There are dams in the world whose situation makes them far more crucial: those which sit upriver of major cities, especially those blocking large rivers which would create waves of tremendous size. The Aswan High Dam in Egypt is perhaps the most (in)famous example: Cairo, with its population of nearly ten million people, would be directly in the line of fire of any (gods forbid!) failure.
There is a lesser-known example out there, and unlike the Aswan Dam, its situation is precarious enough that engineers are losing sleep over it: the Mosul Dam in northern Iraq. It dams the Tigris, one of the great rivers of the Near East, and its failure would first send a tidal wave directly through the cities of Mosul, Tikrit, and Samarra (about 3 million people), before destroying a second dam. Baghdad, (population 7.2 million) a few days downriver, would probably be spared a direct tidal wave, but would be struck by floods which dwarf Katrina's. (This assuming that the dam failed at high water; at low water, the damage would be less, but dams are less likely to fail at low water)
And unlike Aswan High Dam, the Mosul Dam is in critically bad condition. Its construction was dubious from the beginning, sitting atop ground layers of clay and gypsum – two substances easily eaten away by water. As a result, it has required constant maintenance ever since its construction, adding grout almost nonstop. But with the nearby city of Mosul in ISIS hands, maintenance has become highly irregular, and large voids have been detected in its body. The dam engineers have considered the "most dangerous in the world" for over a decade has managed to become even more unsafe.
Disasters which reduce cities to ruin have become (alas) not uncommon in the past few years: whether it be the immense destruction of New Orleans by Hurricane Katrina, or the reduction of Syria into rubble by civil war. Beyond the immediate consequences, such events can send millions of people far and wide, in search of a new home, with all of the consequences which may follow from that. It's honestly hard to conceive of what might happen if one of the largest cities in the Middle East were overnight laid to ruin, and its population scattered into an already politically-unstable desert, but I can promise that nobody other than the ravens and the vultures would benefit by it.
This morning, the LIGO observatory announced a historic event: for the very first time in history, we have observed a pair of black holes colliding, not by light (which they don't emit), but by the waves in spacetime itself that they form. This is a tremendously big deal, so let me try to explain why.
What's a gravitational wave?
The easiest way to understand General Relativity is to imagine that the universe is a big trampoline. Imagine a star as a bowling ball, sitting in the middle of it, and a spaceship as a small marble that you're shooting along the trampoline. As the marble approaches the bowling ball, it starts to fall along the stretched surface of the trampoline, and curve towards the ball; depending on how close it passes to the ball and how fast, it might fall and hit it.
If you looked at this from above, you wouldn't see the stretching of the trampoline; it would just look black, and like the marble was "attracted" towards the bowling ball.
This is basically how gravity works: mass (or energy) stretches out space (and time), and as objects just move in what looks like a straight path to them, they curve towards heavy things, because spacetime itself is bent. That's Einstein's theory of Relativity, first published in 1919, and (prior to today) almost every aspect of it had been verified by experiment.
Now imagine that you pick up a bowling ball and drop it, or do something else similarly violent on the trampoline. Not only is the trampoline going to be stretched, but it's going to bounce -- and if you look at it in slow-motion, you'll see ripples flowing along the surface of the trampoline, just like you would if you dropped a bowling ball into a lake. Relativity predicts ripples like that as well, and these are gravitational waves. Until today, they had only been predicted, never seen.
(The real math of relativity is a bit more complicated than that of trampolines, and for example gravitational waves stretch space and time in very distinctive patterns: if you held a T-square up and a gravitational wave hit it head-on, you would see first one leg compress and the other stretch, then the other way round)
The challenge with seeing gravitational waves is that gravity is very weak (after all, it takes the entire mass of the Earth to hold you down!) and so you need a really large event to emit enough gravity waves to see it. Say, two black holes colliding off-center with each other.
So how do we see them?
We use a trick called laser interferometry, which is basically a fancy T-square. What you do is you take a laser beam, split it in two, and let each beam fly down the length of a large L. At the end of the leg, it hits a mirror and bounces back, and you recombine the two beams.
The trick is this: lasers (unlike other forms of light) form very neat wave patterns, where the light is just a single, perfectly regular, wave. When the two beams recombine, you therefore have two overlapping waves -- and if you've ever watched two ripples collide, you'll notice that when waves overlap, they cancel in spots and reinforce each other in spots. As a result, if the relative length of the legs of the L changes, the amount of cancellation will change -- and so, by monitoring the brightness of the re-merged light, you can see if something changed the length of one leg and not the other.
LIGO (the Laser Interferometer Gravitational-Wave Observatory) consists of a pair of these, one in Livingston, Louisiana, and one in Hartford, Washington, three thousand kilometers apart. Each leg of each L is four kilometers long, and they are isolated from ambient ground motion and vibration by a truly impressive set of systems.
