Saturday, March 14, 2015

I dread this time of year.



The Vernal Equinox is coming up next week. I dread it. Every year, the TV news calls, wanting me to do an interview. I spend the week hiding in my lab, since no one in their right mind would follow me in there. (My grandfather Viktor would have been proud.)

The TV news people don't want to hear what I have to tell them: it simply is not possible to explain the Vernal Equinox to a TV audience. It requires that they keep at least three unfamiliar concepts in their minds simultaneously. They'd much rather change the channel.

Nevertheless, here’s what I have in case I'm cornered. I designed it so that if I'm interrupted at any point between paragraphs, it still makes sense (to me, at least).


The Vernal Equinox is the beginning of Spring in Earth's Northern Hemisphere. It is the date and time when Earth's equator points directly toward the Sun's center, during this time of year.

Because of this, the Sun rises due east, and sets due west, on the day of the Vernal Equinox.

This also means there should be 12 hours of daylight and 12 hours of night during the Vernal Equinox. In fact, the daylight is 4 minutes longer, because of refraction in Earth's atmosphere.

The Vernal Equinox is traditionally on March 21. It can be between March 19 and 23, because of leap years, which happen because Earth's year isn't exactly 365 days long. This year, it's on March 20, at 3:45 p.m. Pacific Daylight Time.

It takes over a month for Earth's oceans and atmosphere to warm up. This is why it can be weeks after the Vernal Equinox for the weather to feel like Spring.

23 comments:

  1. "Equinox" would be a good name for a baby. Or a nightclub. Or a sleeping pill.

    ReplyDelete
    Replies
    1. I thought Equinox was some kind of additive for gasoline.

      Delete
    2. Nah, it's Midge Ure's old band.

      Delete
    3. Univax might explain the "tears in my eyes" bit.

      Delete
    4. I always thought "The Smegma Boys" would be an excellent name for a punk/thrash/heavy metal band. Univax was an old tube job.

      Delete
  2. This reminds me of how much I hate daylight savings time. What next? Maybe we should completely eliminate March 15 this year, and instead make October 15 last for 48 hours?

    ReplyDelete
    Replies
    1. This comment has been removed by the author.

      Delete
    2. Daylight Saving Time (please note it's Saving, not Savings) would save more energy if we had it all year. We have it because city slickers who didn't have the gracious Southern upbringing you and I had like to stay out late. Richard Feynman would have had no tolerance for it since it's not a law of nature, it's purely a human convention. I trust you remember the disagreements about the Gregorian calendar? This is why Newton was both the same year Galileo died, insofar as he wasn't.

      Delete
  3. Good post, Frod. Is due west related to Mae West?

    ReplyDelete
    Replies
    1. Due West may not be as witty, but she's easily twice the size of Mae West. You did ask!

      Delete
  4. Replies
    1. Knowing TV news, they'll have no problem mentioning this and Due West in the very same broadcast. Somehow, it's reassuring.

      Delete
  5. Thank you, Frod.

    Never mind the amadáns, as my Irish granny used to say.

    ReplyDelete
  6. Makes sense to me (and I learned a few things). Thanks, Frod!

    I have for several years lived in an apartment with an expansive view of the southeastern portion of the horizon, and some easily recognizable landmarks along that horizon. It took me several years to realize that the sun was rising behind different landmarks at different times of year. Presumably I would not make a very good astronomer, since it took me so long to notice, but now I enjoy being able to track the progress of the seasons this way. For a while, I hoped that that my building and the most prominent landmark were so situated that the sun would rise over it exactly at the equinoxes, but, alas, that is not the case.

    ReplyDelete
    Replies
    1. Stonehenge is by no means the only place on Earth where people noticed this. I used to get phone calls about it when I worked at the planetarium in Chicago, which of course is totally flat and has all its streets aligned north-south and east-west, so people notice where the Sun came up and went down. Neil de Grasse Tyson risked his life to get a photo of it in Manhattan, here:

      http://apod.nasa.gov/apod/ap140706.html

      Delete
  7. Thanks, Frod! Brilliant strategy to break it into sound bites.

    They may interrupt you on TV, but at least you say your own words. My husband gets called fairly often by print reporters about some application of his field, and they always misquote or mis-paraphrase him. His parents would be so proud to see him quoted in the newspaper, and would collect extra copies from their neighbors, but he would cringe to see what mistake had made it into print this time.

    ReplyDelete
  8. Oh, you scientists and your methodological naturalism. Everybody knows the sun rises in the east because it revolves around the earth in that direction.

    ReplyDelete
    Replies
    1. In my general-ed astronomy class for non-majors, I have an exercise for students to explain in 1-3 sentences how we know that Earth rotates, even though one can't feel the motion. Another exercise is to explain in 1-3 sentences how we know Earth orbits the Sun, even though it looks like the Sun is moving. A common wrong answer for both (which I specifically warn them not to make, not that many of them read the instructions) is that the Sun and the stars appear to move through the sky. The ancients thought it was obvious that this was because Earth didn’t move, and that the Sun and the stars moved around Earth: how do we know this is wrong?

      (The answers to the first are the Coriolis effect and the Foucault pendulum, and the answers to the second are the aberration of starlight and trigonometric parallax of stars other than the Sun. It cracks me up that the aberration of starlight wasn’t discovered until the year after Newton died, which was nearly 100 years after the trial of Galileo, who died the year Newton was born [in the Julian calendar]. Parallax was first measured three years after the books of Copernicus and Galileo were taken off the Index Librorum Prohibitorum, over 200 years after the trial of Galileo.)

      Believe it or not too, until they get to my class, many students are unaware that the Sun rises in the east and sets in the west, and that the stars do too, and that the stars only come out at night, and that they are still there in the daytime, we just can’t see them because the day sky is too bright because of all the sunlight in it. What do you expect, when they spend every minute of their lives glued to their phones? (And I don't allow in those in class, since I have tenure and give a damn, and am also holding a STAPLE GUN. [TWITCH! TWITCH!])

      Delete
    2. Also: nowadays we have Doppler radar and spacecraft. Since radar can measure lengths, it's better than using a tape measure, since you're more assured of measuring in a geodesic.

      Delete
  9. Things I've been reminded of by this thread: atmospheric lensing extending the daylight by a few minutes, and coriolis effect to prove the earth is spinning. These and the other things are worth the price of admission, i.e., the time to read the thread.

    I am intrigued by how much knowledge I take for granted. For example, what makes it so remarkable that "Earth's equator points directly toward the Sun's center" on the equinox? It's the fact that it doesn't on all the other days, which is of course because of Earth's axis not being parallel to the axis of its orbit around the sun. (I hope I got that right.) Yet so many apparently don't know this relatively simple point nor understand how it affects the daylight and seasons.

    ReplyDelete
    Replies
    1. Thanks, but notice that we're the only ones with attention spans long enough to be still reading this. It worries me.

      You did get this right: the video "A Private Universe treats this topic in detail. If you want to consider something you need to take for granted, consider how difficult it would have been to get a cheeseburger in pre-industrial times.

      Delete