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Jonah Miller
moderator

Science News (Pop Sci)  - 
 
 
LIGO Detected Gravitational Waves!

Here is the real waveform, generated by two merging black holes, each about 30 times more massive than the sun.

The figure came from this paper, which I am still trying to read, because the journal's server has been hugged to death by eager scientists:
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102

Stay tuned. I'll be live-tweeting the panel at the +Perimeter Institute for Theoretical Physics (streamed here: http://link.perimeterinstitute.ca/c/306/11b67d512365bb5854c237e7e95cf8fb48bfdb0e9d91ea181cf487a551db8d72) in about an hour. And I'll write up a blog post tonight.

My twitter handle is @thephysicsmill and I'll use the hashtags #PILIGO   and #gravitationalwaves  
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Thanks, +Jonah Miller​!
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Pasan Madhusankha

Science News (Pop Sci)  - 
 
 
"Where Your Elements Came From"
“The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.”
-Carl Sagan

The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe. The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen. Much of the iron in your body was made during supernovas of stars that occurred long ago and far away. The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts. Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life. The featured periodic table is color coded to indicate humanity's best guess as to the nuclear origin of all known elements. The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research.

Nucleosynthesis | NASA
A star's energy comes from the combining of light elements into heavier elements in a process known as fusion, or "nuclear burning". It is generally believed that most of the elements in the universe heavier than helium are created, or synthesized, in stars when lighter nuclei fuse to make heavier nuclei. The process is called nucleosynthesis.

Nucleosynthesis requires a high-speed collision, which can only be achieved with very high temperature. The minimum temperature required for the fusion of hydrogen is 5 million degrees. Elements with more protons in their nuclei require still higher temperatures. For instance, fusing carbon requires a temperature of about one billion degrees! Most of the heavy elements, from oxygen up through iron, are thought to be produced in stars that contain at least ten times as much matter as our Sun.

Our Sun is currently burning, or fusing, hydrogen to helium. This is the process that occurs during most of a star's lifetime. After the hydrogen in the star's core is exhausted, the star can burn helium to form progressively heavier elements, carbon and oxygen and so on, until iron and nickel are formed. Up to this point the process releases energy. The formation of elements heavier than iron and nickel requires the input of energy. Supernova explosions result when the cores of massive stars have exhausted their fuel supplies and burned everything into iron and nickel. The nuclei with mass heavier than nickel are thought to be formed during these explosions.

Image Credit: Cmglee (Own work) CC BY-SA 3.0 or GFDL, via Wikimedia Commons

+Astronomy Picture of the Day (APoD) 
+STEM on Google+ Community 
+National Science Teachers Association 
+NASA Goddard 

#NASA #Astronomy #Space #Science #Stars #Supernovae #Earth #Elements #Nucleosynthesis #Physics #Chemistry #Geoscience #Cosmos #Universe #Infographic #APoD #CarlSagan
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Neuroscience News

Science News (Pop Sci)  - 
 
Threat of Cytomegalovirus Far Outweighs Zika Risk

As the Zika virus continues to spread across the globe, and gain worldwide attention for its’ potential birth defects, an NAU researcher is calling for greater public awareness of cytomegalovirus, the most common viral cause of birth defects in the United States.


As the Zika virus continues to spread across the globe, and gain worldwide attention for its potential birth defects, an NAU researcher is calling for greater public awareness of cytomegalovirus, the
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A breakdown of Cypriot y-chromosome phylogenies and geography.  Like Sardinia, the British Isles, the Balearic Islands and so on, it appears that Greek Cypriots have been a fairly stable population for a long, long time.  Several distinct phases can be seen going back to the Early Neolithic, and from there, to the Bronze Age.

Add "European Prehistory and Genetics" to your Google+ profile!
https://plus.google.com/u/0/communities/108916193105695988627
Open access at Investigative Genetics: Background: The archeological record indicates that the permanent settlement of Cyprus began with pioneering agriculturalists circa 11,000 years before present, (ca. 11,000 y BP). Subseq...
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Andrew Revkin

Science News (Pop Sci)  - 
 
Oregon Standoff Ends in Time to Prepare Malheur Refuge for Avian Occupiers http://nyti.ms/1PQ3foC
Malheur National Wildlife Refuge near Burns, Ore., last month.Credit Keith Ridler/Associated Press
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Now those kind of occupiers I support!
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Parasites On The Mind
Here's my take on a recently published study which claims chimpanzees infected with the parasite Toxoplasma gondii display a "morbid attraction" to the scent of leopard urine.
 
Of Chimps, Leopards, And Toxoplasma
Some of you may be familiar with the story about a little cat parasite call Toxoplasma gondii. It seems to be able to alter rodent behaviour so that they are more likely to be eaten by a cat, but it can also infect humans (and any warm-blooded vertebrate animal) and supposedly mess with human behaviour as well. Spoooooky. At least that's how the story goes. Like any other story, there is some grain of truth to it, but it is buried within a whole mass of (more sensationalised) dross. Any studies into Toxoplasma and host behaviour manipulation has the potential to go viral as it includes all the elements that makes a good headline - it contains cats, brain parasites, and zombies (in the form of host behaviour manipulation).

