Why can't we observe transits of Venus more often? It is the result of the fact that the orbital plane of Venus is about 3.5 degrees to the ecliptic and the angular diameter of the sun is only 0.5 degrees. Therefore, if Venus is more that 0.25 degrees above or below the ecliptic when it passes between the earth and the sun, we won't be able to see it silhouetted agains the sun. Thus transits can only be observed when Venus is close to its ascending or descending node and the earth is close to a point in its orbit where a line from the sun through the node intersects the earth's orbit.
very nice video. thank you. what is the modern technique to determine the astronomical unit. i think it is a very important thing because this is used to define the parsec unit. unfortunately i am not an astronomer.. perhaps in next life.
One method is measuring the distance to Venus, using radar, and then using Kepler's laws for calculating the length of the major axis of Earth's orbit from that.
Unfortunately, I was not well positioned to observe the transits of Venus, but I was in position, and the weather cooperated, that allowed me to observe the transit of Mercury. I took the afternoon off work and did it.
"How was fraction of "D" to the whole Sun's diameter estimated ?" Huh? He just explained that: you measure the angle which 2.6d represents on the sun, and you measure the angle which corresponds to the diameter D of the sun. Simply dividing these two, you get the desired fraction. And the value of that fraction obviously depends on which value for "d" you choose in your measurements.
The earth travels at 67,000 miles an hour, so times 67,000 by 24 (hours) then times that by 365 (days of the year), ÷ 3 ÷ 2 to find the distance from Earth to the sun. ........67,000 x 24 x 365 ÷ 3 ÷ 2 = 97,820,000 miles.
"the earth travels at 67,000 miles an hour" And how would you know that before you knew the length of its orbit, for which in turn you need to know the radius of its orbit?
@ Sorry for the misunderstanding, I didn't want to know how _you_ know that. I merely pointed out that it's totally unclear how anyone could know the speed of Earth without knowing the distance to the sun beforehand. I. e. my point was that you can't use the speed of Earth for determining the distance to the sun, since you already need to know the distance of the sun for determining the speed of Earth.
Excellent. I will be sharing this video.
Why can't we observe transits of Venus more often? It is the result of the fact that the orbital plane of Venus is about 3.5 degrees to the ecliptic and the angular diameter of the sun is only 0.5 degrees. Therefore, if Venus is more that 0.25 degrees above or below the ecliptic when it passes between the earth and the sun, we won't be able to see it silhouetted agains the sun. Thus transits can only be observed when Venus is close to its ascending or descending node and the earth is close to a point in its orbit where a line from the sun through the node intersects the earth's orbit.
very nice video. thank you. what is the modern technique to determine the astronomical unit. i think it is a very important thing because this is used to define the parsec unit. unfortunately i am not an astronomer.. perhaps in next life.
One method is measuring the distance to Venus, using radar, and then using Kepler's laws for calculating the length of the major axis of Earth's orbit from that.
@@bjornfeuerbacher5514Danke für den Hinweis und Gruss nach Schweinfurt(?)
Unfortunately, I was not well positioned to observe the transits of Venus, but I was in position, and the weather cooperated, that allowed me to observe the transit of Mercury. I took the afternoon off work and did it.
just switch off the Sun, measure the time (8min) it takes before the light disappears on Earth, and multiply with the speed of light. 💥
5:20 How was fraction of "D" to the whole Sun's diameter estimated ? And what is it equal to ?
Thank you for sharing knowledge.
"How was fraction of "D" to the whole Sun's diameter estimated ?"
Huh? He just explained that: you measure the angle which 2.6d represents on the sun, and you measure the angle which corresponds to the diameter D of the sun. Simply dividing these two, you get the desired fraction.
And the value of that fraction obviously depends on which value for "d" you choose in your measurements.
Ummm. A really long tape measure but you measure at night when it's cooler.
The earth travels at 67,000 miles an hour, so times 67,000 by 24 (hours) then times that by 365 (days of the year), ÷ 3 ÷ 2 to find the distance from Earth to the sun. ........67,000 x 24 x 365 ÷ 3 ÷ 2 = 97,820,000 miles.
"the earth travels at 67,000 miles an hour"
And how would you know that before you knew the length of its orbit, for which in turn you need to know the radius of its orbit?
@@bjornfeuerbacher5514 I don't remember how i know that. I was simply answering the question.
@ Sorry for the misunderstanding, I didn't want to know how _you_ know that. I merely pointed out that it's totally unclear how anyone could know the speed of Earth without knowing the distance to the sun beforehand. I. e. my point was that you can't use the speed of Earth for determining the distance to the sun, since you already need to know the distance of the sun for determining the speed of Earth.
Ok, I got my pencil ✏️