Science News
Headlines
. Copenhagen climate summit to limit greenhouse gases
. A light delay (a new kind of trap that can hold light for 1.5 seconds)
. Learning from your food (sea slugs learn from the food they eat)
. Supersonic splash (throwing stones in ponds)
Copenhagen climate summit to limit greenhouse gases
Last month, after two weeks of heated talks, representatives of 193 nations agreed to a bare-bones framework for an international treaty to curtail global warming. But even its proponents admit it falls short of what's needed.
The Copenhagen Accord, named for the Danish city in which it was forged on December 18, would cut releases of climate-altering pollutants by most of the world's leading greenhouse gas emitters. It also would establish a multibillion-dollar-per-year trust fund whereby industrial nations would finance efforts by the poorest countries to cope with a warming world.
"When we launched negotiations two years ago, in Bali, I was firmly convinced that we would be arriving in Copenhagen to adopt a legally binding instrument", says Yvo de Boer, the United Nations' lead climate official. De Boer is executive secretary of the United Nations Framework Convention on Climate Change, which administered the existing climate treaty, the Kyoto Protocol, and would also manage this successor. But the consensus statement just agreed to is not an accord that is legally binding, he notes. Not an accord that, at this moment, pins down industrialized countries to individual emissions-reduction targets.  Not an accord that, at this stage, specifies what major developing countries will do.
Still, United Nations Secretary-General Ban Ki-moon says, We sealed the deal. And it is a real deal. And we will try to have legally binding language as soon as possible in 2010.
Draft language released early in the summit proposed strong, mandatory reductions in greenhouse gas emissions by industrialized nations. Within 40 years, they were to cut emissions by at least 75 and up to 95 percent relative to 1990 levels. The final accord makes no mention of those targets. Industrial nations must commit only to implementing voluntarily set emissions targets for 2020 (values that each nation is supposed to decide on by January 31).
Early drafts of the accord also would have required outside auditing of emissions reductions (including those by developing countries) and of developing nations' disbursements from a new, United Nations-managed Green Climate Fund. (That fund will provide up to $10 billion a year from 2010 through 2012 and up to $100 billion a year by 2020.) China called outside verification a deal-breaker. The accord now states that countries can audit themselves.
The challenge in developing a climate treaty with teeth is that the UNFCCC requires all participating nations to agree on the treaty's language. So any nation can veto a deal.
Not only did the final language nix legally binding requirements, but it also set the target for peak temperature rise at below 2 degrees Celsius.
Yet all ultimately came around by being persuaded that they just had to take note of the new accord.
In U.N. parlance, taking note means nations can formally recognize a document without immediately deciding whether to accept any or all of its provisions, according to de Boer. Here, it allows the new accord to move forward without requiring participating nations to commit to adopting it.

A light delay
It's easy to imagine catching a ball, holding it for a moment and then throwing it in the air again. It's also easy to imagine scooping up a handful of water -- say, from the ocean -- and then releasing it again.  But what about light? Is it possible to catch light and then let it go?
Scientists from Harvard University recently demonstrated a way to catch and release light, but it's not easy. In other words, no one will be using the new method to play a game of catch with flashlight beams anytime soon. The researchers were able to build a trap that held light for about 1.5 seconds. That may not seem like much time to hold anything, but 1.5 seconds is enough time for light from the moon to reach Earth!
The light trap wasn't built from normal materials. Scientists instead used a material called a Bose-Einstein condensate, or BEC. This material is unusual because it does not represent any of matter's usual states: solid, liquid or gas. It's not even a plasma, the fourth state of matter found in high-energy experiments and on the Sun.
Instead, BECs are a fifth state of matter. They exist only at the coldest possible temperatures, a fraction of a degree above absolute zero. (Absolute zero is the coldest possible temperature in the universe. It's so cold that not even atoms can move around.) BECs are one of the strangest known materials. Solids, liquids, gases and plasmas are all made up of individual atoms. But when some materials are cooled to below a critical temperature near absolute zero, their atoms seem to collapse into one teeny-tiny blob (actually the bosons in that matter fall into the same quantum state), and that blob is called a BEC.
The scientists used a BEC to stop light in a way similar to the game of Gossip (also known as Telephone, or Whisper Down the Lane). It's an easy game to play: One person whispers a message to a second person, who listens. That person then turns to a third person and passes on the message. The third person should now have the same message as the one sent by the first person (though it might be slightly different). In this experiment, the light is like the message, and the BEC is like the person in the middle -- who hears the message and then passes it on.
A pulse of light was fired into a BEC at very cold temperatures and the light changed a small group of atoms. These changed atoms (called an imprint) dug a little hole for themselves in the BEC -- like a footprint. The research team then turned off a control laser, which made the light's footprint sit in the BEC, in fact, it can stay there for long periods of time.
The scientists waited for 1.5 seconds and then turned the control laser back on. When they did, the trapped light pulse came out of the BEC.
Just as the message at the end of the game of Gossip might be slightly different than it was at the beginning, the light pulse was a little weaker than it was when it started. And just as the middle person in Gossip uses the memory of the message she has stored in her brain to pass the message on, the BEC uses the imprint to transmit the pulse of light.
Finding new ways to control light might pave the way for the development of technology that uses light to store and transmit information.  Researchers have been working on ways to stop and release light for years, but the Harvard team says its approach is better in some ways than attempts in the past.

