In 1979, John A. Eddy of the High Altitude Observatory and Aram A. Bo

In 1979, John A. Eddy of the High Altitude Observatory and Aram A. Boornazian, a mathematician in Boston, concluded that the sun is contracting at a considerable rate, based on daily measurements of the sun’s image. They estimated the reduction of the sun’s horizontal diameter to be about two seconds of arc, or about 0.1 percent, per century. These findings sparked renewed debate over solar measurement and the possibility that our sun may be shrinking.

Heliologists contend that the brilliance of the sun’s disk, and the imperfect and variable transparency of the earth’s atmosphere, make observations from the earth’s surface unreliable. A better source of data regarding solar shrinkage is the duration of total solar eclipses, while a second statistically independent check is provided by the time the planet Mercury is visible against the solar disk. These observations allow a monitoring of changes in the sun’s diameter at reasonably regular intervals back to about the start of the 18th century, or roughly twice the number of years covered by the data used by Eddy and Boornazian.

When the observations of total solar eclipses over the past three centuries are analyzed in conjunction with the evidence of the transits of Mercury, the data indicate only a negligible change in the sun’s diameter. The percentage of decrease per century has been calculated to be only 0.007, with a 0.0008 percent margin of error.

1. The author argues that Eddy and Boornazian have

a. misrepresented experimental results in order to gain support for their conclusions
b. incorrectly surmised that the sun's diameter is independent of Mercury's orbit
c. probably drawn an incorrect conclusion due to their reliance on unreliable data
d. made several noteworthy breakthroughs in the field of solar measurement
e. wilfully ignored the existence of data pertaining to the duration of solar eclipses


2. According to the author, evidence that the sun is shrinking only at a negligible rate is based on

I. measurement of the length of solar eclipses
II. measurement of the time during which Mercury can be observed crossing the sun's path
III. daily measurements of the sun's image

a. I only
b. II only
c. III only
d. I and II only
e. I, II and III


3. It can be inferred from the passage that all of the following cast doubt on Eddy and Boornazian's conclusion EXCEPT

a. the non-uniformity of atmospheric clarity
b. the calculations used to determine the sun's horizontal diameter
c. atmospheric distortion even during periods of clear skies
d. the sheer intensity of the sun's radiance
e. the comparatively brief period of time their study covers


4. Which of the following, if true, would most seriously undermine the argument put forth by Eddy and Boornazian?

A. The apparent image size of the sun is distorted by atmospheric moisture, which can fluctuate from year to year.
B. Eddy and Boornazian's theory is corroborated by data collected during solar eclipses.
C. Not all heliologists agree that the duration of solar eclipses provides information pertinent to measuring the sun's diameter.
D. Mercury's orbit is erratic and has changed radically on several occasions over the last two centuries.
E. Image measurements of the moon taken from the earth's surface indicate that its size has not changed in the last 200 years.


5. The passage suggests that which of the following statements, if true, would be most useful in corroborating solar image measurements?

A. Image measurements are taken simultaneously from two different locations.
B. Image measurements are recorded while wearing special goggles that cut down on the sun's brilliance.
C. Light refraction measurement tables for atmospheric gases are developed.
D. Climatic variations are minimized by citing image measurement stations in the desert.
E. Image measurements are made by solar radiation-proofed instruments on satellites orbiting above the earth's atmosphere.


6. Which of the following statements, if true, would best support the conclusion that the sun's shrinkage is less than Eddy and Boornazian had reported?

A. Solar eclipses occur on a irregular basis, providing less frequent data collection opportunities than image measurement does.
B. A third statistical check, the amount of UV hitting the earth's surface, corroborates the findings of eclipse duration.
C. Solar eclipses are a phenomenon that have been recorded by modern scientists and ancient astronomers alike.
D. Although Mercury's transit has been recorded for centuries, earlier scientific instruments lacked the precision necessary to make accurate observations.
E. Eddy and Boornazian developed a sophisticated computer model to compensate for atmospheric variations during image measurements.