For Halloween, here's Thoy Bradley's great Ghost Hunters scene. Why post this on SciBricks, you ask? Because it gives me a chance to discuss that great mist effect. First let's enjoy the MOC:
He achieves the effect by putting dry ice in a container of water in a chamber below the scene. You've probably all seen this trick used to make a mist that bubbles out and runs along the ground. Dry ice is actually solid carbon dioxide. Matter generally exists in three phases - solid, liquid and gas. You are certainly used to seeing a simple ice cube melt to form liquid water as it is warmed, and then boil to make steam if it is heated still more. Carbon dioxide actually goes directly from solid to gas phase at one atmosphere of pressure (the air pressure at sea level). Here's the phase diagram:
As you can see on that diagram, to make liquid carbon dioxde you have to be at a fairly high pressure. (As an aside, we used to make dry ice bombs in lab - pack some dry ice into a plastic vial, when it warms up and changes to gas the pressure makes it blow up. If you ever see the liquid inside, you'd better throw that thing darn quick. BTW, always wear safety goggles in lab! ;) ) (And yes, now that I'm old and stodgy, if any of my student were building dry ice bombs in lab they'd get in a lot of trouble.) Okay, back to the smoke technique. Carbon dioxide is a gas at room temperature, but a solid below -78 degrees Celsius. When you throw a chunk in water, it starts bubbling. That's not the water boiling, that's the dry ice rapidly subliming (going directly from solid to gas phase). Since the gaseous carbon dioxide is so cold (starting out at -78 C until it slowly warms to room temp), it is also very dense, so it bubbles out and runs along the ground. But the spooky smoke you see isn't the gaseous carbon dioxide - that would be completely invisible (breathe out and you'll see, or not see to be more precise). Instead as it comes into contact with water vapor in the air, it cools it down enough to condense it to small droplets, an extremely fine mist. And so that's the effect you see in this LEGO creation, or any time dry ice in water is used to create a smoke effect. I've got some dry ice here in a cooler (I actually bought a huge chunk in preparation for potentially losing power in Hurricane Sandy), so I think I'm going to put it in water in a plastic pumpkin on my porch for trick or treaters. Happy Halloween!
Tuesday, October 30, 2012
Unhalfbricking's École de Mathématiques is a playful take on the Fibonacci sequence. It's an imaginary skyscraper housing a math school. The first two sections are each 1 floor high, then there's a 2 story section, then a 3 story section, then 5, 8, 13 and 21.
Thursday, October 25, 2012
Newton famously contemplated gravity when watching an apple fall from a tree (not actually hitting him on the head, as seen here in LEGO by Brother Steven).
... why should that apple always descend perpendicularly to the ground ... [he described is thoughts in a later conversation] ... why should it not go sideways, or upwards? but constantly to the earths centre? assuredly, the reason is, that the earth draws it. there must be a drawing power in matter. & the sum of the drawing power in the matter of the earth must be in the earths centre, not in any side of the earth. therefore dos this apple fall perpendicularly, or toward the centre. if matter thus draws matter; it must be in proportion of its quantity. therefore the apple draws the earth, as well as the earth draws the apple.
Monday, October 15, 2012
Q is for quantum: Physics The smallest amount of a physical quantity that can exist independently - by Lamont Cranston. Serge Haroche and David Wineland shared the 2012 Nobel Prize in Physics for their work on studying individual quanta. Haroche devised a method for slowing down and examining photons, the smallest bits of light. Wineland found a way to trap individual ions (charged atoms) for study.
Friday, October 12, 2012
This year's Nobel Prize in Physiology or Medicine was shared by John Gurdon and Shinya Yamanaka. Gurdon's work goes back fifty years to when he first cloned an adult frog by taking DNA from mature cells and transplanting them into frog eggs to produce new tadpoles. The key thing here was that the mature cell held all of the information to code for all of the cells in the body, that is, a liver cell has all of the information to make blood cells or neurons or whatever, and so could become the basis for a complete organism. Yamanaka's work brings this idea forward, and he developed ways to turn back the clock on mature cells, essentially tricking them into reverting to the same state as embryonic cells that can grow into all sorts of new cells (i.e. they are pluripotent). These are called stem cells, and are one of the most promising areas of medical research today. Towel made these LEGO vehicles based on frogs and tadpoles.
Wednesday, October 10, 2012
Alfred Nobel (here in LEGO form by Michael Jasper) was a chemist who lived from 1833-1896. He invented dynamite, along with other explosives, and this allowed him to amass a great personal fortune. When his brother died, a newspaper erroneously reported it as his death, and they editorialized about how his legacy was this explosive that would kill untold numbers of victims in warfare. He was distressed that he might be remembered as a killer, so he wrote his will to set up a series of annual prizes, now known as the Nobel Prizes, to promote the sciences and the welfare of mankind. It's Nobel week, and I'm a bit behind, but let's take a look at the new Nobel laureates through the lens of LEGO.
Monday, October 8, 2012
Yesterday's Google doodle celebrated that 127 anniversary of Niels Bohr's birth. Bohr developed the planetary model of the atom, with the nucleus in the center and electrons following circular orbits, similar to planets circling the sun. KillerMoth26 designed this LEGO atom.