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Albert Moukheiber
Works at Hopital Chenevier
Attended University of Paris VI: Pierre et Marie Curie
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Albert Moukheiber

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In addition to the awesomeness of having observed gravitational waves, today's announcement is astonishing because it also reminds us of one of Sciences main properties : predictability.
Predictability might be the single most differenciating factor between science and other disciplines and separates completely science from being a "belief system".

We tend to assume that science explains the world but sciences role goes further into predicting how the world would react in a certain set of consequences.

Einstein created a model that he thought could explain the phenomenon he was observing and said, i predict that there are these things that should exist here and here and here for my model to function. Gravitational waves are one of these elements. Nearly a century later, his prediction has just been verified. This encapsulate both the predictability nature of science but also it's falsifiability: had we not detected them, Einsteins' model would have needed to be rehauled.

Some people say science is just another belief or that people are replacing god with science. Predictability and falsifiability shows us that science and belief cannot be further apart.
 
We have observed gravitational waves!

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 1916, 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.

With a four-kilometer leg, this means that LIGO can spot changes in length of about one-quarter of a part in 10²¹. That's the resolution you need to spot events like this: despite the tremendous violence of the collision (as I'll explain in a second), it was so far away -- really, on the other end of the universe -- that it only created vibrations of about five parts in 10²¹ on Earth.

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.

What's next?

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.
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You Are Not Stupid

“So what do you do for a living?” I always cringe a bit when that question comes up among strangers, because when I reveal that I’m an astrophysics professor the response is almost always the same. “Um…wow…. You must be really smart!”

While it’s often intended as a compliment, it really isn’t. Smart didn’t allow me to become an astrophysicist. Hard work, dedication and the support of family and friends did. It’s also one of the most deeply divisive misconceptions about scientists that one can have: scientists are smarter than you. Part of this stems from the idolization of brilliant scientists. Albert Einstein was so smart that fictitious quotes are attributed to him. Media buzzes whenever Stephen Hawking says something about black holes. Any quote by Neil Tyson is a sure way to get likes on Facebook. We celebrate their genius and it makes us feel smart by association. But this stereotype of the “genius scientist” has a dark side.

For one there’s expectation that to do science you must be super smart. If you struggle with math, or have to study hard to pass chemistry, you must not have what it takes. The expectation to be smart when you don’t feel smart starts to foster a lack of self confidence in your abilities. This is particularly true if you’re a girl or minority where cultural biases presume that “your kind” aren’t smart, or shouldn’t be. Lots of talented children walk away from science because they don’t feel smart.

Then there’s the us vs. them mentality that arises from the misconception. Scientists (and fans of science) are smart. Smarter than you. You are stupid. But of course, you’re not stupid. You know you’re not stupid. The problem isn’t you, it’s the scientists. Scientists are arrogant. For example, when I criticized a particular science website for intentionally misleading readers, the most popular rebuttal was that I (as a scientist) was being elitist.

Where this attitude really raises its head is among supporters of fringe scientific ideas. Some of the strongest supporters of alternative scientific ideas are clearly quite intelligent. Presidential hopeful and evolution denier Ben Carson is a neurosurgeon. Pierre Robitaille made great advances in magnetic resonance imaging, but adamantly believes that the cosmic microwave background comes from Earth’s oceans. Physicist and Nobel laureate Ivar Giaever thinks global warming is a pseudoscience on the verge of becoming a “new religion.” None of these folks are stupid.

If there’s one thing most people know about themselves it’s that they’re not stupid. And they’re right. We live in a complex world and face challenges every day. If you’re stupid, you can quickly land in a heap of unpleasantness. Of course that also means that many people equate being wrong with being stupid. Stupid people make the wrong choices in life, while smart people make the right ones. So when you see someone promoting a pseudoscientific idea, you likely think they’re stupid. When you argue against their ideas by saying “you’re wrong,” what they’ll hear is “you’re stupid.” They’ll see it as a personal attack, and they’ll respond accordingly. Assuming someone is stupid isn’t a way to build a bridge of communication and understanding.

One of the things I love about science is how deeply ennobling it is. Humans working together openly and honestly can do amazing things. We have developed a deep understanding of the universe around us. We didn’t gain that understanding by being stupid, but we have been wrong many times along the way. Being wrong isn’t stupid.

