https://www.sciencebits.com/ A random and subjective walk through physics, astrophysics, climate, and scientific computation. en Wed, 19 Aug 2026 00:00:00 GMT https://www.sciencebits.com/posts/measuring-the-atmosphere-from-inside-the-moons-shadow https://www.sciencebits.com/posts/measuring-the-atmosphere-from-inside-the-moons-shadow Wed, 19 Aug 2026 00:00:00 GMT Nir Shaviv A total solar eclipse and its lunar shadow over Valencia de Don Juan turn a panorama into an experiment on the height and cooling of the atmosphere. astrophysics physics climate https://www.sciencebits.com/corona-time-varying https://www.sciencebits.com/corona-time-varying Fri, 17 Apr 2020 18:31:04 GMT shaviv One of the most interesting aspects of the coronavirus is the time dependence of its infection rate. It determines how effective measures like quarantining can be. Spoiler: quite ineffective! notes https://www.sciencebits.com/corona-populations https://www.sciencebits.com/corona-populations Mon, 13 Apr 2020 07:39:41 GMT shaviv The next interesting question to ask when studying the coronavirus, is what is the effect of a mixed population which has different infection rates. That is, that some individuals are more infectious than others (e.g., a cashier in the supermarket vs. a farmer). Spoiler: it turns out that unless there are super-spreaders then all you care about is the arithmetic average of the transmission coefficient. notes https://www.sciencebits.com/corona-simple-models https://www.sciencebits.com/corona-simple-models Thu, 09 Apr 2020 18:47:47 GMT shaviv Armed with the data on the coronavirus such as the serial interval, incubation period, and the base growth rate, we are now in a position to start modeling the pandemic. Note that as the title suggests, these are simple models. Any conclusions drawn from this specific page should… notes https://www.sciencebits.com/COVID-19-Data https://www.sciencebits.com/COVID-19-Data Tue, 07 Apr 2020 21:40:36 GMT shaviv This is the first in a series of posts in which I study the COVID-19 (coronavirus) pandemic. My original goal was to understand the behavior of the pandemic. As a scientists my curiosity forces me to not to leave such problems untouched. I wanted to know what are the possible… notes https://www.sciencebits.com/GWPseudoScience https://www.sciencebits.com/GWPseudoScience Tue, 24 Sep 2019 20:07:01 GMT shaviv The I recently wrote an OpEd for the Epoch Times which tries to succinctly capture my main grievances with the global warming scare. Here is brought again with a few comments (and references) added at its end. climate notes https://www.sciencebits.com/PetersenDiscrepancy https://www.sciencebits.com/PetersenDiscrepancy Sat, 17 Aug 2019 21:21:19 GMT shaviv This paper made some waves in the Media recently. It is based on highly biased data selection, and therefore flawed to its bone. It shouldn't have passed refereeing. climate notes https://www.sciencebits.com/solar-debunking-arguments-are-defunct https://www.sciencebits.com/solar-debunking-arguments-are-defunct Sun, 11 Aug 2019 13:58:43 GMT shaviv An article interviewing me was removed yesterday from forbes. Instead, they published an article by Meteorologist Prof. Marshall Shepherd that claims that the sun has no effect on climate. That article, however, falls to the same pitfalls that pointed out on my blog yesterday.… climate notes https://www.sciencebits.com/forbes-censored-interview-me https://www.sciencebits.com/forbes-censored-interview-me Sat, 10 Aug 2019 16:13:44 GMT shaviv A few days ago I was interviewed by Doron Levin, for an article to appear online on forbes.com. After having seen a draft (to make sure that I am quoted correctly), I told him good luck with getting it published, as I doubted it will. Why? Because a year ago I was interviewed by… astrophysics climate notes https://www.sciencebits.com/22-minute-talk-summarizing-my-views-global-warming https://www.sciencebits.com/22-minute-talk-summarizing-my-views-global-warming Sun, 04 Aug 2019 20:46:28 GMT shaviv Just over a week ago I gave a 20 minute talk (which lasted almost 22 min) about the role that the sun plays in global warming in the Heartland institute's climate conference in DC. Here it is brought again for posterity. astrophysics climate notes https://www.sciencebits.com/bundestag https://www.sciencebits.com/bundestag Fri, 07 Dec 2018 14:17:51 GMT shaviv Last week I had the opportunity to talk in front of the Environment committee of the German Bundestag. It was quite an interesting experience, and frankly, something I would have considered unlikely before receiving the invitation. It was in fact the first time a climate… climate notes https://www.sciencebits.com/climate-debate-cambridge-union-the-video https://www.sciencebits.com/climate-debate-cambridge-union-the-video Sat, 06 Jan 2018 17:22:01 GMT shaviv Two months ago I wrote about the Cambridge Union Debate I participated in. The Cambridge Union has meanwhile posted the debate online. Here is my part of it. (It starts at 32m31s.) [VIDEO::https://www.youtube.com/watch?feature=youtu.be&v=PL2gRaXMMkA&t=32m31s] I should add that… climate notes https://www.sciencebits.com/CosmicRays_Climate_TheMissingLink https://www.sciencebits.com/CosmicRays_Climate_TheMissingLink Tue, 19 Dec 2017 12:30:29 GMT shaviv Our new results published today in nature communications provide the last piece of a long studied puzzle. We finally found the actual physical mechanism linking between atmospheric ionization and the formation of cloud condensation nuclei. Thus, we now understand the complete… astrophysics climate https://www.sciencebits.com/cambridge_union_debate https://www.sciencebits.com/cambridge_union_debate Thu, 02 Nov 2017 21:35:48 GMT shaviv Last week I participated in an interesting debate that was held at the Cambridge Union, the oldest debating club in the world (dating back to 1815. The invite was to be on the side opposing the proposition “This house would rather cool the planet than warm the economy”. Although… climate notes https://www.sciencebits.com/vacuum_birefringence https://www.sciencebits.com/vacuum_birefringence Sat, 10 Dec 2016 10:43:56 GMT shaviv Just over a week ago I received an interesting call from a science magazine reporter. He asked me what do I think about the recent discovery of the Quantum Electrodynamic (QED) produced vacuum birefringence around neutron stars. It was an interesting surprise