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Why is the time between equinoxes different?
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The path of the Earth around the sun is described as being an ellipse, with the Sun being at one of the foci of the ellipse.
Since an ellipse, by definition, is symmetrical with respect to the foci, I would expect the time for the earth to transit any two halves of the ellipse to be the same, so long as it moves at the same speed around the ellipse, or at least the speed characteristics are symmetrical as well.
However, this does not appear to be the case according to the following rounded figures for the time in days between equinoxes and solstices:
Summer Solstice to Winter Solstice 181.0
Winter Solstice to Summer Solstice 184.3
Vernal Equinox to Autumnal Equinox 186.4
Autumnal Equinox to Vernal Equinox 178.9
These values can be found, for example, in astronomer Robert Newton's book of 1976.
Why are the values different?
orbit ephemeris equinox solstice
asked 4 hours ago
Tyler Durden
349114
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up vote
2
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The path of the Earth around the sun is described as being an ellipse, with the Sun being at one of the foci of the ellipse.
Since an ellipse, by definition, is symmetrical with respect to the foci, I would expect the time for the earth to transit any two halves of the ellipse to be the same, so long as it moves at the same speed around the ellipse, or at least the speed characteristics are symmetrical as well.
However, this does not appear to be the case according to the following rounded figures for the time in days between equinoxes and solstices:
Summer Solstice to Winter Solstice 181.0
Winter Solstice to Summer Solstice 184.3
Vernal Equinox to Autumnal Equinox 186.4
Autumnal Equinox to Vernal Equinox 178.9
These values can be found, for example, in astronomer Robert Newton's book of 1976.
Why are the values different?
orbit ephemeris equinox solstice
asked 4 hours ago
Tyler Durden
349114
Side note: use the "equal areas in equal time" law to check the elapsed time along any portion of the orbit. In any case, I think Glorfindel's answer hits it.
– Carl Witthoft
45 mins ago
add a comment |Â
up vote
2
down vote
favorite
up vote
2
down vote
favorite
The path of the Earth around the sun is described as being an ellipse, with the Sun being at one of the foci of the ellipse.
Since an ellipse, by definition, is symmetrical with respect to the foci, I would expect the time for the earth to transit any two halves of the ellipse to be the same, so long as it moves at the same speed around the ellipse, or at least the speed characteristics are symmetrical as well.
However, this does not appear to be the case according to the following rounded figures for the time in days between equinoxes and solstices:
Summer Solstice to Winter Solstice 181.0
Winter Solstice to Summer Solstice 184.3
Vernal Equinox to Autumnal Equinox 186.4
Autumnal Equinox to Vernal Equinox 178.9
These values can be found, for example, in astronomer Robert Newton's book of 1976.
Why are the values different?
orbit ephemeris equinox solstice
asked 4 hours ago
Tyler Durden
349114
The path of the Earth around the sun is described as being an ellipse, with the Sun being at one of the foci of the ellipse.
Since an ellipse, by definition, is symmetrical with respect to the foci, I would expect the time for the earth to transit any two halves of the ellipse to be the same, so long as it moves at the same speed around the ellipse, or at least the speed characteristics are symmetrical as well.
However, this does not appear to be the case according to the following rounded figures for the time in days between equinoxes and solstices:
Summer Solstice to Winter Solstice 181.0
Winter Solstice to Summer Solstice 184.3
Vernal Equinox to Autumnal Equinox 186.4
Autumnal Equinox to Vernal Equinox 178.9
These values can be found, for example, in astronomer Robert Newton's book of 1976.
Why are the values different?
orbit ephemeris equinox solstice
orbit ephemeris equinox solstice
asked 4 hours ago
Tyler Durden
349114
asked 4 hours ago
Tyler Durden
349114
asked 4 hours ago
Tyler Durden
349114
asked 4 hours ago
Tyler Durden
349114
asked 4 hours ago
Tyler Durden
349114
349114
Side note: use the "equal areas in equal time" law to check the elapsed time along any portion of the orbit. In any case, I think Glorfindel's answer hits it.
– Carl Witthoft
45 mins ago
add a comment |Â
Side note: use the "equal areas in equal time" law to check the elapsed time along any portion of the orbit. In any case, I think Glorfindel's answer hits it.
– Carl Witthoft
45 mins ago
Side note: use the "equal areas in equal time" law to check the elapsed time along any portion of the orbit. In any case, I think Glorfindel's answer hits it.
– Carl Witthoft
45 mins ago
Side note: use the "equal areas in equal time" law to check the elapsed time along any portion of the orbit. In any case, I think Glorfindel's answer hits it.
– Carl Witthoft
45 mins ago
add a comment |Â
1 Answer
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This is because the summer and winter solstices (approx. June 21st and December 21st) do not correspond to the aphelion and perihelion (approx. July 5th and January 4th). Therefore, the average distance from the Sun is longer in the period from the Summer Solstice to Winter Solstice than vice versa, so the Earth is moving slower (on average) and it takes longer.
I think the values you mentioned are incorrect (switched around); 181.0 is a more likely value for Winter to Summer (February is a few days shorter than August).
answered 4 hours ago
Glorfindel
1,3861721
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
This is because the summer and winter solstices (approx. June 21st and December 21st) do not correspond to the aphelion and perihelion (approx. July 5th and January 4th). Therefore, the average distance from the Sun is longer in the period from the Summer Solstice to Winter Solstice than vice versa, so the Earth is moving slower (on average) and it takes longer.
I think the values you mentioned are incorrect (switched around); 181.0 is a more likely value for Winter to Summer (February is a few days shorter than August).
answered 4 hours ago
Glorfindel
1,3861721
add a comment |Â
up vote
3
down vote
This is because the summer and winter solstices (approx. June 21st and December 21st) do not correspond to the aphelion and perihelion (approx. July 5th and January 4th). Therefore, the average distance from the Sun is longer in the period from the Summer Solstice to Winter Solstice than vice versa, so the Earth is moving slower (on average) and it takes longer.
I think the values you mentioned are incorrect (switched around); 181.0 is a more likely value for Winter to Summer (February is a few days shorter than August).
answered 4 hours ago
Glorfindel
1,3861721
add a comment |Â
up vote
3
down vote
up vote
3
down vote
This is because the summer and winter solstices (approx. June 21st and December 21st) do not correspond to the aphelion and perihelion (approx. July 5th and January 4th). Therefore, the average distance from the Sun is longer in the period from the Summer Solstice to Winter Solstice than vice versa, so the Earth is moving slower (on average) and it takes longer.
I think the values you mentioned are incorrect (switched around); 181.0 is a more likely value for Winter to Summer (February is a few days shorter than August).
answered 4 hours ago
Glorfindel
1,3861721
This is because the summer and winter solstices (approx. June 21st and December 21st) do not correspond to the aphelion and perihelion (approx. July 5th and January 4th). Therefore, the average distance from the Sun is longer in the period from the Summer Solstice to Winter Solstice than vice versa, so the Earth is moving slower (on average) and it takes longer.
I think the values you mentioned are incorrect (switched around); 181.0 is a more likely value for Winter to Summer (February is a few days shorter than August).
answered 4 hours ago
Glorfindel
1,3861721
answered 4 hours ago
Glorfindel
1,3861721
answered 4 hours ago
Glorfindel
1,3861721
answered 4 hours ago
Glorfindel
1,3861721
1,3861721
add a comment |Â
add a comment |Â
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Side note: use the "equal areas in equal time" law to check the elapsed time along any portion of the orbit. In any case, I think Glorfindel's answer hits it.
– Carl Witthoft
45 mins ago