Neutrinos travel faster than light?

Wow. This is sensational news if true. Really, really astonishing stuff with massive implications for Physics and our understanding of the nature of reality.

The full paper is on the archive server now.

This blog post interprets the paper.

It is a very nice measurement. The experiment, OPERA, measures the centroid of the "Probablity Density Function" of the time of time of flight from the CERN accelerator to the Gran Sasso Laboratory in Italy.  (This in itself is pretty amazing since the neutrinos are detected after travelling through 730 km of solid rock!)

Of couse there are two fundamental systematic uncertainties one must take into account. The first is the measurement of the difference between the time of neutrino creation at CERN and the time of measurement in Italy. The second is the distance between CERN and the detector.

The time difference was obtained by synchronized atomic clocks with greater than 1 ns precision. There is now a massive industry based on precison measurements of distance. This is the world-wide GPS system which allows measurement errors in positions of the order of centimeters. Its extremely hard to see how they could have screwed these up. For example the April 7th, 2009 L’Aquila Earthquake in Italy resulted is an easily identified 7 cm shift in position. (See below.)

The biggest uncertainty is establishing the original time structure of the proton beam that created the neutrinos. The proton pulse is of the order of 10 microseconds in width. The measured effect is a 60 nano-seconds shift from expectations with a 7 nanosecond uncertainty. That means they've established the centroid of their proton pulse width to a precision of better than one part in one thousand. Since they have recorded 16,000 events they have sufficient statistics to do this. The question is whether they've correctly determined the shape in time of the original proton beam.

This is determined from the proton beam intensity which is continuously montored. They compared the this to the measured time profile in their detector.   The measured original proton beam intensities as a function of time are shown below. The CERN SPS has two extraction profiles which are easily distinguished.

The observed time structures of the events recored in Italy are shown below. The red lines show the superimposed average time structures of the proton beams with and without the flight time to Italy.

By eye the original time structure of the CERN proton beam appears well reproduced in the detected neutrinos.

After a full blind-analysis they find that their neutrinos travelled (60.7 ± 6.9 (stat.) ± 7.4 (sys.)) ns faster than light over the same distance.

The first uncertainty is the statistical precision of the measurement. The second is their estimate of the systematic uncertainty.  Their systematic uncertainty was obtained by a quadratic sum of 12 potentional sources of error. The largest (5.0 ns) was the calibration of the detector that measures the time of the proton beam extraction at CERN.

Overall their measurement gives:

(v-c)/c = (2.48 ± 0.28 (stat.) ± 0.30 (sys.)) ×10-5

This is consistent with an earlier but less precise measurement from an experiment in America with the Fermilab accelerator:

(v-c)/c = 5.1 ± 2.9×10-5

But substantially different from the neutrinos detected from Supernova 1987a which gives a limit on the anti-neutrino velocity difference of:

|v-c|/c < 2×10-9

So what happens now? There are two other high statistics long-baseline experiments in operation in Japan (at the KEK laboratory where I do my CP-violation experiments) and an updated experiment using the Fermilab accelerator in America. You can be certain that both experiments will do their best make the most precise measurements of the neutrino velocities they can. If all three agree what then? Well we will have to wait to see if they do.... As I said this is a most incredible result.

One final point about this. If the neutrinos from SN1987A had had the increase in velvocity over photons measured by the OPERA experiment they would have arived 4 years earlier than the light...

(All images are reproduced from

Making a difference

Hi everyone,

When writing free software we sometimes get caught up in all the stuff that doesn't work. All the things we need to fix to make our programs better. At least I do! So it is really nice to see that our efforts do generally work and can make a difference.

Here is a great video of the OLPC XO's being used in remote Australia.

Congratulations to OLPC-Australia and the World-Wide effort that produced these transformational devices. These would not be possible without the Free-Software community and the many, many other like minded people who have donated their varied talents.

The stupidest bug in firefox..

I have a large presentation on my work computer. My colleague wants me to send it to him. I'm at home. I could copy it to my home PC then attach it to an email. The problem is that my home machine has a nice fast (1 megabyte/sec) download connection to work but only about 60 kilobits upload. Sending it from home will be slow...

