Why were ancient people unable to detect stellar parallax?
they couldn't measure small angles
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Not if they have the faintest clue what they're doing. Parallax is used to measure distance, not temperature.
They didnt have precise tools
ï¬From the ground, the atmosphere makes stars twinkle. ï¬This is called seeing. ï¬The breeze also can shake the telescope. ï¬At the observatory sites seeing… is about 1". ï¬The record (at dome C in antarctica) is 0.07". ï¬Seeing makes stars blobs in photographs. ï¬Seeing limits ground based parallax measurements to the closest stars.
The reciprocal of the parallax is taken. For example, if the stellar parallax is 1 second, the distance is 1/1 = 1 parsec; if the parallax is 0.1 second, the distance is 1/0.1… = 10 parsecs, etc.
The stellar parallax for a star at 20PC distance is 1 / 20 of a second of angle. That's not much of an angle. It's the apparent width of a dimethat's about 46 miles away from… you. I have no idea how astronomers can measureit. This particular star is about 65.2 light years from us. This isn'tall that far when you talk about stars, and it gives us an idea of why theparallax method of measuring distance is only useful for the nearest stars.
Friedrich Wilhelm Bessel was the first person to find the parallax of a fixed star.
Because stellar paradox is so tiny that you cannot see it, and there were no precision instruments capable of measuring such tiny angles back then.
Stellar parallax is very small - for the nearest star it is less than one arc-second. Therefore it is hard to measure.
Why did the existence of stellar parallax not convince people in Copernicus time that his model was better than Ptolemys geopcentric model?
Stellar parallax could not be observed until hundreds of years after Copernicus: the effect is very small. Rejection of the Copernican system was not irrational.
Among other things, the stellar parallax is evidence of the Earth's movement around the Sun. The fact that stellar parallax was not immediately detected is because the paralla…x angle is very small - less than one arc-second, even for the closest stars.
Parallax is the apparent shift (i.e. left to right) of a "foreground" object against the background when viewed from two different points. If you close one eye and view your f…inger against a distant tree, telephone post, etc. and then do the same with the other eye, your finger will have shifted left-to-right against the background. It is very obvious. To use parallax to measure the shift of a relatively close star, scientists can use the two different viewpoints available in June and then December (for example) when comparing the location of the closer star against the background of distant stars. Stellarium, a free celestial program, provides the parallax value (in seconds of arc) for any selected star. The above is written by a student of astronomy, not a scientist. I believe that description is accurate. I hope it helps! :-) Fred
To use parallax, one needs "unaffected" background stars, so the most distant stars cannot be ranged by this method.
Earth's orbit around the Sun.
Is it Jupiter's orbit, a parsec, the average diameter of theEarth's orbit or a light year? Please choose one of the following.