as my colleague… notes https://www.sciencebits.com/reply-eschenbach https://www.sciencebits.com/reply-eschenbach Sat, 15 Aug 2015 08:18:59 GMT shaviv Willis Eschenbach had a post on wattsupwiththat.com attacking my post on this blog , which explains why the new sunspot reconstruction may be irrelevant to the solar climate link and also discusses the recent paper I have co-written. I am not writing it as comments on… notes https://www.sciencebits.com/sunspots_2.0 https://www.sciencebits.com/sunspots_2.0 Mon, 10 Aug 2015 13:40:03 GMT shaviv After being asked by 5 independent people about the new sunspot number reconstruction and that it doesn’t show that the sun should have contributed any warming to the 20 th century, I decided to write about it here. I have one word to describe it – irrelevant. It is also a good… astrophysics climate notes https://www.sciencebits.com/he-who-controls-past-controls-future-vanishing-global-warming-hiatus https://www.sciencebits.com/he-who-controls-past-controls-future-vanishing-global-warming-hiatus Tue, 16 Jun 2015 14:30:14 GMT shaviv Two weeks ago a science magazine paper appeared claiming that once various systematic errors in the sea surface temperature are corrected for, the global warming “hiatus” is gone. Yep, vanished as if it was never there. According to the study, temperatures over the past 18 years… notes https://www.sciencebits.com/bill-nye-not-so-good-science-guy https://www.sciencebits.com/bill-nye-not-so-good-science-guy Sat, 06 Jun 2015 05:29:29 GMT shaviv Bill "the science guy" Nye says that I am a denier. I recently stumbled on a transcript of Bill “the science guy” Nye’s interview on CNN last week. In it, he said that climate skeptics (i.e., people like myself), are at least as bad as people who deny that smoking causes cancer.… climate notes https://www.sciencebits.com/Overholt_Melott_Pohl_is_really_wrong https://www.sciencebits.com/Overholt_Melott_Pohl_is_really_wrong Sun, 26 Apr 2015 05:31:15 GMT shaviv Last month I visited the U of Washington to give a talk in which I discussed the effects of cosmic rays on climate. At the end of it, not one, but two people independently asked me about Overholt et al. , which supposedly ruled out the idea that passages through the galactic… astrophysics climate notes https://www.sciencebits.com/bits-science-roundup-1 https://www.sciencebits.com/bits-science-roundup-1 Fri, 27 Mar 2015 04:27:51 GMT shaviv Since I look for interesting science bits (mostly astro bits) for the Monday coffee of our astrophysics group, I realized that I could share it with the readers including some interpretation (and hopefully some added value) by your humble servant. So, here’s my try. If it works… astrophysics https://www.sciencebits.com/funding-witch-hunt https://www.sciencebits.com/funding-witch-hunt Sun, 22 Mar 2015 04:26:01 GMT shaviv The recent bashing of Willie Soon from the Harvard Smithsonian Center for Astrophysics in the NY Times exemplifies, I think, how the climate debate has long left the realm of science, and it also demonstrates how scientific research is most often funded, quite the opposite of… notes https://www.sciencebits.com/Order-of-Magnitude https://www.sciencebits.com/Order-of-Magnitude Fri, 13 Mar 2015 22:56:05 GMT shaviv Since I began teaching "Order of Magnitude" physics a few years ago, I collected many examples of physics estimates from daily life (and the daily life of physicists... which I admit does not necessarily reflect the population as a whole). Here are several examples. More should… notes https://www.sciencebits.com/estimating-electric-dipole-radiation https://www.sciencebits.com/estimating-electric-dipole-radiation Thu, 12 Mar 2015 03:47:54 GMT shaviv An electric dipole is characterized by the dipole moment $d$ which depends on both the charge $e$ and a the separation $s$ (but not independently on each). Estimating the power radiated by an oscillating electric dipole is an excellent example for the usage of dimensional… physics https://www.sciencebits.com/sights-field-trip-milky-way https://www.sciencebits.com/sights-field-trip-milky-way Wed, 11 Mar 2015 13:29:58 GMT shaviv I was recently asked to write an article to “The Institute Letter” of Institute for Advanced Study at Princeton, where I am spending a wonderful sabbatical year. It briefly describes a very interesting discovery that my colleagues and I made, which is that the 32 million year… astrophysics climate https://www.sciencebits.com/calder https://www.sciencebits.com/calder Tue, 01 Jul 2014 18:36:12 GMT shaviv I just found out that a dear friend had passed away. Nigel Calder was the voice of rationality within a sea of extreme, something which is very much missing in the global warming debate. He didn't accept things for granted, but on the other hand didn't make extreme claims in the… climate notes https://www.sciencebits.com/about-author https://www.sciencebits.com/about-author Sun, 19 Jan 2014 17:26:32 GMT shaviv My name is Nir Shaviv. I am a full professor at the Racah Institute of Physics in the Hebrew University of Jerusalem. My main research interests revolve around the following topics: - The behaviour of very luminous astrophysical objects, so luminous that their radiation pressure… notes https://www.sciencebits.com/content/standard-model-lagrangian https://www.sciencebits.com/content/standard-model-lagrangian Fri, 17 Jan 2014 06:57:03 GMT shaviv If you're wondering about the equation in the banner, it is the Lagrangian of the standard model . It is the most succinct way of writing the laws governing the strong, electromagnetic and weak forces and their interaction with the known particles. The origin of this hand written… physics https://www.sciencebits.com/AR5-FirstImpressions https://www.sciencebits.com/AR5-FirstImpressions Wed, 02 Oct 2013 19:11:01 GMT shaviv The IPCC summary for policy makers is out, and as I started writing these lines so was the last draft of the main report. Of course, it will take a while to digest the 2200 pages of the full report (it has a lot of starch!). Until I do, here are my first impressions from having… notes https://www.sciencebits.com/GravityWavesInTheArava https://www.sciencebits.com/GravityWavesInTheArava Sat, 27 Apr 2013 20:24:23 GMT shaviv Spring weather here in Israel was rather strange. Although winter with most of its precipitation should have been over, we had a few very rainy days. We're