Submitted by shaviv on Sat, 2011-08-27 00:53
The CLOUD collaboration from CERN finally had their results published in nature, showing that ionization increases the nucleation rate of condensation nuclei. The results are very beautiful and they demonstrate, yet again, how cosmic rays (which govern the amount of atmospheric ionization) can in principle have an affect on climate.
Submitted by shaviv on Fri, 2010-07-30 13:12
Submitted by shaviv on Fri, 2010-07-30 13:09
Solar Activity and Climate
It is already more than 200 years since Sir William Herschel claimed that variations in solar activity affect climate on Earth. Since he did not have any reliable temperature measurements, Herschel looked for indirect proxies. He compared the price of wheat in the London wheat exchange to the solar activity as mirrored in the sunspot number, and found a correlation between them.
Submitted by shaviv on Sun, 2010-06-27 14:52
Submitted by shaviv on Thu, 2007-12-13 08:59
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?
Submitted by shaviv on Sat, 2007-06-30 10:19
A few astro photographs, including one of Saturn under horrible seeing!
Submitted by shaviv on Fri, 2006-10-27 23:13
From time to time, I hear the statement that Earth's magnetic field is important because it protects earth from "deadly" radiation, and that when the magnetic field will reverse, this lethal radiation will be... very bad. One such example is this
promo for a NOVA program called "magnetic storm". Well, I have news. Nothing really bad will happen to us!
Submitted by shaviv on Wed, 2006-10-25 12:32
After finding out that Earth is
not a planet (it didn't clear out its orbit...), I now learned that Earth's doesn't have life on it. Sounds strange? Well, Navarro-González et la., in a
recent paper that appeared in PNAS, showed that the same tests used on the Viking program and that came out negative for life on Mars, showed negative results also in ...
Submitted by shaviv on Wed, 2006-10-04 09:56
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).
Submitted by shaviv on Sun, 2006-09-17 10:58
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.
Submitted by shaviv on Sat, 2006-09-16 02:07
General Remarks
The manuscript submitted by Jahnke is an attempt to repeat analyses previously carried by myself (Shaviv PRL, 2002, New Astronomy, 2003). Although Jahnke raises a few interesting aspects, his analysis excludes several critical problems, because of which he obtains his negative result, that is, that there is no statistically significant periodicity in the data.
By far, the most notable problem is that Jahnke's analysis does not consider the measurement errors. In his analysis, poorly dated meteorites were given the same weight as those with better exposure age determinations. As I show below, this has a grave effect on the signal to noise ratio (S/N) and consequently, on the statistical significance of any result.
Submitted by shaviv on Fri, 2006-09-15 20:32
My colleague and friend, Prof. Jan Veizer of the University of Ottawa, has written a review on the climatic role of carbon dioxide, cosmic rays and solar variability over different time scale. Unlike other material you will find on this web site, which was written with my subjective physicist's point of view, this review was written by one of the world's leading geochemists. Originally, Prof. Veizer set out to collect the most comprehensive geochemical data set, to reconstruct the paleoclimate variations over Phanerozoic (the past 550 Million years over which there are multicellular fossils to work with). His goal was to find the climatic signature of carbon dioxide in the data. To his disappointment, there was no clear correlation between his paleoclimatic reconstruction and the CO2 reconstruction (e.g.,
Submitted by shaviv on Fri, 2006-08-25 02:13
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!
Submitted by shaviv on Tue, 2006-06-13 20:57
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.
Submitted by shaviv on Wed, 2006-05-31 10:16
Many physical systems have a tendency to equilibrate the energy between different subcomponents. Sometimes it is exact, and sometimes not. For example, in an acoustic wave, the wave's energy is on average half kinetic (motion of the gas) and half internal (pressure). In the interstellar medium, there is roughly the same energy in the different components, such as internal energy, turbulent energy, magnetic field and energy of the cosmic rays. Stars are no different. In the sun, there is roughly the same binding energy (which is negative) as there is thermal energy. This can also be shown using the virial theorem. In white dwarfs, the thermal energy is unimportant, instead, there the degenergy energy of the electrons is comparable to the binding energy. We can use this tendency for equipartition to estimate different stellar parameters.
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