The literature on Toxoplasma and host behaviour is MASSIVE - some of it is good science, others are more like tabbies dressed as tigers. But for this post, I'm going to focusing on one story within a larger narrative, I want to talk about a paper recently published in Current Biology which had whipped the media into a frenzy (again) about how human behaviour is affected by Toxoplasma. http://www.cell.com/current-biology/abstract/S0960-9822%2815%2901517-1

Here's a tl;dr version of the study. The study found that compared with uninfected chimps, chimpanzees infected by Toxoplasma are not as averse to the odour of leopard (their natural predator) urine. The researchers concluded that this is because Toxoplasma is manipulating the chimps' behaviour so that they will be more likely to be eaten by a leopard (the final host for Toxoplasma are felines).

1) While the media coverage seems to be focused on how the parasite affects human behaviour, this experiment was done on chimps, and the media is extrapolating the conclusion of that study to humans. Humans and chimps may be genetically similar on some level, we have been separated by 5-7 million years of evolution, and our ancestors evolved in very different environments. There are some very key differences in the behaviour of chimps versus humans.
 
2) The study was not only correlative in nature, it was based on testing chimps for presence of Toxoplasma antibodies - not the parasites themselves, just a potential indicator of the parasites presence (having antibodies for something doesn't guarantee the presence of the said thing in the body). The researchers didn't confirm the presence of the parasites themselves. I understand they can't exactly do the latter for ethical reasons, in which case, maybe don't cannonball your way into such sensationalised conclusions?

3) The study tested how chimps response to the odour of urine and other big cats - the question is, just how much of a role does the sense of smell play in chimpanzees' predator avoidance repertoire? There is surprisingly little research on that. Is the sense of smell that important for predator avoidance compared with their other senses? Also, considering that chimpanzees are social animals, they would also rely upon other individuals in the group to warn of the presence of predators - you can't consider the vulnerability of a chimp to predation without the context of its social structure.

4) They mention potential behaviour variations between individuals (i.e. personalities) which may account for different level of aversion towards leopard urine odour which are pre-existing, regardless of the parasite. Good. But then, they just dismiss that possibility outright, by citing a single study that has found Toxoplasma is associated with disrupted fear response - in rat. Studies in other animals have shown that propensity for "recklessness" varies between individuals, even without the influence of parasites. So they're essentially saying Toxoplasma is the only possible explanation for why those chimps behaved slightly differently (in one aspects - response to leopard urine odour), even after bringing up the possibility that these behaviour variations exists regardless of parasitism, and discounting the dozens of other equally valid potential explanations. Not Wow.

5) Furthermore, when I dig into the methods, I found that the study was conducted on captive chimpanzees. Captive animals (especially behaviourally complex animals such as chimps) are known to exhibits behaviour which deviate significantly from their wild relatives. So we have no way of establishing whether such behaviour is representative of how they would behave in a natural setting (let alone extrapolating it to humans as the media has done). Once again, I understand that it would be extremely difficult to conduct such a study on wild chimps, in which case, the point I bring up in (2) still applies - don't jump to such sensationalised conclusions

6) Given the correlative nature of the study, we have no way of establishing how these chimps would have behaved before getting infected with Toxoplasma. So you can't rule out that maybe the chimps that behaved "oddly" are simply more likely to pick up Toxoplasma. They did mention this possibility, but they dismissed it just as quickly in the same manner as I described for (4).

7) The paper has 10 references in total (the supplementary material has 2 additional reference, but they were for methodological techniques), but did not cite a review recently published in 2014 in Advances in Parasitology which discussed at length the wide array of inconsistencies and seeming contradictory results from rodent-toxoplasmosis behavioural studies.
https://books.google.com.au/books?hl=en&lr=&id=ftnEAgAAQBAJ&oi=fnd&pg=PA109

And that's all I have to say about that. Peace out.
MFW I read another over-hyped "Toxoplasma gondii + host behaviour modification" paper pic.twitter.com/hOf8i62zWn · Tommy Leung – @The_Episiarch. I don't always subtweet, but when I do, it's about papers on Toxoplasma gondii and behavioural modification. Embedded image. 5:27 PM - 10 Feb 2016 ...
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+José Arcángel Salazar Delgado since you are familiar with the character,  you'll understand why it is absolutely appropriate to have Hanekawa in a post about toxoplasmosis ;-)
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AstroCamp

Science Bytes (Memes, Cartoons, Images)  - 
 
An atom consists of three types of building blocks: protons, neutrons, and electrons. Protons and neutrons stick together in the center, or nucleus, of the atom, while electrons whiz around the outside at breakneck speed.