Sometimes it’s the only way we can learn.
One of the most deeply divisive misconceptions about scientists is that they are smarter than you.
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On science
 
The Shoulders of Giants

“If I have seen further, it is by standing on the shoulders of giants.” It’s a quote often attributed to Isaac Newton, though similar statements were made as far back as the 1100s. The sentiment behind the idea is that great scientists don’t live in a vacuum. They build upon the ideas of their predecessors and peers. Take, for example, the curious case of Roger Bacon.

Bacon lived in the 1200s, in the heart of what is sometimes referred to as the “dark ages.” It’s easy to see Bacon as a man centuries ahead of his time. He advocated experimental approaches over appeals to authority, saying “Plato is my friend, but truth is a better friend.” Like Newton he studied optics, and found that light could be split into a rainbow of colors by water. He proposed a model based upon the reflection of light to explain this effect. He also studied astronomical calendars, and noted that the Georgian year of 365.25 days was slightly off. He studied alchemy, which is something Newton spent a great deal of time studying as well.

Bacon’s rejection of the blind following of earlier authorities and his view of personal experiments as the ideal seems to be much more in tune with Newton’s era than the medieval world, but Bacon was truly a product of his times. In 1178 there were reports of a bright light appearing on the Moon, which some think could have been due to a meteor collision. Gervase of Canterbury saw the event, but also collected the observations of five monks who also witnessed the event. Gervase didn’t simply trust his own eyes, but gathered data to confirm his observations. In the early 1200s, Vincent of Beauvais wrote about the Earth as a spherical globe, and noted that gravity pulled everywhere toward its center. He even speculated on what would happen if you dropped a stone into a hole going through the globe.

The science of these medieval scholars wasn’t exactly the same as the methods we use today. They were deeply rooted in the philosophical and theological scaffolding of the time. However it is clear that their ideals of a search for truth was much like our own, and their rudimentary methods did show how knowledge could be gained through experimental tests and thought experiments. Later scholars such as Newton refined their methods, just as we have built upon Newton’s.

We often think of science as a specific tool that stands objectively outside our own worldview. But science has evolved over the centuries. It’s become an increasingly powerful tool as a result. So that today by standing on the shoulders of giants, we can see very far indeed.
Scientists don't live in a vacuum. They build upon the ideas of their predecessors and peers. Take, for example, the curious case of Roger Bacon.
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Has +Artem Russakovskii​ moved to support at Google Photos Help because these questions fall smack in the middle of his comfort zone... 
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To those that always think that 'the media' does this or that, a small reminder that anthropomorphizing media is just intellectual laziness. They are made of complex individuals, just like any other company.
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Lebanon is rising. Keep it going. #مستمرّون #طلعت_ريحتكن #youstink
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Framing is when you manipulate how you frame data to convey a message.

The first picture is Bloomberg reporting on the effect of the Greek No on the euro. One would say the Euro has plummeted to unknown depth. Notice that that the Y-axis they used goes from 1.098 to 1.112.

When you take the exact same data and look at it over 5 months (pic 2), with a different Y-axis the drop isn't so meaningful anymore.

Being aware of these mechanisms help us form better opinions and avoid falling in certain predetermined narratives.
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Heal faster with Jesus Band Aids! 
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Le lapin vert, Joinville le pont
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Expecto Patronum !
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Have him in circles
496 people
Ислом Икромов's profile photo
Филатова Валентина's profile photo
Nadim Haswani's profile photo
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JAMES NDIRANGU's profile photo
CAR CRASHES's profile photo
иван маркин's profile photo
Gilles R's profile photo
Work
Employment
  • Hopital Chenevier
    Psychologist | Researcher, 2014 - present
  • Universite paris VIII
    Lecturer, 2012 - present
  • Hopital Pitié Salpêtrière - Paris
    Psychologist | Researcher, 2005 - 2014
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Gender
Male
Story
Tagline
Polymath. Universal Fixer.
Bragging rights
Laziness makes the world evolve
Education
  • University of Paris VI: Pierre et Marie Curie
    Cognitive Neuroscience, 2006 - 2011
    PhD
  • University of Paris VIII: Vincennes - Saint-Denis
    Clinical Psychology, 2005 - 2011
    MS
  • American University of Beirut
    Clinical Psychology, 2000 - 2005
    BS
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Pleasant hotel, nothing too fancy, proportional to the price. Satisfied, was what I had imagined.
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I eat pasta every other day, the pasta alla pomodoro here is by far the best I've ever had. We had to wait outside but the extremely kind woman offered us fried calamari, wine and chair while we wait. The veal is also to die for. Incredible food.
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It was okay, front office was slowish and understaffed, average all around.
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