Today is the autumnal equinox and why, although technically this is true, there is really no equinox between day and night

This year the exact time of the autumnal equinox is September 22 at 14:49 GMT

A chart of the seasons as they appear in the Northern Hemisphere. Right: the winter solstice in December. From Wikipedia
A chart of the seasons as they appear in the Northern Hemisphere. Right: the winter solstice in December. From Wikipedia

Every year there are two days - in September and March - when the sun rises exactly above the equator and the length of day and night are more or less equal. The seasons are opposite on each side of the equator, so in the northern hemisphere the September equinox is called the autumnal equinox, but in the southern hemisphere it is called the vernal equinox.

This year the exact time of the equinox is September 22 at 14:49 Greenwich Mean Time (17:49 Israel Time, just before the clocks are moved and daylight saving time restored). 

The foreign term for equinox - equinox is derived from a Latin word meaning "equal night". However, in reality this is not entirely accurate. In reality, there are not really 12 hours of light and 12 hours of darkness on the equinoxes. The autumnal equinox occurs the moment the sun crosses the celestial equator - the imaginary line in the sky above the Earth's equator, from north to south.

This happens on September 22,23, 24 or XNUMX. Every other day, the sun is tilted at a slightly distant angle toward or away from the sun. However, on the two equinoxes - autumn and spring, the earth's axis does not tilt either towards or away from the sun.

But there is another important thing that causes that, despite everything, there are more hours of light than hours of darkness. In the astronomical definition, for the purpose of calculating the equinox, the day begins when the sun has risen and showed half of its face above the horizon and ends in the same position at sunset. However, from a practical point of view, the day begins immediately when the upper edge of the sun peeks above the horizon at sunrise and ends when the last of the sun's rays emerge from it and it sinks below the horizon. In addition, the sun is visible even when it is slightly below the horizon (in both directions) because its light is reflected from the upper layers of the atmosphere, which sends them in an arc above the horizon.

In other words, if the sun shrunk to the size of a point like a normal star, and we had no atmosphere, we would see a night exactly equal in length to the day.

Comments

  1. As far as I know, it is the ultra-orthodox who decided to ignore science, not the other way around. In any case, a short time later there was a temporary situation where the ultra-Orthodox were not in the government, and then a law was passed that more or less links us to the changing of the clocks in Europe. Except that in Europe itself they will decide to switch to permanent summer time.

  2. Dear father, there is no point in introducing anti-Orthodox politics into a scientific article.
    Writing like this presents you as a person for whom the emotion of hatred outweighs logic and it's a pity.

    (What's more, opinions of this type are inappropriate in a democratic country where every person from every group has the right to choose and be elected to any position and to promote his world view.)

    It is recommended to correct the article.

  3. This happens on September 22,23, 24 or XNUMX. Every other day, the sun is tilted at a slightly distant angle towards or away from the sun. However, on the two equinoxes - autumn and spring, the earth's axis does not incline either towards the sun or away from it... Father, I have a question... How can there be a situation where the equator is parallel to the Milka plane, after all there is a constant inclination like the sun??!! !Thank you… 🙂

  4. If we assume that the day begins about half an hour before sunrise and the night begins about half an hour after sunset, then when is the true equinox?

  5. I undertake (without a vow) not to enter your site that claims to be scientific anymore.
    Last answer and you won't see me here anymore:
    People here shout about any deviation from the scientific coverage, only that many of the deviations here are in an anti-Orthodox direction, there are also anti-Republicans and just anti-people who annoy the writers of the website. If you had mixed in your words a statement about surrendering to March that leads to the budgeting of left-wing organizations, I would also scream.

    The Ministry of Housing builds projects for all sectors. Also closed projects. There are projects for Bedouins, there are projects for the rich, there are projects for "quality people" (indeed, there were several cities that were founded by an admissions committee that did not accept those it did not like. Most of the time it was religious people who were not accepted - well-known examples are Arad and Yamit). And yes, the ultra-orthodox have housing needs and they also deserve to live somewhere. Even if Maccabi Tel Aviv fans were organized they would have their own projects.

    By the way, thanks to the ultra-Orthodox, billions invested in Harish were saved and almost went to waste because of the well-known Harish High Court. For years, almost no one agreed to live there until the ultra-Orthodox jumped at the chance.

    It's a shame that the only website that claims to be scientific in Israel, isn't either.
    Peace.

  6. It's not a worn-out argument, it's a conditioned reflex with you, but you never have the same sensitivity towards other people's feelings. And as I said, daylight saving time is just one of the small things in your abuse of the tax paying public, a billion and a half for plowing is something much bigger but it has nothing to do with science so I can't write about it. The subject of daylight saving time, in the article talking about the fall equinox which happens to happen on the same day, is relevant.

  7. The advance of summer time does not make it any easier for those who fast on a frosty day anyway, the fast will last 25 hours anyway. If there is any resentment and anger against the ultra-Orthodox on any issue in the world, I think that a post like this, and this website in general, is not the right place to express them, even if they are justified. All the fussing and making of this issue, especially when it is carried out by the editor himself, lowers the level of the site and makes it populist, cheap and not much higher in level than the talkbacks scattered on the net. By the way, the well-worn argument that "only the religious are allowed to be offended" is really not relevant here .

