Anais Rassat2013-05-22T00:11:05-04:00Anais Rassathttp://www.huffingtonpost.co.uk/author/index.php?author=anais-rassatCopyright 2008, HuffingtonPost.com, Inc.HuffingtonPost Blogger Feed for Anais RassatGood old fashioned elbow grease.Einstein Was Not Wrong, But Was He Right?tag:www.huffingtonpost.com,2012:/theblog//3.16112442012-06-20T04:24:30-04:002012-08-19T05:12:08-04:00Anais Rassathttp://www.huffingtonpost.com/anais-rassat/issued a press release regarding the faster-than-light neutrinos that the OPERA collaboration had reported detecting last September, saying that they did, after all, respect the cosmic limit put forward by Einstein in his theory of special relativity. The spurious results were in fact due to a faulty element of the experiment's fibre optic timing system.
The original results in September suggested that neutrinos travelling the 730km from CERN to Gran Sasso were arriving too early, 60 nanoseconds earlier than if they were travelling at the speed of light. This made them 'superluminal'. Confirmation of the anomalous results would have led to a scientific revolution, no less. As CERN Research Director Sergio Bertolucci said, this instantly "captured the public imagination", and news sites worldwide were relating the news that Einstein's theory may be wrong.
The science community, however, reacted which much more moderation. Few physicists believed that the results would stand in light of future experiments, whether internally conducted at OPERA, or at competing collaborations in the US.
Why so much skepticism, amongst a community that might be eager to find a new playing field for fundamental physics? The key reason is that scientists are rarely "surprised" by scientific revolutions (though they may be by discoveries, which is not the same thing). Scientific revolutions often arise after years, if not longer, of mounting evidence of flaws in an underlying theory, acting as signals that a major shift in our understanding of nature is approaching. This is what Thomas Kuhn described in the "Structure of Scientific Revolutions".
As much as scientists would have enjoyed an incredible result regarding the neutrinos, there were no precursor signs to suggest it could be serious. When the news came out that the fault had been found, none were surprised, although a few may have been disappointed.
So Einstein was not wrong, but was he right? Other parts of Einstein's work are currently under intense scrutiny. His theory of general relativity, different from special relativity, explores the laws of gravity on cosmological scales. It explains how the Universe expands and how the largest structures in the Universe, giant filaments of galaxies, form and grow under gravitational collapse.
Yet today, there is much that Einstein's theory of general relativity cannot explain: for example, why is the Universe not only expanding but also accelerating? This was discovered in the 1990s and Perlmutter, Schmidt and Riess were awarded the Nobel Prize in Physics for this last year. This acceleration could be explained by the presence of a mysterious and exotic form of energy dubbed dark energy. But to explain current observations, the dark energy would have to be the dominant form of "stuff" in the Universe today, about 75% of everything in the Universe. Yet there is currently no theory explaining what it could be. Some theorists have postulated that dark energy is not actually required, and that it is the laws of Einstein's general relativity themselves that should be modified. For cosmologists worldwide, a scientific revolution seems close at hand.
In order to reach it, scientists agree that they need to confront their ideas with more observational data. They should be able to construct 3-dimensional maps of galaxies (where galaxies are used merely as points tracing the much larger filamentary structure) and study gravitational lensing over unprecedented large regions of the sky.
There are several competing projects set out to do this. One of them is the European space mission Euclid (of which I am part), the largest existing astronomy collaboration in the world with nearly 1000 scientists from over 100 European laboratories and some US institutes, which has just been adopted today by the European Space Agency (ESA). Launch is planned for 2020 with results from 2025. Many in the field believe that this mission will bring with it a scientific revolution, either through a new understanding of gravity or a new comprehension of the mysterious dark energy.
The best is still to come, because while scientists can predict the arrival of a scientific revolution, they never can predict the advances that will arise from this change of worldview.
The Euclid mission was selected in October 2011 alongside Solar Orbiter as one of the first two medium class missions of the Cosmic Vision 2015-2025 plan. On 20th June 2012, Euclid received the final approval necessary from ESA's Science Programme Committee to move the project into the full construction phase, leading to its launch in 2020. ]]>Nothing Superluminal After All?tag:www.huffingtonpost.com,2012:/theblog//3.12980952012-02-23T21:11:37-05:002012-04-24T05:12:02-04:00Anais Rassathttp://www.huffingtonpost.com/anais-rassat/Nature blog post reports on some possible sources of error that may rule out the problem of the superluminal neutrinos reported by the OPERA team earlier in September 2011.