If a gravitational wave were to strike LIGO, it would create a very characteristic compression and expansion pattern first in one L, then the other. By comparing the difference between the two, and looking for that very distinctive pattern, you could spot gravity waves.
How sensitive is this? If you change the relative length of the legs of an L by a fraction of the wavelength of the light, you change the brightness of the merged light by a predictable amount. Since measuring the brightness of light is something we're really good at (think high-quality photo-sensors), we can spot very small fractions of a wavelength. In fact, the LIGO detector can currently spot changes of one attometer (10⁻¹⁸ of a meter), or about one-thousandth the size of an atomic nucleus. (Or one hundred-millionth the size of an atom!) It's expected that we'll be able to improve that by a factor of three in the next few years.
So what did LIGO see?
About 1.5 billion light years away, two black holes -- one weighing about 29 times as much as the Sun, the other 36 -- collided with each other. As they drew closer, their gravity caused them to start to spiral inwards towards each other, so that in the final moments before the collision they started spinning around each other more and more quickly, up to a peak speed of 250 orbits per second. This started to fling gravity waves in all directions with great vigor, and when they finally collided, they formed a single black hole, 62 times the mass of the Sun. The difference -- three solar masses -- was all released in the form of pure energy.
Within those final few milliseconds, the collision was 50 times brighter than the entire rest of the universe combined. All of that energy was emitted in the form of gravitational waves: something to which we were completely blind until today.
Are we sure about that?
High-energy physics has become known for extreme paranoia about the quality of its data. The confidence level required to declare a "discovery" in this field is technically known as 5σ, translating to a confidence level of 99.99994%. That takes into account statistical anomalies and so on, but you should take much more care when dealing with big-deal discoveries; LIGO does all sorts of things for that. For example, their computers are set up to routinely inject false signals into the data, and they don't "open up the box" to reveal whether a signal was real or faked until after the entire team has finished analyzing the data. (This lets you know that your system would detect a real signal, and it has the added benefit that the people doing the data analysis never know if it's the real thing or not when they're doing the analysis -- helping to counter any unconscious tendency to bias the data towards "yes, it's really real!")
There are all sorts of other tricks like that, and generally LIGO is known for the best practices of data analysis basically anywhere. From the analysis, they found a confidence level of 5.1σ -- enough to count as a confirmed discovery of a new physical phenomenon.
(That's equal to a p-value of 3.4*10⁻⁷, for those of you from fields that use those)
So why is this important?
Well, first of all, we just observed a new physical phenomenon for the first time, and confirmed the last major part of Einstein's theory. Which is pretty cool in its own right.
But as of today, LIGO is no longer just a physics experiment: it is now an astronomical observatory. This is the first gravity-wave telescope, and it's going to let us answer questions that we could only dream about before.
Consider that the collision we saw emitted a tremendous amount of energy, brighter than everything else in the sky combined, and yet we were blind to it. How many more such collisions are happening? How does the flow of energy via gravitational wave shape the structure of galaxies, of galactic clusters, of the universe as a whole? How often do black holes collide, and how do they do it? Are there ultramassive black holes which shape the movement of entire galactic clusters, the way that supermassive ones shape the movement of galaxies, but which we can't see using ordinary light at all, because they aren't closely surrounded by stars?
Today's discovery is more than just a milestone in physics: it's the opening act of a much bigger step forward.
LIGO is going to keep observing! We may also revisit an old plan (scrapped when the politics broke down) for another observatory called LISA, which instead of using two four-kilometer L's on the Earth, consists of a big triangle of lasers, with their vertices on three satellites orbiting the Sun. The LISA observatory (and yes, this is actually possible with modern technology) would be able to observe motions of roughly the same size as LIGO -- one attometer -- but as a fraction of a leg five million kilometers long. That gives us, shall we say, one hell of a lot better resolution. And because it doesn't have to be shielded from things like the vibrations of passing trucks, in many ways it's actually simpler than LIGO.
(The LISA Pathfinder mission, a test satellite to debug many of these things, was launched on December 3rd)
The next twenty years are likely to lead to a steady stream of discoveries from these observatories: it's the first time we've had a fundamentally new kind of telescope in quite a while. (The last major shift in this was probably Hubble, our first optical telescope in space, above all the problems of the atmosphere)
The one catch is that LIGO and LISA don't produce pretty pictures; you can think of LIGO as a gravity-wave camera that has exactly two pixels. If the wave hits Louisiana first, it came from the south; if it hits Washington first, it came from the north. (This one came from the south, incidentally; it hit Louisiana seven milliseconds before Washington) It's the shift in the pixels over time that lets us see things, but it's not going to look very visually dramatic. We'll have to wait quite some time until we can figure out how to build a gravitational wave telescope that can show us a clear image of the sky in these waves; but even before that, we'll be able to tease out the details of distant events of a scale hard to imagine.
