Nightmare on Meyrin Street

’tis gone.
What seemed to hold the promise of a revolution in physics has fizzled out. Disappeared into oblivion. Is there really nothing more than the Higgs for the LHC to discover? Will the experiment just wander in an energy desert for the rest of its life? It is the most feared scenario physicists could have thought of before switching on the machine at CERN: a true nightmare. What now? Someone is probably hoping this nightmare will let us save money on curiosities that only experts care about and are of no public good for the majority. So wrong!

I have friends who work in theoretical particle physics: they are passionate, capable scientists and I’ve always wished the results found at LHC would help them land the permanent position they deserve to keep doing what they’re best at. Now that everyone in the field is back to square one, my friends are among the best positioned to start a new conversation with Nature through the screen of a blackboard: they are still professionally young enough to be as audaciously bold as the situation requires. So far, in fact, the community of theoreticians has mostly played by decade-old rules: no wonder we’re stuck. It is then a great opportunity to make tabula rasa and be daring. I’m confident the revolutionary men and women that’ll get us out of this morass are already born: hopefully they’re already at work and they are collaborating with each other to enjoy the benefits of complementarity.

However, things could turn out bad: the work toward a new description of Nature might take more time than my friends have to secure a job. As numerous as they can be, and even if they may come from your own country, I don’t think the destiny looming on them will move you. However, in such a case, a catastrophe will be pending above us all.

While it may look like CERN hunts for Pokemon-like entities in reality it does much more: it creates the basis for our future wellbeing. The past week, together with the sad announcement of the aborted physics revolution, CERN celebrated the 25th anniversary of the World Wide Web. It was invented there and you use it to read this piece or the news, to book the flight to go on holidays, to buy shoes and do many more things that are now given for granted in our everyday life.

CERN also has a medical research unit, where particle physics know-how from theory and experiments is put to service for health applications such as treating cancers. Moreover, for its computing needs CERN has been instrumental in the development of Grid computing, which

“… offers a way to solve Grand Challenge problems such as protein folding, financial modeling, earthquake simulation, and climate/weather modeling. Grids offer a way of using the information technology resources optimally inside an organization. They also provide a means for offering information technology as a utility for commercial and noncommercial clients, with those clients paying only for what they use, as with electricity or water.”

There is much more that CERN does for us all but I’m confident the overview I’ve given you can already let you share my concern that if we stop doing research in particle physics we stop creating needs that only this type of research can create, while their satisfaction provides the most fertile conditions for our future wellbeing and prosperity.

Before concluding, it is worth mentioning that the non-discovery of a new particle does not mean CERN should close shop just yet. In fact, knowing that the particle is not there is already a precious piece of information: we could not know beforehand, so disposing of a new piece of (non-)evidence is very useful, though painful.

At the same conference where the sad non-discovery announcement has been made a flood of other new results has been shared with the public by CERN. They still have some twenty years of activity in front of them to let the LHC machine continue its tremendously accurate and reliable work. This persistence is needed to allow new rare phenomena to show up in a significant way. Therefore, we can be “disappointed but not discouraged” as a physicist says at the end of a BBC Horizon documentary that just aired.

Last but not least, a note is in order about the title: Meyrin Street is CERN’s address for the public.

New physics, is that you?

Mysterious hints of long-awaited physics beyond the Standard Model seem to have emerged at CERN’s Large Hadron Collider

The collaborations behind ATLAS and CMS, the two general-purpose experiments at CERN’s Large Hadron Collider, have just published their latest reports. Their new data show a suspicious bump, similar to the one that gave away the existence of the Higgs boson: a detour in an otherwise smooth trajectory across the energy region explored by means of particle collisions. The reason why the new results could either hold great potential or have physicists endure a longer nerve-wracking wait has to do with how searching for the unknown works.

