ay45c1-page5 - Note there is a geometrical magni cation...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Note there is a geometrical magni cation factor that helps: D = 0:72 : d 0:28 So from di erent latitudes on  one sees di erent tracks. Separation is here exaggerated! It is only ~ 1 Venus diameter. Sun How to measure small separation from opposite sides of globe? Not by subtracting measurements of height from \top" of sun | too imprecise. Rather, take the average height to get the geometry, and use the di erence of transit ingress/egress times or durations to infer the small di erences. Order of magnitude (ignoring magni cation factors, geometry, etc.):  and diameters  12000 km  104 km + diameter  1:5  106 km  106 km +  velocity  10 km= s ) 103 s to move diameter, 105 s  1 day to move across + In 1761 and 1769 various discrepant results 10% were obtained. Not until 1835 was an accurate value obtained (by Encke) from these same measurements: Gauss had, in the meanwhile, discovered least squares tting for combining observations! 5 ...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online