Protons are defined as having positive charge and electrons as having negative charge. Neutrons are– you guessed it– neutral. It’s a law of nature that like charges repel each other and opposites attract. Put a lot of negatively charged electrons in one place, and if they’re free to move, they’ll spread out as much as possible. Getting a lot of negatively charged particles in one place and allowing them to move through a circuit is one common way to generate electrical power.

Large-scale generators get electrons moving using a different trick: electromagnetic induction. Moving magnetic fields spur charged particles into motion, creating electrical activity in wire coils.

For more on circuits and electricity, including a video explanation, check out today's blog!!
Electricity may seem mysterious, but it’s just electrons moving in an organized way!
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I thought electrons disappear?
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Russ George

Science News (Pop Sci)  - 
 
We are spending billions for windmills. There are now tools that cost a fraction of these giant ocean windmills that will restore the oceans http://russgeorge.net/2016/02/11/tilting-at-ocean-windmills/
For a fraction of the cost of ocean windmills restoring ocean pastures will repurpose our CO2 into billions of additional fish to feed the world
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Jonáš Melichar's profile photoMelinda Green's profile photoDelwar Hossain's profile photo
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You're posing a false choice. The question is not what other good might be done with the money for a wind farm, but what's the best way to spend an available amount of money to generate electricity in a given situation. Would you prefer a new nuke or fossil fuel plant to an off-shore wind farm?
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We see a lot of posts on the first confident detection of the gravitational wave. You may not know that the theoretical proposal of the detection infrastructure was made by Carlton M. Caves et al. based on his discovery of the squeezed states of vacuum and related quantum metrology techniques. Check out the review of Caves in 1980: http://journals.aps.org/rmp/abstract/10.1103/RevModPhys.52.341
The monitoring of a quantum-mechanical harmonic oscillator on which a classical force acts is important in a variety of high-precision experiments, such as the attempt to detect gravitational radiation. This paper reviews the standard techniques for monitoring the oscillator, and introduces a new technique which, in principle, can determine the details of the force with arbitrary accuracy, despite the quantum properties of the oscillator. The sta...
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Kenneth Rothey's profile photoCharles Filipponi's profile photo
 
I first encountered this intergalactic phenomenon when studying the words of Abraham when he first entered Egypt. We are now blessed with instrumentation and theory which confirms Abraham's prophecy.
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Kahil Nettleton

Science Bytes (Memes, Cartoons, Images)  - 
 
Here's a great place to get all of the Retro Space Travel Agency posters from NASA and Space X.  They have all of them...old and new.  :)
 
SALE - 10% OFF - How fortuitous!  We just updated our #Retro   #NASA   #Space   #Travel  poster listing to include the nine new posters just released, and our printer goes and has a sale on posters!  So we're passing that discount on to you!  These HD posters are printed on durable 12CS #poster  stock.  To help visualize that, think of a thick, premium  poster board.  That means these posters and made to last and are ideal for mounting.  Gotta collect them all!
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That's awesome! 
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Lord Satan

Science Bytes (Memes, Cartoons, Images)  - 
 
 
The Hubble Space Telescope is the first and only space telescope in operation. The telescope is nearly 26 years old, being launched into low Earth orbit in 1990. The first image is from 2010, when to commemorate Hubble Telescope's 20th Birthday, NASA released several of Hubble's findings. This Wide Field Camera 3 image, dubbed "Mystic Mountain", was one of those images. The next image is the Butterfly Nebula, imaged  in 2009. The third is the star cluster Pismis 24 with its nebula. I am astonished and joyed by the fact that we have this telescope to uncover and capture the beauty, glory, mystery, and deep unknown that is deep space.
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Beautiful! 
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About this community

Science on Google+ is a community moderated by scientists, for all people interested in science, both professionals and the general public. The primary goal of this community is to bring real scientists to the public, for science outreach. A secondary and long-term goal is to create an environment that fosters interdisciplinary collaborations; thus, enabling and promoting cloud collaboration between scientists. See Guidelines and Rules section for additional details.

Jonah Miller
moderator

​​​Physical  - 
 
The Poetry of Gravitational Waves

As a gravitational physicist, it's hard for me to express how excited I am by the LIGO #gravitationalwave announcement. The #physics and the #science of the discovery is staggering. And the result is beautiful.

This is my attempt to capture some of the science—and the poetry—of LIGO’s gravitational wave announcement.
 
The Poetry of LIGO’s Gravitational Waves

Yesterday the LIGO scientific collaboration announced that they had detected the gravitational waves from the in-spiral and merger of two black holes, shown in figure 1. It would not be an overstatement to say that this result has changed science forever. As a gravitational physicist, it is hard for me to put into words how scientifically important and emotionally powerful this moment is for me and for everyone in my field. But I’m going to try. This is my attempt to capture some of the science—and the poetry—of LIGO’s gravitational wave announcement.

To read this post in blog form, see here: http://www.thephysicsmill.com/2016/02/12/ligo-gravitational-wave-source/

The Source

About 1.3 billion years ago and as many light years away, two spinning black holes, each about thirty times the mass of the sun (one a bit bigger, one a bit smaller) ended their lives as separate entities. These two monsters had probably lived out many separate lives together: first as a binary system of two massive stars and most recently as two black holes orbiting each other. Somewhere in between, each one probably briefly outshone the entire galaxy as a core-collapse supernova.

