Slime molds have been popping up in the news quite a bit lately. A few weeks ago, they made headlines by mimicking the Japanese rail system. Now, a paper published in the Proceedings of the National Academy of Sciences shows that slime molds can make complicated choices about the amount and variety of nutrients they eat.

It might not seem like a big deal that an organism—whether mold, mouse, or man—can make complex decisions about how to feed itself.

Except that they have no brains. These amoeboid creatures have no specialized center dictating all their actions. So, as they spread across a landscape, they have no “mission control” to which to report their nutritional requirements.

In the recent study, scientists placed 11 different foods around the outside of a Petri dish, each with a different protein-to-carbohydrate ratio. They then plopped a slime mold into the center of the dish. The researchers found that the slime mold altered its growth pattern and migrated to contact the foods that provided it with the best proportion of nutrients. That’s a pretty great feat of coordination for a blob without a brain.

Speaking of which, the last time a slime ball got this much attention, The Blob was sweeping through 1950’s drive-ins. For now, I wouldn’t be worried—there have been no reports of bloodthirsty slime molds terrorizing quaint suburban neighborhoods. But don’t underestimate the slime. It’s smarter than you think.

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By Anna Rothschild. This article is provided by Scienceline, a project of New York University’s Science, Health and Environmental Reporting Program.

Image: Flickr / Kristie’s NaturesPortraits

If we celebrate provocative new experimental findings, we should also celebrate the careful null results (experiments that agree with existing theories) on which much of science is based. Back in October we pointed to a new analysis that used observations of gravitational lensing by large-scale structure to test Einstein’s general relativity on cosmological scales, with the intriguing result that it didn’t seem to fit. And the caveat that it probably would end up fitting once we understood things better, but it’s always important to follow up on these kinds of clues.

So now we understand things a bit better, and a number of people have been working to dig into this apparent anomaly. Here is a new paper from this week, that presents their own way of using these kinds of data to test GR against large-scale structure.

Testing General Relativity with Current Cosmological Data
Authors: Scott F. Daniel, Eric V. Linder, Tristan L. Smith, Robert R. Caldwell, Asantha Cooray, Alexie Leauthaud, Lucas Lombriser

Abstract: Deviations from general relativity, such as could be responsible for the cosmic acceleration, would influence the growth of large scale structure and the deflection of light by that structure. We clarify the relations between several different model independent approaches to deviations from general relativity appearing in the literature, devising a translation table. We examine current constraints on such deviations, using weak gravitational lensing data of the CFHTLS and COSMOS surveys, cosmic microwave background radiation data of WMAP5, and supernova distance data of Union2. Markov Chain Monte Carlo likelihood analysis of the parameters over various redshift ranges yields consistency with general relativity at the 95% confidence level.

One issue, as we noted way back when, is that it’s very hard to “test GR” without committing yourself to a model of the mass and energy sources that are causing the curvature of spacetime. So the game is to make some plausible assumptions and see where you go from there. This group seems to have assembled a sensible framework for testing deviations from Einstein, and come back with the answer that everything is on the right track.

We keep getting new and better data, of course, so we’ll keep testing. I suspect Einstein will continue to be right, but probably a lot of people thought Newton would continue to be right a century ago.

I have a fondness for bipolar nebulae: double-barreled gaseous clouds formed when stars are born, and sometimes as they age and die. I’ve seen a lot of them, and studied a lot of them, so I was surprised to see this image from the Gemini North telescope of a BPN I’m not that familiar with, called Sharpless 2-106:

Oooo, pretty! Sharpless 2-106 is about 2000 light years away, located in a region of the galaxy known for birthing stars. The nebula is only about two light years across — small for a star-forming region, but still over 2,000 times bigger than our entire solar system!

Deep in the middle of the cloud is a star struggling to be born. It may have about 15 times the mass of the Sun, big enough to put it squarely into the "massive star" category. It’s flooding the nebula with ultraviolet radiation, causing the gas to glow. Different atoms glow at characteristic colors, allowing us to identify what elements are present, at what quantities, and even at what temperatures. In this case, special filters were used to pick out the elements helium (purple), hydrogen (red), oxygen (green), and sulfur (blue). The result is not really a true-color image — it’s not what your eye would see if you were out there floating around — but it’s close. Amazingly, to me, each filter was exposed for only 15 minutes, resulting in a one-hour total exposure time for this image!

[Note: the purple glow surrounding that bright star is just an internal reflection, light scattering around inside the telescope. That's most likely a bright foreground star blasting out more light in the purple filter than the others; it doesn't mean that star has a giant shell of helium around it!]

The nebula is double-lobed because the star is probably surrounded by a thick disk of material: gas, dust, silicates and other junk swirling around that forms the star itself (and perhaps planets, though we can’t tell in this case because there’s simply too much stuff there obscuring our view). A typical disk is on the order of the size of our solar system, so is invisibly tiny in this image.

But the star is blowing out material too in a stellar wind. It gets stopped by the equatorial disk, so it can only blow up and down, above and below the disk, forming these two great lobes that stretch for trillions of kilometers.