I know,I think, I'll just ssh -X into seviorpc at work, open upfirefox, connect to my webmail and send it from there......

Whoops! I forgot about the stupidest bug in firefox.

If it detects a local instance, instead of redirecting the graphics of a remote instance, it just opens up a another local window which means I can't just attach that file on my remote machine after all.

The crazy thing is that the firefox devs must have tried REALLY HARD to implement this bug. I have no idea why they thought it was a good idea.

OLPC in remote Australia

I came across this remarkable article and photograph in todays online edition of the TheAustralian.

It appears OLPC Australia has been successful in persuading Telstra, News Corp and the Commonwealth Bank to support a mass deployment of the OLPC laptops in remote Australia. Apparently up to 400,000 of them!

Australians are normally very cynical about big corporations and especially Telstra, News Corp so the achievement of OLPC Australia is a wonderful triumph of vision.

A big congratulations to everyone concerned for this! From a personal point of view I'm especially pleased to have made a contribution to the software inside these :-)

AbiWord back for Google Summer of Code in 2010

(Banner recycled from Ryan Pavlik:

Thank you Google for once again selecting AbiWord as participating project in Google Summer of Code for 2010.

If you are a student interested in earning USD$4500 over the Northern Hemisphere summer of 2010, head on over to

AbiWord Collaborative Word Processor project has a very interesting collection of potential projects here:

However if you have your own idea for improving AbiWord, we'd also love to hear from you!

Contact us on our IRC channel:


if you'd like to chat before submitting an application.

Telstra Mobile Broadband and Fedora 12

I'm off to the beach (Apollo Bay) next week and decided I needed to remain connected to the net. After checking around I found that Telstra is the only carrier that has coverage down there. Further checks implied that their USB broadband modems worked under Linux. After checking out the option I bought Telstra's casual plan and their "Telstra Turbo" USB mobile. This has the advantage of being able to be discontinued between uses. The price per GB is about 5 times greater than other Australian carriers. On the other hand, Telstra really do have a very wide coverage and this really is expensive. The other carriers are essentially limited to just metropolitan areas.

I spent an hour or so futzing around with settings, searching the internet etc until I eventually discovered the SIM card was not properly inserted! Hint make sure the lights show blue not flashing orange :-)

After getting it properly seated I just clicked on network manager, chose mobile broadband, chose Australia, Telstra, default settings, clicked OK, requested a connection to Telstra and hey presto it worked!

Yay! This is exactly the experience I want :-)

Congratulations to Fedora 12 and the network manager team.

Using ( from within AbiWord

This post is public domain. Feel free to copy and paste where ever you like

The combination of the AbiWord word processor and the webservice provides world-leading real-time collaborative functionality available nowhere else for any price at all. Now that Fedora 12 is out and distributes AbiWord-2.8 it is easy for Linux users to try it out and see if they find it useful.

My previous blog posts about focused on the use of the service from within a browser. You can find them here:

1. Basic operations including how the AbiWord “save” function sends the document back to
2. How one could go about finding the friend you want to collaborate with.
3. How to setup a real time collaboration
4. The use of  Groups, View, Export in


AbiWord also has additional hooks back into the webservice that are accessible from within the “collaborate” menu.

To start with we need to establish the connection with the service. This is done with the “account” menu item.

I’ve already got an account set up based on my gmail email address. However if I didn’t or if I wanted another based on a different email address, I just click “add” and fill the details as shown.

Besides the web service one can connect to other AbiWord using either TCP/IP (if you know the IP address) or via the jabber XMPP protocol. The webservice is much easier for users and connect with. Everyone on the internet has an email address. 

Clicking the button on “connect on application startup” means you don;t have to go through this step again.
If I now go back to the “collaborate” menu and choose “open shared document”, AbiWord connects to the webservice and presents me with a list of the documents I have to on

Here are the list of groups and user accounts which contain documents I’m allowed to edit. The 3 Martin Sevior’s show up because I have 3 separate accounts on the service :-) 
Of course clicking the table expander arrow shows me all the eligible documents. As you can see I use the service and find it a convenient way to keep my work in synch across my 3 different work environments. (Work workstation, laptop and home PC).


