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WolfKC
2003-May-23, 01:57 PM
http://www.space.com/spacewatch/annular_eclipse_030523.html


Also, because of this unusual circumstance, instead of moving in a typical west-to-east fashion, as is the case with most solar eclipses, the shadow’s movement will actually run in reverse – from east to west.

This makes no sense to me. I cant visualize it. :(
Is it some sort of retrograde motion effect?

SeanF
2003-May-23, 02:18 PM
Wolf,

The Earth is tilted towards the sun right now. The North Pole is in sunlight, as is much of the Earth's surface all around the Pole. Visualize that for a second. The North Pole is not at the "top" of the Earth, right?

Now, the moon is in such a position that its shadow is being cast at the very "top" of the Earth. In other words, the moon's shadow is on the "other side" of the North Pole from the moon itself. That's why the shadow's movement is opposite (in terms of East-West) than it would be if it were on the same side of the North Pole as the moon.

EDIT: NASA's website on this eclipse is here (http://sunearth.gsfc.nasa.gov/eclipse/ASE2003/ASE2003.html).

girlgeek
2003-May-23, 05:04 PM
SeanF,

Thanks for the explanation. I was confused about that as well. Too bad I live too far south to take advantage!

girlgeek

WolfKC
2003-May-24, 07:03 AM
Yes thanks. I can visualize it somewhat, i think. :)
But for some reason I keep seeing this solar eclipse happening at night. :(
I guess if you are far enough north in summer, you sort of have a visable sun at night :)

PS: But, as you look at it your still seeing essentially the same image from alaska as you are in russia right, it's just that ... it's just that.. i need to get my globe, a lamp and an orange back out. :lol:

WolfKC
2003-May-24, 07:20 AM
Makes me think earth directions are good references for sky objects. If you are standing on the north pole I guess everything moves south. 8)

kilopi
2003-May-24, 12:07 PM
The Earth is tilted towards the sun right now. The North Pole is in sunlight, as is much of the Earth's surface all around the Pole. Visualize that for a second. The North Pole is not at the "top" of the Earth, right?
Excellent post, and that is an excellent point SeanF. I am curious though--why did you then say that the Earth was tilted towards the Sun right now?

Kaptain K
2003-May-24, 12:40 PM
But for some reason I keep seeing this solar eclipse happening at night.

A solar eclipse is an eclipse of the Sun by the Moon. By definition, it occurs in the daytime (when the Sun and Moon are on the same side of the Earth).

A lunar eclipse is an eclipse of the Moon by the Earth. By definition, it occurs in the daytime (when the Sun and Moon are on opposite sides of the Earth).

Donnie B.
2003-May-24, 01:46 PM
But for some reason I keep seeing this solar eclipse happening at night.
A lunar eclipse is an eclipse of the Moon by the Earth. By definition, it occurs in the daytime (when the Sun and Moon are on opposite sides of the Earth).
Um, you mean 'nighttime' here, don't you?

I think the problem in the earlier post is one of semantics. Above the arctic circle in (northern-hemisphere) summer, it's always "daytime" in the astronomical sense, i.e. the Sun is always above the horizon. But if your notion of "day and night" is more oriented toward the clock than the sky, you might say that midnight is nighttime, even in the land of the midnight sun.

WolfKC
2003-May-24, 04:11 PM
But for some reason I keep seeing this solar eclipse happening at night.A lunar eclipse is an eclipse of the Moon by the Earth. By definition, it occurs in the daytime (when the Sun and Moon are on opposite sides of the Earth).Um, you mean 'nighttime' here, don't you?
I think the problem in the earlier post is one of semantics. Above the arctic circle in (northern-hemisphere) summer, it's always "daytime" in the astronomical sense, i.e. the Sun is always above the horizon. But if your notion of "day and night" is more oriented toward the clock than the sky, you might say that midnight is nighttime, even in the land of the midnight sun.

