the limits of the universe
“On the outskirts of Paris, eight metres below ground in a climate-controlled vault, sits a 143-year-old platinum alloy cylinder. Standing just 39 mm tall, it has never been touched by human hands. Like a delicate Russian doll, the cylinder is caged inside three nested glass bells in a room that can be accessed only with three keys kept by three different people. Surrounding the mysterious object are ‘the witnesses’: six ‘identical’ cylinders cast from the same platinum alloy.
“Though preservation efforts rival those of the Turin Shroud, the cylinder is not a sacred religious object. It is the International Prototype Kilogram (IPK), the one and only true kilogram against which all others are measured. Housed in the Pavillon de Breteuil – home to the International Bureau of Weights and Measures (BIPM) – the IPK will soon lose its unique status and become a relic of a bygone age. It will then be as quaint as the International Prototype Metre (IPM) – a platinum alloy bar also housed at the BIPM – that served as the world’s official metre until 1960.”
Benjamin Skuse, SI gets a makeover
Good article about the history of the kilogram and the new definition that was officially adopted yesterday (November 16th).
About the vote, another article: “Scientists for whom the update represents decades of work clapped, cheered and even wept as the 50-plus nations one by one said “yes” or “oui” to the update in the French city of Versailles on Friday (local time).
Nobel prize winner William Phillips called it “the greatest revolution in measurement since the French revolution”, which ushered in the metric system of metres and kilograms.
Researchers confirm Earth’s inner core is solid: Holy Grail found
A new study by researchers at The Australian National University (ANU) could help us understand how our planet was formed.
Associate Professor Hrvoje Tkalčić and PhD Scholar Than-Son Phạm are confident they now have direct proof the earth’s inner core is solid.
They came up with a way to detect shear waves, or “J waves” in the inner core – a type of wave which can only travel through solid objects.
“We found the inner core is indeed solid, but we also found that it’s softer than previously thought,” Associate Professor Tkalčić said.
“It turns out – if our results are correct – the inner core shares some similar elastic properties with gold and platinum.
The inner core is like a time capsule, if we understand it we’ll understand how the planet was formed, and how it evolves.”
Inner core shear waves are so tiny and feeble they can’t be observed directly.
In fact, detecting them has been considered the “Holy Grail” of global seismology since scientists first predicted the inner core was solid in the 1930s and 40s.
So the researchers had to come up with a creative approach.
Their so-called correlation wavefield method looks at the similarities between the signals at two receivers after a major earthquake, rather than the direct wave arrivals.
A similar technique has been used by the same team to measure the thickness of the ice in Antarctica.
“We’re throwing away the first three hours of the seismogram and what we’re looking at is between three and 10 hours after a large earthquake happens.
We want to get rid of the big signals,” Dr Tkalčic said.
“Using a global network of stations, we take every single receiver pair and every single large earthquake – that’s many combinations – and we measure the similarity between the seismograms.
That’s called cross correlation, or the measure of similarity.
From those similarities we construct a global correlogram – a sort of fingerprint of the earth.”
The study shows these results can then be used to demonstrate the existence of J waves and infer the shear wave speed in the inner core.
While this specific information about shear waves is important, Dr Tkalčić says what this research tells us about the inner core is even more exciting.
“For instance we don’t know yet what the exact temperature of the inner core is, what the age of the inner core is, or how quickly it solidifies, but with these new advances in global seismology, we are slowly getting there.
“The understanding of the Earth’s inner core has direct consequences for the generation and maintenance of the geomagnetic field, and without that geomagnetic field there would be no life on the Earth’s surface.”
The research has been published in Science Magazine.
source of this article phys.org
Donna Strickland, from Canada, is only the third woman winner of the award, along with Marie Curie, who won in 1903, and Maria Goeppert-Mayer, who was awarded the prize in 1963.
Dr Strickland shares this year’s prize with Arthur Ashkin, from the US, and Gerard Mourou, from France.
It recognises their discoveries in the field of laser physics.
Excerpt: “Mars Calling” on Amazon Video.
Today, we and the National Science Foundation (NSF) announced the detection of light and a high-energy cosmic particle that both came from near a black hole billions of trillions of miles from Earth. This discovery is a big step forward in the field of multimessenger astronomy.
But wait — what is multimessenger astronomy? And why is it a big deal?