The neutrinos are subatomic particles produced at CERN near Geneva that arrive 2.4 milliseconds later in Italy after travelling unperturbed under the Alps. In Italy, they are measured by detectors from the OPERA team in Gran Sasso.
In September, the OPERA team reported an anomaly in the speed the neutrinos were taking to travel the 700 or so kilometres from Switzerland to Italy. The anomaly meant the neutrinos were arriving 60 nanoseconds too early. That may seem like nothing, but it was enough to be travelling faster than the speed of light.
The OPERA team physicists were extremely wary of annoucing such a discovery - if the neutrinos were indeed superluminal, this would violate Einstein's theory of special relativity. They searched their data for 3 years in order to verify possible sources of errors.
The main difficulty in measuring this contentious speed was to measure with extremely high precision both the distance and time travelled. The first is extremely difficult because neutrinos hardly interact with anything and so when they travel they just race through mountains and even the Earth's crust. Since physicists cannot travel unperturbed through the Earth's crust, they have to make the measurement in convoluted ways.
Measuring the travel time is also difficult, because you have to make sure your clocks in Geneva and Gran Sasso are synchronised to a much better accuracy than 60 nanoseconds.
Yesterday, the OPERA team announced through a CERN press release that they have found two potential sources of error in their time measurement to do with their GPS synchronisation.
However, to first approach the problem is not quite solved: the first potential source of error would actually reduce the anomaly, whilst the second would increase it. The OPERA team cannot conclude anything until they run further tests in May which will hopefully clear the problem.
So watch this space, but most probably only to confirm that Einstein's theory still works down here on Earth. ]]>A Bright Future for Dark Energy Physicstag:www.huffingtonpost.com,2011:/theblog//3.9947622011-10-04T15:53:56-04:002011-12-04T05:12:07-05:00Anais Rassathttp://www.huffingtonpost.com/anais-rassat/Dark Energy Physics gets a Nobel Prize and a dedicated Space Mission in one day.
The Nobel Prize in Physics was awarded on Tuesday to Saul Perlmutter, Brian P. Schmidt and Adam G. Riess for their leadership of theteams that discovered the apparent "accelerating expansion of the Universe through observations of distant supernovae" in 1998.
At the time, the teams were seeking to measure whether the Universe was expanding at a continuous rate or slowing down, and the measurement of the acceleration was a complete surprise. The only way to explain the observed acceleration within the framework of general relativity was to hypothesise a mysterious field called 'dark energy' which acts as a form of anti-gravity pushing galaxies apart.
Just a few hours after the Nobel news, the European Space Agency (ESA) announced it had selected two new space missions for its Cosmic Vision programme. The Cosmic Vision programme started as a competition in 2004 and after several rounds the original 50 projects were whittled down to the final two yesterday. One of the two selected missions, called Euclid and scheduled to launch in 2019, is coincidently designed to investigate the nature of dark energy and further understand the observed accelerated expansion of the Universe.
Why do we still need to study dark energy and the Universe's expansion? Simply because more than 10 years after the Nobel-worthy discovery, the nature of dark energy is still completely unknown.
Cosmologists have used several methods along with the supernovae observations to measure the amount of dark energy in the Universe. These show the Universe is composed of roughly 73% dark energy, meaning nearly three quarters of the Universe is a bizarre form of energy. The rest is 22% dark matter (an exotic form of matter which doesn't emit or absorb light), and only about 5% of the Universe is the 'normal' matter that makes up the stars and other things like planets, DNA, and the computer you're reading this from. This distribution of 'stuff' in the Universe is called the Standard Model of Cosmology.
Knowing how much dark energy there is out there is not enough. Scientists are aiming to discover the actual nature of the dark energy, without excluding that it may turn out to be a fluke that could be explained away by rewriting the laws of gravitation.
It turns out one of the best ways to study dark energy is to look at gravitational lensing, an effect predicted by Einstein's theory of general relativity. General relativity predicts that space-time is curved by matter. Since light-rays are forced to follow the curvature of space-time, distance objects can appear distorted or lensed if there is a lot matter between the source and the observer.
If the distortion is very big, the effect is called strong lensing - this has been beautifully observed by the Hubble Space telescope, which shows distant galaxies completely warped into elongated arcs. In the majority of cases though the distortion is faint, just enough to lens a round galaxy into a slightly elliptical one. This is called weak lensing and affects almost all galaxies we see in the sky.
