is appropriate:

http://xkcd.com/774/

Want to get to reach people better? Re do all this as a video.

This may seem like a "elementary" question ... but, doesn't it look like the expansion of the "universe" is the diametric-opposite of a black hole? ... that the "Big Bang" is the expression or effusion of a "Black Hole" that has ripped through a weak point in the membrane of a"space/time/energy" barrier?

It's good to know that ''The Big Bang is safe'' but I am curious about the ''the observed Hubble expansion of the galaxies''. Can you tell me which actual observation(s) or measurement(s) demonstrates that the distance between all galaxies increases over time to verify that the universe is expanding?
And I understood that the CMB contains no emission or absorption lines, so how is its redshift calculated ?

Come back in 100 million years time and we'll have the data.

Or should that be
"Seven and a half ..."
"What? Not till next week?"
"Million. Million years. I told you it would be a long time".

Weekend Diversion: Discovering the Universe

esiegel — Sun, 16 Dec 2012 17:22:52 +0000

Weekend Diversion: Discovering the Universe

"The vastness of the heavens stretches my imagination. It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined it." -Richard Feynman

What did you think about, wonder about, and dream about the first time you saw the true magnificence of the night sky? Did you wonder about planets orbiting each of the thousands of points of light you saw? Did you think about the possibilities of rocky worlds with liquid water, of life, and even of intelligent aliens? Or did you perhaps think on even larger scales, about what stars, galaxies, and the entire Universe was like beyond the mere capabilities of your eyesight? Whatever it was that you thought about -- and whatever it is that you think and wonder about now -- I hope that this beautiful song by Benjamin Francis Leftwich,

Atlas Hands,

helps you to appreciate just how the view of what lies beyond our Earth unifies us all.

Image credit: F. Ringwald.

Beyond our sight, of course, are billions of stars, hundreds of globular clusters, and uncounted regions of star formation, death, and rebirth. And that's just in our galaxy alone. Just 100 years ago, the leading school of thought was that the Milky Way comprised the entirety of the Universe, and that every object ever observed was simply a part of our galaxy. Newtonian gravity was the best theory we had as to what ruled our Universe on the largest scales, and the nuclear secrets of the Sun and the stars remained unknown.

Image credit: Tony Hallas.

But today, we have a deep and fascinating knowledge about the entirety of the Universe, including the laws that govern it, the matter and energy that comprised it, and how it got to be the way it is today. It's a story that we all share, and a story that I try to bring you a little part of each and every time I write for you.

But this time, there's something more I have to tell you. You may remember that in November, I tried my hand at writing a fictionalized history of discovering the Universe. What I didn't tell you then was that that was practice for the real thing.

It's time for me to write a book for all of you.

Image credit: World Scientific / Imperial College Press.

The story of what we know about the Universe and how we know it -- in my estimation -- is the greatest achievement in all of human history. I was privileged enough to get to learn all about it for myself, and now I want to tell that story to you.

I'm in the process of writing the official proposal right now, and the (tentative) working title is Beyond The Galaxy: How Humanity Looked Past The Milky Way And Discovered The Entire Universe.

Image credit: NASA's Goddard Space Flight Center.

There are going to be a tremendous series of stories in there, including all we had learned by the dawn of the 20th Century, the new ideas and confirmation of Einstein's General Relativity, the discovery of the expanding Universe and the nature of other galaxies, learning what elements make up our Universe, the story of the Big Bang and how it bested all the alternatives, the Cosmic Microwave Background, the story of Dark Matter, the ideas and predictions of cosmic inflation, the discovery of dark energy, and the fate of our Universe.

And one of my goals is to write this book in the exact same style I write Starts With A Bang, and to tell the entire story without using a single equation.

Image credit: NASA, ESA, R. Windhorst, S. Cohen, M. Mechtley, and M. Rutkowski (Arizona State University, Tempe), R. O'Connell (University of Virginia), P. McCarthy (Carnegie Observatories), N. Hathi (University of California, Riverside), R. Ryan (University of California, Davis), H. Yan (Ohio State University), and A. Koekemoer (Space Telescope Science Institute).

It's the story of where everything in existence comes from, how it got to be the way it is today, and what's going to happen to all of it in the future. It's the story of you, me, and everything we've ever experienced here in this Universe.

And today, you're finding out that it's happening. I can't wait to share it with you -- and to relive it for myself -- all over again.

esiegel Sun, 12/16/2012 - 12:22

Tags

Do it Ethan, good luck. I'll buy a copy.

I need to remind you of some of the privileged info you have. You did sign the non-disclosure agreement. Dark matter and dark energy are to remain dark! We know you can do this.

I had never seen a sky full of stars, and I do mean full, until I traveled to North Carolina for the first time. This was well into my 4th decade of life too!

I was on NC17 between Elizabeth City and Edenton when I noticed my rear view mirrors were completely black. That was unusual enough to get me to notice it.

