We have received a couple of letters in response to our articles on aberration in the last two issues. The most extensive is from Dick Elmendorf. I shall quote him point by point and my response will appear in italics between the points:

(1) How do you know you are pointing a telescope “forward" to see a star, as is described in the stovepipe analogy? Aren't you just pointing the telescope so as to see the star, without knowing whether that is forward, backward, sideways or straight-on? In other words, how do you know where the star is in the first place?

Bradley's original telescope was fixed immovably to the earth. Modern telescopes are mounted on a pier which is inserted into the earth down to bedrock. Part of the telescope includes a series of gauges called setting circles. If the setting circles are large enough, a resolution of a minute of arc or less is easily achieved. The most fundamental of all position determination instruments, however, was the transit circle. Here the telescope could only move along a north-south meridian. The error of a typical transit circle observation is only 0".2, one hundredth the size of aberration. Aberration showed up in two forms there. First of all, in a yearly north-south variation as the star crossed the meridian and secondly, as a variation in the time when the star crossed the meridian. For half the year the star was early, and the other half it was behind the mean transit time. A third means involves occultation timings, of which more later.

(2) How do you know that light is particles, and that the stovepipe analogy is even valid?

Whether or not light consists of particles or waves, experiments in the lab (e.g., those of Fresnell) show that aberration is real.

(3) Are the same stars used for determining both aberration and parallax, or are they different stars? If they are different stars in any particular case, aren't you just assuming that both categories of stars rotate in unison and that the phase difference is therefore a meaningful argument?

As seen under point (1), there are no reference stars used for determining aberration. That determination is made from a coordinate system rigidly fixed on the earth. To measure parallax a star's position is measured with respect to the stars seen around it. Sometimes the star is closer than those faint, presumably background stars, sometimes it is not. It is important to realize that the measurements are repeatable, that a star always behaves the same way with respect to the background stars. Modern intercontinental interferometry yields consistent results which are 10 to 100 more accurate than the uncertainties encountered 20 years ago. And that includes aberration as well as parallax. In other words, the arguments based on the uncertainties in the measurements which the small universe proponents have been using, were valid twenty years ago, but are no longer valid.

(4) Is having all stars and the sun at equal distances, as is apparently Walter van der Kamp's model, a necessary premise for arguing that aberration is really a parallax. Aren't they two separate issues?

Of course they're separate issues. That's my whole point. For years Walter's been arguing that aberration is parallax, it is not. Walter's argument is equivalent to claiming that holding one's finger a foot in front of one's face, and then alternately opening one eye while closing the other will make the finger jump up and down instead of from left to right.

(5) How do you know that the moon, streetlights and artificial satellites do not exhibit aberration because they are just too close to measure aberration?

See the following.

Two other minor comments are that your dismissal of Walter's distance ideas with that “conspiracy" comment is mere rhetoric la Galileo style, and that your 20".496 figure should better be shown as 20.496", or perhaps as 20.5", in view of the possible error in the figures.

What I said was that since all the planets exhibit aberration, as does the sun, that according to Walter's argument all these objects should be 58 light-days from earth along with the stars. Then I added: “This runs afoul of all evidence, including the U.S.A. and former U.S.S.R.'s space programs unless, of course, one wants to claim some grand conspiracy on the part of scientists and engineers around the world. I know of no such conspiracy, nor any reason to suspect one." I know some do claim that the space program is a hoax, and hence my reference. As for the notation, 20".496 is the correct way to write 20.496 seconds of arc. 20.496" on the other hand, means 20.496 inches. See, for example, the “Explanation" in The American Ephemeris and Nautical Almanac for, e.g., 1968. At this point the uncertainty in less than 0".0005, but in 1968 which was the last reference I have, the uncertainty was no more than 0".001, To contract that to 20".5 implies an uncertainty of 0".1, not 0".001. To change 20".496 to 20".500 is unwarranted, although that is what I would have to have done if I were to take your suggestion. Would you do that as an engineer on a project?

² Tom van Flandern, 1993. “Galilean Special Relativity," Meta Research Bulletin, 2(4):48-65. Subscriptions to the quarterly are $15 per year and can be ordered by writing to: Meta Research Bulletin, PO Box 15186, Chevy Chase, MD 20825-5186, U.S.A.