now in the midst of a heat wave with temperatures as much as 20°C higher than just a week before. In between there was a… notes https://www.sciencebits.com/SN2010mc https://www.sciencebits.com/SN2010mc Fri, 15 Feb 2013 13:49:38 GMT shaviv A very interesting paper recently appeared in nature . It describes the detection of a precursor eruption of a supernova progenitor more than a month before the supernova explosion itself. It is particularly interesting because this detection was not serendipitous—it was based on… astrophysics physics notes https://www.sciencebits.com/Munich-2012 https://www.sciencebits.com/Munich-2012 Tue, 15 Jan 2013 07:09:17 GMT shaviv Last month I participated in EIKE's (Europäisches Institut für Klima und Energie) conference on Climate Change. They video record the lectures, which means that mine is now online. I thought I'd share it with you. Have fun. notes https://www.sciencebits.com/node/250 https://www.sciencebits.com/node/250 Wed, 02 Jan 2013 17:58:21 GMT shaviv My wife and I had our kitchen renovated aaa. Since this involved breaking a few walls (and cutting out a new window), we knew it would raise a lot of dust. Mind you, here in the middle east houses are built from concrete and concrete blocks, not wood. To minimize the dust… physics https://www.sciencebits.com/WorstBEST https://www.sciencebits.com/WorstBEST Thu, 06 Dec 2012 16:51:58 GMT shaviv I was asked by quite a few people about my opinion on the BEST analysis of Richard Muller and his group in Berkeley. Since I didn’t want to keep my friends without an answer, I took a more careful look into the analysis. Here is what I think of it. [Edit 2019: I noticed that the… climate https://www.sciencebits.com/node/245 https://www.sciencebits.com/node/245 Fri, 16 Nov 2012 22:45:25 GMT shaviv After being busy with the submission of two research proposal and trying to stay afloat with the pretty heavy teaching load I have this semester, I decided I should take a short break and post something on my blog. I actually have quite a few things I have been wanting to write… notes https://www.sciencebits.com/retirement_fund https://www.sciencebits.com/retirement_fund Mon, 12 Nov 2012 22:34:10 GMT shaviv Estimate the future value of a retirement fund, including payment and yearly fund commissions. notes https://www.sciencebits.com/Shakun_in_Nature https://www.sciencebits.com/Shakun_in_Nature Sat, 21 Apr 2012 14:49:41 GMT shaviv Over the past two weeks, perhaps a dozen people asked me about the recently published paper of Shakun et al. in Nature. It allegedly demonstrates that the global temperature followed CO 2 around the warming associated with the last interglacial warming, between 20 to 10 thousand… climate https://www.sciencebits.com/pension https://www.sciencebits.com/pension Mon, 02 Apr 2012 07:01:18 GMT shaviv Estimate a retirement fund and the extra money lost to payment and yearly fund commissions. notes https://www.sciencebits.com/LetToSchiff https://www.sciencebits.com/LetToSchiff Thu, 19 Jan 2012 19:49:56 GMT shaviv Dear Rep. Adam Schiff (representing California's 29th district). Although I presently live outside the US, I am a registered voter in the 29th district which you represent. I kindly ask that you will drop your support of SOPA. The continuing infringement of intellectual property… computing notes https://www.sciencebits.com/ClimateChangePollResults https://www.sciencebits.com/ClimateChangePollResults Mon, 16 Jan 2012 16:42:44 GMT shaviv Out of curiosity, I opened a few weeks ago a poll asking the visitors of this site, what do they think is the primary cause of global warming. 429 people answered the poll (thanks to all of you!). The results can be summarized as follows. First, the visitors of this site have the… climate notes https://www.sciencebits.com/IPCC_nowarming https://www.sciencebits.com/IPCC_nowarming Mon, 09 Jan 2012 05:00:00 GMT shaviv A few days ago I had a very pleasant meeting with Andrew Bolt . He was visiting Israel and we met for an hour in my office. During the discussion, I mentioned that the writers of the recent IPCC reports are not very scientific in their conduct and realized that I should write… climate notes https://www.sciencebits.com/LC-Circuit https://www.sciencebits.com/LC-Circuit Tue, 27 Dec 2011 08:25:37 GMT shaviv An LC circuit is one which has a capacitor and an inductor connected to each other. It exhibits oscillations just like a mass on a spring (a harmonic oscillator). In fact, the analogy is quite accurate with the capacitor playing the role of the spring and the inductor playing the… physics https://www.sciencebits.com/Equipartition-HydrogenAtom https://www.sciencebits.com/Equipartition-HydrogenAtom Mon, 26 Dec 2011 22:08:16 GMT shaviv Peering into the hydrogen atom . The standard way to obtain the size of the hydrogen atom, also known as Bohr's radius, is to solve Schrödinger equation for the hydrogen atom. This is a somewhat detailed calculation requiring the usage of generalized Laguerre polynomials and… physics https://www.sciencebits.com/ClimateChangePoll https://www.sciencebits.com/ClimateChangePoll Thu, 22 Dec 2011 14:39:40 GMT shaviv Archived results of the original ScienceBits expertise and climate-change-cause poll. climate notes https://www.sciencebits.com/ClimateGate2.0 https://www.sciencebits.com/ClimateGate2.0 Wed, 21 Dec 2011 06:25:24 GMT shaviv A few weeks ago, the hacker/whistleblower has done it again. A new release of a large amount of e-mails from the same source (University of East Anglia) has surfaced in Russia. It is most likely from the same original batch because the last of the new e-mails is from 2009. Here… climate notes https://www.sciencebits.com/Faster-than-light-neutrinos https://www.sciencebits.com/Faster-than-light-neutrinos Tue, 27 Sep 2011 20:44:01 GMT shaviv Three weeks ago I visited the underground laboratory of Gran Sasso near l'Aquila. Little did I know that it would make headline news so soon, for "discovering" particles moving faster than the speed of light. Since a few people asked me what did I think of it, I decided to write… physics notes https://www.sciencebits.com/CLOUDresults https://www.sciencebits.com/CLOUDresults Fri, 26 Aug 2011 20:53:01 GMT shaviv 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… astrophysics climate https://www.sciencebits.com/Masada-to-Messina https://www.sciencebits.com/Masada-to-Messina Fri, 31 Dec 2010 