Open convection cells over the Negev?

OpenCellRadar Jerusalem was under siege, again. Last time it was Bush. This time, it was snow because of which we had two snow days. So, I didn't have to teach and instead could build a snowman with my kids. I could also look at the rain radar, which appeared to exhibit a few interesting phenomena.

One of the phenomena appears to be that of open-cell convection, i.e., air rising (and precipitating) on the cell boundaries.

A Nice Black Hole Merger Simulation

I recently stumbled upon a nice black hole merger simulation.
Since it is not in my habit of just regurgitating stuff I see on the internet, here is my added value. How can one estimate the quadrupole gravitational radiation of a binary? How close does the binary have to be for it to coalesce within the age of the universe?

Parhelic Circles, Ice Haloes and Sun dogs over Jerusalem

A few weeks ago, a few students saw a nice phenomenon in the sky. Knowing I liked this kind of stuff (and that I may be able to explain it), they called me out of the office to look at the sky. Above us was a nice and almost complete parhelic circle. Unlike the usual 22° halo, often seen around the moon and occasionally around the sun, the parhelic circle keeps a fixed angle from the horizon, not from the bright object.

Influenza and a Human Chain Reaction

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Some time ago, I pondered about the effects that mass hysteria could have on a flu epidemic. In particular, on how a fright about flu vaccination (which happened in Israel a few months ago) would cause less people to be vaccinated, and thus be responsible for a larger flu outbreak. A recent news item, though, made me rethink.

The Best Proof that Paranormal Phenomena do not Exist

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Alleged paranormal phenomena tend to pop-up from time to time. The best example is probably that of Uri Geller. He became famous in the 70's with his "abilities" to bend spoons, read thoughts, etc. Unfortunately, Uri Geller decided to return back to his native Israel, and worse, got a prime time television program, presumably to find an heir.

Climate Sensitivity - an interesting IPCC bias

Some time ago, I noticed an interesting bias in the TAR scientific report (the third assessment report of the IPCC - the intergovernmental panel for climate change) regarding the climate sensitivity, that is by how much the average global temperature will increase if we double the amount of CO2. The report mentions quite a few times that climate sensitivity "is likely to be in the range of 1.5 to 4.5°C". Why is this interesting? Because ...

Flu Vaccinations - Another example of group stupidity

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Most people, when let alone, are not dumb. They can make reasonable decisions if given the right information. However, when people are part of large groups, somehow it seems, the IQ of an average individual, and even the effective IQ of the group as a whole, appears to decrease. Members of the group can then do really dumb things.

One such example of group stupidity is the case of Influenza vaccinations here in Israel.

On Ramadan, the lack of arctic muslims, and why autumn is ideal for the Yom Kippur

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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.