  8. Ophir Pines is a politician and until there was no noise about it, daylight savings time was an issue that even secular politicians would have preferred to use as the meatball they threw to the ultra-Orthodox.
    The difference between Labor and Likud has always been about who will sit with Shas in the government...

  9. 1. We will try to explain again in one sentence. There is no problem with a scientist expressing his opinion, the problem is mixing the expression of opinion with science. If all the propagandists of evolution did not bind the support of evolution to opposition to religion, the evangelicals would not bind religion to opposition to evolution. In an ideal world, a scientist would be careful in his scientific work to talk only about science and not about his beliefs, the rest of the time he is free to do whatever he wants.

    2. As you know, since Popper science does not claim truth and proofs but only arguments that can be refuted. Religion cannot be refuted and therefore is not scientific, but the opposition to it cannot be refuted either and therefore is not scientific. Which makes all involvement in the field unscientific. Evolution can be disproved (to a certain extent) and is therefore scientific. This is the entire scientific Torah on one foot.

    3. a. It was Ofir Pines who introduced the summer time that is now used in Israel.
    on. What to do, as I pay tax money for the Broadcasting Authority, the Chamber Theater and the rescue of a failed commercial channel even though I think the state should not spend a shekel on them. So you also have to spend money on things you don't believe in. (I have no idea if daylight saving time is beneficial to the economy or not. I have a feeling that your enthusiastic support for daylight saving time stems from the opposition of Shas ministers).
    third. I think you might be interested in reading this-
    http://www.scientificamerican.com/article.cfm?id=does-daylight-saving-times-save-energy

  10. I did not understand the complaint. Religious people are allowed to have their religion be the only criterion for consideration and atheists are not allowed just because they are scientists or because they write on a scientific website?
    Amnon Yitzchak speaks nonsense and this nonsense is one of them, why believe specifically in the God of Amnon Yitzchak and not the God of Jesus or the flying spaghetti monster? What imaginary monopoly should one create over others? No one has a monopoly, because they are all imaginary.
    As for the summer time, if all over the world it is followed until November and here just to prove who is in control it ends in the middle of September, it is an upsetting thing because there is a scientifically proven reason for the introduction of daylight saving time. Any religious excuse - by the way, also from Muslims who want to stop fasting earlier in Ramadan and there it is a whole month - is between the believer and himself, I don't have to finance any madness.

  11. Father, you are the only one who introduced feelings here. Everyone else talked about introducing politics into a popular science article. Unlike the experts here, I have no idea if summer time is good for the economy and if winter time is good for Yom Kippur (as a religious person it really doesn't matter to me, it may matter a lot to others). The question is not whether you are right or wrong, the question is why you have trouble separating political opinion from scientific truth.

    As you know, scientific philosophy has worked hard to establish the solidity of scientific evidence and to differentiate between a scientific theory and a non-scientific theory. In your mixing of science and politics you are working against this trend and causing wrong opinions about science. Science deniers feed on science supporters who do not separate politics and science.

    If the scientists were careful to separate their personal opinions from science, there would not have been all the extreme evangelical movements in the United States (and following them in ultra-Orthodox Judaism in Israel), who suddenly began to interpret the story of Genesis in the Bible as it was written and in its words. Or in more blunt words, any mixing like you did in this article, Feeds Rabbi Amnon Yitzchak who "proves" to his listeners that all science stems from the fact that scientists do not want to believe in the existence of G-d.

  12. It is interesting that only one side in the debate has feelings, it is forbidden to hurt religious people of any kind, but they are allowed to hurt others freely and it is even a mitzvah for them.

  13. I don't particularly like Eli Yishai and detest the political reason, which is quite disgusting to me, for the change about a month and a half earlier than the world to "make it easier" to fast on Yom Kippur.
    What are Haredim doing in the rest of the world? What does it matter because it doesn't shorten the fast?
    The problem is different: there is a serious claim that the subject of Daylight Saving Time was invented and came into widespread use in the world close to 100 years ago. At that time, the main consumer of electricity was the lighting, which helped to save electricity.
    The problem is that today there are a large number of other consumers and one of the biggest of them is air conditioning and in this case the solution actually extends the hours of use of the air conditioner.
    That is, daylight saving time may need to be completely canceled all over the world and this will save electricity.
    Of course, sunset at 19:30 instead of 18:30 encourages sports, a trip with the children, etc.
    Read more on Wikipedia
    http://en.wikipedia.org/wiki/Daylight_saving_time
    In the bottom line, it cannot be claimed with certainty that moving an hour saves electricity!

  14. Indeed an accurate nickname, your ultra-Orthodox claim to be the robbed Cossack. Indeed, the tens of millions that will be wasted on the early winter time are nothing compared to the billion and a half in plowing.

  15. How do you manage to push the religious to anything? The religious are also to blame for the tilting of the earth's axis, and also for the big bang and a number of other bigger things. We will not discuss the question of whether summer time is justified. Suppose not. The state is willing to invest a little in reaching out to the religious, just as the state invests in sports or other things that the religious do not consume. Why increase hatred? How many secularists have to pay for the fact that the religious serve significantly more in the army, while the secular evade (tens of percent who don't enlist?)

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