
#19
May2203, 06:58 PM

Astronomy
Sci Advisor
PF Gold
P: 22,800

I just went out into the garden and there was a lot of lightand some things flying around pollinating the fruit trees or whatever they do. And I thought of the Income Tax Form called the "TenNinetyone"
Because tenninetyone is the occupancy of space by sunlight. There are 10^{91} photons per unit volume of sunlight at this distance. It is clear because 10^{119} is the solar constant and the average energy per photon is 10^{28} and one subtracts 28 from 119 and gets 91. Trivial arithmetic. How many photons are in a cubic meter, if you like working with them? So if I want to know the photons per cubic mile I just multiply by the cube of E38, which is E114, and get (since 114  91 is 23) that there are E23 photons in a cubic mile of sunlight. Or if I'm looking at a square pace of groundE35 by E35and wonder how many photons would impinge on it in a minuteE45in vertical sunlight....Then I just add those exponentsE115and multiply by the occupancy "tenninetyone" number E91. That tells me E24a trillion trillionphotons would land on that square patch of ground in a minute. Oh, E45 is 54 seconds, so only 9/10 of a minute. Had better add it to the dictionary. ********* Here's the current dictionary: E601.7 billion years E459/10 of a minute E44a million miles E38a mile E35a pace E6 22 grams E501.2 micronewtons Here's the list of constants etc, for review: the proton compton wavelength2.103E14 meter13E18 the CMB temperature2.725 kelvin1.93E32 the Hubble time4.35E17 seconds8.06E60 average sunlight photon2E19 joulesE28 the distance to the sun150 million km93E44 earth orbit speed30 kilometer/secondE4 solar constant1380 watts/sq.meterE119 2.701k3.73E23 joule/kelvin2.701 sigma5.67E8 watt/sq.meter kelvin^{4}pi^{2}/60 a (the aT^{4} law)7.565E16 joule/cub. meter kelvin^{4}pi^{2}/15 


Register to reply 
Related Discussions  
Natural Units  General Physics  0  
Problem with natural units in Cosmology  Advanced Physics Homework  3  
E=mc^2 in natural units  General Physics  6  
New more precise natural units at nist.gov  General Discussion  9  
force constants and seminatural units  General Physics  3 