If we compare this image to one taken in the infrared by Subaru, we learn even more:

Like the Orion Nebula picture the other day, the IR image shows that a cavity is being carved out the surrounding gas, most likely from the winds from that massive star. Streamers of gas can be seen on the left, probably formed as the outflowing gas slams into dense knots of surrounding material, a bit like a sandbar that forms when water flows around a patch of sand. You can also see lots more stars than in the optical image, including many bright ones you don’t see at all in the optical. The thick dust surrounding Sharpless 2-106 blocks the optical light from stars, but IR can pierce that veil and reach our telescopes, showing us the hidden treasures.

We see bipolar nebulae all over the place… I have another one I’ll be telling you about soon, one of my very favorite objects in the whole sky. If you’ve been reading my blog for more than a couple of weeks you’ve already seen it, probably without even knowing it. But that’s the only hint I’ll give for now. Stay tuned and I’ll tell you all about it. Promise!

Until then, soak in the beauty of this nascent star, which, in a few million more years, will blow away the tattered remnants of its cocoon, and emerge as another bright blue-white star to light up our galaxy.

The International Space Station is almost done. Astronauts on board the current space shuttle Endeavour completed the first of three spacewalks to install the last major component of the ISS: the Tranquility module. Its huge windows will offer ISS residents 360-degree view of space, the station, and our home world.

The U.S. Tranquility module — shaped like a soda can — is the last major American addition to the station, now 98% complete. Its placement completes 11 years of U.S. construction work on the outpost, which the United States has spent more than $50 billion building [USA Today]. An Italian team designed the module’s magnificent dome, which measures 10 feet in diameter. Seven windows provide the panoramic view.

With Tranquility’s power hookup now in place, astronauts will install the plumbing during their second space walk. Tranquility will house functional items like exercise equipment, toilet, and water recycling system. But there’s another reason the astronauts are keen to see it open its huge windows. NASA readily acknowledges the observation deck and its 360-degree views will improve the quality of life aboard the orbital outpost, where astronauts spend six months at a stretch [AP].

Plus, it’s just nice to be approaching the finish line, especially with only a few shuttle flights remaining before they go into retirement this year, and the future of human spaceflight uncertain in the United States. “What this mission symbolizes, I think, in a lot of ways, it’s like the Transcontinental Railroad. And our flight is kind of like putting the Golden Spike in the Transcontinental Railroad,” shuttle pilot Terry Virts said [USA Today].

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Image: NASA

This is the fifth in a series of guest posts by Joel Barkan, a previous contributor to “The Intersection” and a graduate student at the Scripps Institution of Oceanography. The renowned Scripps marine biologist Jeremy Jackson is teaching his famed “Marine Science, Economics, and Policy” course for what may be the last time this year (along with Jennifer Jacquet), and Joel will be reporting each week on the contents of the course.

In my favorite movie of all time, Jurassic Park, scientists clone a bunch of dinosaurs from the blood of prehistoric mosquitoes. I’m sure you’ve seen it. In the sequel, The Lost World, a Tyrannosaurus rex escapes from a cargo ship on mainland U.S. soil and wreaks havoc on my current hometown of San Diego—if this happened in real life, San Diegans would just shrug, grab their surfboards, and look for the next set of good waves. What if the T-Rex hadn’t been tranquillized and returned to its island? What if multiple dinosaurs had propagated on our continent and formed stable populations? We would label them invasive species. Or would we? After all, dinosaurs were native to North America about 70 million years ago. But I digress.

In our most recent class, we unfortunately did not discuss whether the repopulation of our country with dinosaurs would constitute a species invasion. We did, however, talk about many of the vectors that transport invasive species through the marine environment. One such vector is the ballast water of ships: a freighter will fill its ballast tank in one part of the globe with water and various organisms, traverse an ocean to deliver its cargo, and empty the water and non-native organisms into a new, unsuspecting region. The result is an invasion of crustaceans, mollusks, and algae that might out-compete native species in new habitats. The most famous ballast tank stowaway is probably the zebra mussel, native to the Black and Caspian Sea, which has invaded North American lakes.

There are several methods of managing invasive marine species, most of which are costly and none of which are easy. One student shed light on some interesting technological advancements that might tackle the ballast water problem. A ship could heat its ballast water to 40° Celsius with microwaves to kill any invader that may have hitched a ride. Purging oxygen from a ballast tank with nitrogen could also wipe out the hitchhiking organisms, with an added benefit of preventing corrosion of the tank’s interior.

One method that almost always seems to spectacularly fail is biocontrol—introducing a new species to get rid of a problematic invasive species. The history of biocontrol is rife with notorious blunders: cane toads were introduced to Australia in 1936 to combat beetles that were ravaging cane fields. The cane toads didn’t take well to the cane fields, however, and quickly spread throughout the country, reducing reptile biodiversity along the way. In Hawaii, mongoose were introduced in the 1870s to control the rat populations (also invasive) that were eating valuable sugar cane. Except the mongoose preys during the day, while rats feed nocturnally. Whoops. The mongoose instead decided to eat some endemic Hawaiian birds and threaten their fragile populations.

As globalization continues, more species invasions are inevitable, to the point where the term “native species” will become increasingly irrelevant. Once established, invasives are extremely difficult to eradicate. Prevention seems to be the most effective and most cost-effective way of dealing with this issue. In the future, it will be interesting to see how marine ecosystems respond to more and more invasions. To be honest, I’m not too worried. After all, to quote the famous chaotician Dr. Ian Malcolm, “Life finds a way.”