New Research Confirms The Existence of Dark Matter
Image: Don Dixon
Fans of dark matter can rest easy. A study published last month raised eyebrows by suggesting that our cosmic neighbourhood is empty of the extra mass needed to hold the galaxy together. But a re-analysis shows that the dark matter was there all along.
Dark matter is the mysterious, invisible stuff that makes up 83 per cent of the matter in the universe. It is responsible for keeping galaxies from flying apart despite their high spinning speeds, and has aided our understanding of how structures in the universe formed.
The most popular theories say that dark matter is a hitherto undetected particle called a WIMP (weakly interacting massive particle) that is shy of interacting with ordinary matter through any force except gravity.
But several underground detectors waiting for WIMPs have come up empty, or with conflicting results. If the galaxy is so full of dark matter, why hasn’t it shown up yet?
In April, a team led by Christian Moni-Bidin of the University of Concepcion in Chile thought they had a solution: the WIMPs aren’t actually there.
The team tracked the motions of more than 400 stars within 13,000 light years of Earth to estimate the mass of matter – visible and dark – in the sun’s local neighbourhood. They concluded that the mass they found could be explained by the visible matter alone, with no need for dark matter.
But the team made a subtle error, say Jo Bovy and Scott Tremaine of the Institute for Advanced Study in Princeton, New Jersey.
Moni-Bidin and colleagues considered stars whose orbits take them far above or below the Milky Way’s main bright disc, and used the speed at which they orbit the centre of the galaxy to figure out how much of a pull they feel from the nearby mass of stars and dark matter. They assumed that the stars’ speeds would be the same no matter how far they were from the galactic centre. Observations of dust clumps have shown that this assumption is true for young stars orbiting in the galactic disc, which mostly move in a near-perfect circle.
But the stars that orbit high above or far below the disc can’t have circular orbits, Bovy says. The only stars that reach such great heights have been kicked away from the disc by matter in the galaxy’s spiral arms, which sent them on highly elliptical orbits.
Full Article: Crisis averted: Dark matter was there all along
Could your next hard drive be made with DNA?
Okay, so maybe not your next one, but in a few year’s time? Maybe your storage will be writ across DNA itself. Researchers at Stanford have developed a method to store binary code on DNA. Dubbed the “recombinase addressable data (RAD) module,” the method controls the synthesis and degradation of two proteins, integrase and excisionase. With RAD, a particular section of a microbe’s DNA is tweaked to glow either red or green under ultraviolet light — and it can be switched back and forth at will.
What really sets this biological bit apart from others is that it can be reliably, and non-destructively, switched back and forth. It took the researchers three years to come up with the precise cocktail of proteins to achieve this feat. Since the switch is programmed into the microbes, it remains in its current state while the cell doubles, and can then be modified if needed.
“Programmable data storage within the DNA of living cells would seem an incredibly powerful tool for studying cancer, aging, organismal development and even the natural environment,” said synthetic biologist Drew Endy, but we’re a while from getting it to a more useful computational state. It’s currently got around a 30 minute switch time. As Endy put it, “We’re probably looking at a decade from when we started to get to a full byte.”
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These high speed photographs of colored water are captured in a way to mimic the shape of blooms, leaves, and even pots. Photographer Jack Long creates cocktails of dyes, thickeners, and pigments for each component of the shot and then blasts them through a customized mechanism before snapping a perfectly timed capture.
