Less Lithium means more planets

These guys found a correlation between the amount of lithium and planets around a star. So if there’s less lithium then the star is more likely to have planets. The correlation is strong and makes for a very good predictor.

• Lithium clue for planet-hunters (BBC 11/11/09)
• Study

In addition to the articles, you might be interested in how the science is done. I’ll leave it to the articles to tell you how planets get rid of lithium. But I can tell you how they find planets and how they find lithium.

Funny enough, both are accomplished using spectroscopy. Just like a prism, a spectroscope breaks light up into a spectrum and then measures the brightness all through the rainbow. Chemical elements near the star absorb light and leave dark lines in the spectrum. Each element leaves a different set of lines. So it’s easy to tell which elements are around the star. The most common are hydrogen and helium. They’re the lightest elements. (Think balloons and blimps.) Lithium is also light but it’s less common, which makes the absorption line lighter. The lightness is used to measure the amount of lithium.

It’s hard to actually see a planet through a telescope. So astronomers have figured out better ways. The best is to see if a star wobbles. Planets make stars wobble as they go around. If you’ve ever seen the hammer throw in the Olympics then you might have noticed that the athlete has to lean back while spinning. That’s to counterbalance the pull of the hammer. Well stars do the same thing to counterbalance the gravitational pull of the planet. If things are lined up right, then the star moves closer and farther from us.

That movement causes the absorption lines in the spectrum to shift. That shifting is called the Doppler Effect. If you’ve ever noticed the pitch of a siren change as a police car passes by, then you’ve heard the Doppler Effect. As the car is heading toward you, the sound waves bet pushed together and sound higher. As the car goes away, the waves get separated and sound deeper.

The same thing happens with light from a wobbling star. (Doppler Spectroscopy) As the star moves closer, the absorption lines get shifted toward the blue end. And as the star moves away, the lines shift toward the red. Astronomers track this information for months and years. 

There are other methods for finding planets but spectroscopy is has found the most. Another method is to see if a planet crosses in front of the star. (The transit method) It’s hard to do since few systems are lined up just right and you have to keep your telescope on the star all the time. Recently, NASA launched the Kepler Mission to watch a large field of stars for transits.

The Taste of Blood

This was supposed to be my Halloween post but I’m a little late. What does blood taste like to you? Does it taste like metal, coins or water? It tastes like that because of the iron in your blood. (Sometimes you get a metal taste in tap water too.) Your body uses iron to transport all kinds of elements around your body. The most common example is oxygen. Your red blood cells use iron to transfer oxygen from your lungs to all of your cells. Just how iron is used to grab oxygen and then release it at just the right time is interesting to me. It’s surprising to me just how much of our body’s function is dedicated to this process.

Red blood cells contain hemoglobin, which is a protein that holds iron. Iron is unique in that it is like a magnet plus it rusts. Rust is formed when iron combines with oxygen. That bond is hard to break. But hemoglobin has a way of weakening that bond. The protein molecule is large yet holds just 4 iron atoms. Each iron atom is held in a ring of 74 other atoms (called a heme group). The protein molecule is wrapped around those rings. So you can see, it takes a lot to control that bond.

When the blood cell reaches a place where the amount of carbon dioxide is high enough, the hemoglobin changes shape to pop out the oxygen atom and attach to the carbon dioxide. When the blood cell gets back to the longs where the oxygen levels are much higher, the carbon dioxide breaks off leaving the hemoglobin ready for more oxygen. And that’s why you breath out carbon dioxide. If this whole process doesn’t work well, then you get anemic. Two common causes of this are iron deficiency and sickle-cell anemia.

That bit about iron being like a magnet and it rusting is misleading. The iron in our blood is an ion, which means it has a different number of electrons than most iron. You can make a refrigerator magnet out of iron but not out of iron ions. So they’re not magnetic enough for an MRI to pull them out of place. Iron ions don’t rust either. But they do oxidise just like rusting. That just means they can bind to oxygen. And just like rust, an oxidised iron ion turns red. That’s why your blood is red. Actually, your blue blood is red too. It’s just less red so it looks more blue.

