What is the autumnal equinox?

Royal Museums Greenwich ^ | I can't find it. | They don't say

[kawhill]

The autumnal equinox occurs in September each year, and in the northern hemisphere the date marks the end of summer and beginning of autumn.

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TOPICS: Astronomy; Education; History; Science
KEYWORDS: autumn; equinox

[Alas Babylon!]

When the Sun is directly above the Equator at noon(?). Same as the Vernal Equinox in Spring.

[HandyDandy]

And so therefore, the hours of daylight equal the hours of nighttime.

[Hatteras]

Halfway to St. Patrick’s Day?

[Billthedrill]

It’s a plot by the Heliocentrists. You can’t trust those guys...

[Political Junkie Too]

When the Sun is directly above the Equator at noon(?).

Unless you're on Daylight Savings Time.

-PJ

[Verginius Rufus]

For half the globe, the autumnal equinox occurs in March.

The French Revolutionary Calendar replaced the traditional Roman months with 30-day months with names suggestive of the weather...but very northern-hemisphere-centric.

[Eccl 10:2]

“And so therefore, the hours of daylight equal the hours of nighttime.”

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So, if you’re a flat earth believer, every day is the Autumnal Equinox, no?

[odawg]

The Spring and Fall equinoxes actually do bring in their name sake weather, whereas the Summer soltice and the Winter soltice do not — the name sake weather has been in place for some time. I notice that in Europe, the Summer soltice is called midsummer.

I see these idiot weather people on TV look into the camera and talk about the hot/weather and proclaim, “It is hot/cold and Summer/Winter is not even here yet.”

[j.havenfarm]

I’m a weather geek. Interested to learn recently that the decrease in the length of days this time of year, and increase in the first half of the year, does not occur at the same daily rate

[HandyDandy]

I can’t for the life of me understand why that would be!

[desertsolitaire]

What does Joe Bastardi say about this? And the hurricaines, while we are on weather.

[j.havenfarm]

It was one of those articles they put on the Weather Channel site and it didn’t explain such an extraordinary thing. Didn’t bother to think about it a whole lot until I saw your reply. So I’m going to take a completely speculative theoretical run at it: since th earth’s orbit is elliptical, not round, the gravitational pull of the sun is not equal at the time, and that affects the speed of the planet’s rotation. That’s my best guess

[ridesthemiles]

WHEN DAYLIGHT & DARK ARE ABOUT AS EQUAL AS CAN BE.

[KarlInOhio]

The orbit around the sun doesn't affect the rotational speed of the earth*. What does happen is that around January when the Earth is closest to the sun, it is moving its fastest so 24 hours isn't enough time to go from a location pointing at the sun to pointing at the sun the next day (solar noon to solar noon). Instead it takes a few seconds longer. Similarly, in July the Earth is farthest from the sun and moving the slowest, so a full 24 hours overshoots solar noon.

*There is a slight variation based on weather. In winter in the northern hemisphere snow falls on the mountains, so a slight amount of Earth's weight is farther from the axis and the rotational speed slows down. When it melts and goes down hill Earth speeds up again to maintain angular momentum. Look for pictures of spinning ice skaters for more demos. Since more of the Northern Hemisphere has land than the Southern Hemisphere, northern winter has more effect. But this changes day length in the millisecond range.

[j.havenfarm]

Thanks for the explanation! Interesting

[skinny old man]

Buy a Farmer’s Almanac,gives lots of info,and a good explanation.