The Large Hadron Collider at CERN offers one the most favorable views of the Universe. Its behemoth experiments collide particles like bumper cars: in the particle dodgem debris are carefully scrutinized to reveal secrets about the interiors of the clashing entities and new types of particles can materialize into existence by converting the energy made available by the collision. Millions of particles are smashed into each other millions of times per second in order for the little sparse hints of every strike to accumulate into relevant information about the microscopic world.

Artist's rendition of a high-energy collision inside a particle detector (Image: CERN)

Artist’s rendition of a high-energy collision inside a particle detector (Image: CERN)

An everyday life equivalent of this would be tossing millions of coins millions of times and counting how many heads or tails you get. Both heads and tails being equally probable you should find that each occurs roughly 50% of the times. That’s in theory. In practice, if you throw a coin 10 times you can get heads 7 times in a row: how’s that possible?

It could be that your coin is rigged: knowing for sure this is not the case is what scientists call characterizing the experimental setup. Maybe your coin is responding to its surroundings in some unexpected way; before you can claim to have a magic coin you have to make sure you understand your environment and how this might interfere with your experiment. It could also be that, while you think you’re just throwing a standard coin, the one you got is no ordinary coin: it’s a completely new one that behaves in an unconventional way with respect to the others you have thrown in the past. More prosaically, it is possible that you did not conduct your experiment enough times to make any statistically significant claim, as scientists would say. When you toss a standard coin your outcomes will approach the 50-50% separation as you increase the number of tosses.

Counting occurrences and comparing results with expectations also characterized the hunt for the Higgs boson, when ATLAS and CMS were like Columbus’ caravels on their course to the Indies: they had to navigate an energy stretch delimited, though loosely, by previously available maps of the microscopic world; their promised land was the particle associated with the Brout-Englert-Higgs mechanism. We all know how the story went: Columbus found America instead, while the Higgs boson was indeed discovered and the duo Higgs-Englert was awarded the Nobel Prize for physics, absent the late Brout.


Professor Englert and Professor Higgs speaking at the Higgs seminar announcement at CERN in July 2012 (Image: CERN)

Since then CERN has been making history, though in a peculiar sense. Its LHC works in fact as a time machine, by concentrating energy to values that characterized the Universe only immediately after the Big Bang. Now we can rewind a movie no one has ever watched before and directly witness the story unfold as if it were the first time. We have some expectations about the movie but this time around the situation is trickier than in the Higgs-Columbus days: we have left America. The map we could use until then, the so-called Standard Model, is not adequate anymore.

Every model is a description of Nature that is optimized for a specific set of its features and the Standard Model makes no exception: it is very accurate in its domain but cannot explain 95% of the Universe. These dark sectors are like very dim, unexplored rooms in a castle: to build a detailed map of these rooms we need to probe them, to understand their architecture and the variety of their furniture we need landmarks that inform our bearings.

ATLAS and CMS scientists have just finished analyzing information that seem to suggest a new landmark could exist, what exactly is still up for debate: it could be as familiar as a cousin of the Higgs boson or as novel as a manifestation of extra dimensions. This uncertainty represents science in the making and is very fruitful for researchers because it compels them to go through a checklist that resembles the one about the coin toss: are we dealing with a completely new coin? Or will new tosses wash away the seven-heads-in-a-row occurrence?

Only time and more data will tell if we have finally found new physics beyond the Standard Model: after all we have just started watching the movie about the history of the Universe.

Reflections on a black mirror


If I ever write a novel “Reflections on a black mirror” would be a tempting title. In the meantime it is the typical title of an entry in the “gr-qc” bulletin, which comes out Monday to Friday, holidays permitting, and lets you find out what’s up in the world of “General Relativity and Quantum Cosmology” research.

You would think it is too much of an arcane world to be interesting to the uninitiated and you wouldn’t be wrong. However this research is done by men and women that live in the same world as we do. It just so happens then that sometimes researchers express esoteric concepts by appealing to common language and expressions from the pop culture.  Here you are a few peculiar entries in this sense for your own surprise and amusement: I’d like them to serve as an entry door for you to this branch of physics. Pick the most tempting title and go read the relative abstract; then feel free to ask me to expand on your favorite one.

