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I find it more satisfying and clearer to say it's when day/night are the same length everywhere on earth/for everyone on earth. For me that prompts thinking ab

I find it more satisfying and clearer to say it's when day/night are the same length everywhere on earth/for everyone on earth. For me that prompts thinking about the earth with its tilt in relation to the sun and the two points in its orbit where that could be true. Within that framework you could bring up pendantry how "definitions" of day/night mean this doesn't imply day and night are each 12 hours. Actually I find such pedantry more interesting in this framework; it's just clearer that we're saying globally there is always more day than night under this particular definition. It also IMO prompts the even more interesting pedantry discussed in this thread about it crossing this point at some random time during the day, we don't hover in that point of the orbit for 24 hours.

kazinator 3y ago
1. It's nowhere near night time the moment the sun sinks halfway past the horizon. It's around early evening. Only on a planet with no light-scattering atmosphere does night being at the completion of sundown. And even then, since the star is larger than the planet, more than 50% of the planet is illuminated: night is nevertheless shorter.¹ 2. Did you consider the poles? -- 1. Someone claiming to be a mathematician posted some calculations on quora.com claiming that 50.23% of the Earth is illuminated directly due to the relative size of the Sun and the Earth. https://www.quora.com/What-percentage-of-planet-earth-is-illuminated-by-the-sun-at-the-same-time-in-average https://www.quora.com/What-percentage-of-planet-earth-is-ill...
wouldbecouldbe 3y ago
Haha yeah his definition is from a perspective of need of structural consistency the rest of us wants the definition of day to be useful and represent when it’s light
mmcnl 3y ago
It's my go to fun fact whenever the situation is suitable for it. People often have never realized this. (My other fun fact is that South America in its entirety lies East of Florida, and not below North America, most people memorize South America as being completely South of North America.)
- dessimus 3y ago
  Florida is also further west than most people realize, as Miami is longitudinally close to Cleveland, OH rather than New York City.
  - lb1lf 3y ago
    And, while on the subject - Norway is squarely in Western Europe, no? Yet the town of Kirkenes in arctic Norway (somewhere around 70 degrees latitude) lies to the east of Istanbul.
    - deleted 3y ago
      [deleted]
- johnchristopher 3y ago
  What were the odds, got this tweet today https://twitter.com/Locati0ns/status/1705703590181187640?t=2keR1xr6_dG-UwJGe0B4Hg&s=19 https://twitter.com/Locati0ns/status/1705703590181187640?t=2... > The entirety of continental South America lies east of Michigan" means that, in terms of geographical positioning on the Earth's surface, all of the landmass of South America is located to the east of the state of Michigan in the United States. This is a factual statement based on the Earth's geography. It highlights the vast eastward extent of South America compared to the location of Michigan in North America.
- dghughes 3y ago
  My geographic fun fact is my tiny Canadian province of Prince Edward Island (PEI) is the only Canadian province that doesn't border another country (but there is one territory that also doesn't border any country). From British Columbia (BC) on west coast to New Brunswick (NB) and Nova Scotia (NS) on the East coast they all have a southern border with the USA. NS has a maritime border with the USA. Newfoundland and Labrador border two countries although technically each is not what you think. To its south the island of Newfoundland borders France via the small cluster of islands which are a territory of France called St. Pierre and Miquelon. The Labrador border is an eastern maritime border with Denmark/Greenland. Not a province but the territory of Nunavut also border Greenland/Denmark. It even has a land border via Hans Island a now shared island which Canada and Denmark used to both "fight" over. The Yukon in the north-west borders the USA state of Alaska. That leaves Northwest Territories (NWT) it has no border with any nation just its territory neighbours and the prairie provinces to the south.
thaumasiotes 3y ago
> I find it more satisfying and clearer to say it's when day/night are the same length everywhere on earth/for everyone on earth. By the definition given in the article, that isn't true either. They point out that the equinox is in fact the point when day and night are of equal length as long as you define them in a consistent way. But if you instead define day as "whenever the sun is visible" [or would be visible in the absence of clouds], day and night aren't equal on the equinox. But, if that's your definition of "day", it can never be the case that day and night are the same length everywhere on earth. The presence of mountains will affect when it is or isn't "day".
ldng 3y ago
Assuming a perfect sphere which earth is not ?
- HPsquared 3y ago
  Equinox is when the Earth's axis of rotation is perpendicular to the path from Earth to Sun. That is, when the poles are neither tilting "towards" the Sun (which happens in summer) nor "away" from the sun (which happens in winter).
shkkmo 3y ago
It's the point where day and night would be the same length everywhere IF the earth stopped moving around the sun and just kept spinning. Each point along a line of latitude is going to experience slightly different lengths of the day or night when the earth crosses the equinox point.
hddqsb 3y ago
> I find it more satisfying and clearer to say it's when day/night are the same length everywhere on earth/for everyone on earth. ...except at the poles! (There the sun will appear to be moving along the horizon, and there is no day/night in the usual sense.) And when you take the pedantry into account (top vs centre of sun, refraction) the length of the day/night is no longer the same around the globe, since the effect in terms of time is different at different latitudes.