So I pulled over and got out of the car. What I saw was stunning - the entire band of the Milky Way was visible, along with a field so loaded with stars it was hard to identify a lot of them. And of course I left the camera back in Edenton.

Been down there a bunch of times since but the skies don't want to cooperate.

I am really looking forward to your book. I really enjoy the clarity and style of your writing, I am sure your book will be a best seller.

This is fantastic news, Ethan! The way in which you write this blog has helped me understand and appreciate the stuff of the universe better than anything else I've come across. I'm really looking forward to my nieces and I spending time with your book.

Great, will try to have the book here in Switzerland.
Will you look at the "time flow" right after the Big Bang and now?
E.g. Is at a specific observation point, after billions of years, the time still "flowing" the same way? Space itself expands; why should time itself be steady ?
Thank you for the always impressive and clear explanations.

Ethan, I know this is going to be a shot in the dark, but is there any chance you could manage to add a cd to your book?
The musics you share in your "weekend diversion"s are just great, and they'd make a great soundtrack to your story!

I'll make sure it gets some attention here in Sweden when it comes out!

Really great idee, I'm looking forward to the publication! :-)

(and will probably buy it, although I know most of the stuff already... ;-) )

You are the only blog I read completely. That's because you're a great writer. I teach high school astronomy and I'll have my kids buy your book. It is the very story I want them to learn to love.

will definately read it when its available

I hope you get the proposal accepted, I'm looking forward to reading the book.

Sounds awesome! I'll definitely buy a book when available. Strongly recommend thinking up a better title, though.

Ethan, fantastic news. Best of luck with the writing.

Looking forward to the book. But I want to be clear -- I will not buy a copy unless it contains a prominent photo of you dressed as a professional wrestler. Just saying.

Chemistry of the Quantum Kind

jhalper — Thu, 11 Oct 2012 23:00:50 +0000

Chemistry of the Quantum Kind

Today’s post is about some cool chemistry – very cool. About 0.01°Kelvin, as a matter of fact (that is, one hundredth of a degree above absolute zero). Physics experiments conducted at such temperatures are already old hat, but chemistry is another story, altogether. Scientists have been attempting to produce chemical reactions at ultra-low temperatures for at least 50 years; a Weizmann research team has finally achieved that goal.

Why try to get reactions to take place in these conditions, which are wholly unfavorable to the usual lab-type chemistry? The answer is that when temperatures drop as low as they can go, quantum effects take over from the classical physics we’re used to. Particles, for instance, begin to act as waves. So any chemical reactions taking place in that range are likely to be as weird and wonderful as the laws of quantum physics, themselves. Plus, we know that chemical reactions do take place at the lowest end of the temperature range, out in the frigid expanses of interstellar space.

The coldest atoms and molecules – that is, matter in its lowest possible energy state – need some help if they are going to interact chemically. So scientists have approached the task by creating very fast, cold beams of atoms and/or molecules, and throwing them at one another. This creates collisions and chemical reactions ensue, but the high-speed collisions generally also involve relatively large amount of kinetic energy, flipping these experiments out of the possible quantum range.

The Weizmann team’s innovation was to create two parallel beams and merge them. That way, collisions could still occur but, since the molecules were all moving at the same speed relative to the others, the net energy of the collisions was nil.

The setup: One beam flies straight, the other is bent to meet it, all in an ultra-frigid vacuum chamber

When the scientists observed the chemical reactions in the merged beam, quantum effects indeed emerged below about 3°K, and certain predictions about how such reactions occur were confirmed. For instance, the reactant atoms and molecules formed transient bonds in which they orbit one another. This gives them a chance to react chemically (in the case of the Weizmann experiment, by exchanging an electron). The reactions took place in peaks, at specific energies – a demonstration of the tunneling that occurs when quantum particles act as waves.

Research group head Dr. Ed Narevicius hopes the new findings will bring about no less than a comprehensive revision of existing theoretical models for chemical reactions. “We’ve shown that our understanding of even the simplest ionization reaction is far from complete,” he says.

jhalper Thu, 10/11/2012 - 19:00

Tags

particle-wave duality

Look , when you start looking at having to manipulate anything then you look at energy, no matter how small or undetectable. What is the point of this?

It is true that practical applications are probably not right around the corner. On the other hand, the findings could provide insight into everyday chemical reactions, be used to create ultra sensitive probes for certain types of chemistry, and reveal how complex compounds are being formed in the interstellar medium, where the average temp. is 2K.

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At the start of my physical chemistry classes, I like to tell students we live in a very cold environment where most metals are frozen solid. I say that we are lucky because chemical bonds form easily at 300 K but not at 3 K and not at 3000 K. In contrast physics looks at all temperature, from zero to the big bang.

Even though chemical bonds are purely quantum, looking at chemical reactions at very low temperature gives us more insight into quantum effects. I believe at these temperature anomalies will be found that will challenge us to explain. I think that low temperature physics is as important as high energy, and a lot less expensive too.