To conclude, I’d like to show you an example that best encapsulates the take-away message from this post: science is an open business, where even gravity is still up for a deeper explanation! The example I chose is among the plainest I could find. It relates on the nature of gravity, and uses many topical expressions of the research world, such as: perspective, concordance, implications, evidence, approach, attempts, problem, solution, (mis)understanding, alternative. This is how the research community let the Universe speak through gravitational waves, this is how humanity will get to the conquests of tomorrow, both scientific and technological: with such brainstorming as the one daily hosted on the “gr-qc” bulletin.

CERN at Rio’s Carnival

Hello everyone,
it’s been a while and I wanted to break my silence with a short post. I would like to share with you a curious video that a friend of mine just sent me: it is nothing less than CERN physics showcased at Rio’s Carnival! Go to 27′ and 40” and see for yourself; of course you can also watch the video in its entirety.

As we can read from the Facebook post that CERN dedicated to the occasion:

“Last year’s winning samba school, Unidos da Tijuca, presented a Swiss-themed procession at Rio de Janiero’s Sambadrome, including 200 people with costumes representing CERN’s “Acelerador de Partícula”. 

The school’s parade, in collaboration with swissnex Brazil and Swissando, featured everything from William Tell to Swiss chocolate to Einstein and included CERN’s flagship particle accelerator, which crosses the border between France and Switzerland.”

For more geeky moments at Rio’s carnival you can take a look here.
I hope this will keep you cheerful until my next post: I have a couple of drafts that have been lingering for a while now and I wish I had already shared them with you.

Talk to you soon!

Memories of a colorful life

It was Tuesday, December 4, 2012 and I was having an ice-cream for lunch. The temperature was pretty warm in College Park, a few metro stops from Washington D.C. and I had not yet tasted the famous local ice-cream of the University of Maryland. It was a few days before I would leave the U.S. at the end of my postdoc stint and I wanted to soak in all I could of that place, the last where I would spend time doing research in theoretical physics.

My plane back to Rome was due in a couple of weeks and I had decided to spend that remaining time traveling with a friend. Before that I had one more trip waiting for me: later that afternoon I would visit a very special place, the past. My guide was Oscar Wallace Greenberg, Professor of Physics at the University of Maryland. “Wally”, as he wants to be called, had agreed to time-travel together to let me meet Einstein and other giants of physics who had shaped the last century outside their domain of expertise.

My Virgil had already told me a few anecdotes over lunch once, when he had joined me and other scientists working on gravitational waves, while his fellow particle physicists had gone eating out and he found it more convenient to stay inside. He told us he had been friends with Joe Weber, the first who had tried to build a microphone to listen to gravitational waves, the sounds of the universe caused by massive astrophysical objects, when they hit on the fabric of space and time as mallets on a drum membrane. The two of them used to go on mountain hikes but, out of respect for a friend, Wally would never ask Weber about his controversial research results. I already knew that Weber’s findings had never been replicated by anyone else but listening to a more personal side of the story made me want to know more. This is one of the reasons why I wanted to talk further with Wally; soon after I realized that the man who used to take the stairs to our department on the fourth floor wasn’t just a walking trove of treasures from the history of physics: he had his own story, too and I wanted to know it.


Oscar Wallace “Wally” Greenberg, Emeritus Professor of Physics at the University of Maryland.

I then asked him if he’d let me interview him and he agreed to do it on that extraordinarily warm day of December 2012. Since then I have gone back and forth to the idea of writing about this personal encounter that I cherish a lot. Because life has a funny sense of humor, I have just found out the iPhone screenshot above in this post, which brought me back to that day and the desire to tell you something about Professor Greenberg.