You can read the full paper at http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 , including all of the technical details. Many congratulations to the entire LIGO team: you've really done it. Amazing.
Incidentally, Physical Review Letters normally has a strict four-page max; the fact that they were willing to give this article sixteen pages shows just how big a deal this is.
Permalink here: http://www.scitechdigest.net/2016/02/better-gene-delivery-better-dna.html
Better gene delivery, Better DNA aptamers, Light effect transistor, Rejuvenation advances, Atomically precise materials, Integrated photonics modem, Electronic nematicity, Deep learning chips, Graphene lenses & electrodes, Flexiramic materials.
1. Delivering Genes Across the Blood Brain Barrier
Using high-throughput screening techniques combined with methods of directed evolution, researchers screened millions of viral variants to create a novel, modified adeno-associated virus that is able to efficiently get past the blood-brain-barrier and deliver genes and genetic engineering tools to neurons and other cells of the brain http://www.caltech.edu/news/delivering-genes-across-blood-brain-barrier-49679. This obviates the need to drill a hole through the skull to inject these vectors and provides a far more elegant tool that can be used for CRISPR-powered modifications. In related news rats have been cured of a genetic liver disorder with a more effective CRISPR-delivery system involving a different adeno-associated virus carrying guide RNA and repaired-gene-insert and lipid nanoparticles carrying Cas9 mRNA instructions http://news.mit.edu/2016/crispr-curing-disease-repairing-faulty-genes-0201; 6% of liver cell transformations are sufficient for disease curing, which is 15 times more effective than other methods, but the group hope to boost this % in future.
2. Better DNA Aptamer Technology
DNA aptamers can be artificially engineered to target and bind any molecular target in the body - proteins, viruses, bacteria, cells, tumours - but are limited by poorer binding-efficiency and instability due to enzymatic digestion. These two limiting factors have now been addressed http://www.a-star.edu.sg/Media/News/Press-Releases/articleType/ArticleView/articleId/4496.aspx with (i) the inclusion of an artificial base into the DNA that boosted binding ability by 100 times compared to existing aptamers, and (ii) the inclusion of a DNA-mini-hairpin structure that serves to restrict enzymatic digestion and boost lifetime in the body from hours to days. DNA aptamers like these could in theory be used instead of antibodies for therapeutic and diagnostic applications but are cheaper, quicker, and simpler to produce and obviate potential inflammatory side effects.
3. Developing a Light-Effect-Transistor
Prototype light effect transistors have been developed with the aim of replacing standard field effect transistors in future chip designs https://www.technologyreview.com/s/600702/the-nanodevice-aiming-to-replace-the-field-effect-transistor/. A light effect transistor comprises a wire that conducts electricity when exposed to light and insulates when it is dark; a light-controlled switch in which light functions like a gate and with benefits including no reliance on dopant atoms and the ability to achieve smaller size dimensions to continue Moore’s Law. The demonstrations include semiconducting nanowires whose conduction changes by six orders of magnitude when switched, and can also function as an optical amplifier that performs logic operations when two or more laser beams are used. But the biggest unsolved question is how a chip would accurately address more than a billion nanowires with light?
4. Rejuvenation via Senescent Cell & Amyloid Clearance
First, venture-backed company Unity Biotechnology joins competition with Oisin Biotechnology aiming to develop and launch therapeutics that clear senescent cells from adult animals https://www.fightaging.org/archives/2016/02/25-median-life-extension-in-mice-via-senescent-cell-clearance-unity-biotechnology-founded-to-develop-therapies.php. Their latest work extends the median lifespan of mice by 25% and should help to attract additional funding and support for this approach; investors will want to get this into humans as soon as possible. And back in the lab another group finds a 35% lifespan extension by clearing senescent cells http://newsnetwork.mayoclinic.org/discussion/mayo-clinic-researchers-extend-lifespan-by-as-much-as-35-percent-in-mice-2/. Second, a partnership between companies Pentraxin and GSK is slowly bearing fruit with clinically-tested drug therapies that very effectively clear amyloid (misfolded protein clumps that accumulate) deposits from tissues and body fluids, intended for Alzheimer’s and other diseases but providing a platform for this area of rejuvenation therapies https://www.fightaging.org/archives/2016/02/what-next-for-transthyretin-amyloid-clearance-therapies.php. Boosting mitophagy also rejuvenates cells to a more youthful state http://www.eurekalert.org/pub_releases/2016-02/nu-mst020316.php.