Just how red blood cells are formed is too complex for this post. But I can tell you how they die. The spleen uses enzymes to slice open old or damaged blood cells. It also cuts the hemoglobin. I bet you were wondering what the spleen was for. The parts go back into the blood stream. The liver cuts open the rings holding the iron. That creates Bilirubin. That’s the yellow stuff that makes your poop brown and your pee yellow.

The Space-Time Diagram

You can tell that the right guns were fired first because the circle around them is bigger. As time goes on, the circles get bigger. A space-time diagram can show how that works. 

 In this diagram, the blast starts at the bottom tip of the cone. It show how the circle gets bigger. A space-time diagram isn’t usually this fancy. Usually, it just show distance over time. That makes it flatter and easier to draw.

In the case of light, it’s common to use 45 degrees for the speed of light. For every year, light travels a light year. So a year is the same length as a light year.

Kennedy and the First Roberts Court

This past summer, the Supreme Court lineup changed when Souter retired. So now’s a good time to look back at some statistics for the First Roberts Court. It started when O’Conner retired and then Rehnquist died in 2005. That ended the second Rehnquist court, which lasted 10 years. It was one of the longest lasting lineups. From Fall 2005 to summer 2009, the First Roberts Court made over 300 decisions.  But O’Conner sat in for Alito for several of these until Alito got up to speed. So I limited the decisions to April 17, 2006 through June 2009, which contains 275 decisions. Roughly 1/3 of those were unanimous, 1/4 were 5-4 splits, and the rest fell somewhere in between.

The 5-4 splits are where the drama is especially when you consider the ideological split in the court. This split is clear when you line up the justices next to the one with which they most often agree.

This is an agreeable court.  Notice at the ends of the spectrum, Stevens and Thomas agree half the time. If you look closely you’ll see the ideological split falls between Kennedy and Breyer. Breyer is considered moderately liberal and Thomas is the most conservative. Yet Kennedy agrees with them equally. This puts Kennedy in a powerful position. Out of 63 5-4 split decisions, Kennedy was the deciding opinion on all but 10. The best anyone else did was 22 dissenting opinions.

This chart shows all the decisions during the First Roberts Court.Green – majority opinionsYellow – dissenting opinionsWhite - abstainedS – Stevens, Souter or ScaliaG – GinsburgB – BreyerK – KennedyR – RobertsA – AlitoT – Thomas

Thomas is holding tight to the conservative end. He disagrees with the liberal end more than any other. Plus, out of 19 lone dissenting opinions, 8 are from Thomas. In the Second Request Court, O’Connor was the swing vote. [See this and this.] Out of all 275 decisions, Kennedy had a dissenting opinion only 22 times. That’s 8%. Twice as many 5-4 splits along ideological lines were conservative than liberal.

Even though the justices are likely to agree, it’s fun to see how much they disagree. This graph is similar to the agreement matrix above except it shows how much the justices disagree with each other.

You can see which justices are ideologically similar. You can see that Kennedy disagrees with the liberal end of the bench more than the conservatives.

No Special Speed in the Universe

That title is a twist on the Copernican Principal that we hold no special place in the universe. It led Copernicus to conclude that the Earth is not the center of the solar system. Nine decades later (1543-1632), Galileo stated his principal of invariance. Basically, the laws of physics stay the same even if you’re moving. We hold no special speed. That means you can juggle in a jet. Galileo used a ship for his example.

Still, that’s no reason to think the Galilean Invariance principle holds at speeds approaching the speed of light. That is until the most famous failed experiment: the Michelson-Morley experiment in 1887. At the time, the speed of light wasn’t known. These guys came up with an ingenious way to measure even the slightest change in the speed caused by our orbit. It failed! There was no change in the speed of light no matter which direction or when. How can that be unless the earth really isn’t moving?