He, too, has been a pioneer of physics in the 20th century: he was the first to see that the subatomic world had to be a colorful place. In much the same way as green, red and blue conjure to give you white when superposed, Greenberg understood that something like it was at work for quarks making up neutrons and protons. Even though elementary particles are not colored in the sense we think, this analogy is common parlance in physics: protons and neutrons are colorless conglomerates of quarks because their constituents combine their green, red and blue color charges in such a way as to neutralize them. That this mechanism was at play in the invisible world  of microscopic particles had dawned on Wally when he was visiting Princeton in the 60’s as an assistant professor, on leave from the University of Maryland. He had already been at Princeton during his formative years as a student, the same Princeton where Einstein worked once he fled Europe due to the persecution against the Jews.

On a Spring afternoon of the early 50’s, together with other students, Wally had the chance to meet Einstein and ask him some questions; surprised by the humbleness of the great scientist and filled with emotion for the encounter, he later wrote a poem to celebrate this life changing experience. It is called “Mercer Street”, from the name of the road where Einstein used to live, and synthesizes the feelings and the physics that shaped that afternoon:

Mercer Street

A Spring afternoon
A line of nine walk though the town
A musty house, the shutters drawn
A sage lives within

His key turned the lock
For twenty years to unify
Electric field, magnetic field
Space-time matter, too

A calm beyond time
A humble man received his guests
To talk, to feel the breath of youth
To hand them the key

The day turned to dusk
The parting time. Advice was sought
For these young men who start the path
He lost long ago

He shrugged. Scratched his head,
Discomforted, at sea, he sent
Them out with “Who am I to say?”
Cool air cleared their heads

Unfortunately the experimental evidence necessary to do justice to Wally’s intuition and prediction took years to come; when it did, he received only a few citations but not the full credit he deserved. In spite of this, the words Wally spoke to me did not contain resentment or accusations: he was just happy about the journey through the physical world that his whole life has been … and still is! When I asked him if he was satisfied with what had been his personal exploration of science through physics he answered proudly:

“Yes but I’m still doing it! What I’m working on right now is muonic hydrogen: if you do very accurate spectroscopy of the hydrogen atom you can infer the charge radius of the proton…” 

As Wally explained to me, the data on muonic hydrogen were very different from the theoretical expectations and he thought he could help clarify the situation because he had experience in a calculation tool that particularly suits the problem. If this sounds technical, it is; suffice it to say that I’ve recently found out that Wally is participating in an international collaboration to deepen the investigation of muonic hydrogen. This attachment to physics as a life mission is something I love to recognize because it resonates with me a lot; seeing it at play in an 80 year old man, to me, is as joyful as witnessing my niece coming to grips with stairs: the pleasure of the novelty and finding things out is never enough.

My conversation with Wally went on for an hour or so. He told me about that time he was waiting for a cab in the blistering cold with a soon-to-be Nobel Prize awardee and they shared a chewing gum to have some sugars in the blood. He told me about that time when, as a student, he fell asleep during a class given by another giant of physics because he was under medications. He told me about that time at lunch when a rising star in theoretical physics started throwing bread crumbs at the table to call for attention. If you want to know more about Wally, you can listen to an account in his very own voice here:

I will end by saying that going through my remembrances for writing this piece made the long wait very worthy. One day, if I live long enough to grow old, I’d like to be asked about the tale of my own journey through physics: that day I will start by telling of the time I sat with Wally.


An open mike for Einstein

Yesterday the European Space Agency launched a new satellite: called LISA Pathfinder, its role is to pave the way for the ambitious LISA mission by conducting crucial tests of its technology.

LISA stands for Laser Interferometer Space Antenna and basically is an open mike for Einstein, who imagined the universe as a very lively Sunday market, where people go by or bump into each other, they salute by a mere gesture or take time to exchange about their condition. Much in the same way as the market conveners can talk softly or loudly, if at all, the universe is filled with tales of stars grazing each other, exploding, fusing into one, falling into black holes or witnessing them merge in an even stronger monster.

