Jamie noticed an interesting map of
critical thinking and science done in a sort of subway style. You can track Newton and Einstein and Tesla and so on. It’s actually pretty interesting to navigate.
Source: The Map of Critical Thinking and Modern Science
An anonymous reader writes “Einstein worked on Brownian motion (the movement of small particles in a fluid as they collide with the fluid’s molecules) in 1905, but said it would be ‘impossible’ to determine the speed and direction of a single particle during this dance. Now researchers have gone and done it, by suspending a dust-sized glass sphere in air (which slowed down its dance moves, since it had fewer collisions with spaced-out air molecules than it would have had with water molecules). The researchers held the sphere in place with ‘laser chopsticks,’ and then watched how the glass bead bounced around to determine its direction and speed (abstract).”
Source: Physicists Do What Einstein Thought Impossible
A team of scientists led by Mark Raizen at the University of Texas at Austin had the gumption to take on Einstein. And according to their new paper in Science, they won. The point of contention? The lovechild of statistical mechanics and thermodynamics: Brownian motion.
Here’s how they did it.
Step 1. Learning the Moves
In the 1820s, Scottish botanist Robert Brown looked through a microscope at plant bits floating in water, and wrote [PDF]:
“I observed many of them very evidently in motion . . . [these motions] arose neither from currents in the fluid, nor from its gradual evaporation, but belonged to the particle itself.”
To make sure that the pollen wasn’t alive–actually swimming around–Brown tried it with coal dust. Dust had the same moves.
Today, we understand that Brownian motion, the random break dance of these tiny particles, comes from the water molecules bumping against them. In 1907, Einstein determined the properties of the liquid and the particles that would help describe their wanderings and the motion of molecules. But he also said that it was “impossible” to determine at any moment the speed and direction of a single particle during this dance.
Step 2. Water Into Air
The reason for Einstein’s doubt? The particles bumped around too quickly to ever measure their speed and direction:
He believed that it would be impossible in practice to track this motion, given the incredibly short timescales over which the Brownian fluctuations take place. [PhysicsWorld]
How quick is too quick? A very tiny glass sphere (think micrometers) in water would change direction almost every 100 nanoseconds (about the time it takes light to travel 30 meters). Raizen wanted to make the time between moves longer, so they didn’t use water. They put the glass beads on a dance floor with fewer partners, using a medium whose molecules are farther apart: air.
Step 3. Floating on Air
Pollen doesn’t float on air. Neither does a micrometer-sized glass bead. Raizen’s team needed something to hold the glass up. They decided that the answer was light particles in a pair of laser chopsticks:
In 1907, Einstein likely did not foresee a time when dust-sized particles of glass could be trapped and suspended in air by dual laser beam “optical tweezers.” Nor would he have known that ultrasonic vibrations . . . would shake those glass beads into the air to be tweezed and measured as they moved in suspension. [ScienceDaily]
They could control a glass bead’s motion to the precise point where it was still dancing the Brownian, but not too fast to follow. But the lasers allowed them to do more than suspend the glass: By looking at how the glass bead deflected the light while it was buffeted by air molecules and bounced about on the chopsticks, the researchers could determine what Einstein dubbed impossible, a bead’s instantaneous direction and speed.
Step 4. Future Directions
Understanding these discrete steps will help wherever Brownian motion rules: everywhere from cell guts to the scent of perfume wafting through apparently stagnant air.
“It is certainly an important achievement to be able to directly measure the velocity of the Brownian particle at these short times,” says Christoph Schmidt of the University of Göttingen in Germany. “Technically it is now becoming possible to track individual particles with very high time and spatial resolution, limited in the end only by how many photons per second one can get to interact with the particle.” [New Scientist]
Source: Refuting Einstein in 4 Easy Steps: Physicists Measure Brownian Motion
In another step forward in the quest to create artificial life in a test tube, a team of genetic engineers led by Craig Venter has built a synthetic genome and proved that it can power up when placed inside an existing cell.
Dr. Venter calls the result a “synthetic cell” and is presenting the research as a landmark achievement that will open the way to creating useful microbes from scratch to make products like vaccines and biofuels. At a press conference Thursday, Dr. Venter described the converted cell as “the first self-replicating species we’ve had on the planet whose parent is a computer.” [The New York Times]
The technical achievement is worth crowing about. The researchers built on Venter’s trick from last year, in which he took the genome from one bacterium, transferred it the hollowed-out shell of a different bacterial species, and watched as the new cell “booted up” successfully. In this new step, the researchers built a genome from scratch, copying the genetic code from a bacterium that infects goats and introducing just a few changes as a “watermark”; then they transferred that synthetic genome to a cell. As the researchers report in Science, the cell functioned and replicated, creating more copies of the slightly altered goat-infecting bacterium–now nicknamed Synthia.
But the reactions to Venter’s accomplishment have been mixed–while some celebratory headlines trumpeted the creation of artificial life, many scientists said the reaction was overblown, and took issue with Venter’s claim of having created a truly synthetic cell. Here, we round up a selection of responses from all corners of the science world.
Bioethicist Arthur Caplan finds the philosophical ramifications of the work fascinating:
“Their achievement undermines a fundamental belief about the nature of life that is likely to prove as momentous to our view of ourselves and our place in the Universe as the discoveries of Galileo, Copernicus, Darwin and Einstein.” [Nature News]
But many experts say that since Venter copied a pre-existing genome, he didn’t really create a new life form.