14:44:16 GMT shaviv Masada, the Dead Sea, the Messinian Salinity Crisis and Augustus Ceasar, all in one post. physics climate notes https://www.sciencebits.com/NothingNewUnderTheSun https://www.sciencebits.com/NothingNewUnderTheSun Fri, 30 Jul 2010 09:14:35 GMT shaviv After a long lull in activity, I decided it's about time I write an update about my thoughts on global warming. Here it is. climate notes https://www.sciencebits.com/NothingNewUnderTheSun-III https://www.sciencebits.com/NothingNewUnderTheSun-III Fri, 30 Jul 2010 09:12:23 GMT shaviv Cosmic Rays and Climate astrophysics climate notes https://www.sciencebits.com/NothingNewUnderTheSun-II https://www.sciencebits.com/NothingNewUnderTheSun-II Fri, 30 Jul 2010 09:09:37 GMT shaviv This is the second of the three part article on the climatic role of the sun. astrophysics climate notes https://www.sciencebits.com/NothingNewUnderTheSun-I https://www.sciencebits.com/NothingNewUnderTheSun-I Sun, 27 Jun 2010 10:52:07 GMT shaviv With the exception of those who have been living in a dark cave, it is well known that Earth has warmed over the 20 th century. Anyone who reads papers or watches TV knows that it is humans who are those responsible for this warming. According to most media sources, and… astrophysics climate notes https://www.sciencebits.com/Expert-credibility-in-climate https://www.sciencebits.com/Expert-credibility-in-climate Sat, 26 Jun 2010 16:48:24 GMT shaviv I recently stumbled upon one of the most meaningless papers I have ever seen. The paper "proves" that the scientists advocating an anthropogenic greenhouse warming (AGW) are statistically more credible than the "unconvinced". Their main goal is to convince people that they should… climate notes https://www.sciencebits.com/stromboli https://www.sciencebits.com/stromboli Wed, 03 Feb 2010 15:04:24 GMT shaviv Last May I had a conference in the island of Vulcano. During the conference I had a half day excursion to the Island of Stromboli, where I climbed the mountain and got to see one of the most impressive geological phenomena one can see... Here are my impressions, photos and even a… physics notes https://www.sciencebits.com/node/211 https://www.sciencebits.com/node/211 Sun, 13 Dec 2009 14:02:45 GMT shaviv After being asked once too many about the climategate scandal, I decided it would save me some time if I simply wrote down my opinion about it. notes https://www.sciencebits.com/node/210 https://www.sciencebits.com/node/210 Fri, 20 Nov 2009 09:09:16 GMT shaviv There are 12, but that's not the main point of this blog entry... notes https://www.sciencebits.com/node/209 https://www.sciencebits.com/node/209 Sat, 26 Sep 2009 09:35:42 GMT shaviv (On the hebrew translation of the "Chilling Stars") לאור העובדה שלא מעט מקוראי האתר בעברית מתענינים בנושא של השפעת השמש על האקלים, מצאתי לנכון "לפרסם" תרגום לעברית של הספר "chilling stars" של הנריק סוונסמרק ונייג`ל קולדר, שהם ידידי. הספר "הכוכבים המקררים" יצא לאור זה עתה בהוצאת… astrophysics climate notes https://www.sciencebits.com/EarthDayBlackout https://www.sciencebits.com/EarthDayBlackout Tue, 05 May 2009 06:12:50 GMT shaviv A week ago was Earth day, and just like the trend elsewhere, Israel joined with an hour long blackout. In principle, I am very much in favor of environmental awareness, and if it brings some, so be it. But if you ask me, overall, this event is a rather pointless gimmick. Why? climate notes https://www.sciencebits.com/nohotlinking https://www.sciencebits.com/nohotlinking Thu, 16 Apr 2009 06:08:54 GMT shaviv Please do not re-post whole content without permission. Would you like me to copy your site? You can re-post up to half an article, and make sure you add a link to the original page If you take images of which I am the originator, please save the file locally on your server and… notes https://www.sciencebits.com/calorimeter https://www.sciencebits.com/calorimeter Sun, 12 Apr 2009 17:48:49 GMT shaviv I few months ago, I had a paper accepted in the Journal of Geophysical Research. Since its repercussions are particularly interesting for the general public, I decided to write about it. It's called, using the "Oceans as a Calorimeter to quantify the solar radiative forcing". climate notes https://www.sciencebits.com/touch-and-go https://www.sciencebits.com/touch-and-go Sat, 11 Apr 2009 16:47:35 GMT shaviv I recently returned from Lijiang (in Yunnan, China). One of my legs was a flight from Chengdu to Beijing, and it is certainly a flight I will never forget. notes https://www.sciencebits.com/auroras https://www.sciencebits.com/auroras Thu, 26 Mar 2009 20:34:11 GMT shaviv I recently attended the 3rd Space Climate Symposium which took place in Saariselkä, about 250 km north of the arctic circle in Finnish Lapland. Because of the prolonged solar minimum, my hopes were for a high auroral activity, but my expectations were not. Luckily, it was my… astrophysics climate https://www.sciencebits.com/welcome https://www.sciencebits.com/welcome Mon, 23 Mar 2009 12:16:24 GMT shaviv A random and subjective walk in science and physics in particular. notes https://www.sciencebits.com/SloanAndWolfendale https://www.sciencebits.com/SloanAndWolfendale Fri, 11 Apr 2008 08:19:06 GMT shaviv Just recently, Sloan and Wolfendale published a paper in Environmental Research Letters, called "Testing the proposed causal link between cosmic rays and cloud cover". In the Institute of Physics Press Release, it said, "New research has deal a blow to the skeptics who argue that… astrophysics climate https://www.sciencebits.com/RealClimateSlurs https://www.sciencebits.com/RealClimateSlurs Wed, 12 Mar 2008 08:36:49 GMT shaviv Realclimate.org continues with its same line of attack. Wishfulclimate.org writers try again and again to concoct what appears to be deep critiques against skeptic arguments, but end up doing a very shallow job. All in the name of saving the world. How gallant of them. This time… astrophysics climate notes https://www.sciencebits.com/Climate_Debate https://www.sciencebits.com/Climate_Debate Tue, 26 Feb 2008 13:03:21 GMT shaviv By: Nir J. Shaviv & Ján Veizer Background Counter to claims by anthopogenic global warming enthusiasts, there is ample evidence to support the idea that cosmic rays do indeed affect climate (evidence will soon be summarized on this site). Thus, it is no surprise that we find in… notes https://www.sciencebits.com/RadarOpenCell