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What is wrong with this computation, plase? I am getting the result of 4291.65 W m^{-2} instead of 1361 W m^{-2}. Thank you very much

import numpy as np

R_S = 6.957e8  # m
au = 149597870700 # m
sigma_SB = 5.670374419e-8 # W m-2 K-4

# Sun parameters
R = 1 * R_S
d = 1 * au
T = 5777.2  # K


Earth_factor = R**2 * np.pi / d**2

E = sigma_SB * T**4 * Earth_factor
print('SB', E)
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  • 2
    $\begingroup$ Here's a tip: What's the ratio between the obtained and the expected result? $\endgroup$
    – pela
    Nov 28, 2023 at 12:41
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    $\begingroup$ Also: May I suggest using astropy.units? It's great for keeping track of units (although that's not your problem here). $\endgroup$
    – pela
    Nov 28, 2023 at 12:43
  • $\begingroup$ Thank you, pi. is the factor, but I do not know why. $\endgroup$
    – Anna-Kat
    Nov 28, 2023 at 15:23
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    $\begingroup$ Your Earth_factor is the ratio between the surface area of the Sun and the surface area of the sphere at which the Earth revolves (so to speak). The former is $4\pi R_\odot^2$, the latter is $4\pi(1\,\mathrm{AU})^2$, so both the 4's and the π's cancel. That is, Earth_factor = (R_S/d)**2. $\endgroup$
    – pela
    Nov 28, 2023 at 20:20

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