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*To*: KellySt@aol.com, kgstar@most.fw.hac.com, stevev@efn.org, jim@bogie2.bio.purdue.edu, zkulpa@zmit1.ippt.gov.pl, hous0042@maroon.tc.umn.edu, rddesign@wolfenet.com, David@InterWorld.com, lparker@destin.gulfnet.com, DotarSojat@aol.com*Subject*: Problems with beaming*From*: T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)*Date*: Sat, 06 Apr 1996 20:58:24 +0100

To Lee, >There are two problems really. First of all; there is the inverse square >law, the intensity (and therefore the power) of radiation decreases as the >inverse square of the distance. I have not seen anyone's calculations here >take into account the amount of power that must be generated HERE in order >to provide a reasonable amount of power THERE. Yes, but lasers keep a tight beam and thus their diametre (cross-section) does not increase with distance and the energy-density (per surface) stays the same. So I don't see a problem here. >The second problem involves another aspect of basic optical diffraction >theory; the Rayleigh criterion defines the required diameter of the laser >transmitter. For yellow light, a 400 km aperture transmitter would be >required to just fill a light sail at Tau Ceti, 11 light years away. The criterion of Rayleigh states that two wavelengths l and l+dl are just resolved in the n-th spectral order when the maximum of one spectral-line falls upon the first minimum of the other. I don't see what resolvement has to do with beaming power, could you explain what I missed? (What formula did you use?) Timothy

**Follow-Ups**:**Problems with beaming***From:*Steve VanDevender <stevev@efn.org>

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