I received an email earlier this week from Christy about sunrise/sunset times:
In class, we discussed how, due to the refraction of light, the sun is seen for approximately two minutes prior to actual sunrise, and about two minutes after sunset. This then led to the debate. They then wanted to know, if on the news, the weather said sunrise at 6:42 am, was that the actual "rising" time, or was that when it would be predicted to be visible (and actually rising at 6:44 am). Some think, as scientist, you announce the actual rise time, taking into account the the minutes. Others think that the aforementioned students are "splitting hairs," and since no one will really care about the difference, the time announced is about when the sunrise will be seen.
Here is my response:
I actually remember calculating sunrise/sunset times in school, so this is taking me back :)
Sunrise and sunset calculations DO take into account refraction. However, this isn't a perfect science. Different kinds of conditions (warm versus cold, different kinds of clouds) will create more or less refraction. So you have to take the average refraction of the sun under a "normal" atmosphere.
I hope that makes sense. Basically both groups of kids could be right...we take refraction into account, but it's not precise to the second.
Here is a website that further explains the topic:
http://aa.usno.navy.mil/faq/docs/RST_defs.php#top
Aaron
In class, we discussed how, due to the refraction of light, the sun is seen for approximately two minutes prior to actual sunrise, and about two minutes after sunset. This then led to the debate. They then wanted to know, if on the news, the weather said sunrise at 6:42 am, was that the actual "rising" time, or was that when it would be predicted to be visible (and actually rising at 6:44 am). Some think, as scientist, you announce the actual rise time, taking into account the the minutes. Others think that the aforementioned students are "splitting hairs," and since no one will really care about the difference, the time announced is about when the sunrise will be seen.
Here is my response:
I actually remember calculating sunrise/sunset times in school, so this is taking me back :)
Sunrise and sunset calculations DO take into account refraction. However, this isn't a perfect science. Different kinds of conditions (warm versus cold, different kinds of clouds) will create more or less refraction. So you have to take the average refraction of the sun under a "normal" atmosphere.
I hope that makes sense. Basically both groups of kids could be right...we take refraction into account, but it's not precise to the second.
Here is a website that further explains the topic:
http://aa.usno.navy.mil/faq/docs/RST_defs.php#top
Aaron
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