Archive | December, 2011

Lunar eclipse

9 Dec

Don’t miss the total lunar eclipse tomorrow. The earth will pass between the sun and the moon, covering the moon with earth’s shadow and making the moon appear red. The moon normally appears white or grey in color because it reflects the light from the sun directly and encompasses the entire visible spectrum. During an eclipse, the direct sunlight will be blocked by the earth. The only light that will reach the moon will be the light redirected by the earth’s atmosphere, which will cause the moon to be sunset red in color.

This will be the last total lunar eclipse visible from North America until 2014. The eclipse will begin at about 4:45am, and be full from 6am to 7am tomorrow morning, Pacific time. Set your alarms and get up a little early. It will be worth it!

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Black holes: Friend or Foe?

7 Dec

Too often, black holes are depicted as prowling, hungry, colossal beings that swallow everything in their path and wreak havoc on the Universe. Although that makes for good science fiction, it is pretty far from the truth. Here’s what’s up with black holes:

How they’re born:

Black holes are born when massive stars die, meaning they explode and collapse inward on themselves. Smaller stars that die turn into white dwarfs. More massive stars that collapse turn into neutron stars. Stars bigger than about three solar masses, however, are too massive to support any structure, even one as dense as a neutron star. These super massive stars turn into black holes when they die.

What they are:

A black hole is a region of space where the gravitational force is so large that the escape velocity is greater than the speed of light, meaning that even light cannot escape the region. It contains a singularity inside that region of space, or a point of infinite density. The matter from the core of the star collapses so far that there is no longer any force to stop it from collapsing and it collapses to a point of zero radius and infinite density, meaning that the surface gravity is infinite at that point as well. There is some debate as to whether the point at the center of a black hole is actually a singularity of zero radius. Some say that there cannot be singularities in nature and that the collapse must halt at some extremely small radius (like way, way smaller than a proton). But in practice, it doesn’t really matter either way. You still have your crazy-dense point surrounded by a region that light cannot escape from.

To understand black holes a little better, let’s step back for a minute and talk space-time. Einstein is the one that discovered the link between space and time. Space and time are cut from the same cloth: the fabric of the Universe, a material that we now call space-time. Gravity exists because objects with mass warp space-time, and cause other objects with mass to fall towards them because of that warping. It would be as if you had a sheet pulled tight at all edges and put two heavy balls near each other on the sheet. The balls would roll towards one another because of the dents they put in the sheet. This is the same phenomenon that causes gravity, except in two dimensions. Black hole singularities warp space-time so much that it wraps around upon itself again, and nothing can escape this region of super-warped space-time. This is known as the event horizon.

How they live:

There are many different kinds of black holes, mainly the differences are size (which is proportional to how much matter the black hole has consumed), rotation, and electrical charge. Black holes with rotation and charge have very large, complex magnetic fields surrounding them that actually spew out a stream of matter along the magnetic poles (not matter from inside the black hole, just some of the stuff that approached it). The stuff being spewed out of the black holes are called jets. See photo above. There is a visible accretion disk of matter surrounding the black hole, and long jet streams coming out of the magnetic poles.

Why you don’t have to lock your doors at night because of them:

So far, so good. It is true that nothing can escape from inside a black hole and that as far as we know, they can continue swallowing matter indefinitely. The misconceptions begin when people start talking about black holes like we are in danger of being swallowed by a black hole at any second. The truth is that the force you feel from a black hole is the same as the force you’d feel from any form of matter with an equivalent mass, unless you get up really close.┬áIn fact, if you were to replace our sun with a black hole of equivalent mass, we would not feel the difference gravitationally. The earth would continue to orbit around the black hole the same way that we do now around our sun. Of course the lack of light would be a bit noticeable after a couple of minutes, but you get the idea. It is true that our galaxy might collide with another galaxy someday, and there’s a chance that we’d end up at the center of that galaxy’s black hole in the process, but it is extremely unlikely, and it’d be so far into the future that odds are none of us’d be around to witness it anyways.

Semi-recent discoveries have indicated that there are black holes at the center of every galaxy, ┬áincluding our own Milky Way Galaxy. The truth is that black holes are really a natural, benign part of our Universe, holding galaxies together and intriguing scientists on this insignificant little planet called earth. So where’s the love?

Here’s a shoutout to the reader that asked an awesome question about black holes and inspired this post. There’s some good black hole reading here if you’re interested in learning more.

Transparent crab shell

6 Dec

Scientists in Japan have turned a crab shell completely transparent. They used a variety of chemicals and acids to strip the shell of anything with color: fats, lipids, proteins, etc. What was left was a material called “chitin,” which is a long-chain polymer.

Besides looking really cool, this material has some exciting technological implications. Once ground down, treated with a monomer and polymerized, this clear crab shell dust can then be infused into other polymers to create a material similar to that used in flat panel displays, except that it has a much lower coefficient of thermal expansion. This means that the material can withstand greater heat without expanding to much or breaking down. In fact, it is ten times more stable at high temps than traditional materials like glass-fiber epoxies. This heat resistance allows the material to be molded into shapes, or to be made into bendable screens. This is just one more example of mama-nature showing us how it’s done.

Abstract here. Image courtesy of Royal Society of Chemistry/Kyoto University.