Posts Tagged ‘Neutrino’

Faster Than Light Particles! So, Warp Speed Ahead, Right???

September 22, 2011 3 comments

The OPERA detector at Gran Sasso National Laboratory in Italy

I’ll have more to say about this story once I see the work on arXiv, but I feel I should comment now because this story is exploding.

The interwebs and blogospheres are abuzz with the news that researchers at CERN have measured the velocity of neutrinos which seem to be travelling faster than light.

Neutrinos are nearly massless  subatomic particles which have been known to travel near the speed of light. But, like all other things in the universe, they are not supposed to be able to travel faster than light.

Basically the experiment involves the creation of neutrinos at CERN in Geneva, Switzerland, and the neutrinos travelling 730 km to a laboratory 1,400 meters underground in Italy. There, an experiment called OPERA (Oscillation Project with Emulsion-tRacking Apparatus) detects those neutrinos and measures how quickly it took them to make the trip.

The neutrinos arrived 60 nanoseconds sooner than they should have. This means they were travelling at a speed of about 299 800 km/s, which is slightly higher than the speed of light, which is about 299 792 km/s.

This discovery will rock the very foundation upon which modern physics is built. Seriously, this is like the discovery that the world is round or wave-particle duality; it’s a complete game-changer.

If it’s true.

Like a lot of folks out there, I am quite skeptical of this discovery. Think of it this way: which of these two scenarios is more likely,

  1. Particles can travel faster than light, completely re-writing modern physics and decades of previous research. Or,
  2. These guys made an innocent mistake.

Now, it is certainly possible that this discovery will turn out to be genuine. However, it is much more likely that there was some kind of error or misinterpretation which has led to this result.

I would like to point out that the researchers have revealed their work in the proper way. They are excited, but very skeptical themselves and are asking the academic community to review their work and try to find a flaw. Antonio Ereditato, a physicist at the University of Bern in Switzerland and OPERA’s spokesman said in an interview

Whenever you are in these conditions, then you have to go to the community

THIS is science in action, folks! A group of physicists think they have discovered something awesome. But they haven’t started trumpeting their results like they have been absolutely confirmed, no emails were leaked suggesting the discovery, and they didn’t go to some rogue publication to get their work in print prior to peer-review.

Beautiful, isn’t it?

I am very hopeful this turns out to be a genuine discovery. I can’t wait to read the papers and hear the response from the scientific community.


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The World’s Coldest Physics Lab

January 17, 2011 7 comments

An overview of the South Pole with the South Pole Station to the left of the runway and IceCube to the right. (Photo: NSF - Photographer: Forest Banks)

On December 18th, 2010, construction of the IceCube Neutrino Observatory in Antarctica was completed.

IceCube is

a massive ice-bound telescope that fills a cubic kilometer of deep Antarctic ice. The main IceCube detector now contains 5,160 optical sensors on 86 strings embedded two kilometers below the National Science Foundation’s Amundsen-Scott South Pole Station.

These researchers used a large water drill to bore 86 holes into the ice of Antarctica. The holes are approximately 2.5 kilometers deep and each took an average of 48 hours to drill.

Next, they installed sensors into each of these holes designed to detect neutrinos.

A sensor descends down a hole in the ice as part of the final season of IceCube. (Photo: NSF/B. Gudbjartsson)

Neutrinos are subatomic particles which are extremely abundant and rarely interact with matter. In fact, as Darren Grant, a University of Alberta physicist explained on this weeks episode of Quirks  & Quarks, 10 billion neutrinos pass through your thumbnail every second! We never notice them though, because they very rarely interact with matter.

However, if you install enough detectors in the right kind of medium, eventually a neutrino will interact with that material and you will be able to see it.

So why ice? Well the Antarctic ice is both very thick and very transparent. When a neutrino eventually interacts with an ice molecule, it will emit what is called Cherenkov radiation. This is the same type of radiation that causes the weird blue glow in a nuclear reactor.

Cherenkov radiation glowing in the core of the Advanced Test Reactor. Via Wikipedia

On Quirks and Quarks, Dr. Grant explains that Cherenkov radiation is kind of like a “an optical equivalent of a sonic boom”. Basically after the neutrino interacts with the ice it will eject a muon from the ice molecule (a muon is an elementary particle similar to an electron, but 200 times bigger). As the muon travels through the ice, it travels faster than the speed of light through ice. This disrupts the electromagnetic field of neighbouring particles and generates the blue glow of Cherenkov radiation, which is then detected by IceCube.

[Aside:  Some of you may be thinking “Whoa! How can it travel faster than the speed of light?”. Be assured that relativity still holds in this situation. That is because the muon is still travelling slower than the speed of light in a vacuum. Since light moves more slowly through ice than it does in a vacuum, the muon will travel faster than light through ice, but still slower than light through a vacuum.]

So why study neutrinos? Well they are quite useful to astronomers because they can travel from distant stars and galaxies without interacting with magnetic fields or matter. Thus they are like a direct messenger from whatever it is the scientist is studying.

Because of IceCube’s size, it is able to detect the highest energy neutrinos, allowing scientists to study supernova, gamma ray bursts and even dark matter.

You can listen to Dr. Grant’s Quirks & Quarks interview here.