But nothing lasts forever. Einstein tells us that mass distorts spacetime, warping distance and duration. And an accelerating mass (like a black hole in an orbit) releases some of its energy in ripples of this distortion. And so, over the billions of years of their shared lives, our black holes lost energy to these gravitational waves and their orbit decayed. They slowly, inevitably, spiralled towards each other.

As the partners approached, their orbit sped up and their slow, stately waltz gradually transitioned into a frantic tarantella toward coalescence. Eventually the partners came within about 500 kilometres of each other (about the distance from Paris to Frankfurt!). By this time, they were orbiting each other about thirty-five times per second!

The black holes spiralled towards each other at roughly the same rate about five more times before they suddenly plunged together, spinning around their shared centre of mass 250 times per second. But this stage didn’t last that long. Before even one second had passed, the black holes’ event horizons overlapped, and they merged into a single rapidly rotating object. This new single black hole oscillated wildly as it settled down into its final configuration, emitting gravitational waves all the while.

In-spiral. Merger. Ringdown. After (possibly) millions of years in a slowly decaying orbit, the final plunge took less than a fifth of a second. In those last moments, gravitational waves carried away 1.8x10^(47) Joules. That’s three times the energy contained in our Sun. Three suns, released as ripples in spacetime.

This is a computer simulation of the in-spiral and merger of two black holes much like the ones I described, produced by my friends and collaborators in the Simulating Extreme Spacetimes collaboration:
https://youtu.be/I_88S8DWbcU

(Note my calculations of distances are based on extremely rough Newtonian approximations. They are not very accurate. Maybe not even by an order of magnitude. But at these scales, it's not super important.)

Gravitational Waves

But what of the gravitational waves emitted by our ill-fated dance partners? These ripples in distance, in the very fabric of space and time, travel outwards from their source at the speed of light. Space is large and empty and it is mostly a lonely journey. Perhaps they pass through a cloud of gas and dust. Perhaps they don’t. If they do, the distortions of distance move the gas. Some gas particles move apart, some together. The gravitational waves might move a ring of gas particles, as shown in figure 2.

The effect is small; if the gas cloud were a few kilometres in width, the gas particles would move a distance less than one one-thousandth of the width of a proton. But they would move. And if they moved enough (they don’t) they would make a sound—the sound of the merging black holes:
https://youtu.be/QyDcTbR-kEA

Detection

Eventually, after about 1.3 billion years, on September 14th, 2015, the gravitational waves reached Earth. They were too weak to make a sound, but we could detect them. A gravitational wave is a distortion in distance, one that travels. So we can measure this distortion with a very precise ruler. And light is one of the best possible rulers.

Actually, we used two gigantic, perpendicular light-rulers, each several kilometres long. As a gravitational wave passed the rulers, it shrank distance in one direction and grew it in the other. The scientists who use these light-rulers call this discrepancy a “strain.” The paired light-rulers themselves are called “interferometers.”

We’ve built several interferometers to detect gravitational waves. There’s one in Livingston, Louisiana (https://www.ligo.caltech.edu/LA), which is shown in figure 3, and one in Hanford, Washington (https://www.ligo.caltech.edu/WA). There’s another in Sarstedt, Germany (http://www.geo600.org/) and another in Cascina, Italy (https://www.ego-gw.it/public/about/whatIs.aspx). One, destined for India, is in storage (http://gw-indigo.org/tiki-index.php?page=LIGO-India). And another is under construction underground in Kamioka, Japan (http://gwcenter.icrr.u-tokyo.ac.jp/en/).

On that fateful day, only the detectors in Livingston and Hanford were active. (Some of the others aren’t even sensitive enough for their intended purpose. When people first started building gravity-wave detectors, it wasn’t clear how far away the sources would be.) The waves hit Livingston first, at exactly 3:50:45 AM local time. About seven-thousandths of a second later, they reached Hanford and distorted the light-ruler there, too. And a fifth of a second after that, they were gone. The sound of the black holes had passed us by and continued its journey into the void.

But they did not pass without a trace. No, the Livingston and Hanford detectors recorded their passage, shown beautifully in figure 4. The 1.3 billion-year-old waveform passed through our world and changed us forever.

Learning from the Waves

We already knew gravitational waves exist. That measurement took 30 years and won the Nobel prize (http://www.nobelprize.org/nobel_prizes/physics/laureates/1993/press.html). And we had a pretty good idea of what they should look like. But the only way to confirm that they looked like we expected was to observe them. So the first thing the LIGO team did was to use sophisticated statistical techniques, without any assumption about the final waveform, to extract the true wave from the noisy signal shown in figure 4.