5. Atomically Precise Materials and Devices
Structural DNA technology can self-assemble nanoparticles into diamond-shaped crystal lattices https://www.bnl.gov/newsroom/news.php?a=11810. The DNA forms the rigid frame of the material, while complementary DNA binding ensures the nanoparticles bind in specific locations, leading to a diamond lattice about 100 times larger than conventional diamond; interesting platform for novel materials development. Bacteria produce self-assembled microcompartments to concentrate enzymatic production of certain molecules, and these compartments are being used as templates to engineer variants with novel functions and molecular production capabilities https://newscenter.lbl.gov/2016/02/04/toward-nanoscale-chemical-factories/, slowly building a platform of contained molecular production machinery that might one day be introduced inside human cells for exmample.
6. NASAs Integrated Photonics Modem
NASA is building the first fully integrated photonics modem, simplifying optical on-chip systems design, and reducing the size of the large prototype down to conventional system-on-chip scales http://www.nasa.gov/feature/goddard/2016/nasa-engineers-tapped-to-build-first-integrated-photonics-modem. The chip uses lasers to encode and transmit data at 10 - 100 times faster than equipment available today. While testing of the device in space won’t begin until 2020 we might see commercial applications of this earlier, particularly in data centers and Internet backbone lines.
7. Electronic Nematicity Key in Superconductivity
New studies indicate that the phenomenon of electronic nematicity, in which electron clouds in a material snap into an aligned and directional order, is a generic property common to high-temperature superconductors https://uwaterloo.ca/stories/waterloo-physicists-discover-new-properties. The electrons involved in superconductivity form patterns that exhibit different symmetries that preferentially align in one direction and which can compete with, co-exist, or enhance superconductivity. Hopefully this understanding allows for the future design of higher-temperature superconductors.
8. Dedicated Deep Learning Chips on Smartphones
Eyeriss is a newly designed and developed dedicated deep learning chip for use in smartphones and other low-power applications http://spectrum.ieee.org/tech-talk/semiconductors/processors/a-deep-learning-ai-chip-for-your-phone. The chip is designed to allow these devices to run computationally demanding neural network algorithms quickly and efficiently on the device without offloading to the cloud, and using only one tenth of the energy of a typical mobile GPU. Agnostic to the type of neural network being run the chip can process image, sound, and other types of data as needed and might also find deployment in autonomous platforms such as cars and drones. In related news Google’s DeepMind game-playing AI can now also navigate environments in first-person-shooters https://www.newscientist.com/article/2076552-google-deepmind-ai-navigates-a-doom-like-3d-maze-just-by-looking/ and I wonder if this can be transferred to robots to help in realworld environments, perhaps by using these dedicated chips.
9. Graphene Lenses and Electrode Benefits
First, graphene has been formed into a clever fresnel lens by using a laser to pattern concentric rings of graphene oxide on its surface, and allowing optical focusing in the visible and infrared down to scales of 200nm http://www.swinburne.edu.au/news/latest-news/2016/01/focus-on-results.php. Second, graphene-coated electrodes turn out to be an excellent option for applications involving interfacing with neurons http://graphene-flagship.eu/graphene-based-interfaces-do-not-alter-target-nerve-cells. Finally, graphene cages formed around silicon anodes appear to enable higher capacity batteries that avoid the problem of cracking that such materials are usually limited by http://spectrum.ieee.org/nanoclast/semiconductors/materials/graphene-cages-cover-silicon-anodes-for-high-capacity-batteries.
10. Flexiramics: Ceramics that Act Like Paper
A new material dubbed flexiramics is being developed and commercialised by a company called Eurekite http://arstechnica.com/science/2016/02/dutch-researchers-have-created-flexiramics-flexible-ceramics-for-circuit-boards/. Flexiramics appear to be a new class of materials that possess the mechanical properties of paper or thin textiles in being thin, foldable, and flexible while also exhibiting the properties of ceramics in being fireproof and nonconducting. The fabrics withstand 1,200 degrees Celsius for 24 hours without burning or melting. Printed PCBs will be the first application apparently but the possibilities are endless.
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The problem is that we evolved to be targeted, shallow information consumers in unified, deep information environments. As targeted, shallow information consumers we require two things: 1) certain kinds of information hygiene, and 2) certain kinds of background invariance. (1) is already in a state of free-fall, I think, and (2) is on the technological cusp. I don’t see any plausible way of reversing the degradation of either ecological condition, so I see the prospects for traditional philosophical discourses only diminishing.
In particular, one thing that makes things difficult is how non-linear the relationship between breakthroughs and results can be (e.g. a huge amount of work for a small improvement or a small amount of work for a large improvement as in residuals in training NNs).
The best we can do would be to have an active prediction market going as a leading indicator.
If we look at the recent case of AlphaGo, the power it utilized will be ~13kW for training and 100-170kW (~ 40 homes) for playing (15 W is human). At 160,000 games it was over-fitting--showing poor generalization. It took millions of games to get to where a human can get to in < 15,000 games. We've still got a very long ways to get to the sort of generalization capability of a human.
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