Finally one can upload your current document to the web service. This is a very convenient way to both share your work with your colleagues and to upload it to the service and make it accessible to a different workspace.

To this click on “share document” in the collaborate menu. You have the option of sharing the document with as many of your groups and friends on the service as you wish.

Once uploaded to the document is of course available to be shared with your friends and colleagues and easily available at all your work spaces. 

Like my previous posts this document has been uploaded to and is available at: 





How to use ( Part 4

Groups, View, Export in

This post is public domain. Feel free to copy and paste where ever you like

The first 3 articles of this series showed some basic operations of, how one could go about finding the friend you want to collaborate with and then how to setup a real time collaboration.

In this post I will talk about the Groups, View and Export features of


One often has a collection of colleagues, friends and co-workers with similar interests who need to work together on documents. The webservice makes it easy to allow collections of people to form a group and to work together on common documents.

For testing purposes I've created a number of identities for myself and I'll use these to show how one creates such a group.

Simply click on the "my groups" link.

You see the list of groups for which you have membership.

To view the documents held by the group or the membership click on “view documents” or “view members”. The screen shot below shows the membership of the “abicollab” group. We’re the group that directly codes and tests the webservice. Marc and I are administrators of the group. Either of us can approve whether an applicant can join the “abicollab” group. Applicants to the group are shown in the “Aspiring members list”.

To create a new group, click on the “create a group” link, type in the name you wish and click “save group”.

The new group is created with you as the administrator.

Here I’ve created a group called “MartinSeviors”. Now suppose another user called “M. Edmund Sevior” wants to join this group. He navigates to “my groups”, searches for the group by typing in it's name, then clicks “Join a group”.

Now the administrator of the group receives an email of this request which also shows up as a message in his “message central” region.

I can now accept or decline the request. After accepting the request, navigating to “my groups” and clicking the member list shows the updated member list.

Any group administrator can promote any other member to become an administrator too.


The “view” link associated with every document shows the contents of your document in your browser. What you see is what you would get if you exported the document to html. With this one one can quickly tell if you have selected the right document to edit, without having to download it into AbiWord.


Every document on can be exported into a number of common word processing formats. This is accomplished via the “export” link. One chooses the preferred format then clicks “export".

This post is available on at the link:

How to use ( Part 3

Real time collaboration

This post is public domain. Feel free to copy and paste where ever you like.

My first two posts showed some basic operations of and how one could go about finding the friend you want to collaborate with.

Now I'll talk about the killer feature: Real Time Collaboration!

To set up a document for Real Time Collaboration, one simply sets the permissions to "view & collaborate" for the friend with whom you want to work with the "share" link associated with the document.

Then choose who you want from your list of friends.

Click on "save settings" and the permissions are set!

The document now appears in the list of documents available for your friend. Since you've allowed your friend to collaborate on the document, it shows up on the list of documents he can work on. The friends "my documents" view is shown below.

Now you open the document by just clicking on its name and it opens in your AbiWord. Remember you need version 2.8 or later. You start typing away....

(Your version of AbiWord shown below)

OK, now your friend logs in and sees a new document, shared with him. He decides to edit it too and so opens it. It loads into his version of abiword.

Hey presto we have a Real Time Collaboration!
So both of you can type away in the document, editing as you wish while you see each others changes in real time. If either press "save" in their AbiWord, the current version gets saved into the history of the document on the website.

I just want to point out a couple of things. Your friend did not actually download the document from the website. It had never even been saved! Instead what has happened is that the two have established a peer-to-peer collaboration via a router daemon. The website joined a connection from you to a connection to your friend and passed traffic between the two of you. After that the two AbiWord's transferred the document and established the collaboration.

Consequently everyone is guaranteed to always see the absolute latest version of the document!

We've totally eliminated the edit=>email to colleague=> update/comment/fix => email =>update/comment/fix => email... cycle.

There are many other very cool things about AbiWord's real time collaboration but I'll save them for other posts.

You can find this post on at: