Eclipse Day

Aug. 21st, 2017 10:24 pm
darkoshi: (Default)
[personal profile] darkoshi
It was partly cloudy here today.

I got to see a lot of the partial eclipse. A few minutes before totality, a big cloud moved in front of the sun, so I didn't get to watch that most special part. But I did get to experience the sky darkening (not nearly as dark as in the middle of the night; more like shortly after sunset), and the temperature dropping, and the wind whipping up, and a few cicadas starting to buzz, and part of the horizon looking pink.

It was very similar to big thunderstorm building up. That's what the dogs seemed to think, anyway, as they rushed for the porch and pawed at the front door to be let inside. I let them in and then us humans remained outside to watch.

One curious thing is that the partial eclipse started with the moon entering the upper right portion of the sun, and ended with the moon leaving the upper left portion of the sun (when viewing generally southwards for both). That's not what I had expected.

Many people here in town did get to see the totality; it just depended on where one was, and where the clouds were.

My neighbor was visiting a relative at the hospital this afternoon, and she told me that a lot of the hospital staff went outside to view the eclipse (but staff who were needed inside stayed in). She said that the Emergency Room remained open, but the normal operating rooms were closed for that time period. That answers one of the things I had wondered about.

Click to enlarge...


Brian Aldiss (1925 - 2017)

Aug. 21st, 2017 11:14 am
james_davis_nicoll: (Default)
[personal profile] james_davis_nicoll
David Langford reports that Aldiss died in his sleep.

Interesting Links for 21-08-2017

Aug. 21st, 2017 12:00 pm
andrewducker: (Default)
[personal profile] andrewducker
darkoshi: (Default)
[personal profile] darkoshi
This was a very interesting read. Several of the things mentioned in the article made me think of my niece, who was born in 1995; things which I thought were simply traits of hers, but which may be more general traits of her generation.

Have Smartphones Destroyed a Generation?

amusing sentences

Aug. 20th, 2017 11:44 pm
darkoshi: (Default)
[personal profile] darkoshi
What a Border Collie Taught a Linguist About Language
Despite their name, sheep are not sheepish and often act on their own closely held ideas about where to go.

Authorities are Treating August's Solar Eclipse, a First in 99 Years, Like it's the End of the World
National Construction Rentals, which rents portable toilets across the U.S., hasn’t seen a spike in demand, but “there most likely will be last-minute requests as the date approaches,” says the company’s sales and marketing director, Scott Barley. “We advise customers not to spend too much time in our portable toilets on the actual date of August 21, or they may miss this very brief but memorable event.”

yay, trigonometry!

Aug. 20th, 2017 06:48 pm
darkoshi: (Default)
[personal profile] darkoshi
Follow-up to this post.

In the prior post, I pondered about angles. In particular, about the ~13 degrees per day that the moon orbits around the earth, and whether that angle would still look like 13 degrees to me, when measured from the surface of the earth.

The angle would *not* be exactly the same. However, because of how far away the moon is compared to the size of the earth, the difference in angle is very small. That difference can be calculated using trigonometry.

Here's a new diagram. All figures mentioned below are approximations or averages.



The angle measured from the center of the earth is 13 degrees.
"X" is the corresponding angle measured from the surface, which will be calculated.
"D" is the distance from the center of the earth to the moon: 384400 km
"R" is the radius of the earth : 6371 km

I've drawn 2 right triangles such that both have the same "opposite" side, with length "O".
The length of the adjacent side for the X-angled triangle is "A".
The length of the hypotenuse for the X-angled triangle is "B".
The length of the adjacent side for the 13-degree-angled triangle is A + R.
The length of the hypotenuse for the 13-degree angled triangle is D.

sin 13 degrees = O / D
O = D * sin 13 = 384400km * 0.2249511 = 86471 km

cos 13 degrees = (A + R) / D
A = (cos 13) * D - R = (0.9743701 * 384400) - 6371 = 368176.85

tan X = O / A
X = arctan(O / A) = arctan (86471 / 368176.85) = 13.217

So, the corresponding angle from the surface of the earth is ~13.2 degrees.

40 Years Ago Today

Aug. 20th, 2017 04:56 pm
james_davis_nicoll: (Default)
[personal profile] james_davis_nicoll
The United States of America, then an independent nation, launched Voyager 2

I wonder if any of the people involved realized it would still be going two generations later?

Read more... )

Something Awful indeed

Aug. 20th, 2017 09:57 am
jewelfox: A portrait of a foxgryphon with a beak, black fur, magenta hair, fox ears, and a neckband with a large jewel on it. (Default)
[personal profile] jewelfox

SA has been hitting it out of the park lately, with its Onion-esque takes on current events. Check these out if you need to laugh in order to keep from crying!

(Content note: Refers to, and skewers the subjects of, recent depressing news stories that you may not want to be reminded of.)

Read more... )

(no subject)

Aug. 20th, 2017 02:50 am
[personal profile] martianmooncrab
Friday went pretty much as planned, except I havent quite leveled that one section of fence yet, I am saving that for sunday. Got most of the fence done today, with just a bit more to go. got everything painted and installed as it were on the posts.

