“The Sun makes fantastic natural experiments” Henrik Svensmark says, “that allow us to test our ideas about its effects on the Earth’s climate.” Most dramatic are the events called Forbush decreases. Ejections of gas from the Sun, carrying magnetic fields, can suddenly cut the influx of cosmic rays coming to the Earth from exploded stars.
CERN’s CLOUD experiment has just published a paper on the effect of cosmic rays on aerosols that can affect cloud formation. I’ll have something to say on that shortly, but Nigel Calder gives a good writeup on other experimental evidence for cosmic rays affecting cloud formation. It is a bit long, but an important read for anyone who wants to understand Dr. Svensmark’s hypothesis. The executive summary: Svensmark demonstrates experimental evidence for GCR influence on cloud formation, and explains the reason critics failed to find such evidence.
Posted by Fred on August 27, 2011
Once they were used to the iPad, the keepers started using the device in a back area where the orangutans could reach through a cage door and touch it. Last week, the two had their first chance to go completely hands and feet on with the device, though it still isn’t allowed in the enclosure with them.
The orangutans both have their favorite apps, often spending quite a bit of time finger-painting with DrawFree, watching television shows and even playing games. They’ve tried iFishPond, Flick Kick Football and seem to really love the interactive book The Fantastic Flying Books of Morris Lessmore.
Yeah, I’m a sucker for the headline.
Posted by Fred on August 17, 2011
Back in July, I had the great opportunity to attend the 2011 CTEQ Summer School in Madison, Wi., where for 10 days we talked about this equation:
Now, this is not just any ordinary equation, it is arguably the most important equation for any physicist working at the Large Hadron Collider, the Tevatron, or any of the other half-dozen atom smashers on this planet. In fact, this equation is precisely what inspired the name Paper vs. Protons.
Since quantum physics is inherently statistical most calculations result in computing probabilities of things happening. The formula above allows you to compute the probability of what happens when you collide protons, something experimentalists can measure, by simply calculating the probability of something happening when you collide quarks, something undergraduates can do!
Richard Ruiz carefully walks us through the equation so we can understand what is happening at the conceptual level. The equation tells us the probability of producing an electron (e–) and a positron (e+) if you smash two protons (p) into each other. And the results from this equation will tell us if the predictions for the Higgs particle match what Nature tells us.
Posted by Fred on August 15, 2011
Nice video by NASA if you are curious about the recent solar flare. h/t Bad Astronomy
Posted by Fred on August 14, 2011
Inside atomic nuclei, protons and neutrons fill space with a packing density of 0.74, meaning that only 26 percent of the volume of the nucleus in is empty.
That’s pretty efficient packing. Neutrons achieve a similar density inside neutron stars, where the force holding neutrons together is the only thing that prevents gravity from crushing the star into a black hole.
Today, Felipe Llanes-Estrada at the Technical University of Munich in Germany and Gaspar Moreno Navarro at Complutense University in Madrid, Spain, say neutrons can do even better.
A new paper is out that claims under exceptionally high pressure, neutrons can switch form spherical symmetry to cubic symmetry. If true, this will have a major effect on our understanding of neutron stars massive enough to reach the necessary internal pressure.
Posted by Fred on August 13, 2011
Astrophysicists have now spotted more than 500 planets orbiting other stars and all of these systems seem entirely different to our Solar System. They’ve seen entirely new class of planets such as the Super-Jupiters that are many times larger than our biggest planet with orbits closer than Mercury.
But the one we’re interested in here has a mass that spans the range from Earth to Uranus, exactly the range that is missing from our Solar System.
There are 30-odd Super-Earths known today, rocky planets in a mass range totally absent from our solar system, and they are forcing a rethink of what we understand about planetary formation.
Oh, and they seem to be good candidates for the development of life. So why aren’t we seeing any evidence of intelligent exolife? Everywhere we look we see planets, and now new kinds of planets amenable to life. A Fermi Paradox Great Filter?
Posted by Fred on August 4, 2011
Git’s problem is its complexity. Half of that is because it’s actually more powerful than the other systems: it’s got features that make it look scary but that you can ignore. Another half is that Git uses nonstandard names for about half its most common operations. (The rest of the VCS world has more or less settled on a basic command set, with names such as “checkout” and “revert”. Not Git!) And the third half is the index. The index is a mechanism for preventing what you commit from matching what you tested in your working directory.
Oliver Steele offers a git workflow that you see above. Benjamin Sandofsky has another workflow article with fewer diagrams. With git, diagrams are good, so read Steele’s first. I like the simplicity of this diagram from Steele’s post, and it should be the first diagram for a git newbie.
I’m still working out what I want git to do, but it is interesting to see how other developers use this tool.
Posted by Fred on August 3, 2011
OK, look at the deep_fetch gist. I’ve been puzzling this one out for a couple of hours. Finally, Das Licht ging an.
The main magic I needed was to know how Kernel#throw and Kernel#catch works; I didn’t have the right behavior for #catch. After looking it up, well, things made more sense.
Then one needs to understand Array#fetch in all three forms. The && in assignment is a very common idiom, so at least I had that correct.
After all that, you’ll be able to run through the various ways deep_fetch might work, given the examples in the gist. And it really is simple, but I’m pretty much awed to think how anyone would come up with the code from scratch.
Posted by Fred on August 3, 2011