They then compared that waveform to the wave predicted by general relativity. The two agree spectacularly. Score one for Einstein! Of course, there are possible modifications of general relativity such that a black hole in-spiral wouldn’t look any different. So only time, and more gravitational waves, will tell if those modifications are wrong. But for now, this result is a triumph of relativity.

Independently, the LIGO team matched the raw data to a “template bank” of possible gravitational waves, each generated for a different configuration of the black holes—different masses, different rotation rates, different orientations, et cetera. Eventually, they found a match. (Actually they found several, all of which were very similar.) And, fantastically, this match agreed perfectly with the wave extracted using the statistical technique. The extracted waveforms from the two detectors, calculated in both ways, are shown in figure 5.

As a huge bonus, matching the waveform in this way told the LIGO team the masses and rotation rates of the initial black holes and the final black hole that they became.

From the ripples in spacetime, they had extracted astrophysics!

Two Detections

I want to emphasize that one reason we can be so confident in the LIGO detection is that it happened twice, once for each detector. Both detectors are extremely sensitive—they could easily see an earthquake or a car driving down the highway and misinterpret it as a gravitational wave. But the gravitational wave was seen at both detectors, and the odds of them both getting exactly the same false positive are extremely low.

What We’ve Learned

In this one detection, we’ve learned a tremendous amount…some of it very definitive, some of it not. But at the very least, we now know the following:

1. Gravitational waves look very much like we expected.

2. Black holes definitively exist. No other two objects in the universe could have been so close before colliding. Of course, we had pretty good evidence that black holes existed before now (see: https://briankoberlein.com/2015/08/16/do-black-holes-really-exist/).

3. Binary black hole systems definitely exist. A few years ago, it was not obvious that these systems formed. To get a pair of black holes orbiting each other, you need a pair of supernovae. And that could easily destroy the orbit.

What We Stand to Learn

For most of the history of astronomy, humans relied on their unaided eyes to look at the stars. In the early 1600s, telescopes were invented and the universe opened up. Suddenly the twinkle of stars and planets resolved into gas giants and moons, clusters and nebulae and galaxies. In the 1930s, we discovered a new kind of telescope: the radio telescope. Once again, we saw space in literally a whole new light. Suddenly objects we thought we understood looked very different. And wild new things appeared, like radio pulsars. Every advance in telescope technology sparked a huge leap in our understanding of the universe. We could, essentially, see a whole new side of the universe.

This is just as big. Now we can hear the universe. We’re going to learn so, so much.

Related Reading

If you enjoyed this post and want to learn more about general relativity and gravitational waves, you may be interested in my series on #howgrworks :

1. In Galileo Almost Discovered General Relativity, I explain the motivating idea behind general relativity and how Galileo almost figured it out.

http://www.thephysicsmill.com/2015/07/26/galileo-almost-discovered-general-relativity/

2. In General Relativity Is the Dynamics of Distance, I explain how simple arguments can tell us that gravity stretches or shrinks space and time.

http://www.thephysicsmill.com/2015/08/03/general-relativity-is-the-dynamics-of-distance/

3. In General Relativity Is the Curvature of Spacetime, I describe how the distortion of distance and duration from gravity translates into curvature, and how this bends the path of light (and other stuff).

http://www.thephysicsmill.com/2015/08/15/general-relativity-is-the-curvature-of-spacetime/

4. In Distance Ripples, I explain how gravitational waves work.

http://www.thephysicsmill.com/2015/08/23/distance-ripples-how-gravitational-waves-work/

5. In Our Local Spacetime, I present a visualization of the curvature of spacetime near Earth.

http://www.thephysicsmill.com/2015/09/06/our-local-spacetime/

6. In Classical Tests of General Relativity, I explain a little history.

7. In the Geodetic Effect, I talk about how we can use gyroscopes to directly measure the curvature of spacetime.

Further Reading

Here are some nice lay resources on the recent LIGO discovery. (Thanks to +Johnathan Chung  for finding some of these.)

1. This is LIGO’s online press release. It contains, for example, a number of fantastic videos.

https://www.ligo.caltech.edu/detection

2. In this video, Brian Green explains the take-home message.

https://www.youtube.com/watch?v=s06_jRK939I

3. This is a great explanation of gravitational waves by quantum gravity physicist +Sabine Hossenfelder

http://backreaction.blogspot.com/2016/02/everything-you-need-to-know-about.html

4. This is the lay article about the discovery by the American Physical Society:

http://www.nature.com/news/einstein-s-gravitational-waves-found-at-last-1.19361

5. +Yonatan Zunger wrote up this nice explanation:

https://plus.google.com/+YonatanZunger/posts/DUp4TPcrFfJ

6. This is a nice article by +Brian Koberlein  on the existence of black holes.

https://briankoberlein.com/2015/08/16/do-black-holes-really-exist/

7. This is the press release for the Nobel prize awarded for the indirect discovery of gravitational waves:

http://www.nobelprize.org/nobel_prizes/physics/laureates/1993/press.html

8. This Nature article talks about several questions we can answer with gravitational waves:

http://www.nature.com/news/gravitational-waves-6-cosmic-questions-they-can-tackle-1.19337

Scholarly Reading

For the very brave, here are my academic sources.

