N-Curvature

BIOLOGY: Why do we age ?

At the moment there seems to be only one robust method to slow down ageing in a wide
variety of animals, namely restricting caloric intake.

There have been thousands of scientific papers on this topic and many explanations have been put forward. Mostly people try to identify specific molecular mechanisms.

As a physicist I have always been quite sceptical to pin this effect down to something genuinely biological because in physics ageing is a commonly studied phenomenon (e.g. spin glasses, polymers) without being able to allude to mitochondria, hormones etc.

Therefore it is not surprising that the model I favour most at the moment stems from a physicist, Jeoffrey West, who has done quite interesting work in biology about scaling laws.

Here are the transparencies of a talk where he, among other things, explains this inofficial model of ageing which I find highly plausible:

1 2 3 4 5 6 7 8

The basic input into the model is the finding that branching networks that supply the body with nutrients and energy scale as M^0.75 (they are fractal!), where M is the body mass. (Naively one would expect M^1.0).
This way the well known one quarter power law for life expectancy T, T ~ M^0.25 is reproduced.

Interesting are also West's remarks, that lifespan per se is not given genetically. What is given genetically is the repair rate. So if one wants to manipulate lifespan, one would have to modify the repair rate and there is nothing else one could do.
(Interpreted this way, the difference in life expectancy between a dog and a human being for example is not due to their different genetic makeup but due to their mass specific energy expenditure, whereas the exceptionally long life expectancy of birds in regard to their low body mass, is due to their comparatively good repair mechanisms).

MISCELLANEOUS: Technological progress exponential ?

Technological progress is accelerating, this is the credo of futurist and inventor Ray Kurzweil.















I have always been quite sceptical about this statement, for various reasons, some of them being:

• Resources are limited and any growth will settle once a system approaches these limits.
• Some things grow exponentially (e.g. computer power, number of sequenced nucleotides), others don't (e.g. number of proteins being structurally analyzed). So this growth behaviour were less a general law than a data selection effect.
• Technological growth rates might be correlated with the population growth rates which are also exponential and which can't hold forever (same reson as in 1).
• Growth is strongly due to availability of oil. After we have reached (world) "peak oil" things might change.
  

However the following video is quite impressive and lets me rethink the whole issue:
Innovation Everywhere—How the Acceleration of “GNR” (genetics, nanotechnology, robotics) Will Create a Flat and Equitable World

PHYSICS: Derivation of the standard model of particle physics

When I took a course in theoretical high energy physics at university, the professor wrote down the Lagrangian of the standard model, mentioning that that is the current world formula, as it
describes everything we know of in physics at the moment (back in 1993 at least), except for gravity. The formula is not quite enlighting, being a collection of many summands.

Now Alain Connes has derived this Lagrangian from geometric principles (noncommutative geometry, spectral triples), which I find extremely remarkable. Even better, it even contains gravity (in the form of the Einstein Hilbert term).

Here is a very impressive audio representation of his findings (although no transparencies are available, it is still worth listening to get the idea):
Noncommutative geometry and the standard model with neutrino mixing

And here is the result which is supposed to describe all known physics (plus the Higgs particle):

















More can be found in the following paper:
Noncommutative Geometry and the standard model with neutrino mixing
Or more explicitely here:
Gravity and the standard model with neutrino mixing

ARTS: Virtual worlds

This picture I rendered with "Terragen", my absolute favourite piece of software. More of my humble computer arts can be found here >><<.

PHYSICS: The good old double slit experiment

According to Richard Feynman the double slit experiment has in it the heart of quantum mechanics and containts its (only) mystery.

Here is the ultimate video that explains the double slit experiment.