on size and composition

We live a bit in the past.  Light strikes our eyes and it takes a bit of time for the signal to process and an image to form in our brain.  We stub our toe and it takes some time for the signal to propagate along a neural pathway and finally register.  Different signals arrive at somewhat different times, but but we tend to have a concept of now that synchronizes some of our perceptual signals.  A very tall person lives a tiny bit more in the past than someone who has shorter neural pathways.

 

It makes you wonder about the optimal size of a cognizant being.  A curious observation is that our brains are about midway between the size of an atom and that of the Earth.

 

You need enough molecules to support some type of processing, but there is a point where the communication time between elements becomes so long that further growth becomes counterproductive.  WIth our evolution a few kilograms of brain is close to being optimal, but it seems likely that other intelligent beings wouldn’t be terribly different in scale - sort of between a small dog and a whale.  It would be odd to imagine a flea sized intelligent being or one the size of a planet. 

 

But you have to being that brain out of something.

 

Hydrogen makes up about 75% of the observable mass of the universe and helium is next at around 24%.¹  The rest of the elements quickly trail off.  We, on the other hand, have a very different makeup.  I weigh about 70 kilograms, so along with the percentages of mass and atoms for some of the common elements that make us up, I add  my mass and number of atoms by element.

 

 

	% mass	% atoms	mass(kg)	number of atoms
oxygen	65	24	43	1.61 * 1027
carbon	18	12	16	8.03 * 1026
hydrogen	10	63	7	4.22 * 1027
nitrogen	3	0.58	1.8	3.8 * 1025
calcium	1.4	0.24	1.0	1.6 * 1025
phosphorus	1.1	0.14	0.78	9.6 * 1024
potassium	0.25	0.033	0.14	2.2 * 1024
sulfur	0.25	0.038	0.14	2.6 * 1024
sodium	0.15	0.037	0.10	2.5 * 1024
chlorine	0.15	0.024	0.095	1.6 * 1024
magnesium	0.05	0.007	0.019	4.7 * 1024
iron	0.006	0.00067	0.0042	4.5 * 1024
...

 

 

Since a lot of me is water, a good number of my atoms are hydrogen, but since hydrogen is very light only about ten percent of my mass is that common element.  All of the other stuff was forged in the center of stars.  Most of it came from a few supernova explosions that took place before the formation of our solar system

 

I am - we are - made of stardust.

 

 I find it difficult to imagine a more beautiful origin.

 

It turns out all of the other elements that make us up other than hydrogen are rare in the Universe - add them up and you get less than one ten thousandth of a percent of the Universe’s elemental mass.  We happen to live on the surface of a planet that happens to be extremely concentrated with very rare elements.

 

As the real estate agents suggest location is very important.

 

Happy New Year!

______

 

¹ Although hydrogen makes up most of the mass of the known matter in the universe, something less than five percent of the Universe’s mass can be accounted for by “normal” matter.  Dark matter accounts for about 25% and dark energy about 70%.  The evidence for dark matter and dark energy is overwhelming, but the fundamental nature of each is unknown at this time and lurks at the frontiers of physics.