Applied Optics

Magazine Overview

Title: Applied Optics
Issue Date: 15 August 1979
Volume: 18
Issue: No. 16
Publisher: Optical Society of America
Country: USA
Language: English

This issue of Applied Optics features a significant exchange of letters concerning the hypothesis that insects might be responsible for certain unidentified flying object (UFO) sightings. The primary focus is a critical comment by Kyaw Tha Paw U on an earlier article by P. S. Callahan and R. W. Mankin, followed by a reply from P. S. Callahan.

Insects as unidentified flying objects: comment

Kyaw Tha Paw U, from Yale University, critiques the Callahan and Mankin article, finding it "somewhat unrealistic." Paw U raises several points:

• Electric Field Strengths: He asserts that the electric field strengths cited by Callahan and Mankin (1.7-2.2 kV/cm) were an order of magnitude higher than boundary-layer values reported by other researchers. He notes that literature generally indicates atmospheric fields substantially below 1 kV/cm, and typically de in nature, not the high-frequency ac used in Callahan and Mankin's experiments.
• Coronal Discharge: Paw U questions whether coronal discharge can be demonstrated for moderate to large numbers of insects. He cites sources (Chalmers, Uman, Loeb) indicating that coronal discharge involves current flow, which would reduce the potential difference and electric field, thus attenuating gradients necessary for such a display. He argues that Callahan and Mankin did not establish the existence of coronal discharge for insect swarms in their laboratory experiments.
• Thunderstorm Activity: A key point of contention is the establishment of strong electric field conditions or thunderstorm activity during the times of the UFO sightings. Paw U states that meteorological literature does not support the idea that boundary-layer fields during thunderstorms are as high as claimed. He also doubts that triboelectric phenomena could account for significant potential gradients due to high relative humidity.
• Fair-Weather Fields: He contrasts the claimed high fields with typical fair-weather fields averaging around 0.0013 kV/cm, and even thunderstorm fields reported by various researchers (Johnson, Shvarts, Imyanitov and Chubarina, Chalmers, Uman) which are generally below 0.37 kV/cm.
• Experimental Validity: Paw U criticizes the use of a high-frequency ac Tesla coil to simulate natural conditions, stating that natural fields are typically de and associated with lightning discharges. He also notes that Callahan and Mankin did not report radiant flux measurements for their experimental fields, only for the high-frequency Tesla coil fields, which were ten times stronger than reported natural fields.
• Synoptic Data: Paw U challenges Callahan and Mankin's claim that meteorological data for the Uintah region was unobtainable. He suggests that synoptic maps could indicate possible thunderstorm activity. He also points to Salisbury's report on UFO sightings, noting that out of seventeen detailed sightings, ten included sky observations, with seven cases reporting clear skies and only three having clouds. Thunderstorm activity was not mentioned in these reports.
• Specific Sighting: Paw U highlights a sighting from 1 September 1966, mentioned by Callahan and Mankin, where the witness explicitly noted a clear sky, directly contradicting the hypothesis that thunderstorm activity was the cause.

Paw U concludes that insects were likely not creating significant optical phenomena in most, if not all, of the Utah UFO cases. He expresses concern that the Callahan and Mankin hypothesis, despite its flaws, has gained public traction and might be used by entomologists to misinterpret insect migration reports.

Insects as unidentified flying objects: author's reply to comment

Philip S. Callahan, from the USDA, replies to Paw U's comment, asserting that Paw U "overlooks certain forces in nature" and is unaware of the literature covering "St. Elmo's glow."

• St. Elmo's Glow: Callahan implies that St. Elmo's glow is a phenomenon related to electric fields and could be relevant to insect visibility.
• Ball Lightning: He states that ball lightning is accepted as a natural phenomenon, though a good physical explanation is lacking, suggesting it might be related to similar phenomena.
• Experimental Conditions: Callahan defends the use of high-frequency ac fields, suggesting they are relevant to the phenomena observed. He also presents a PPI scope image (Fig. 2) from a 9.425-GHz radar showing insects over agricultural fields in Arizona. This image, taken on 6 April 1976, at 1:44 a.m., shows insects grouping and layering, which Callahan describes as "insect plankton." He notes that layering and grouping of insect plankton is not unusual.

Callahan does not directly refute Paw U's specific points about electric field magnitudes or the lack of established coronal discharge for insect swarms but instead broadens the scope to include other atmospheric electrical phenomena and presents radar evidence of insect aggregation.

Other Content

• Figure 1: A scanning electron microscope photograph of an Indian meal moth (Plodia interpunctella), showing its proboscis and scales. This figure is provided to illustrate insect morphology.
• Figure 2: A PPI scope image from a 9.425-GHz radar showing insects over agricultural fields in Arizona. This image is used to demonstrate insect aggregation and layering.

Recurring Themes and Editorial Stance

The recurring theme in this exchange is the scientific debate surrounding the explanation of UFO sightings, specifically the hypothesis that insects, under certain atmospheric electrical conditions, could be responsible. The editorial stance, as evidenced by publishing both the critical comment and the reply, appears to be one of fostering scientific discourse and allowing different viewpoints to be presented. The inclusion of detailed references and figures suggests a commitment to rigorous scientific discussion within the field of optics and related atmospheric phenomena.

The debate highlights the challenges in correlating experimental findings with natural phenomena and the importance of robust meteorological data and direct field measurements when proposing scientific explanations for unexplained observations.