Archives for the 'physics' Category
Escape Velocity
Published on 3 Mar 2008 at 5:41 pm.
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Filed under physics.
Every now and then, you hear physicists, astronomers, or rocket scientists talking about “escape velocity.” So, what is escape velocity?
To put it very simply, escape velocity is the speed needed to pull away from an object’s gravitational reach. Now, let me explain this. You can imagine throwing an object upwards. From […]
Happy Mole Day!
Published on 23 Oct 2007 at 11:58 am.
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Filed under physics.
My chemistry friends tell me that this is National Mole Day. A mole is the amount of a subestance equal to one Avogadro’s number of molecules or atoms of that substance. Avogadro’s number is about 6.0221418×1023. Almost universally in textbooks this is truncated to three significant figures for solving homework problems, so students learn Avogadro’s […]
Einstein was right
Published on 15 Apr 2007 at 12:46 am.
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Filed under physics.
Well, it looks like Einstein was right. The initial results of the Gravity Probe B mission have been released, and the geodetic precession predicted under Einstein’s general theory of relativity has been measured to better than 1% accuracy. The gyroscopes precessed just as predicted. This is the first non-electromagnetic test of general relativity, and it […]
Testing Relativity
Published on 7 Apr 2007 at 11:17 pm.
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Filed under physics.
In 1915, Albert Einstein set forth his general theory of relativity. Like the special theory, general relativity shows that time and space are relative rather than absolute quantities. Special theory has been tested many times. General theory, though, is a bit tougher to test in full. Among the predictions of general […]
How YORP Works
Published on 8 Mar 2007 at 11:45 pm.
3 Comments.
Filed under asteroids, physics.
There’s been talk lately about YORP. It even made a major non-science news site. So, what is YORP, and what does it do? Well, YORP is basically an extension of the Yorkovsky Effect that I blogged about back a bit over five months ago. In fact, the “Y” in YORP stands […]
Aberration of Starlight
Published on 20 Feb 2007 at 5:30 pm.
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Filed under astronomy, physics.
The star Gamma Draconis (γ Dra) plays an interesting and important role in the history of astronomy. It isn’t really all that impressive of a star to look at. Gamma Draconis, also known variously as Etamin, Eltamin, or Eltanin, is magnitude 1.5, a bit brighter than Polaris. It is a red giant […]
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Talking with the planets
Published on 2 Feb 2007 at 10:25 am.
4 Comments.
Filed under amusement, physics, planets.
A few days ago I was trying to get across to someone just how big the Solar System is. I have an exercise that I do with my students in which they build a scale model of the Solar System. I don’t mean making just the planets to scale, but also putting them […]