People learn about different objects through their senses: sight, touch, taste, hearing and smell. Similarly, multimessenger astronomy allows us to study the same astronomical object or event through a variety of “messengers,” which include light of all wavelengths, cosmic ray particles, gravitational waves, and neutrinos — speedy tiny particles that weigh almost nothing and rarely interact with anything. By receiving and combining different pieces of information from these different messengers, we can learn much more about these objects and events than we would from just one.
Lights, Detector, Action!
Much of what we know about the universe comes just from different wavelengths of light. We study the rotations of galaxies through radio waves and visible light, investigate the eating habits of black holes through X-rays and gamma rays, and peer into dusty star-forming regions through infrared light.
The Fermi Gamma-ray Space Telescope, which recently turned 10, studies the universe by detecting gamma rays — the highest-energy form of light. This allows us to investigate some of the most extreme objects in the universe.
Last fall, Fermi was involved in another multimessenger finding — the very first detection of light and gravitational waves from the same source, two merging neutron stars. In that instance, light and gravitational waves were the messengers that gave us a better understanding of the neutron stars and their explosive merger into a black hole.
Fermi has also advanced our understanding of blazars, which are galaxies with supermassive black holes at their centers. Black holes are famous for drawing material into them. But with blazars, some material near the black hole shoots outward in a pair of fast-moving jets. With blazars, one of those jets points directly at us!
Multimessenger Astronomy is Cool
Today’s announcement combines another pair of messengers. The IceCube Neutrino Observatory lies a mile under the ice in Antarctica and uses the ice itself to detect neutrinos. When IceCube caught a super-high-energy neutrino and traced its origin to a specific area of the sky, they alerted the astronomical community.
Fermi completes a scan of the entire sky about every three hours, monitoring thousands of blazars among all the bright gamma-ray sources it sees. For months it had observed a blazar producing more gamma rays than usual. Flaring is a common characteristic in blazars, so this did not attract special attention. But when the alert from IceCube came through about a neutrino coming from that same patch of sky, and the Fermi data were analyzed, this flare became a big deal!
IceCube, Fermi, and followup observations all link this neutrino to a blazar called TXS 0506+056. This event connects a neutrino to a supermassive black hole for the very first time.
Why is this such a big deal? And why haven’t we done it before? Detecting a neutrino is hard since it doesn’t interact easily with matter and can travel unaffected great distances through the universe. Neutrinos are passing through you right now and you can’t even feel a thing!
The neat thing about this discovery — and multimessenger astronomy in general — is how much more we can learn by combining observations. This blazar/neutrino connection, for example, tells us that it was protons being accelerated by the blazar’s jet. Our study of blazars, neutrinos, and other objects and events in the universe will continue with many more exciting multimessenger discoveries to come in the future.
Want to know more? Read the story HERE.
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There are many ways to repel droplets from a surface: water droplets will bounce off superhydrophobic surfaces due to their nanoscale structures; a vibrating liquid pool can keep droplets bouncing thanks to its deformation and a thin air layer trapped under the drop; and heated surfaces can repel droplets with the Leidenfrost effect by vaporizing a layer of liquid beneath the droplet. But all of these methods will only work for certain liquids under specific circumstances.
More recently, researchers have begun looking at a different way to repel droplets: moving the surface. The motion of the plate drags a layer of air with it; how thick that layer of air is depends on the plate’s speed. (Faster plates make thinner air layers.) Above a critical plate speed, a falling droplet will impact without touching the plate directly and will rebound completely. This works for many kinds of liquids – the researchers used silicone oil, water, and ethanol – across many droplet sizes and speeds. The key is that the air dragged by the plate deforms the droplet and creates a lift force. If that lift force is greater than the inertia of the droplet, it bounces. (Image and research credit: A. Gauthier et al., source)
A diamond-bearing space rock that exploded in Earth’s atmosphere in 2008 was part of a lost planet from the early Solar System, a study suggests.
The parent “proto-planet” would have existed billions of years ago before breaking up in a collision and was about as large as Mercury or Mars.
They argue that the pressures necessary to produce diamonds of this kind could only occur in planet of this size.
William Bragg, (1925), Concerning the Nature of Things, Dover Publications, Inc., New York, NY, 1948
http://www.skyandtelescope.com/astronomy-news/black-hole-flees-behemoth-galaxy/Better late than never! Here’s a scary story about runaway black holes!
Starring guest speaker Lapetus!
It’s black hole Friday! Lets celebrate by enjoying black hole related comics!