https://www.sciencebits.com/RadarOpenCell Mon, 04 Feb 2008 19:29:24 GMT shaviv 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… climate notes https://www.sciencebits.com/strike https://www.sciencebits.com/strike Fri, 25 Jan 2008 22:52:23 GMT shaviv A few words about the longest strike ever in the Israeli Universities, a strike which ended last week. No science in this post. Sorry. notes https://www.sciencebits.com/EntangledBush https://www.sciencebits.com/EntangledBush Thu, 10 Jan 2008 21:00:26 GMT shaviv On my personal views of President Bush's visit to my humble town of Jerusalem. A few thoughts about quantum mechanics and the speed of sound. physics notes https://www.sciencebits.com/dot_product https://www.sciencebits.com/dot_product Mon, 07 Jan 2008 21:52:15 GMT shaviv The dot product. physics https://www.sciencebits.com/vector_algebra https://www.sciencebits.com/vector_algebra Wed, 02 Jan 2008 19:58:16 GMT shaviv Scalars : Scalars are mathematical entities which include only a magnitude (and no direction). Physical examples include mass and energy. Vectors : Vectors are mathematical entities which include both a magnitude and a direction . Note that the location of the vector (for… physics https://www.sciencebits.com/CorpuscularRays https://www.sciencebits.com/CorpuscularRays Fri, 28 Dec 2007 23:30:43 GMT shaviv A few days ago, I stayed in the Vatican (more about this one day symposium in another post). During the stay, I naturally visited St. Peter's Basilica. Near Bernini's Altar, I saw corpuscular rays. It may seem like some godly thing (quite appropriate for the location), but from a… physics https://www.sciencebits.com/MR_Stokes_Drag https://www.sciencebits.com/MR_Stokes_Drag Thu, 13 Dec 2007 20:26:08 GMT shaviv Let us study a somewhat more complex case of motion in a gravitational field. Instead of just the force of gravity, let us add a drag force which is proportional to the velocity, that is: $$ { F} = - { v}. $$ In other words, at every instant, the drag force is proportional to the… physics https://www.sciencebits.com/MS_Newton_Laws https://www.sciencebits.com/MS_Newton_Laws Thu, 13 Dec 2007 13:57:27 GMT shaviv Newton's laws and other laws of nature cannot be "derived" or "proved" like proofs in Math. Instead, physical laws are conjectured and then studied through experiments. These laws can be verified under different limits, in which case the conjected laws become accepted theory, or… physics https://www.sciencebits.com/Transformation-Forces-Relativity https://www.sciencebits.com/Transformation-Forces-Relativity Thu, 13 Dec 2007 13:50:01 GMT shaviv We have previously seen that the velocity does not transform from one reference frame to another using the standard Lorent transformation to 4-vectors, simply because the velocity is not a 4-vector. Similarly, the force is not one either (nor is it part of one, such as the… physics https://www.sciencebits.com/node/175 https://www.sciencebits.com/node/175 Thu, 13 Dec 2007 13:45:21 GMT shaviv Until now, we have avoided using forces in Relativity. We did so for a good reason. The definition of force even in classical mechanics is somewhat problematic, let alone in relativity. Nonetheless, let us try and see whether we can generalize classical relations to get a… physics https://www.sciencebits.com/node/174 https://www.sciencebits.com/node/174 Thu, 13 Dec 2007 13:41:52 GMT shaviv Chapter 13: A Few Extras physics https://www.sciencebits.com/node/173 https://www.sciencebits.com/node/173 Thu, 13 Dec 2007 13:40:29 GMT shaviv Chapter 12: Relativistic Dynamics physics https://www.sciencebits.com/node/172 https://www.sciencebits.com/node/172 Thu, 13 Dec 2007 13:38:05 GMT shaviv Chapter 11: Relativistic Kinematics physics https://www.sciencebits.com/node/171 https://www.sciencebits.com/node/171 Thu, 13 Dec 2007 13:36:48 GMT shaviv Chapter 10: Rigid Body physics https://www.sciencebits.com/node/170 https://www.sciencebits.com/node/170 Thu, 13 Dec 2007 13:36:01 GMT shaviv Chapter 9: Non-Inertial Frames physics https://www.sciencebits.com/node/169 https://www.sciencebits.com/node/169 Thu, 13 Dec 2007 13:35:15 GMT shaviv Chapter 8: Central Force physics https://www.sciencebits.com/node/168 https://www.sciencebits.com/node/168 Thu, 13 Dec 2007 13:34:37 GMT shaviv Chapter 7: Harmonic Motion physics https://www.sciencebits.com/node/167 https://www.sciencebits.com/node/167 Thu, 13 Dec 2007 13:33:26 GMT shaviv Chapter 6: Center of Mass & Angular Momentum physics https://www.sciencebits.com/node/166 https://www.sciencebits.com/node/166 Thu, 13 Dec 2007 13:32:47 GMT shaviv Chapter 5: Energy physics https://www.sciencebits.com/node/165 https://www.sciencebits.com/node/165 Thu, 13 Dec 2007 13:32:18 GMT shaviv Chapter 4: Momentum physics https://www.sciencebits.com/node/164 https://www.sciencebits.com/node/164 Thu, 13 Dec 2007 13:31:33 GMT shaviv Chapter 3: Newton's laws, forces, equations of motion physics https://www.sciencebits.com/MR_Units_Dimensions https://www.sciencebits.com/MR_Units_Dimensions Thu, 13 Dec 2007 12:45:47 GMT shaviv Units are part of physical quantities. This implies that a physical variable will have a value and may include a dimension such as length, time, mass or combinations of them. For example, x = 5 meters , t = 3 seconds , v = 5/3 meter per second = 5/3 m/sec , m = 10 kg or E = 2 J… physics https://www.sciencebits.com/BlackHoleSimulation https://www.sciencebits.com/BlackHoleSimulation Thu, 13 Dec 2007 05:59:16 GMT shaviv 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… astrophysics physics notes https://www.sciencebits.com/MR_Short_History https://www.sciencebits.com/MR_Short_History Wed, 12 Dec 2007 23:43:22 GMT shaviv The first to seriously ponder about the nature of nature where the ancient Greeks. However, following the Aristotlian views, logic was more important than experiment. Since it is logical that heavier bodies fall faster to the ground, it necessarily is the case. For example, an… physics https://www.sciencebits.com/node/161 https://www.sciencebits.com/node/161 Wed, 12 Dec 2007 23:40:44 GMT shaviv Some necessary mathematical background physics https://www.sciencebits.com/node/160 https://www.sciencebits.com/node/160 Wed, 12 Dec 2007 23:35:27 GMT shaviv If you are reading these lines, you either accidentally stumbled upon or deliberately looked for Mechanics and Relativity course notes. These notes are used in the first year physics