Wednesday, September 17, 2008

Anti crackpot blog and falsifyability

There is a new blog dealing with crackpots in HEP. It probably grew out of the recent hype about LHC being the doomsday machine. I left a comment to the first post that I would like to pull out of the comment threat so I reproduce it here:

You would like to add that I think that criteria for good science are unfortunately slightly more complicated than just asking for "falsifyability".

This notion comes from the (pre war) neo-positivist school of thought with Karl Popper being one of the major figures. It is a tremendous progress after realising that strictly speaking you will never be able to prove empirical statements like "all ravens are black" (the classic example) by looking only at a finite subsample of all ravens.

This is how far the education of a typical physicist in philosophy of science goes.

Unfortunately, falsifyability is not a good criterium either from the standpoint of logic at least: The thing is that non-trivial scientific statemens are much more complex than a simple "all ravens are black". When you say such a thing (or write it in a paper), there are many qualifyers that go with it, at least implicitly. You have to know what exactly "raven" means, what exatly you call "black" and not "dark grey", you have to say how you measure the color and that might come with a theory of itself that makes sure your measuring aparatus acutally measures color (as for example percieved by the eye).

Speaking in terms of formal logic, all these presuppositions are connected to the "all ravens are black" by a long long chain of "and"s.

Now imagine you observe a white raven (after having seen a million black ravens). At least you would be tempted to further investigate whether that bird is really a raven or was painted white. It's typically not the first reaction to throw away the "black ravens" theory if it had a lot of support before. Often the reaction is that you rather fiddle with the presuppositions of your theory (for example by changing slightly the definition of what you call 'raven').

The "all ravens are black" part is somewhat protected after receiving some positive evidence for some time and you rather add bits and pieces to the silent background theory before giving up the big statements.

Thus we have to agree that it's not that easy to falsify even simple statments like "all ravens are black" that easily. Furthermore, this is not what happens in science (historically speaking)! You could probably still find an ether theory where the ether is dragged along by the earth in its orbit around the sun and that has many more very unusual properties that is not ruled out empirically. Still nobody in her right mind believes in it since relativity is some much more successful!

All this is much better explained in Thomas Kuhn's "Structure of Scientific Revolutions" and I urge everybody with a slight interst in these matters to read this classic. He argues much more for the consensus of the scientific community to be the relevant criterium (which might be a self referential criterium for science consiracy theorists).

I believe that naive following this wrong criterium of "falsifyability" has gotten beyond the standard model theory in a lot of trouble in the public perception. I would attribute a lot of this to trying to follow the wrong criterium.

Monday, September 15, 2008

Timing of submissions

I have learned an interesting fact from Paul Ginsparg's talk at Bee's Science in the 21st Century conference: around the middle of his presentation he showed a histogram of at what time of the day people submit their preprints to the astro-ph archive. This histogram showed an extremely pronounced peak right after the deadline. After. I had suspected that preprints would pile up before the deadline because people still want to make it into tomorrow's listing because they fear to be scooped. But this is not the case. People want to be on the top of the listing!

My immediate reaction was that the number of nutters amongst astrophysicists is higher than expected. But the next news was at least as shocking: It seems to work! The papers submitted just after the deadline accumulate 90 citations on the average compared to 45 for generic astro-ph papers.

There seem to be two possible explanations of this fact (which is still there for other archives but not quite as pronounced): It could just work and the reader's attention span is so short (you might want to blame Sesame Street with its 1'30" spots for it) that they get distracted before they reach the end of the listing of new papers (this is the only place where submission time matters according to Ginsparg). Alternatively, people who care to submit right after the deadline also care about their citation count a lot and use all means to get it up.

Some further investigation seems to show that the second effect is much stronger than the first. Somebody from the audience suggested to study the correlation with self citations and small citation circles with submission time.

What I would want to look at would be if those are also the people that have a large percentage of their citations from revised versions of preprints (i.e. are those the people who care to write these emails begging for citations --- I have to admit I was one of them today)?

Friday, September 12, 2008

New Toy: Acer Aspire One 150L

Since yesterday 11pm I have my shiny new toy: A Acer Aspire One 150L Netbook Computer. Intel Atom CPU, 1GB RAM, 1200x600 pixels and less than 1kg of weight should make it the ideal travel companion. The "L" in the name means that this is the first computer I ever bought that came with Linux preinstalled. What distinguishes it from its competitors (like the Asus Eec PC) is that it has a proper hard drive which has comfortable 120GB and not just a tiny solid state disk. The thing comes for 349 Euros from (I have seen it for US$350 at Best Buy in San Francisco).

Of course, such a brand new device comes with a number of things to tweek. And not all solutions easily found by just googling. Therefore, I will keep updating this post to record what I have done so far:
  • The thing comes out of the box and boots in a few seconds into some desktop with application icons all over the place. What is missing is a terminal window! But you can use the file system browser to run /usr/bin/terminal which is a good start.
  • During set-up you have to come up with a password. It turns out, this is then set both as root password and as a password for the preconfigured user "User". I have not yet dared to set the root password to something else and to rename user "User" to "robert" since the build in applications might assume that I am User.
  • Once you have a terminal you should run (as root) xfce-setting-show as this allows you to turn on the pop-up menu when right clicking on the desktop.
  • In this pop-up menu you can find a package manager. I becomes obvious that this Linux is based on fedora and the conflict resolution just plain sucks. But it's better than nothing and you can eventually install openssh to be able to log in to uni. I hope that I will have a Debian running on this machine but currently the corresponding web sites still look a bit scary.
  • They have preinstalled a vpnc client. But they forgot to include the tunneling kernel module tun.ko . This gives nasty error messages about /dev/net/tun . Luckily, this module is available here . Just download it to /lib/modules/ and reboot (or insmod it).
Update: Included some links.