Learning from your food
For decades, people have been telling each other, "You are what you eat", meaning that the nutrition in a person's diet affects his or her health. It doesn't mean, for example, that if you eat a plant, you become a plant.
At least, not for people.
For a certain kind of sea slug, however, those words are more than just a reminder to eat well. The Elysia chlorotica is a sea slug that looks like a leaf and eats by sucking the insides out of strands of algae.  (Yum!) These algae, like plants, get their food by using sunlight to help make sugar.
Recently a surprising observation was made about these algae-eating sea slugs.  These sea animals, just like plants, have the right chemical tools to turn sunlight into food. Surprisingly, the sea slugs aren't simply stealing what they need to do this from the algae. They've also stolen the recipe for how to make chlorophyll, a chemical that is vital to the process, and can make chlorophyll themselves. In other words, they have started to behave like their food!
This could be a fusion of a plant and an animal!
Inside their cells, plants have tiny structures called chloroplasts.  These chloroplasts turn carbon dioxide and water into sugar using sunlight and a chemical called chlorophyll.  The process of the chloroplasts using chlorophyll to make sugar is called photosynthesis.
Like plants, the algae that get eaten by the sea slugs also use photosynthesis. When slugs eat algae, they separate out the chloroplasts. Instead of digesting and excreting the chloroplasts, the sea slugs absorb them inside their own cells. Once a slug has chloroplasts inside its cells, it can use photosynthesis to make food -- which means it may not even have to eat for the rest of its life (about a year). Other animals, like coral, have been known to stash cells containing chloroplasts and use some of the food they make.
But the chloroplasts use up the chlorophyll during photosynthesis, and a fresh supply is needed. Where does it come from? One idea was that when an animal absorbed the chloroplasts, they came with a lifetime supply of chlorophyll. But as it turns out, that's not the case with these sea slugs. It turns out that, unlike other animals, sea slugs can make their own chlorophyll -- which means that they have stolen more than just the chloroplasts.
Deep inside almost every living cell are genes, which function like recipes for how to make what the organism needs. A plant has genes, for example, that contain the instructions for chlorophyll. As it turns out, so do sea slugs.
So sea slugs not only ingest the chloroplasts -- they've also adopted part of these genetic instructions from their food. In other words, these sea slugs are truly becoming what they eat.

Supersonic splash
Supersonic means faster than the speed of sound, which is about 1300 km per hour in air. That's a speed limit that can be broken -- by jets and bullets, for example, or by the space shuttle as it returns to Earth.
However, you can also make air move faster than the speed of sound by doing a simple little trick: throw a rock in a pond. In a recent study, it was found that, after a rock drops into a body of water, a tiny jet of air shoots upward faster than the speed of sound.
In an earlier study, it was shown that, as a rock falls into a flat surface of water, like a pond, it carves out a tiny tube of air. This tube connects the sinking rock to the air above the pond. The tube doesn't exist for very long, though. Almost immediately, the surrounding water pushes on the sides. This pressure is stronger in the middle than at the ends. As a result, the tube looks like an hourglass, where the middle gets smaller and smaller as the water forces the air out.
There's not room in the hourglass for water and air, so as the water comes in the air escapes upward -- and fast. These tiny jets of air can blast faster than the speed of sound.
Scientists took pictures with a camera that captured 15,000 frames every second. (That's faster than most movie cameras.) After the experiment, the researchers could slow down the movie and, aided by computer simulations, calculate the speed of air as it blew out of the hourglass-shaped tube.
But there's one aspect of supersonic air that the scientists didn't observe. When a jet exceeds the speed of sound, the air around it produces a noise like thunder, called a sonic boom. So far, however, the tiny air jets aren't making even a teeny, tiny boom -- but the researchers will keep listening.