
Einstein and Pi  - ghosh
http://www.preposterousuniverse.com/blog/2014/03/13/einstein-and-pi/
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andyjohnson0
_" 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.

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scott_s
It's a joke. The author of the post makes it clear that it's a coincidence.

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andyjohnson0
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.

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dfxm12
14 March would be rendered as 3/14 in middle _and_ big endian styles
(3/14/2014 and 2014/3/14).

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andyjohnson0
Neat. And next year it will be 3/14/15 in middle-endian.

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itcmcgrath
... and will extend to the first 10 digits of Pi if you include time:

3/14/15 9:26:53 am

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pedrocr
_> 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 :)

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kej
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](http://www.qwantz.com/index.php?comic=955)

~~~
pedrocr
Thanks, that was a great comic.

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swamp40
This is a great article.

It is incredibly hard to take a difficult mathmatical concept and break it
down into pieces that _normal_ people can understand.

This author did a fantastic job of that.

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GrantS
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)?

[1] [http://hyperphysics.phy-
astr.gsu.edu/hbase/forces/isq.html](http://hyperphysics.phy-
astr.gsu.edu/hbase/forces/isq.html)

~~~
yk
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.

[3]
[https://en.wikipedia.org/wiki/Polarization_density](https://en.wikipedia.org/wiki/Polarization_density)

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GrantS
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.

