echo_oddly

9 anni fadiscuss

Average power of radiation over the whole earth is 164 W/m^2 according to https://en.wikipedia.org/wiki/Sunlight. Global power consumption in 2013 was 18 TW (1.575 × 10^17 Wh/y) according to https://en.wikipedia.org/wiki/World_energy_consumption. So 164 W/m^2 × 100×10^6 m^2 = 16.4 GW. That's a factor of 1000. But that's comparing to the average solar radiation striking the Earth. Are there places such as a desert which receive 1000 times the energy of the rest of the earth?

echo_oddly

10 anni fadiscuss

Doing a Fourier transform is simply applying a set of inner products from the function, f, onto a set of orthonormal basis functions. Put a post in the ground, measure the length of the shadow cast by the sun. That's how to do an inner product. So you can at least describe the process using few dimensions. Then you can scale it up to higher dimensions from there.

echo_oddly

11 anni fadiscuss

We can show with a few assumptions that the police thought that the prior probability of the leaves being marijuana (before the field test) is at least 41%.

A = leaves in trash are marijuana B = field test result is positive

First use Bayes' to get P(A|B) = P(B|A)P(A) / [P(A)P(B|A)+P(-A)P(B|-A)]

Assume the false positive rate, P(B|-A) = 0.7. Assume the true positive rate, P(B|A) = 1.

The result is P(A) = 0.7P(A|B)/(1-0.3P(A|B))

Assume to get a warrant the police need P(A|B)>0.5. This puts P(A)=0.41. However, probable cause is more strict. Assume we need P(A|B)>0.90. This puts P(A)=0.86.

So if you go to a garden store and you drink tea, the police are 86% sure there are illegal substances in your home.

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