major's classical mechanics course. They were prepared over the course of 3 semesters whilst I… physics https://www.sciencebits.com/node/159 https://www.sciencebits.com/node/159 Wed, 12 Dec 2007 23:33:07 GMT shaviv Some Introduction physics https://www.sciencebits.com/node/158 https://www.sciencebits.com/node/158 Wed, 12 Dec 2007 23:17:38 GMT shaviv Online notes for a physics major's classical mechanics and relativity course. The course notes are still in the making, and will be added during January / February 2008 physics https://www.sciencebits.com/HUdebate https://www.sciencebits.com/HUdebate Mon, 03 Dec 2007 15:28:55 GMT shaviv The panel. From left to right: Prof. Colin Price, Prof. Nathan Paldor, Prof. Dan Yakir, and myself. On Sunday last week, a global warming debate was held at the Hebrew University, in front of a large public audience. The speakers included myself, and Prof. Nathan Paldor from the… astrophysics climate notes https://www.sciencebits.com/GWHebrew https://www.sciencebits.com/GWHebrew Sun, 25 Nov 2007 07:00:37 GMT shaviv התחממות גלובלית, מי יודע מדוע וכמה? A short "open letter" in hebrew about global warming. To all my english readers, sorry. This is a one time quirk. notes https://www.sciencebits.com/ship_tracks https://www.sciencebits.com/ship_tracks Sat, 25 Aug 2007 22:58:43 GMT shaviv On of the interesting manmade climate phenomenon is that of Ship Tracks , whereby a ship, with all the exhaust particles it releases, can change the characteristics of clouds in its wake. Last week, I saw first hand how a boat can pollute so much. climate notes https://www.sciencebits.com/VenusOccult https://www.sciencebits.com/VenusOccult Sat, 30 Jun 2007 06:19:17 GMT shaviv A few astro photographs, including one of Saturn under horrible seeing! astrophysics notes https://www.sciencebits.com/FittingElephants https://www.sciencebits.com/FittingElephants Sun, 10 Jun 2007 10:56:34 GMT shaviv A few weeks ago, while debating the issue of global warming with an alarmist, my colleague pointed out two facts which appear to be consistent with the "standard" anthropogenic scenario, but not the one I advocate, that the natural climate drivers are large and that Earth's… notes https://www.sciencebits.com/IceCoreTruth https://www.sciencebits.com/IceCoreTruth Sun, 27 May 2007 07:35:27 GMT shaviv One of the "scientific" highlights in Al Gore's movie is the discussion about the clear correlation between CO 2 and temperature, as is obtained in ice cores. He leads his audience to beleive that this correlation implies a clear CO 2 →ΔT link, but does it really? climate notes https://www.sciencebits.com/Gliese581 https://www.sciencebits.com/Gliese581 Fri, 27 Apr 2007 17:03:24 GMT shaviv The recent discovery of a terrestrial like planet (i.e., one which is stony and not gaseous like Jupiter) gave rise to a minor media hype, with statements like "We may be witnessing the start of a cosmic real estate boom" being commonplace. However, is Gliese 581C really a place… notes https://www.sciencebits.com/ParhelicCircle https://www.sciencebits.com/ParhelicCircle Sun, 22 Apr 2007 06:54:45 GMT shaviv 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… physics climate notes https://www.sciencebits.com/KHoverJerusalem https://www.sciencebits.com/KHoverJerusalem Sat, 10 Feb 2007 17:40:31 GMT shaviv Kelvin Helmholtz cloud rolls Yesterday, I noticed (and photographed ;-) ) Kelvin-Helmholtz Clouds forming in Jerusalem's sky. This instability arises when very large shears are present in the velocity fields, in this case, just below the jet stream. climate https://www.sciencebits.com/NoInterview https://www.sciencebits.com/NoInterview Mon, 05 Feb 2007 10:01:02 GMT shaviv Yesterday I was surprised to find out that the IPCC didn't really come out with the Fourth Assessment Report (4AR). I was also surprised to find an article with something which appeared to look like an interview of me. Since I am not senile (getting there, but not just yet) I… climate notes https://www.sciencebits.com/human_chain https://www.sciencebits.com/human_chain Tue, 16 Jan 2007 07:45:18 GMT shaviv 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… notes https://www.sciencebits.com/RandiPrize https://www.sciencebits.com/RandiPrize Fri, 15 Dec 2006 07:29:17 GMT shaviv 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… notes https://www.sciencebits.com/IPCCbias https://www.sciencebits.com/IPCCbias Mon, 04 Dec 2006 18:56:48 GMT shaviv 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… climate notes https://www.sciencebits.com/OnClimateSensitivity https://www.sciencebits.com/OnClimateSensitivity Thu, 30 Nov 2006 22:16:55 GMT shaviv What is climate sensitivity? The equilibrium climate sensitivity refers to the equilibrium change in average global surface air temperature following a unit change in the radiative forcing. This sensitivity (often denoted as λ) therefore has units of °C/(W/m 2 ). Often, instead &… climate notes https://www.sciencebits.com/FluShots https://www.sciencebits.com/FluShots Wed, 08 Nov 2006 09:25:33 GMT shaviv 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.… notes https://www.sciencebits.com/NotReallyAProtection https://www.sciencebits.com/NotReallyAProtection Fri, 27 Oct 2006 19:13:01 GMT shaviv 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… astrophysics https://www.sciencebits.com/NoLife https://www.sciencebits.com/NoLife Wed, 25 Oct 2006 08:32:30 GMT shaviv 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… astrophysics notes https://www.sciencebits.com/HUNobel https://www.sciencebits.com/HUNobel Sat, 07 Oct 2006 14:55:55 GMT shaviv 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. notes https://www.sciencebits.com/SkyResults https://www.sciencebits.com/SkyResults Wed, 04 Oct 2006 05:56:56 GMT shaviv 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… astrophysics climate https://www.sciencebits.com/Ramadan https://www.sciencebits.com/Ramadan Sat, 30 Sep 2006 19:36:06 GMT shaviv 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… notes https://www.sciencebits.com/ACwater https://www.sciencebits.com/ACwater Wed, 20 Sep 2006 07:21:16 GMT shaviv 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… notes https://www.sciencebits.com/nature_comment https://www.sciencebits.com/nature_comment Sun, 17 Sep 2006 06:58:52 GMT shaviv 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… astrophysics climate notes https://www.sciencebits.com/JahnkeResponse https://www.sciencebits.com/JahnkeResponse Fri, 15 Sep 2006 22:07:47 GMT shaviv 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… astrophysics climate https://www.sciencebits.com/GeoscienceCanadaVeizer https://www.sciencebits.com/GeoscienceCanadaVeizer Fri, 15 Sep 2006 16:32:29 GMT shaviv 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… astrophysics climate https://www.sciencebits.com/PlutoPlanetoid https://www.sciencebits.com/PlutoPlanetoid Thu, 24 Aug 2006 22:13:28 GMT shaviv The Plutonian system : Pluto and two moons viewed from a third. 