Saturn’s rings to disappear Tuesday
The rings shine because they reflect sunlight. But every 15 years, the rings turn edge-on to the sun and reflect almost no sunlight.
Category Archives: Physics
Particle Physics Publishing = Real Estate
Timing and location count when announcing particle physics results
Together, these points make it clear that researchers in HEP don’t use journals to communicate scientific ideas. They may notice a paper is published, and they certainly value the peer-review and other functions provided by the journals, but they don’t communicate using the journals; instead they use arXiv, which is much faster.
Pick a Peck of Pixels
A pixel, from Earth to the Moon, to the infinite and beyond
How big of a screen would you need to resolve the Apollo craft as a single pixel in an image which includes the earth and the moon?
Speaking of higher resolution, while I was contemplating Olbrich’s image I started thinking of what would be the size of Apollo space shuttle in the image. It would certainly be so tiny that it would be invisible to us. The next geekiest question would be: what should be the image’s minimum resolution to make the modules appear as a single pixel?
Diffracti-O's
Physics Buzz: How to Build a Spectrometer with Just Three Household Items
How to build a cereal box spectrometer.
Getting All Charged Up
I bought another toy recently. A “fun fly stick,” which is a static electricity generator. Here are two of my colleagues playing with it. The levitating object is some aluminized mylar, i.e. tinsel.
The low ceiling in my office makes it difficult to truly appreciate it, but does show some physics. You can see the tinsel collapse when it touches the ceiling and discharges, and then pop open again when it’s free. The charges on the aluminum repel each other, and spread out as much as they can in order to minimize their energy. That’s what we are taught in E&M, and it’s easy to see this with a deformable object rather than the canonical rigid sphere.
The tinsel does actually get charged (rather than having some induced charge distribution), which you can feel on the occasions where you get too close and it attacks your face. Not too much of a shock, though. I tried aluminum foil, but it’s too heavy. (foil = fail) Packing peanuts didn’t repel like I expected, but that may work better in drier weather. The tinsel targets are a bit delicate and I have empirical evidence that they do not stand up to the treatment of two/three year-olds.
This is an ad from ThinkGeek (not where I got this particular toy) that uses a little more free space.
Brahe had a Sponsor. Kepler Works.
The bottom plot is the same thing but zoomed in to see more detail. That second dip is a lot more obvious. It’s not another planet blocking starlight, which is what you might first guess. It’s actually the light from the planet being blocked by the star!
The planet is reflecting light from the star, just like the Moon reflects sunlight, allowing us to see it. When the planet passes behind the star, we don’t see that light anymore, so the total light from the system drops a wee bit. It’s not much, and totally impossible to see from the ground, but Kepler was able to spot it. And that’s critical, because it turns out this dip is about the same thing we’d expect to see if a planet the size of the Earth were to pass in front of the star. In other words, the drop in light from a giant planet going behind its star is about the same as we’d expect from a smaller planet passing in front of the star.
The fact that Kepler spied this dip at all means that, if somewhere out there an Earthlike world is orbiting a star, Kepler will be able to detect it!
Incredible.
This is pretty cool.
It's a Small World, After All
Looking from human perspective Earth may appear as an enormous object, a HUGE rock we’re living on. In space measurements, the size of our planet is infinite small. This comparison between Earth and “most popular” planets and stars really adds a new twist to the whole story.
Good Morning, or Good Night?
A world map showing current sunlight and cloud cover
Appears to be rounded to the nearest hour.
The hemispherical projection lets you more readily see the effect of the earth’s tilt
Thinking Outside the Ball
Physicists trap light in a bottle
To get light into an optical cavity, it has to fit. That is, when the photon travels a complete circuit of the sphere, it must travel a whole number of half-wavelengths. The spheres are tiny, so the color difference between two wavelengths that fit is huge. This becomes a problem because we can’t precisely control the size of the spheres during manufacture, and nature chooses which colors of light atoms will interact with—the two rarely end up matching.
The usual solution is to make a bajillion spheres and find one that is close to right. Then you can heat the sphere so that it expands until you get to exactly the right color. It would be much better to just have a resonator that could adapt itself to any color of light.
What Can Brownian Do for You?
I don’t know, but here’s an applet demonstrating Brownian motion