Observing weak lensing can tell you a lot about the matter that's acting as a gravitational lens, incidentally permitting us to study the otherwise invisible dark matter. Since the dark matter is being pushed away by dark energy, weak lensing is also a powerful tool to study dark energy and general relativity on very large scales. The effect is small though, and only useful if you can measure it on a large number of galaxies over a large area of the sky. The shape measurements also need to be very high resolution, which is very difficult from earth due to atmospheric distortions: this makes a space mission ideal.
This is exactly what Euclid will do. It will measure from space the shapes of over a billion galaxies over nearly half of the sky (the other half is mostly obscured by the Milky Way), giving us an amazing new tool with which to test Einstein's theory of general relativity and understand the mysterious dark energy. It will also make 3D maps of 50 million galaxies, which is another powerful way to investigate the Universe's expansion.
With funding for the Euclid mission secured, dark energy physics has a bright future ahead, perhaps paving the way towards the next Nobel prize.
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The original articles by the High-z Supernova Search and the Supernova Cosmology Project are available here:
Perlmutter et al 1998: Supernovae Cosmology Project: http://arxiv.org/abs/astro-ph/9812133
Riess et al 1998 (including Brian P. Schmidt), High Redshift Supernovae Search Team http://arxiv.org/abs/astro-ph/9805201
The other space mission selected by ESA for the Cosmic Vision programme is Solar Orbiter, whose aim is to study the Sun's magnetic fields.
]]>Scientists are Wary of Superluminal Neutrinostag:www.huffingtonpost.com,2011:/theblog//3.9787122011-09-23T20:57:37-04:002011-11-23T05:12:02-05:00Anais Rassathttp://www.huffingtonpost.com/anais-rassat/OPERA collaboration released a pre-print last Thursday suggesting some neutrinos had been found travelling faster than the speed of light. If the OPERA collaboration results are confirmed, this means the beginning of a new era in our understanding of the cosmos, no less.
So even though I work only a few kilometres from CERN, I decided to catch the OPERA team's seminar at CERN on the webcast along with 15000 other enthusiasts, since events like this are bound to be full. For the event CERN prepared three different webcasts and so I watched, along with the packed main auditorium, Dario Autiero present the results for the OPERA team on Friday afternoon.
Neutrinos are ultra-light neutral particles that hardly interact with anything, meaning they can travel long distances before bumping into something, like a detector. The OPERA experiment uses a beam of neutrinos created at CERN in Geneva and detects them 730km away at Gran Sasso in Italy 2.4 milliseconds later. This fact alone should be enough to get you excited about particle physics.
Neutrinos come in different types and naturally switch or "oscillate" from one to the other as they travel long distances. The original aim of the OPERA experiment was to detect these neutrino oscillations. The experiment also allowed a measurement of the speed at which the neutrinos were travelling, but this was not at all the original goal. To their great surprise, the team found that the neutrinos were travelling faster than they should have. In fact, faster than the speed of light, making them "superluminal".
Their measurements were so incredible - and carried so many implications about theoretical physics - that the team spent the last three years re-doing their calculations and calibrations in search of some mistake.
Two main issues are that to measure a speed, you need to measure the precise distance travelled, as well as the exact time it took to travel that distance. This is no easy feat, and this is where the largest possible blunders can lie.
Even if you measure the distance properly once, it is possible that the earth dynamics (think of continental drift or earthquakes) can distort the path somewhat and falsify your results over time. But the team's results showed that whether the data was taken in 2009, 2010 or 2011, whether it was taken during the day or the night, during summer or autumn, it always showed this: the neutrinos travelling from Geneva to Gran Sasso arrived too early by 60 nanoseconds. That's 0.00248% faster than the speed of light.
As amazing as this sounds, you should still temper your enthusiasm. The hour-long seminar took us through a long list of possible problems in the distance measurement, and more so in the time measurement. In fact, Dario Autiero seemed almost apologetic when he announced the final results, as if, in spite of the team's best efforts, they just couldn't get rid of their fluke measurements.
His conclusion was to speak with "words of caution" and not to attempt any "theoretical or phenomenological interpretation of the results". In fact, as the Q&A session started, the chair explicitly asked that questions be related to the possible errors in the time and distance measurements, rather than talk about the reason everyone was here: was this a major discovery in physics? Detractors were promptly reminded that this was a technical seminar about calibration issues, not about wormholes.