“To my mind Craig has somewhat overplayed the importance of this,” said David Baltimore, a leading geneticist at Caltech. Dr. Baltimore described the result as “a technical tour de force” but not breakthrough science, but just a matter of scale…. “He has not created life, only mimicked it,” Dr. Baltimore said [The New York Times].
In addition, many experts note that the experimenters got a big boost by placing the synthetic genome in a preexisting cell, which was naturally inclined to make sense of the transplanted DNA and to turn genes on and off. Thus, they say, it’s not accurate to label the experiment’s product a true “synthetic cell.”
Meanwhile, physicist Freeman Dyson backed his way into paying the researchers a compliment in his own inimitable way:
This experiment, putting together a living bacterium from synthetic components, is clumsy, tedious, unoriginal. From the point of view of aesthetic and intellectual elegance, it is a bad experiment. But it is nevertheless a big discovery. It opens the way to the new world of synthetic biology. It proves that sequencing and synthesizing DNA give us all the tools we need to create new forms of life. After this, the tools will be improved and simplified, and synthesis of new creatures will become quicker and cheaper. Nobody can predict the new discoveries and surprises that the new technology will bring [The Edge].
And while some horrified environmentalists called for an immediate halt to such experiments, arguing that unnatural life forms could cause unknown disasters if released into the wild, Paul Keim of the National Science Advisory Board for Biosecurity was quick to reassure the public.
Keim said there is no new hazard because the Venter team manufactured a genome whose structure and function were already understood. The researchers didn’t create a novel life form. “We have a long way to go before we see a totally synthetic organism that does something important or dangerous,” he said. [Washington Post]
Source: Did Craig Venter Just Create Synthetic Life? The Jury Is Decidedly Out
The theory of general relativity: It works. OK, it’s not exactly Earth-shattering news that Albert Einstein’s century-old idea works in real life. That’s been shown over and over. But what had been difficult for researchers to do until now was verify the theory on truly massive scales beyond the solar system, that of whole galaxies and clusters of galaxies. This week in Nature, Reinabelle Reyes and colleagues report that they did it, and that Einstein was proven correct once more.
While the find is a nice coup for Reyes’ team, its importance goes beyond just reaffirming the great scientists of yesteryear with yet another “Einstein was right” story. The existence of dark matter and dark energy is based on the assumption that Einstein’s gravity is affecting galaxies billions of light-years from Earth in the same way that it affects objects in our solar system [National Geographic]. However, if the study had shown that general relativity needed a slight adjustment at vast distances (like the nudge Einstein himself provided to Newton’s physics), that could have altered prevailing ideas about dark matter and energy. This research indicates those pesky ideas may be here to stay [Space.com].
Reyes’ approach combined the study of galaxies’ gravitational lensing (how much they bend the light from surrounding galaxies), their velocities, and how and where they formed clusters. All of these measurements combined created a system to test theories of gravity independent of particular parameters in the theories [Space.com]. What they found closely matched what you’d predict under general relativity. They tested two alternative gravitational theories, too. One, called tensor-vector-scalar (TeVeS), gave results beyond the study’s margin of error. Another, called f(R), didn’t work as well as general relativity. But it fell within the margin of error, so the scientists say it will take more research to disprove it.
Meanwhile, as the spirit of general relativity is reaffirmed in the pages of Nature, the pages upon which Einstein formulated the theory are going on display in Jerusalem. Elsa, his wife, gave the pages to Hebrew University, and they are currently part of 50th anniversary festivities at the Israel Academy of Sciences and Humanities. Each of the 46 pages, labored over between November 1915 and their publication in May 1916, has its own case, each lighted dimly in a room that has been darkened to protect the paper. There on Page 1 is the now familiar title in German: “The Foundation of the General Theory of Relativity” [The New York Times].
However, if you need more Einstein and can’t make the trip to Israel, check out his mustachioed mug on the cover of the April DISCOVER issue, on newsstands this week.
Image: Ferdinand Schmutzer
Source: Einstein Proven Right (Again!) by the Movements of Galaxies
eldavojohn writes “Petr Horava, a physicist at the University of California in Berkeley, has a new theory about gravity and spacetime. At high energies, it actually snips any ties between space and time, yet at low energies devolves to equivalence with the theory of General Relativity, which binds them together. The theory is gaining popularity with physicists because it fits some observations better than Einstein’s or Newton’s solutions. It better predicts the movement of the planets (in an idealized case) and has a potential to create the illusion of dark matter. Another physicist calculated that under Horava Gravity, our universe would experience not a Big Bang but a Big Bounce — and the new theory reproduces the ripples from such an event in a way that matches measurements of the cosmic microwave background.”
Ponca City, We love you writes “The NY Times reports that after a journey of 7.3 billion light-years, a race between gamma rays ranging from 31 billion electron volts to 10,000 electron volts, a factor of more than a million, in a burst from an exploding star, have arrived within nine-tenths of a second of each other. A detector on NASA’s Fermi Gamma-Ray Space Telescope confirmed Einstein’s proclamation in his 1905 theory of relativity that the speed of light is constant and independent of its color, energy, direction or how you yourself are moving. Some theorists had suggested that space on very small scales has a granular structure that would speed some light waves faster than others — in short, that relativity could break down on the smallest scales. Until now such quantum gravity theories have been untestable because ordinarily you would have to see details as small as the so-called Planck length, which is vastly smaller than an atom — to test these theories in order to discern the bumpiness of space.”
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