I Don’t Wanna’ See a Spiral! – Part I
Proof that the second illusion is concentric circles: This is not a spiral
Monthly Archives: April 2010
A Matter of Perspective
Fly Me to LEO
The Big Picture: Journeys to the International Space Station
April 12th marked the 49th anniversary of human spaceflight, when Yuri Gagarin became the first person to orbit the Earth in 1961. At this moment, 13 humans are currently in low-Earth orbit, aboard the International Space Station. Several were already aboard the ISS when a Soyuz TMA-18 brought a fresh crew up from the Baikonur Cosmodrome on April 2nd – they were later joined by the crew of the Space Shuttle Discovery on the 131st shuttle mission to date (only three remaining launches scheduled). NASA recently signed a new deal with Russia for six more round-trips to the ISS, at a cost of $55.8 million per seat. Collected here are recent photos of the Space Station, its current crew, their launch vehicles, and the views from above. (38 photos total)
Here’s a neat picture from the collection (larger version at the link)
The water bubble acts as a lens and inverts the image, but the air bubble inside also acts as a lens, inverting the image once again. A lens made of air? Well, sort of. Light refracts at the interface of any two media with different indices, so you can look at it as a lens. If we lived in water, we’d probably think of air bubbles in that way. Alternately, you can think of the bubble as dividing the water bubble into two lenses for the light traveling through it, while the light not going through it passes through only one lens.
A variant on this would be if you were to inject a small sphere of a liquid with a larger index inside the water bubble, if you were on the ISS, or use glass with two different indices here on earth.
Is Anyone Listening?
Maniacal Rage: Photoshop Crash Reports
I changed the canvas size (added 400 pixels to the height while anchoring the existing canvas to the top in case you’re interested in the little details) and everything disappeared. Luckily, I had just saved. I’ve been pretty lucky about that with Photoshop in the past — I’m an over-saver. I save all the time. Probably got into the habit because of applications with terrible stability patterns- You know, like your application. Photoshop. Also, Microsoft Word. Remember that junk? I’m sure you do. You probably refer to that as the ‘Adobe Photoshop of Word Processing’ and laugh and laugh and count your money.
It’s almost like blogging in a crash report dialog window.
Paaaaark Weeeeek!
Should We Dress Them Alike?
Quantum fun: how identical must “identical photons” be?
The basic idea of the experiment is simple. Take two objects that emit single photons that are identical to each other. Detect these photons after they have been mixed together using a beam splitter. If they are identical, both photons will appear on the same output port of the beam splitter and set off the same detector. If they are different, they can appear on different output ports and set off different detectors.
Something the article really doesn’t delve into is a discussion of what is interfering and why you get his articular correlation. This isn’t the familiar case of two waves that are 180º out of phase giving you destructive interference, which is called second-order interference (by some, anyway, it’s the same authors using the terminology across multiple papers, so I don’t know if it’s standard or them hoping it will catch on). One reason we know that this isn’t interference of this type is that this has been tested with independent sources, such that the beamsplitter where they combine is far enough away that the travel time exceeds the coherence time of the light. There can not a be a well-defined phase in that case, so you will not see an interference pattern emerge from this effect.
This is fourth-order interference, involving Fock states* (photon-occupation states) and this is QM with no classical analogue, so I don’t really have a good ball-and-stick description which I can share to explain why this happens. (That is to say I don’t have one, not that I have one and am precluded from sharing it for some reason of national security. As far as you know.) You have photon occupation states leaving the beamsplitter, for travel in the two directions, A and B. You can have |2,0> or |0,2>, for two photons going to one detector or the other, and there’s a |1,1> state, for a photon going to each detector. But really there are two |1,1> states, that look the same when we can’t tell the difference between the photons. And since you add amplitudes before “squaring” them (multiplying by the complex conjugate), the |1,1> terms cancel if the amplitudes are the same, i.e. if you have a 50/50 beamsplitter, leaving you with the photon pairs as the only possibility, as long the photons are identical. Which then raises the question which the paper is trying to address.
* Yes, really. Innuendo galore. Anything you can think of has probably been done before.
WIkipedia article on the HOM effect, as this is called.
The Plutonic Relationship
“It’s not easy being a public enemy,” writes Neil deGrasse Tyson in his book The Pluto Files. When Neil’s museum grouped Pluto not among the planets but rather with icy comets in an obscure region called the Kuiper Belt, he heard from thousands of outraged Pluto defenders. It’s tough being called a heartless Pluto-hater, particularly by a dismayed eight-year-old. Below, peruse a few of the letters elementary schoolkids sent Neil, and see how their tone shifted over the years, as the public slowly came to accept Pluto’s fall from planethood.
It's My Party, and I'll Cry if I Want To
Court to hear suit over “Tea Party” name
Nearly three dozen people and groups who called themselves part of the Tea Party movement filed suit against O’Neal and two associates in January, accusing them of trying to “hijack” the movement and confuse the public.
Reminiscent of the tussle between the Judean Peoples’ Front and the Peoples’ Front of Judea. (Thtwike him, centuwion! Thwow him to the gwound!)
Size Matters
Abraham Lincoln was once asked, “How tall should a man be?” “Tall enough that his feet reach the ground,” was his reply.
Building A Shrink Ray? Consult This Grisly Physics Paper About Exploding Horses
Making something giant-sized looks cool in science fiction. Seeing it basically disintegrate under the strain of its own weight wouldn’t look nearly as cool. Okay, maybe it would. But it wouldn’t make for an interesting fight for the protagonist.
The “grisly” paper is On Being the Right Size by J. B. S. Haldane.
An insect, therefore, is not afraid of gravity; it can fall without danger, and can cling to the ceiling with remarkably little trouble. It can go in for elegant and fantastic forms of support like that of the daddy-longlegs. But there is a force which is as formidable to an insect as gravitation to a mammal. This is surface tension. A man coming out of a bath carries with him a film of water of about one-fiftieth of an inch in thickness. This weighs roughly a pound. A wet mouse has to carry about its own weight of water. A wet fly has to lift many times its own weight and, as everyone knows, a fly once wetted by water or any other liquid is in a very serious position indeed. An insect going for a drink is in as great danger as a man leaning out over a precipice in search of food. If it once falls into the grip of the surface tension of the water—that is to say, gets wet—it is likely to remain so until it drowns. A few insects, such as water-beetles, contrive to be unwettable; the majority keep well away from their drink by means of a long proboscis.
Just as I Suspected
You were right: It’s a waste of your time. A study says much computer security advice is not worth following.
Please do not change your password
[U]sers are admonished to change passwords regularly, but redoing them is not an effective preventive step against online infiltration unless the cyber attacker (or evil colleague) who steals your sign-in sequence waits to employ it until after you’ve switched to a new one, Herley wrote. That’s about as likely as a crook lifting a house key and then waiting until the lock is changed before sticking it in the door.
You change passwords for much the same reason you would change codes — to keep ahead of someone who is stealing periodically updated information from you. But it’s not going to help protect static information, like your credit card information and bank account numbers. Once you’re hacked, that will be compromised.