The particle physics community will be working hard to reproduce or disprove these results in the next few years, and the world is watching. And though we all want to witness a scientific revolution, it is overly optimistic to start re-writing physics textbooks.
Note: The exact results of the OPERA team show that the neutrinos arrived at Gran Sasso early by 60ns ± 6.9ns (stat.) ± 7.4ns (sys.), where the first error bar corresponds to statistical errors, and the second to systematics. The main challenge is to ensure the systematic errors are correctly accounted for.
]]>Women in Sciencetag:www.huffingtonpost.com,2011:/theblog//3.9580682011-09-12T07:29:01-04:002011-11-12T05:12:02-05:00Anais Rassathttp://www.huffingtonpost.com/anais-rassat/40% of PhD students in mathematics, physics and computing in Europe are women (35% for astrophysics in the UK where I did my PhD). In engineering the numbers are not so good, but in my opinion the most urgent problem is not the low number of women entering science, but the low number of women making it to the top jobs in science.
Women in science fall victim to an unfortunate "selection process" called vertical segregation. In science and engineering overall, while boasting reasonable numbers of female PhD students, only 8% of professors are women. When Dame Bell Burnell was appointed professor of astrophysics at the Open University in 1991, she doubled the number of female astrophysics professors in the UK.
Some of this vertical segregation may be due to a generation effect, because the proportion of women professors today is related to the proportion of women PhD students a few decades ago, which was lower than it is today. You can sort this out by looking at the age of professors, and it turns out the generation effect cannot explain the low number of women in the top jobs today.
If only this problem were isolated to science, we might just be able to explain that women's brains are just not wired for doing science at the top, as Larry Summers, then president of Harvard, once suggested (this lead to his resignation). But surprise, surprise, it's not just in science. Throughout academia, this vertical segregation survives. In social sciences, where no one asks if you are the only women in the lab, roughly half of PhD students are women, but less than a fifth of professors are.
Differentstudies have shown that part of this "leaky pipeline" is due to discrimination, sometimes unconscious, but discrimination nonetheless. The blogosphere is crowded with anonymous female scientists venting their frustration of being repeatedly faced with sexist hostilities (just to name one, the amazing Female Science Professor). Others argue that women's career paths are different from men's because of child-rearing, which is particularly difficult to combine with the long-winded and highly competitive selection process in academia (by the way this institutional sexism is also a problem in itself).
Yet outside of academia, where permanent jobs are up for grabs early on in your career, there still is a discrepancy between men and women's careers. A recent study called Pipeline's broken promise showed that women with MBAs were more likely to start their first post-MBA job at a lower position and get paid $4,600 less than their male counterparts. The study showed this was true even when accounting for men and women who did not have children, so child-rearing cannot be the cause. Even outside of university ivory towers and elite MBA executive programmes, women continue to face workplace bias everywhere. A class action suit against Walmart (on behalf of as many as 1.5 million women) was recently dismissed on technical issues, but one of the judges and several specialists commented that there was nonetheless evidence of gender bias.
How can we bridge the gender gap? The Economist recently did a special report on the lack of women at the top and the solution they presented was this: do nothing. They bet the market will self-regulate and that "wise firms will strive to remove barriers for women". I noticed that only 23% of their journalists are women, so I'm not sure their laissez-faire strategy is successful. The conclusion from the European Commission's 160-page report on gender equality in science is quite different. They say that there is absolutely no evidence of a "spontaneous movement towards equality" and that without proactive policies, the gender gap will take decades to close. Why wait more, when women have already waited so long? This reminds me of Nina Simone's song describing the struggle to fight racial inequalities: "To do things gradually / Would bring more tragedy".
So the point is that women in science face exactly the same challenges as professional women in all domains: discrimination, pay gaps and glass ceilings (the European Commission sadly has something called the GCI - the glass ceiling index). Some policies might need to be adapted to the particularities of academia or science, but policies are direly needed in all fields. In my opinion, these policies should address vertical segregation first before they attempt to bring more women into the lower echelons.
Should the Huffington Post have a "women in science" section on their Tech page? I think this is a great idea. Why not go further though and have a "women's" section on your Politics page since the issue is not confined to the world of white lab coats but affects half the world's population. By the way, the Huff Po's US site already has a women's page that has only two sections: 'healthy living 'and 'parents' - in my opinion that page can go. ]]>