Yes that's exactly what I mean. Although the sun is visable in this area where the eclipse shadow is running reverse from normal, it's only that way becuase it's in an area that is on the oppisite side of the north pole. And, correct me if I'm wrong, this could only be visable in areas above the artic circle, above the level of tilt of the earth towards the sun.
So, you can still see the sun (and the eclipse) even though you are behind where the night half of the world would be if the earth was not tilted.

Here's a follow-up question. At what location and/or time does the west-east shadow be/become an east-west shadow.

WolfKC
2003-May-24, 04:37 PM
Here's a nice graphic (www.chipman.org/starhoax/eclipse-ew.jpg) that I've hightlighted to show the area I belive will have the reverse direction shadow. The thing is I'm not really certain where that highlight goes, I just generally made it perpundicular (sp?) to where I thought the sun would be more or less. In any case looking at say the 5 to 5:30 UT band and locations in Russia and Alaska, you can see Alaska is behind the north pole and therefore the east-west relationship is reversed.
Is this area techncially day or night, guess that depends on your definition. :)

PS:

why did you then say that the Earth was tilted towards the Sun right now? The earth's tilt doesn't really change (except on a 26000 year cycle) but as it moves around the sun so a different part of the tilt is pointed towards the sun. Hence wherever it is summer is where the tilt is towards the sun. The tilt is lined up with the sun on the first day of summer (U.S. standard) and that's the longest day of the year.....
I hope that answers your question. :)

kilopi
2003-May-24, 05:11 PM
H
why did you then say that the Earth was tilted towards the Sun right now? The earth's tilt doesn't really change (except on a 26000 year cycle) but as it moves around the sun so a different part of the tilt is pointed towards the sun. Hence wherever it is summer is where the tilt is towards the sun. The tilt is lined up with the sun on the first day of summer (U.S. standard) and that's the longest day of the year.....
I hope that answers your question. :)
No.

In fact, looking back, I misunderstood SeanF's point. I thought he was making the point that the North part of the Earth is not the "top" of the Earth, but now I see that he wasn't.

So, I'll make it. The Earth is not tilted towards the Sun right now--the northern hemisphere is tilted towards the Sun. The only way you could say that the Earth was tilted towards the Sun is if the Earth had a "top" and a "bottom."

WolfKC
2003-May-24, 05:13 PM
The only way you could say that the Earth was tilted towards the Sun is if the Earth had a "top" and a "bottom."Sure, in a way the north and south pole can be considered a "top" and "bottom". But then there's that whole symantics definition thing again. I supposed Astralians might consder it reversed, then again dont they say they're 'down under'? :) PS: sorry if i made that sound overly simplistic. I dont know who's new to astronomy or who is experienced. (or how much so).

kilopi
2003-May-24, 05:16 PM
The only way you could say that the Earth was tilted towards the Sun is if the Earth had a "top" and a "bottom."Sure, in a way the north and south pole can be considered a "top" and "bottom".
AFAIK, that's a convention on maps. The top of most maps is north--that's not to say that the top of the Earth is north.

WolfKC
2003-May-24, 05:22 PM
The top of most maps is north--that's not to say that the top of the Earth is north. Agreed.
But getting back to the topic and my question, what do you think about my eclipse map (http://www.chipman.org/starhoax/eclipse-ew.jpg) and the location of where the shadow goes e-w rather than w-e?
PS: I'm wondering if it's actually a little more complicated than that graphic and the actual being 'behind the north pole' isn't fully accurate? And if it is, wont that position change as the sun & moon move across the sky? Is it potentially possible that you might technically be seeing the shadow moving w-e and then a minute later you are actually seeing it moving e-w? Of course I'm not talking about the shadow physically changing directions but just the technical name of east and west changing.
I know that sounds crazy but it's a bit like walking across the date-line. How can walking 2 feet change the day, it's a matter of definition.

kilopi
2003-May-24, 05:35 PM
But getting back to the topic and my question, what do you think about my eclipse map (http://www.chipman.org/starhoax/eclipse-ew.jpg) and the location of where the shadow goes e-w rather than w-e?
That's a nice map. Are you referring to your question:

Here's a follow-up question. At what location and/or time does the west-east shadow be/become an east-west shadow.
Notice that that map has times in UT marked along it. And lines which follow 20% eclipses, 40%, 60%, 80%, as well as the full eclipse. Normally, an eclipse footprint is a line, but because it is an annular eclipse, the footprint is an area. You can follow the UT times, and see how the eclipse progresses.