1. This is the LIGO detection paper. Already peer reviewed. Kudos to the LIGO collaboration for going through peer-review before announcing their result!

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102

2. This is the LIGO paper describing how they extracted the mass and spin of the black holes.

https://dcc.ligo.org/LIGO-P1500218/public

3. This paper describes the LIGO team’s investigation of whether or not the December detection could have been a mistake. (Obviously, they concluded it was real, or I wouldn’t be writing this blog post…)

https://dcc.ligo.org/LIGO-P1500238/public

4. This paper describes the LIGO team’s model-agnostic approach to measuring the wave. This is how they know they’re not falling victim to wishful thinking.

https://dcc.ligo.org/LIGO-P1500229/public

5. This technical paper describes how the LIGO team estimated their noise and error

https://dcc.ligo.org/LIGO-P1500248/public

6. This paper discusses how we’ve tested general relativity with this observation.

https://dcc.ligo.org/LIGO-P1500213/public

7. This is an assessment of the rates of black hole binary mergers in the universe based on the measurements LIGO has made so far.

https://dcc.ligo.org/LIGO-P1500217/public

8. This is a related paper on what that means for detectors.

https://dcc.ligo.org/LIGO-P1500222/public

9. This paper is a search for neutrinos from the black hole merger that LIGO observed. (None were found.)

https://dcc.ligo.org/LIGO-P1500271/public

10. This is the population model for binary black holes which may be wrong.

http://iopscience.iop.org/article/10.1086/523620/meta

#howgrworks #physics #science #ScienceEveryDay #gravitationalwaves #astronomy #astrophysics
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Luv u physics
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Vignesh Karthick

Science News (Pop Sci)  - 
 
 
February 12 is reserved to Charles Darwin
The mystery of the beginning of all things is insoluble by us; and I for one must be content to remain an agnostic.

Naturalist Charles Darwin was born in Shrewsbury, England, on February 12, 1809. In 1831, he embarked on a five-year survey voyage around the world on the HMS Beagle. His studies of specimens around the globe led him to formulate his theory of evolution and his views on the process of natural selection. In 1859, he published On the Origin of Species.

But, did you know that the word ‘evolution’ does not appear in Charles Darwin’s On the Origin of Species once? Or that evolution simply refers to change and not to progress, which is a common misconception. 
It is curious that, although the modern theory of evolution has its source in Charles Darwin’s great book On the Origin of Species (1859), the word evolution does not appear in the original text at all. In fact, Darwin seems deliberately to have avoided using the word evolution, preferring to refer to the process of biological change as ‘transmutation’.
Charles Darwin died on April 19, 1882, in London.

Happy Darwin Day!

On the Origin of Species - Read it online:
https://archive.org/details/originofspecies00darwuoft

Bio:
http://www.biography.com/people/charles-darwin-9266433

#history   #CharlesDarwin   #originofspecies  
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Johnathan Chung's profile photoHyder Noori's profile photo
 
A related phrase commonly misattributed to Darwin is "survival of the fittest". It came from Herbert Spencer who incorporated some of Darwin's ideas with his economic principles after he read On the Origin of Species. Darwin subsequently adopted the phrase and explicitly mentions Spencer in the 5th edition of the book published in the late 1860s.

Edit: I have a copy of the book, but obviously not the original. Since there were several different editions, you can often tell which is the real original one based on typos, errors in formatting, binding/material, and other anomalies: 
http://darwin-online.org.uk/EditorialIntroductions/Freeman_OntheOriginofSpecies.html

In addition to the Archive.org link in the OP, people can obtain different formats of the book here (e.g., audio book, plaintext on the web, e-book, etc.): 
http://www.gutenberg.org/ebooks/search/?query=%22origin+of+species%22&go=Go
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Vincent Granville

​​​Physical  - 
 
The Riemann Hypothesis is arguably the most important unsolved problem in mathematics. It falls into an area called Analytic Number Theory which is essentially number theory with complex numbers thrown into the mix. The hypothesis states that all non-trivial zeros of the Reimann Zeta function fall on the critical line. 
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Mouhamadou Kane's profile photoMOUHAMADOU KANE's profile photo
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How does gravity waves sounds like?
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Marshall Shuler's profile photoHenry Leighton Fulmer's profile photoAlwin Arrasyid's profile photoVijay gowda N's profile photo
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Sort of twilight zone-ish, which I suppose is apropos.
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Kevin Clift

Science Bytes (Memes, Cartoons, Images)  - 
 
 
Mirror Hanging Super Precision

How do you suspend 40kg mirrors at room temperature and minimize vibrations due to the dissipation of their thermal energy through the ties? Professor Sheila Rowan, head of the Institute for Gravitational Research at the University of Glasgow where she earned her bachelor's and PhD degrees in physics, knows!

PT: Is there any advance that you have made or contributed to that you are particularly proud of?

