Starship Asterisk*

Anthony Barreiro wrote:

geckzilla wrote:
But are there any turtles there?

Not in my neighborhood, that I know of. There are native turtles in surviving wetlands in and around San Francisco, as well as lots of nonnative turtles. If you're commenting on my signature, Turtle Island is a Native American name for North America, and by extension for the world.

http://en.wikipedia.org/wiki/Turtle_Island_%28North_America%29 wrote:
<<The Lenape myth of the "Great Turtle" was first recorded between 1678 and 1680 by Jasper Danckaerts. According to Iroquois oral history, Sky Woman fell down to the earth when it was covered with water. Various animals tried to swim to the bottom of the ocean to bring back dirt to create land. Muskrat succeeded in gathering dirt, which was placed on the back of a turtle, which grew into the land known today as North America.>>

geckzilla wrote:But are there any turtles there?

neufer wrote:

Anthony Barreiro wrote:
The sidewalk might not be perfectly level.

They have level sidewalks in San Francisco

Anthony Barreiro wrote:
The sidewalk might not be perfectly level.

Nitpicker wrote:

Anthony Barreiro wrote: I measured my shadow at solar noon yesterday, three hours after the moment of solstice. I'm 169 cm tall, and my shadow was 330 cm long. What was the height of the Sun in the sky? What is my latitude? And how do you calculate these numbers? I've tried to brush up my long-forgotten trigonometry, but I've given up for now. I expect there's a mathematician here for whom these are easy questions. I'm planning to try to measure my shadow when the Sun is at each multiple of 30 degrees ecliptic longitude and see what pattern emerges.

Based on your measurements, the elevation of the Sun was:
arctan(169/330) = 27.1&deg;

From the equator at the solar noon nearest the solstice, the elevation of the Sun would have been 66.6&deg;.

The difference gives you your latitude, 39.5&deg;. This is ~200km further North than San Fran, so either you are currently out of town, or there are some errors in your measurements.

Anthony Barreiro wrote: I measured my shadow at solar noon yesterday, three hours after the moment of solstice. I'm 169 cm tall, and my shadow was 330 cm long. What was the height of the Sun in the sky? What is my latitude? And how do you calculate these numbers? I've tried to brush up my long-forgotten trigonometry, but I've given up for now. I expect there's a mathematician here for whom these are easy questions. I'm planning to try to measure my shadow when the Sun is at each multiple of 30 degrees ecliptic longitude and see what pattern emerges.

rstevenson wrote:

Anthony Barreiro wrote:It makes the most sense to me to consider the solstices and equinoxes as the midpoints of their respective seasons. And we here in the northern hemisphere still refer to this time of year as midwinter, and the longest days as midsummer.

I don't think you can speak for the entire population of the northern hemisphere, Anthony.

Those terms are rarely used here in eastern Canada, and certainly never in relation to the solstices and equinoxes. Maybe you'd hear the occasional spaced-out astrologer use the terms, but not most folk.

Rob

Anthony Barreiro wrote:It makes the most sense to me to consider the solstices and equinoxes as the midpoints of their respective seasons. And we here in the northern hemisphere still refer to this time of year as midwinter, and the longest days as midsummer.

Nitpicker wrote:...

In pure terms of solar angles of incidence on the Earth, the solstices and equinoxes would mark the middle of each season. However, the effects of the air, ocean and land on Earth, combine to cause a thermal lag, such that temperatures tend to lag behind what the solar angle might otherwise indicate. In some parts of the world, "astronomical seasons" are considered to be a better fit to the measured thermal lag, and in other parts -- especially those more regulated by the oceans -- "meteorological seasons" are preferred.

Happy Solstice!

Boomer12k wrote:
The Sun has many facets, and you need multiple ways to study it....

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geckzilla wrote:
It isn't clear what the credit for NASA is in that image. It could be just one of the little sun images. I tried an image search on it and could only find it at the ISRO website so I think the whole chart was not created by anyone at NASA.

Cousin Ricky wrote:The visible spectrum in that diagram is way too broad, covering most of the range between 1 nm and 1 µm. It should actually cover 380 nm to something over 700 nm, or a fraction of the range between 1 µm and the tick mark above it (100 nm). I don't normally expect the government to tell the truth, but I figured NASA would be an exception.

neufer wrote:

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Cousin Ricky wrote:
So why is the visible-light portion of the Sun shown in false color?