The following experiment was carried out in the Hudson Laboratories 

 by the author to investigate the infrared in a manner more suitable for the 

 discovery of a window. Infrared absorption experiments invariably use a 

 beam of narrow frequency range to obtain the highest resolution. Therefore, 

 it is possible that although there may be some penetration in this narrow 

 band, it may be too small to detect. Furthermore, the region of wavelength 

 greater than 50 microns does not seem to be adequately covered. 



The experiment was done in such a way that contributions from any 

 window in the entire infrared, no matter how small, would add up in the 

 detector to give a response. A "Glo-bar" source furnished a black body 

 spectrum throughout the infrared. The radiation was then passed into water 

 contained in an aluminum tray, was reflected from the bottom of the tray 

 and into an Eppley thermopile which served as a detector, A germanium 

 filter was used over the detector to cut out any radiation of wavelength 

 shorter than 1.8 microns, especially the visible which begins at about 

 .75 micron. The sensitivity of the system was such that a microwatt per 

 square centimeter of radiation could have been detected. However, l/2 inch 

 of water was more than enough to stop any radiation whatsoever from reaching 

 the detector. The question of whether or not a more sensitive detector 

 would be worthwhile will be gone into in the next section. 



Discussion 



Gathering together all the theoretical and experimental results 

 presented above, the following pertinent facts stand out: 



o 



1) There is no hope of finding a window at wavelengths of 3500 A 



and shorter. This result is based on the absorptions due to pair production, 

 Compton effect, photoelectric effect, and molecular electronic transitions. 



2) A window does exist in the visible. However, the radiation 

 mean free path of about 80 feet precludes any use of these frequencies 



for detection at distances greater than a mile, and even this is stretching 

 the point. 



3) There does not seem to be any window in the infrared. This con- 

 clusion is based mainly on the work done at Hudson Laboratories. As mentioned 

 above, there remains the question as to whether or not a more sensitive 

 detector should be employed. This question will be considered below along 

 with possible reasons for the lack of a window in the infrared, 



4) The region from the very far infrared to D, C. is adequately 

 covered by standard electromagnetic theory. The only possible window is at 

 very low frequencies where the skin depth approaches distances of interest. 

 However, equipment difficulties in this region seem insuperable at the present 

 time. Thus, it would appear that the use of electromagnetic radiation for 

 detection in sea water is out of the question. As remarked by D. Sternberg , 

 "Evolution is against us." 



There remains the question of why there is no window in the infrared 

 for water when many windows exist for the vapor. Obviously, the reason is 

 connected with the much closer association of molecules in water. Two 

 explanations havie presented themselves: 



-13- 