ROWAN: Yes. The mirror suspensions. They are novel in that they are made using fused silica. The mirror is the point in space that you want to be really very quiet. You want it to sit still and not be disturbed by anything else until a gravitational wave comes along. The mirrors are suspended like a pendulum to try to isolate them and protect them from ground motions.

That was something I worked on as a postdoc. The reason we used these ultrapure glass fibers is that the mirrors are at room temperature, and if something is at room temperature, it has thermal energy, and it's vibrating. How much it vibrates depends on how the thermal energy is dissipated. Ultrapure glass turns out to be a very low-dissipation material, and fused silica in particular dissipates very little.

It was a risky thing to do—to try and hang these mirrors on very fine glass fibers. The mirrors on GEO [in Germany] are about 6 kg. It was very successful, and a scaled-up version is now at Advanced LIGO, where the mirrors are about 40 kg. So far, it's worked well.

Originally the idea to use pure fused silica was from a Russian group. But as a postdoc, working with my PhD adviser Jim Hough, I personally did a lot of hands-on development and demonstration in the lab in making the silica parts work. There are a lot of people in the field, and many people contributed to making it work overall. That whole development is something that I have been particularly proud of being involved in.

More here (interview): http://goo.gl/9pNJpb

Video: http://goo.gl/nk2lzC

Sheila Rowan: http://goo.gl/AZ6cb7

GEO600: http://goo.gl/Q2VZVi

Image: https://goo.gl/AFMFxu
From (more): https://goo.gl/CkTER4
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Kevin Clift's profile photoJonah Miller's profile photo
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+Kevin Clift​ and celebrating! And writing! This is my field, after all!

But that's no excuse. :)
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Science on Google+
owner

Curator's Choice - Mods only  - 
 
We are excited too.
We know you are all excited about the news about gravitational waves. We are too.

However, please keep in mind that link only posts are against the guidelines. Also duplicate posts are against the guidelines, unless you are offering substantial insight and commentary. Please share your excitement by contributing to one of the existing posts.

Thank you.
SoG+ moderators
 
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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Clara Listensprechen's profile photoDelwar Hossain's profile photoBobbie Knopick's profile photosuper max's profile photo
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+Johnathan Chung thanks for the links! These are great!
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Cliff Bramlett

Science News (Pop Sci)  - 
 
OK Go's new video is making the rounds, so I thought I'd share some details about what you are seeing. I actually took a ride like this when I was a kid at - get this - Space Camp. Well, technically it was the Gifted & Talented Institute at Galveston, Texas, but it sure felt like space camp to those of us in it. We met the Challenger crew
https://www.nasa.gov/multimedia/imagegallery/image_gallery_2437.html
and actually do several of the training missions NASA astronauts were expected to master, and tour many others. Of those, one we all got to try was the Vomit Comet, otherwise known as a "parabolic plane" or "reduced gravity aircraft".

To the Science!
Here's how this works: When you are on a parabolic flight, the airplane takes off and flies 45° up, then levels out, noses down some, and reduces thrust. The result is that the plane stops pushing on the things inside it, and the entire outfit - plane, passengers, contents - are in free-fall. It is important to note that this is not zero-gravity. It just feels like it. That's why the things in the OK Go video can move without further interaction, unlike objects on the International Space Station which are much less affected by the Earth's gravitational pull than objects in free-fall. After a while, to avoid crashing, the pilots push the throttle back up pull the plane out of its free-fall. That's the point in the video where it looks like someone turned gravity back on.

Now, usually this free-fall lasts around 30 seconds. The fact that OK Go managed to get approximately 2 minutes and 30 seconds of apparently un-edited video is quite an impressive feat. I'll leave it to viewers to decide if that feat is one of aeronautical engineering or video engineering.

I'm not sure how many takes OK Go had to do to make their video, but I can assure you first hand that getting used to going from normal gravitational flight, to free-fall, and back is not easy for everyone, or a simple matter. There's a reason planes doing this maneuver are called "vomit comets". Many people's inner balance is disrupted by free-fall, and that feeling of vertigo can result in emptied stomachs. Everyone gets a sick bag on a flight like this, just in case.

To say the least, NASA's partnership with the GTI Camp I went to as a teen left a huge impression. NASA is currently coordinated with many educational initiatives, so take a look to see what might be in your area:
http://www.nasa.gov/offices/education/programs/descriptions/All_Alpha.html

If the main link below doesn't play for you, here's one on YouTube that I had to resort to: https://www.youtube.com/watch?v=Y6fyWs8KSdE

More on the aircraft and video:
http://blog.instagram.com/post/139110507002/160211-okgo
https://en.wikipedia.org/wiki/Reduced_gravity_aircraft

OK Go on G+: https://plus.google.com/111638190091197722118/videos

Hat tip to +Melissa Bagley, who managed to be the first in my stream to share the OK Go video and always has some positive photography posts going on.

Edited for grammar, clarity, and to add the OK Go official G+ link.
 