kazinator 3y ago

1. It's nowhere near night time the moment the sun sinks halfway past the horizon. It's around early evening. Only on a planet with no light-scattering atmosphere does night being at the completion of sundown. And even then, since the star is larger than the planet, more than 50% of the planet is illuminated: night is nevertheless shorter.¹ 2. Did you consider the poles? -- 1. Someone claiming to be a mathematician posted some calculations on quora.com claiming that 50.23% of the Earth is illuminated directly due to the relative size of the Sun and the Earth. https://www.quora.com/What-percentage-of-planet-earth-is-illuminated-by-the-sun-at-the-same-time-in-average https://www.quora.com/What-percentage-of-planet-earth-is-ill...

wouldbecouldbe 3y ago

Haha yeah his definition is from a perspective of need of structural consistency the rest of us wants the definition of day to be useful and represent when it’s light

mmcnl 3y ago

It's my go to fun fact whenever the situation is suitable for it. People often have never realized this. (My other fun fact is that South America in its entirety lies East of Florida, and not below North America, most people memorize South America as being completely South of North America.)

dessimus 3y ago
Florida is also further west than most people realize, as Miami is longitudinally close to Cleveland, OH rather than New York City.
- lb1lf 3y ago
  And, while on the subject - Norway is squarely in Western Europe, no? Yet the town of Kirkenes in arctic Norway (somewhere around 70 degrees latitude) lies to the east of Istanbul.
  - deleted 3y ago
    [deleted]
johnchristopher 3y ago
What were the odds, got this tweet today https://twitter.com/Locati0ns/status/1705703590181187640?t=2keR1xr6_dG-UwJGe0B4Hg&s=19 https://twitter.com/Locati0ns/status/1705703590181187640?t=2... > The entirety of continental South America lies east of Michigan" means that, in terms of geographical positioning on the Earth's surface, all of the landmass of South America is located to the east of the state of Michigan in the United States. This is a factual statement based on the Earth's geography. It highlights the vast eastward extent of South America compared to the location of Michigan in North America.
dghughes 3y ago
My geographic fun fact is my tiny Canadian province of Prince Edward Island (PEI) is the only Canadian province that doesn't border another country (but there is one territory that also doesn't border any country). From British Columbia (BC) on west coast to New Brunswick (NB) and Nova Scotia (NS) on the East coast they all have a southern border with the USA. NS has a maritime border with the USA. Newfoundland and Labrador border two countries although technically each is not what you think. To its south the island of Newfoundland borders France via the small cluster of islands which are a territory of France called St. Pierre and Miquelon. The Labrador border is an eastern maritime border with Denmark/Greenland. Not a province but the territory of Nunavut also border Greenland/Denmark. It even has a land border via Hans Island a now shared island which Canada and Denmark used to both "fight" over. The Yukon in the north-west borders the USA state of Alaska. That leaves Northwest Territories (NWT) it has no border with any nation just its territory neighbours and the prairie provinces to the south.

thaumasiotes 3y ago

> I find it more satisfying and clearer to say it's when day/night are the same length everywhere on earth/for everyone on earth. By the definition given in the article, that isn't true either. They point out that the equinox is in fact the point when day and night are of equal length as long as you define them in a consistent way. But if you instead define day as "whenever the sun is visible" [or would be visible in the absence of clouds], day and night aren't equal on the equinox. But, if that's your definition of "day", it can never be the case that day and night are the same length everywhere on earth. The presence of mountains will affect when it is or isn't "day".

ldng 3y ago

Assuming a perfect sphere which earth is not ?

HPsquared 3y ago
Equinox is when the Earth's axis of rotation is perpendicular to the path from Earth to Sun. That is, when the poles are neither tilting "towards" the Sun (which happens in summer) nor "away" from the sun (which happens in winter).

shkkmo 3y ago

It's the point where day and night would be the same length everywhere IF the earth stopped moving around the sun and just kept spinning. Each point along a line of latitude is going to experience slightly different lengths of the day or night when the earth crosses the equinox point.

hddqsb 3y ago

> I find it more satisfying and clearer to say it's when day/night are the same length everywhere on earth/for everyone on earth. ...except at the poles! (There the sun will appear to be moving along the horizon, and there is no day/night in the usual sense.) And when you take the pedantry into account (top vs centre of sun, refraction) the length of the day/night is no longer the same around the globe, since the effect in terms of time is different at different latitudes.