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… astrophysics https://www.sciencebits.com/StandingOnIce https://www.sciencebits.com/StandingOnIce Sun, 13 Aug 2006 20:38:52 GMT shaviv Ever wondered whether it was sufficiently cold for sufficiently long to allow you to stand on ice, without falling in? I once did. Here is an estimate for the duration required to reach a given thickness. Actually, it is a lower limit, since we assume a few simplifying… physics climate https://www.sciencebits.com/SurpassingEddingtonPage2 https://www.sciencebits.com/SurpassingEddingtonPage2 Thu, 10 Aug 2006 05:10:06 GMT shaviv Technical details about super-Eddington atmospheres. Proceed at your own risk. notes https://www.sciencebits.com/Crackpots https://www.sciencebits.com/Crackpots Mon, 31 Jul 2006 08:10:12 GMT shaviv 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… notes https://www.sciencebits.com/Katyusha https://www.sciencebits.com/Katyusha Thu, 27 Jul 2006 08:43:23 GMT shaviv 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. notes https://www.sciencebits.com/JumboHail https://www.sciencebits.com/JumboHail Sun, 09 Jul 2006 09:44:07 GMT shaviv 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! climate https://www.sciencebits.com/TimeIceAge https://www.sciencebits.com/TimeIceAge Thu, 29 Jun 2006 05:30:35 GMT shaviv 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… climate https://www.sciencebits.com/GlasgowScale https://www.sciencebits.com/GlasgowScale Tue, 27 Jun 2006 19:21:14 GMT shaviv 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… notes https://www.sciencebits.com/PlanesAndMeteorites https://www.sciencebits.com/PlanesAndMeteorites Tue, 13 Jun 2006 16:57:30 GMT shaviv 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. astrophysics https://www.sciencebits.com/GeneDegrade https://www.sciencebits.com/GeneDegrade Sun, 04 Jun 2006 21:04:53 GMT shaviv A conversation I had with a friend made me realize something interesting. Modern medical technology is responsible for the constant degradation of the human gene pool. How? Simple, we allow bad genes to propagate. Take me for example... notes https://www.sciencebits.com/StellarEquipartition https://www.sciencebits.com/StellarEquipartition Wed, 31 May 2006 06:16:11 GMT shaviv 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… astrophysics physics https://www.sciencebits.com/node/70 https://www.sciencebits.com/node/70 Sat, 27 May 2006 10:53:04 GMT shaviv Archived results of the original ScienceBits poll about naming silent earthquakes. notes https://www.sciencebits.com/silentquakespoll https://www.sciencebits.com/silentquakespoll Sat, 27 May 2006 07:32:51 GMT shaviv Archived results of the original ScienceBits poll about naming silent earthquakes. notes https://www.sciencebits.com/SilentEarthquakes https://www.sciencebits.com/SilentEarthquakes Fri, 26 May 2006 09:17:55 GMT shaviv Did you know that there are huge earthquakes which aren't felt? Did you know that similar waves appear everyday when two objects with dry friction between them start to move? physics https://www.sciencebits.com/SiteContent https://www.sciencebits.com/SiteContent Mon, 22 May 2006 20:10:40 GMT shaviv Links to the static pages and an archive of the blog entries. notes https://www.sciencebits.com/ExhaleCondCalc https://www.sciencebits.com/ExhaleCondCalc Sun, 21 May 2006 15:56:16 GMT shaviv Determine whether mixed exhaled and outside air condenses and estimate the mixing range and cloud-water content. climate physics https://www.sciencebits.com/SnowProbCalc https://www.sciencebits.com/SnowProbCalc Mon, 15 May 2006 09:47:59 GMT shaviv Estimate the melting temperature and probability that falling precipitation reaches the ground as snow. climate physics https://www.sciencebits.com/SnowAboveFreezing https://www.sciencebits.com/SnowAboveFreezing Sun, 14 May 2006 16:16:03 GMT shaviv Did you ever wonder how can it snow at above freezing temperatures? Well, the naive explanation is that it simple takes time for the snowflakes to melt once they penertrate above freezing air, as they descent downwards to the ground. As it turns out, this is the reaons why hail… physics climate https://www.sciencebits.com/LightningWithoutStorm https://www.sciencebits.com/LightningWithoutStorm Sat, 29 Apr 2006 20:22:44 GMT shaviv When visiting the president, I learned about a strange event that was recorded by the Columbia space shuttle: A lightning flash without a thunderstorm! What could it be?? climate https://www.sciencebits.com/CosmicRaysClimate https://www.sciencebits.com/CosmicRaysClimate Thu, 27 Apr 2006 21:23:21 GMT shaviv A quick review of the cosmic ray / climate link. astrophysics climate notes https://www.sciencebits.com/BoneAge https://www.sciencebits.com/BoneAge Mon, 24 Apr 2006 21:17:29 GMT shaviv My almost 3 year old daredevil son broke his hand in his last escapade. I found the x-ray rather cute, and interesting... you can see how his bones are forming. He learned not to jump from high places, and I learned all about bone age... notes https://www.sciencebits.com/RocketCalculator https://www.sciencebits.com/RocketCalculator Fri, 21 Apr 2006 12:11:56 GMT shaviv Numerically simulate a homemade water rocket and graph its velocity and height over time. physics https://www.sciencebits.com/RocketEqs https://www.sciencebits.com/RocketEqs Wed, 19 Apr 2006 19:55:31 GMT shaviv Water Rockets are simple homemade invensions that model their chemically fueled cousins. Unlike the latter, water rockets operate using water propulsion and hand-pump generated air pressure. Here we describe the equations of the problem. They are also solved numerically in the… notes https://www.sciencebits.com/SurpassingEddington https://www.sciencebits.com/SurpassingEddington Mon, 17 Apr 2006 13:45:20 GMT shaviv This article succinctly