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B Today's Solar eclipse A dud

  1. Aug 21, 2017 #1
    Why didn't the earth get dark? Apparently, even in a total eclipse the moon doesn't block out the total circumference of the sun. Is it a matter of geometry?
     
  2. jcsd
  3. Aug 21, 2017 #2
    I was watching a live stream of the eclipse in OR and at totality it looked like midnight there.
     
  4. Aug 21, 2017 #3

    phyzguy

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    Where were you? Were you in the path of totality? If you were in the path of totality, the moon covered the entire photosphere of the sun (the bright part) but it never covers the solar corona, which is much larger. The total light from the corona is (I think) about equivalent to the light from the full moon, so it doesn't get totally dark.
     
  5. Aug 21, 2017 #4
    No dud here in Salem OR, it was the coolest thing I've ever seen (I couldn't resist looking briefly without glasses). Captured this with an iPhone at the end:

    IMG_0553.JPG

    1uh3c2.jpg
    [​IMG]
     
  6. Aug 21, 2017 #5

    russ_watters

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    A full moon + dusk, since the shadow(umbra) is only 70 miles in diameter, the rest of the earth and atmosphere are illuminated, creating a dusk-like look all the way around.
     
  7. Aug 21, 2017 #6

    phinds

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    Yes, it is exactly a matter of geometry. As has already been explained, you clearly don't understand the geometry. The path is only across a tiny part of the Earth's surface.
     
  8. Aug 22, 2017 #7

    Chronos

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    The solar corona is actually quite bright and there is a ton of scattered light in the atmosphere originating from outside the path of totality, as already mentioned. At high alitiudes and anywhere else the air is relatively unpolluted, the scattering effect is less pronounced lending a more nightlike appearance to the sky.
     
  9. Aug 24, 2017 #8
    It did not get dark for me either but It was because the streetlights came on. Next time i willfind a better viewing area.
     
  10. Aug 24, 2017 #9
    Phinds reiterated what I had already conceded, "you clearly don't understand the geometry", without giving me an answer. It seems geometrically strange that I, being in a location with 82% totality saw the sun in the sky as brighter than a normal day. It was a cloudless day and the corona was intense! Only way anyone knew it was an eclipse was by looking through special glasses. It wasn't even close to dusk, but it did get a little cooler and the humidity dropped. I could only imagine that even if I was in 100% totality, the sun would not appear dark because the corona is not blocked.

    Reference https://www.physicsforums.com/threads/todays-solar-eclipse-a-dud.923386/
     
  11. Aug 24, 2017 #10

    phinds

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  12. Aug 24, 2017 #11

    phyzguy

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    You misunderstand how much brighter the main part of the sun is than the corona. The corona is about 1 million times fainter than the main body of the sun. So if you were in a region where 82% of the sun was blocked, the sun's brightness was reduced to 0.18 times normal. This is not much different than a cloud passing in front of the sun, so you don't notice much. If you had been in the region of totality, the sun's brightness would have been reduced to 0.000001 times normal, more like nighttime with a full moon. Being in the path of totality is waaaaay different than being in the partial eclipse region.
     
  13. Aug 24, 2017 #12

    TeethWhitener

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    I actually mentioned to my wife (after hearing a lot of chatter at, e.g., my kid's daycare, etc. about how the sky was going to go dark--we're in DC, so about 80% coverage here) that if this were a representative sample of the population at large, a whole lot of people outside the path of totality were going to be pretty disappointed at the eclipse.

    Also, as @phyzguy mentioned, if you were outside the path of totality, you didn't see the corona.
     
  14. Aug 24, 2017 #13
    Thanks for that clarification. My common perception going in (like teethwhitener shared) was to think that 82% of the sun being blocked would result in a noticeable darkening. In this week's eclipse with the glasses on, we could see the traditional bright crescent and the majority of the sun dark, but without the glasses the sun's corona was blindingly bright and perfectly spherical.
     
  15. Aug 24, 2017 #14

    Drakkith

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    Your eyes and brain adjust to the falling light and so you perceive it to be about the same level of brightness as normal, despite the fact that the brightness had dropped significantly. If you had been inside during the eclipse and then looked outside you most likely would have noticed the drop in brightness. I commented to someone that the partial eclipse was brighter than I thought it would be and they said that when they looked out their window it looked like clouds had covered the Sun.

    Visual perception is a tricky business...
     
  16. Aug 24, 2017 #15

    russ_watters

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    Our eyes see and compress a wide dynamic range; better than a camera. So things have to change a looot in brightness to notice.
    You can't see the Sun's corona except during totality. That was just you being temporarily blinded. Like looking into a car's headlights.
     
  17. Aug 24, 2017 #16
    I can't argue against that, although I don't believe it! My eyes told me the sun was super bright! If my eyes lied to me, well what the heck, I had no other means to argue. Although I don't believe your hypothesis, I am troubled by my own perception. Because from my perspective, the vast majority of solar eclipses over history would have been a dud, a non- event and gone unnoticed. Yet, that is not the case. Solar eclipses are recorded through- out history as very dramatic events. I'm still puzzled.
     
  18. Aug 24, 2017 #17

    davenn

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    AGAIN .... you DONT see the corona outside of totality. Please understand that
    and the corona is NEVER perfectly spherical



    Why ??
    as already explained to your being in totality is Very different to being in partial.... there's just no comparison !

    Dave
     
  19. Aug 24, 2017 #18

    Drakkith

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    Total solar eclipses are dramatic events. Partial solar eclipses are not. Note that partial solar eclipses are very common and I would bet that the vast majority of people in the past never even knew an eclipse occurred unless they were in the path of totality or near-totality.

    Wikipedia's article on solar eclipses in the 1st century has over 100 entries, with the majority being partial or annular. So there have been many thousands of solar eclipses since recorded history started, but only the total eclipses would have been noticed and the path of totality is very narrow and often falls on oceans or uninhabited areas. Still, with thousands of eclipses, plenty of total eclipses fell on inhabited areas, and those are the ones that were recorded.
     
  20. Aug 24, 2017 #19

    TeethWhitener

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    Also keep in mind that, with the exception of yet-undeciphered Olmec (edit: forgot about the Mayans) and Rapa Nui writings, all of written history until ~500 years ago was confined to Eurasia and North Africa. So if last Tuesday's eclipse had happened in the year 1400, there would possibly be an oral tradition among Native Americans about it, but there would not have been any written documentation of the event, even though thousands of people would likely have seen it.
     
  21. Aug 25, 2017 #20

    OmCheeto

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    That was also my experience:

    Pictographic:

    2017-07-26-why-go-to-totality-png.png
    In hindsight, I'm now glad that most people ignored my recommendations, and stayed home, as traffic was delightfully light, both to and from the eclipse.
     
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