What entropy is or is not

A primer of what entropy is or is not at 3 Quarks Daily by Rishidev Chaudhuri and Jason Merrill:

C.P. Snow famously said that not knowing the second law of thermodynamics is like never having read Shakespeare. Whatever the particular merits of this comparison, it does speak to the centrality of the idea of entropy (and its increase) to the physical sciences. Entropy is one of the most important and fundamental physical concepts and, because of its generality, is frequently encountered outside physics. The pop conception of entropy is as a measure of the disorder in a system. This characterization is not so much false as misleading (especially if we think of order and information as being similar). What follows is a brief explanation of entropy, highlighting its origin in the particular ways we describe the world, and an explanation of why it tends to increase. We've made some simplifying assumptions, but they leave the spirit of things unchanged.

Read on.

Perspectives on the Vertical

Cabinet Magazine has an interesting cultural perspective on human's attempts to zoom in and out of nature in the vertical. Particularly they focus on one of my favorite science films ever, Power of Ten.

Powers of Ten was originally inspired by a 1957 book by the Dutch educator Kees Boeke titled Cosmic View. By 1963, the Eameses were experimenting with tracking shots that gave the effect of a camera pulling away with accelerating motion from an object, and in 1968 used these in a film called A Rough Sketch for a Proposed Film Dealing with the Powers of Ten and the Relative Size of Things in the Universe. Shot in black and white, it was followed by an extended color version—the one known as Powers of Ten—made in 1977. The basic set-up of the latter film is well-known. It opens with a picnic scene in a park in Chicago. From a ground level view, the camera then switches to a vertical, aerial position from which it looks down, the frame centered—as we later find out—on an atom in the man’s hand. At this point the narrator tells us that we are one meter away and looking at a square one meter by one meter. Now the camera pulls away vertically and begins to accelerate so that every ten seconds our distance from the initial scene is ten times greater. The camera continues its upward trajectory until just after 10²⁴ meters (100 million light years) when it gradually slows and begins its descent, collapsing beyond its original position and now decelerating through the ever-smaller dimensions of cells, molecules, atoms, and beyond.

Read on.

A likely Supernova in M95

A bright object has appeared conspicusouly in the outer spiral arm of the local galaxy M95 38 million light years away in the constellation Leo. This new illumination in M95 is probably a supernova. While supernova are not all that rare throughout the entire universe, a supernova occurring this close is rare and interesting as it is a chance to gather higher fidelity data. Conveniently Mars happens to currently be, by projection, right next to M95 so if you look at Mars in the next few days consider what lurks beyond. Unfortunately you need a telescope to see the object.

The Stars seen from the the International Space Station

'Dedicated to those who dream of exploring the solar system, and those who are sharing their experiences while doing it.'

ASTRONOMICAL - The Movie

A scale model of our solar system in twelve 500 page volumes printed-on-demand. On page 1 the Sun, on page 6,000 Pluto. The width of each page equals one million kilometres.

This film takes us through the first volume where we encounter the Sun, Mercury, Venus, Earth, Mars and the Asteroid Belt.

Yes, this is just a film of someone flipping through a book that is the solar system to scale. Highlights include the Earth at minute 4:00, Mars at 5:25, and the asteroid belt at 6:40 (actually this is interesting because while even the sun fits on just two pages the asteroid belt spans for several minutes). The entire 12 volume set is available for the discerning and precise sky aficionado. Strange. Cool. Want.

The Thorium Dream

Thorium may be the nuclear fuel of the future. It is clean, abundant, and safe. Check out this video made by the crafty folks at motherboard.tv documenting the grassroots movement to bring back thorium from the dustbin of history.

Sunset

Proffesor Frédéric Pont at the University of Exeter has simulated what sunsets on planets orbiting distant stars  would look like.

What does the sunset look like on HD 189733 b? Amazingly, we know quite accurately. This is because the colour of the sunset is exactly what is measured when collecting the transmission spectrum of the atmosphere of a transiting planet. We have measured the transmission spectrum of ’189 with the STIS spectrograph on the Hubble Space Telescope. STIS covers visible wavelengths, and HD 189733 is bright enough that the precision of the spectrum is sufficient for a precise translation into colours perceived by the human eye.

What does the sunset look like on HD 209458 b?

Temporal Cloak

The physics and optics blog, Skulls in the Stars, ask this what is a “temporal cloak”, anyway?

I’ve been saying for a few years that optical science has entered a truly remarkable new era: instead of asking the question, “What are the physical limitations on what light can do?”, we are now asking, “How can we make light do whatever we want it to do?” Among other things, we can make light travel “faster than light“, we can focus light through a highly scattering material, we can take high-resolution pictures with low-resolution sensors, and even make particles “fly” on a “wind” of light!

Inevitably, though, many of these discoveries get misinterpreted in popular news accounts to the point that their real significance is lost in a haze of science fictional, or even supernatural, hype. A good example of this is the “picosecond camera” that I described last week, which is an amazing achievement but also possesses a number of technical limitations that make it not quite a “camera” in the ordinary sense of the word.

This week, the experimental realization of a “space-time cloak” or “temporal cloak” by researchers at Cornell University has made national news.

Read on.