OK Go's new video is making the rounds, so I thought I'd share some details about what you are seeing. I actually took a ride like this when I was a kid at - get this - Space Camp. Well, technically it was the Gifted & Talented Institute at Galveston, Texas, but it sure felt like space camp to those of us in it. We met the Challenger crew
https://www.nasa.gov/multimedia/imagegallery/image_gallery_2437.html
and actually do several of the training missions NASA astronauts were expected to master, and tour many others. Of those, one we all got to try was the Vomit Comet, otherwise known as a "parabolic plane" or "reduced gravity aircraft".

To the Science!
Here's how this works: When you are on a parabolic flight, the airplane takes off and flies 45° up, then levels out, noses down some, and reduces thrust. The result is that the plane stops pushing on the things inside it, and the entire outfit - plane, passengers, contents - are in free-fall. It is important to note that this is not zero-gravity. It just feels like it. That's why the things in the OK Go video can move without further interaction, unlike objects on the International Space Station which are much less affected by the Earth's gravitational pull than objects in free-fall. After a while, to avoid crashing, the pilots push the throttle back up pull the plane out of its free-fall. That's the point in the video where it looks like someone turned gravity back on.

Now, usually this free-fall lasts around 30 seconds. The fact that OK Go managed to get approximately 2 minutes and 30 seconds of apparently un-edited video is quite an impressive feat. I'll leave it to viewers to decide if that feat is one of aeronautical engineering or video engineering.

I'm not sure how many takes OK Go had to do to make their video, but I can assure you first hand that getting used to going from normal gravitational flight, to free-fall, and back is not easy for everyone, or a simple matter. There's a reason planes doing this maneuver are called "vomit comets". Many people's inner balance is disrupted by free-fall, and that feeling of vertigo can result in emptied stomachs. Everyone gets a sick bag on a flight like this, just in case.

To say the least, NASA's partnership with the GTI Camp I went to as a teen left a huge impression. NASA is currently coordinated with many educational initiatives, so take a look to see what might be in your area:
http://www.nasa.gov/offices/education/programs/descriptions/All_Alpha.html

More on the aircraft and video:
http://blog.instagram.com/post/139110507002/160211-okgo
https://en.wikipedia.org/wiki/Reduced_gravity_aircraft

Hat tip to @111717057215320823486, who managed to be the first in my stream to share the OK Go video. If the main link below doesn't play for you, here's one on YouTube that I had to resort to: https://www.youtube.com/watch?v=Y6fyWs8KSdE

@109783903175191665261
OK Go is a band. They like to make stuff.
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ARSHIYA FATHIMA.M

Science Bytes (Memes, Cartoons, Images)  - 
 
 
What you see here is an example of the Leidenfrost effect.
When a liquid comes into contact with an object that is much hotter than the boiling point of the liquid, a layer of vapor forms that insulates the liquid from the hot object.

We've all seen this phenomenon in action: If you flick droplets of water onto a really hot griddle, they bead up and skitter around rather than simply boiling away. That's because they are riding on a thin layer of steam that insulates the droplet of water from the heat of the griddle.
 In this case, when you drop a red hot steel ball into water like bellow - the object is so hot that it gets encased in a layer of water vapor.

Watch:
www.youtube.com/watch?v=lgOlR0XZkBI

Read & learn:
http://www.engineersedge.com/physics/leidenfrost_effect_13089.htm

Boiling & the Leidenfrost effect:
http://www.wiley.com/college/phy/halliday320005/pdf/leidenfrost_essay.pdf

h/t FYFD

#physics   #leidenfrosteffect  
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Cliff Bramlett's profile photoJohnathan Chung's profile photoAleksandar Anastasijević's profile photo
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+Cliff Bramlett I see. That's unfortunate (and one of the many painstaking reasons why I've reverted to the old version on the web).

This makes the introductory commentary by the sharer of a post even more crucial. Thanks for pointing that out.
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Nico M

Science Policy & Practice  - 
 
There is a reason why unbiased peer review is a critical aspect before "scientific discoveries" are published.  In the following blog post you will see an open letter(s) written to The Lancet.  There have been multiple requests for PACE Trial practices to be shared from the 2011-published study, conducted in the UK.   Yet, the study authors remain resolute in keeping the patient and scientific community in the dark.  I would strongly encourage readers to look at the various hyperlinks to realize how insidious conflicts of interest in a supposed clinical trial can be.  I applaud the open-letter-signatories for their dedication to true science, clean scientific practices, and incorruptible policy.   I think it's also very important to point out, that Tom Kindlon worked tirelessly to read through the study, and analyze it, and ultimately question it without rest.  (Tom, like me, has severe ME/CFS.)  Tom's contribution helped spearhead the collaborative support of medical professionals (as seen in the signatories). 
Finally, I want to yet again extend my thanks to everyone who is truly trying to bring ME/CFS research toward a cure
+Tom Kindlon +Sharon Murgatroyd
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Marc Hamilton's profile photo
 
Its not unbaised....AT ALL!
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