"Did he just have a special love for π, perhaps based on his birthday?"
Einstein lived in Europe for 54 of his 76 years. Since no one in Europe uses the mm/dd/yy date convention, I'd be surprised if this coincidence was significant to him, or even that he was aware of it at all.
I know. I was trying to make a point about basing an otherwise interesting article about Einstein and GR on a numeric coincidence involving an arbitrary birthday and an illogical date format that is essentially only used by one country on the planet. Without appearing to be attacking said country.
The 3/14 thing is called a 'hook [1] - a journalistic practice to make the article relevant to today. I just thought this was unnecessary as the actual science content of the article was, to me, very interesting in its own right. Thats all really.
>it’s Pi Day, because 3/14 is the closest calendrical approximation we have to the decimal expansion of pi, π =3.1415927
This seems wrong. A quick check with a spreadsheet tells me that July 22nd should be Pi Day as 22/7=3,14285 which is 0,00126 off whereas 3,14 is 0,00159 off :)
If you celebrate at 1:59 today, you get more accuracy than July 22 can provide. I also liked Ryan North's take on the matter: http://www.qwantz.com/index.php?comic=955
With that interpretation 14/3 is 4.(6) or using 3/14 just 0.2(142857) and both are way off. But if we stop taking the date more or less as it but allow (arbitrary) computations on the components, we probably can get even closer than 22/7.
My comment was mostly in jest but I was indeed comparing two different interpretations 3/14 to mean 3.14 and 22/7 to mean the fraction. If anything the fraction interpretation seems more natural to me because of the forward slash.
I'm curious how we could get closer than 22/7. With two numbers and a single operation (the slash) what would you do to get closer? 22/7 seems hard to beat.
I had somehow never made the connection that the gravitational inverse square law has the same physical explanation as visible light fall-off [1] -- energy being distributed over a larger area with increasing distance from a point source (with which I'm intimately familiar from computer graphics and vision).
Does anyone with a physics background know: is there any evidence of absorption, reflection, or occlusion of gravitational energy in the same way that we experience with light (and sound)?
Not really. The big difference between electro-magnetism and gravity is, that you have positive and negative charge for EM and only positive charge for gravity. So you can not shield gravity, because the shielding can only add to the gravitational force, not subtract from it. A gravity occlusion in a similar way as most things are opaque does therefore not exist.
Reflection is tied to the electric properties of the reflecting material. [1] So there is no electric field in a conductor, otherwise the electrons would move around until there is no longer a electric field. This means that the field on the surface has also to be zero. So if a electro magnetic wave, light, hits the conductor it has to be reflected, since the energy has to go somewhere and it can not enter the conductor.
Refraction of gravitational waves, well that could be interesting. [2] In non-conductors a passing EM wave induces a EM field in the material, so called polarization. [3] This can be traced back to the large wave length of light compared to the length scale in the crystal lattice. It could well be, that you could generate interference patterns of gravitational waves, if the gravitational waves would pass through a similar arrangement of point masses. ( But this would likely need hundreds of stars aligned on scales much smaller than a light second. )
[1] I am not sure, if the following is fully general. But it covers at least metal mirrors.
[2] I am basing my reasoning on a formal analogy between linearized gravity and the Poisson equation, it may be that it would turn out that refraction can not exist via a more subtle argument, like any such device would collapse into a black hole or something.
Thanks for the explanation! I've spent so long using the aforelinked diagrams to visualize how much light falls onto a surface that thinking about gravity that way brought up a few bizarre possibilities. Thanks for clearing things up -- much appreciated.
Einstein lived in Europe for 54 of his 76 years. Since no one in Europe uses the mm/dd/yy date convention, I'd be surprised if this coincidence was significant to him, or even that he was aware of it at all.