As far as the daytime question--solar eclipses happen in daytime. That is, when the Sun is shining. During the summer, daytime is longer for the northern hemisphere--and at the pole it is 24 hours long. Nighttime on your map is the shaded area. They won't be able to see the eclipse.

Donnie B.
2003-May-24, 11:11 PM
As far as the daytime question--solar eclipses happen in daytime. That is, when the Sun is shining.
Well, since we're being pedantic, I feel compelled to point out that the Sun is always shining... 8)

kilopi
2003-May-25, 02:01 AM
Not on me! :)

WolfKC
2003-May-25, 03:00 AM
So no body has any more comments about the article saying the moon shadow will move in the opposite direction when viewed from certain locations during this eclipse?

The reason I'm not satisfied with SeanF's explanation is that I dont believe the sun&moon will be viewed facing south in Russia while north in Canada. If that were the case, then I could accept it. If a person is facing south then left to right is east-west, if a person facing north then left to right is west-east.
Based on an app I have, the start of the eclipse in Moscow will be east-north-east. The start in north Canada will be north-west.
Here's a little more food for thought should you desire it, although I could possably accpet that my app being wrong at very high latitudes. My north canada location is latitude 80 north of Edmundin (sp?). (http://www.chipman.org/eclipse/eclipse.htm)

I'm beginning to think I've stumped the BABB. :o

nebularain
2003-May-25, 03:19 AM
Well, the only way it can really be understood is to model it. Take a globe of the Earth, a large flashlight, and a small ball. Place the light in such a way that it shines about center of the globe. Tilt the Northern Hemisphere of the globe towards the flashlight. Use the web info to figure the path of the Moon in relation to the time of day. Play around with the globe to figure out what continent is facing the light at what time in relation to the time of the eclipse; then as you spin the globe to mimic Earth's rotation, move your Moon between the light and the globe to mimic the path of the Moon during the eclipse.

From there, see if you can figure out what an Earth-bound observer from different points of the globe in line of the eclipse would see in terms of the East-West / West-East movement.

How's that?

kilopi
2003-May-25, 03:23 AM
Based on an app I have, the start of the eclipse in Moscow will be east-north-east. The start in north Canada will be north-west.

Doesn't that agree with what you said in the OP?


I'm beginning to think I've stumped the BABB. :o
You sure have me. :)

WolfKC
2003-May-25, 03:36 AM
Doesn't that agree with what you said in the OP?
what's OP?

SeanF
2003-May-25, 03:36 AM
So no body has any more comments about the article saying the moon shadow will move in the opposite direction when viewed from certain locations during this eclipse?

The path of total eclipse moves the opposite direction - it's entirely on the "far side" of the Earth (northern tip of Ireland to Iceland to Greenland). Other places where the eclipse is visible (like Alaska) are just partial eclipses, and so aren't actually in the moon's shadow.

How the eclipse visibility moves across Alaska is not really the same as how the moon's shadow moves across the Earth.

BTW, for what it's worth, the definition of "above" (http://dictionary.reference.com/search?q=above) includes "North of." -- so the North Pole is "above" every other point on Earth's surface and is therefore the "top". :)

WolfKC
2003-May-25, 03:37 AM
SeanF wrote:
How the eclipse visibility moves across Alaska is not really the same as how the moon's shadow moves across the Earth.

Well that's the bottom line. I was trying to apply this to a visual of the eclipse and earth references; when actually the only thing this applies to is the shadow location and shadow movement over the earth. I was trying to read more into it than that.
Well ok fine you've got me! :oops: 8)

kilopi
2003-May-25, 04:26 AM
Doesn't that agree with what you said in the OP?
what's OP?
Original Post.