The convener of this universal market is not Sunday, it’s gravity: so LISA will listen to the story gravity has to tell. The stories that this exquisitely sophisticated microphone will be sensitive to sound like this symphony.

If listening to it makes you want to shake your body a bit, I invite you over to this other post of mine, where I describe gravity as the dance of space and time.

Up to speed with TBBT

I have been a fan of The Big Bang Theory show for a while now and I’ve been thinking on and off about its use as an outreach tool, that’s to say I was eager to use the references made in TBBT episodes about physics and science as a handle on the public curiosity to know more of what might lie behind them. I gave it a go on this post of mine a while ago but haven’t gotten back to it ever since.

This past Summer I attended a Teachers Workshops organized by ESA, the European Space Agency, and I had the chance to discuss with inspired folks from all over EU. As I compared notes on practices and challenges in education at 360 degrees, I brought TBBT idea up with a colleague from Scotland and she strongly encouraged me to go forth with that here on my blog. So, thanks to Eileen, here’s my first instance of “Up to speed with TBBT”, where the rhyme is of course intended 😉

Let me start this thread with episodes from Season 9.

  • Episode 1 “The Matrimonial Momentum”. In physics momentum is used to describe mass in motion: it can be linear or angular, according to the motion being a straight trajectory or a rotation. It depends on mass and velocity, that is to say: how fast a mass is moving, how large the mass is and how this mass is distributed in space.
    A typical example of angular momentum is the one of a skater, which also shows how momentum is conserved: when the skater pulls her arms back, she reduces the spread of her mass in space, which gives her body the ability to turn faster on herself than she was doing with her arms wide open.
  • Episode 2 “The Separation Oscillation”. When something oscillates it goes from one position or state to another, like a pendulum or my mood these days. Oscillation is the subject of this year Nobel in Physics, which awarded yet another acknowledgement to the understanding of neutrinos. They are called the chameleons of space because they can change clothes as they move at almost the speed of light and, believe it or not, they are going through your bodies in droves as you read about them, which is why they can only be caught with detectors like this one

Dr Neil DeGrasse Tyson in Super-Kamiokande Neutrino Detector – (Image Credit:

  • Episode 3, “The Bachelor Party Corrosion”. In this episode Sheldon is kidnapped in a van, not just any van but Richard Feynman’s, the late Professor of Theoretical Physics at Caltech. Feynman is famous for playing bongos (as Sheldon does in a previous episode) and for inventing some hieroglyphs that helped physicists communicate and calculate the effects of a theory in the making: these pictograms came to be known as Feynman diagrams and are part of the advancements for which Feynman received the Nobel Prize for Physics in 1965. This is more than enough for anyone to paint them on his van, as Feynman did.

    Professor Feynman poses with his family in front of his van, which he decorated with instances of his very own visual handle on particle physics.

    Professor Feynman poses with his family in front of his van, which he decorated with instances of his very own visual handle on particle physics.

  • Episode 4, “The 2003 Approximation”. In this episode Sheldon’s bothered by the many changes he’s unwillingly going through: due to disruptive discontinuities in his life he can no longer function under the same paradigm he’s followed until then. Just like he’d do with a new, buggy operation system on his laptop or smartphone, he decides to go back to a previous version, in which he was more stable and efficient. I used the expressions “paradigm” and “version” but I could as well said “model”. In fact in science an approximation is a model that accurately describes a phenomenon under certain circumstances but it’s not the whole story: it doesn’t mean the model is wrong but just that you can’t use it for every situation. The Standard Model of particle physics is a good working theory of most of the known elementary phenomena but it does not explain neutrinos’ masses … or dark matter … or dark energy. I plan to talk about the dark side of the universe in a dedicated post but let me stop here for now coz Saturday night is laundry night 😉

Before concluding I’d like to extend my warmest greetings to Eileen and all the teachers from UK who welcomed me in their group, for both professional exchanges and a lot of craic!