shaviv's blog

As is the case in recent years, the Nobel prize announcements last week made me proud of my home institute yet again. This year, Chemistry recipient is Prof. Roger Kornberg, who has been a regular visiting professor at the Hebrew University for already 20 years.

After a long embargo, results from the Danish National Space Center (DNSC) Sky experiment were finally published in the Proceedings of the Royal Society. The results demonstrate a clear link between cosmic ray induced atmospheric ionization and the formation of condensation nuclei, thus strengthening the claims that cosmic rays affect cloud cover and climate (and consequently implying that a large fraction of 20th century global warming should be attributed to the increased solar activity).

While buying diapers on the weekend from my muslim neighbors, I learned that the holy month of Ramadan has just recently started. The hot weather made me realize that Ramadan fast cyclicly varies from an easy obligation to one which is very hard. Fasting in summer implies abstaining from drinking while it's hot, and fasting for more hours a day. In fact, a muslim living north of the arctic circle would not survive a summer Ramadan, implying that no muslim can permanently live in arctic (or antarctic) regions. It also made me think about the Yom Kippur fast which turns out to be ideally placed in the autumn.

The other day I found out to my dismay that the balcony underneath my air conditioner at home leaks water into the living room below it. Instead of sealing the balcony (as I should...) I temporarily solved the problem by placing a baby bath tub underneath. After "recycling" the water on the lawn, I wondered, could A/C reclaimed water be economically useful?

Last week, a report by Jeff Kanipe appeared in nature. In it, Kanipe explains the solar → cosmic-ray → climate connection, and the planned CLOUD experiment in CERN, expected to finally resolve the issue. Given that my work is mentioned in the review, I through I should mention a few relevant points.

In the last general assembly of the international astronomical union, astronomers voted to demote planet Pluto, to strip it of its planetary status. The reasons for the reduced status are clear. (And it was coming for a long while!) The surprising bit, however, was the definition the particular astronomers concocted, eh, came up with. They were looking for a precise definition, and indeed found one, one which is precisely wrong. According to it, Earth is not a planet either!

Recently added material in ScienceBits includes:

• Passing the Eddington limit without getting a ticket: A detailed summary of the theory of porous atmospheres and how they can explain the existance of super-Eddington objects.
• Standing on Ice? Ever wondered how cold should it be and for how long, if the ice is to be thick enough for you not to fall through it?

I just recently read Motl's post on a particularly prolific crackpot, who solved all of the known problems in physics, and then some more. That reminded me of an old story, a true one, which teaches us that you can be a crackpot in many orthogonal ways (that is, in mutually independent ways).

Over the past two weeks, Kaytushas have been falling over Northern Israel causing casualties and damages. Here are some thoughts about the situation and how bad it is.

Here are some pictures and a physicists take of a fantastic hail storm which took place west of Jerusalem in October 2004. The largest stones were up to 5 cm in diameter and several car windshields were shattered!

A few days ago I stumbled upon an interesting article from Time magazine, entitled: "Another Ice Age?". No it is not a recent article. It is politically incorrect to talk about global cooling these days. The article appeared in 1974, after "three decades of cooling" prompted some to believe that an imminent ice-age may be coming. It is interesting to read it in perspective, and perhaps there is a lesson we could learn from it. Here are a few excerpts from it. Read and enjoy.

Everyone in Israel has heard of the Galsgow scale. Why? Because our former prime minister Ariel Sharon was and still is in a coma. The Glasgow scale, of course, measures the level of consciousness (or lack of). Ariel Sharon, for example, scored 6 out of 15. 8 or less is defined as a coma. 6 doesn't sounds that bad, doesn't it? So why am I writing about it? What's so curious?

Anyone who runs a website knows that a successful site has to have a high Google PageRank. Unfortunately, though, Google updates their publicly available PRs only every a few months. Moreover, the PR is only given in discrete increments, so it is hard to know whether a site improved if the actual increase is less than a PR point on average. Given that I am curious about the PR of my site, I thought I should do something. And I did, the bottom line of which is a calculator to estimate the PageRank of any site you wish.

Recently added material in ScienceBits includes:

• Estimate the basic stellar parameters using the tendency for energy equipartition. In particular, the temperature at the center of the sun, the mass-radius relationship of white dwarfs and their Chandrasekhar limit are all estimated. These were taken from my order-of-magnitude course notes.
• Row Row Row your boat, but at which maximum speed? This is a classic example of an order of magnitude analysis giving a lot of physical insight (and impressive predictive power).
• Analysis of the classic homemade water rocket, taken straight out of my first year physics majors classical mechanics notes. There is even a rocket simulator with which the trajectory can be calculated and graphed.

It may sound strange, but you are probably as likely to die from a meteor as you are from a plane crash. Think it's bizarre? Here is the statistics.