describes the theory of porous atmospheres, which naturally gives rise to super-Eddington systems. We quickly review the meaning of the Eddington luminosity and how nature can circumvent it. notes https://www.sciencebits.com/CO2orSolarHYPERLINK https://www.sciencebits.com/CO2orSolarHYPERLINK Mon, 17 Apr 2006 13:40:41 GMT shaviv Is 20th century global warming due to anthropogenic sources (i.e., greenhouse gasses) or natural variability? Find out here. astrophysics climate notes https://www.sciencebits.com/ClimateDebate https://www.sciencebits.com/ClimateDebate Mon, 10 Apr 2006 14:42:49 GMT shaviv A summary of the debate prompted by the "infamous" paper written by Ján Veizer and myself. All the attacks and their rebuttals. Have fun. notes https://www.sciencebits.com/venustransit https://www.sciencebits.com/venustransit Tue, 04 Apr 2006 08:02:29 GMT shaviv Twice every 117 years or so, Venus transits the disk of the sun. Here is some info on the events (and a photograph I took of it). astrophysics physics https://www.sciencebits.com/computerbits https://www.sciencebits.com/computerbits Sun, 02 Apr 2006 21:39:32 GMT shaviv Computer bits and practical computer reference pages. computing https://www.sciencebits.com/astrobits https://www.sciencebits.com/astrobits Sun, 02 Apr 2006 20:23:20 GMT shaviv Various astrophysical and geophysical topics. astrophysics https://www.sciencebits.com/ShasShinuiVolterra https://www.sciencebits.com/ShasShinuiVolterra Sun, 02 Apr 2006 10:13:49 GMT shaviv The demise of Shinui party in the last Israeli parliamentary elections (March 2006), made me realize that Shas and Shinui should probably follow the Lotka-Volterra equation. As I explain below, the problems are not totally equivalent for several reasons. Nonetheless, many of the… notes https://www.sciencebits.com/online https://www.sciencebits.com/online Sat, 01 Apr 2006 10:29:08 GMT shaviv After quite a long while, during which I planned developing such a site, sciencebits.com has gone online. The "raison d'être" behind this site consists of several motives... notes https://www.sciencebits.com/rowers https://www.sciencebits.com/rowers Sat, 01 Apr 2006 08:23:39 GMT shaviv The maximum speed of a rower boat is a classic example of the beauty of dimensional analysis. It was originally derived by McMahon (1971). Here it is brought again for the convenience of the Internet audience, together with updated rowing record data. First, some assumptions… physics https://www.sciencebits.com/ice-ages https://www.sciencebits.com/ice-ages Wed, 29 Mar 2006 20:45:58 GMT shaviv On long time scales, it appears that our journey through the Milky Way is responsible for large climate variations. Each time we pass through spiral arms of the galaxy, we witness a higher flux of cosmic rays, which in turn reduce the global temperature. Read more about the… astrophysics physics climate notes https://www.sciencebits.com/myresearch https://www.sciencebits.com/myresearch Wed, 29 Mar 2006 05:19:37 GMT shaviv About my personal research. notes https://www.sciencebits.com/frostdendrites https://www.sciencebits.com/frostdendrites Tue, 28 Mar 2006 19:51:24 GMT shaviv Under which conditions can you get frost dendrites on your window? physics climate https://www.sciencebits.com/foucault https://www.sciencebits.com/foucault Mon, 27 Mar 2006 22:57:39 GMT shaviv The Foucault Pendulum was conceived by Léon Foucault in the middle of the 19th century, with the goal of proving Earth's rotation through the effect of the Coriolis Force. In essence, the Foucault Pendulum is a Pendulum with a long enough damping rate such that the precession of its plane of oscillations can be observed after typically an hour or more. A whole revolution of the plane of oscillation takes anywhere between a day if it is at the pole, or longer at lower latitudes. Here is a relatively simple derivation of the precession. physics https://www.sciencebits.com/econobits https://www.sciencebits.com/econobits Mon, 27 Mar 2006 06:28:17 GMT shaviv Useful and interesting financial calculations and related entries. notes https://www.sciencebits.com/ReynoldsNumber https://www.sciencebits.com/ReynoldsNumber Sat, 25 Mar 2006 23:25:45 GMT shaviv Reynolds number is a dimensionless number which determines whether a given flow will be laminar or turbulent. It is basically the ratio between the inertial forces $v $ and the viscous forces $ L$. It is given by: $$ R -1pt e= { v L } = {v L }, $$ where $ $ is the density of the… notes https://www.sciencebits.com/exhalecondense https://www.sciencebits.com/exhalecondense Thu, 23 Mar 2006 21:31:29 GMT shaviv Ever wondered why and when does your exhaled breath condense? physics climate https://www.sciencebits.com/constants https://www.sciencebits.com/constants Thu, 23 Mar 2006 20:37:44 GMT shaviv Physical Constants, in c.g.s.: Speed of Light: $ c = 3 10^{10}~ {cm/s} $ notes https://www.sciencebits.com/dimensionlessnumbers https://www.sciencebits.com/dimensionlessnumbers Thu, 23 Mar 2006 19:08:47 GMT shaviv Dimensionless numbers are VERY important in the understanding of physical problems and their solution. In particular, The value of the dimensionless numbers often determine the behavior of the solution. For example, a flow problem with a low Reynolds Number will be laminar, while… physics https://www.sciencebits.com/variousphysics https://www.sciencebits.com/variousphysics Thu, 23 Mar 2006 17:16:59 GMT shaviv PhysicsBits articles and the general-physics blog archive. physics https://www.sciencebits.com/sports https://www.sciencebits.com/sports Thu, 23 Mar 2006 17:14:09 GMT shaviv Sports is fun, but more so if you understand the physics behind it! Balls and Magnus force Skiing and snowboarding --> Rowers on a boat notes https://www.sciencebits.com/about https://www.sciencebits.com/about Thu, 23 Mar 2006 16:13:41 GMT shaviv ScienceBits is Nir Shaviv’s independent, random and subjective walk through physics, astrophysics, climate, computation, and scientific curiosities. notes https://www.sciencebits.com/weatherphys https://www.sciencebits.com/weatherphys Thu, 23 Mar 2006 16:11:31 GMT shaviv Weather and climate physics articles, explanations, and calculators. climate physics https://www.sciencebits.com/formulae https://www.sciencebits.com/formulae Thu, 23 Mar 2006 16:07:36 GMT shaviv Physics and Mathematical Formulae, by topic: Vector Analysis Classical Mechanics Special Relativity notes