The Stone working dude finally showed up today to look at my projects, the paver patio area in the front and the 30 feet of back fence that needs replacing, they will email me a quote.

I feel good that I got things done today. After so long of not really catching up... this is nice.
darkoshi: (Default)
[personal profile] darkoshi
When I have something to add in regards to a post I've made previously (a few hours ago, or a few days, or even months), I'm not sure what's the best approach.

Often I simply update the old post, adding an "Update" section to it. That way if anyone finds the post from a websearch, they'll have all the details right there.

Sometimes I create a new post, and put my update there. That way, anyone on my list who read my original post will get the update on their reading page. I don't usually bother to update the old post to link to the new one... so unfortunately, anyone who finds the original post via a search won't get the whole story.

If the post was either very recent (such that maybe no one else read it yet), or a long time ago, I'm more likely to simply update the original post. If it was in-between but had no comments, I'm also likely to take this approach, as I suppose that none of my readers are very interested in the topic and wouldn't be interested in the update anyway.

If the post had comments/discussion, I may choose either option, but if I update the old post, I am more likely to at least mention and link to the update in a new post.

I've been making a lot of updates to recent posts lately.

What approach do the rest of you take?

Stepping Back

Aug. 19th, 2017 03:13 pm
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[personal profile] digitalraven

As Rich Thomas revealed at GenCon, I stepped back as developer of Werewolf: The Forsaken and Werewolf: The Apocalypse developer at Onyx Path a year and a half ago.

I didn’t say anything at the time as I was finishing the books I’d started — W20: Changing Ways and the Pentex Employee Handbook — but I have not started work on any new projects.

It was my decision as the amount of work at my day-job has stepped up considerably, and I am no longer able to give the lines the attention and time that they deserve. I’m not leaving the industry, but I’m back to doing writing and game design under the guidance and development of others. I’m also going to keep working on my own games, as I can take them at my own pace. I have nothing but respect for Rich and Rose and look forwards to the chance to write on Onyx Path books in the future.

Mirrored from ZeroPointInformation.

(no subject)

Aug. 19th, 2017 03:15 am
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[personal profile] arethinn


Currently listening to a random Cure playlist. Somehow that track brings back memories of Sac'to goth clubs 1999-2000 even tho I don't think they played Pornography, or not that much anyway?. More like it makes me remember what I played at home, which would probably involve Pornography and Faith and Disintegration and such. But now I think of it, what really makes me think of that time is Peter Murphy, either "I'll Fall With Your Knife" or "Mercy Rain".

photos

Aug. 19th, 2017 03:53 am
darkoshi: (Default)
[personal profile] darkoshi
Three vultures and a crow in a dead tree. The crow seemed to be cawing at the vultures.


Impressive power lines.


I call this the "yellow brick road". Yellow flowers grow in this gravel path, and only in the path, not in the surrounding fields of grass.

midday moon pondering (updated again)

Aug. 19th, 2017 01:49 am
darkoshi: (Default)
[personal profile] darkoshi
For the last 3 days, I've seen the crescent moon in the sky during the late morning.

2017/08/16, 10:16am EDT:


2017/08/17, 8:43am EDT:


(On 2017/08/18, I saw the moon around 10:30am, but didn't think of taking a photo.)

But I have been unable to find the moon in the sky around 2:30pm (during my lunch breaks). I've been wondering why I can't find it in the afternoon.

(No wonder I've never paid much attention to the path of the moon in the sky. At night, I'm usually inside or asleep. In the daytime, even when the moon is in the sky, it's hard to see.)

On all 3 days, it's been partly cloudy, with today being the least cloudy. So it's possible the moon was behind a cloud. But as much as I've searched the sky, it seems unlikely it's *always* been behind a cloud.


As of today (2017/08/18) at my location, per the NOAA solar calculator (Find Sunrise, Sunset, Solar Noon and Solar Position for Any Place on Earth), solar noon is around 1:30pm. So at 2:30pm, the sun is still fairly high overhead.

On 8/16, it was 5 days before new moon and the eclipse, so the moon would have been about 5 * 13 = 65 degrees away from the sun. So that was most likely too near the horizon for me to see, as there are some trees and buildings around.

On 8/17, the moon would have been 4 * 13 = 52 degrees away from the sun. I think I should have been able to see it at that angle.

Today on 8/18, the moon would have been 3 * 13 = 39 degrees away from the sun. Surely I should have been able to see it at that angle.

The closer we get to the new moon, the thinner the crescent is. So the harder it is to see. It is hard to find a tiny arc of white in a light blue sky, and even more so when there are distracting white clouds around. But is that the only reason I haven't found it?

Per this page: Finding the Moon, crescent moons are "not observable" except right before sunset or after dawn. But I've seen it at 10:30am which isn't right after dawn. So I think it would be more accurate to say "not easily observable".

If I can see it at 10:30am when the sun is already bright in the sky, why shouldn't I be able to see it at 2:30pm?

I got to wondering whether how I think of the angles in the sky is wrong. I am thinking of 45 degrees as being the distance from straight overhead to a point halfway to the horizon. But the 13 degrees that the moon moves per day is in relation to the center of the earth, not to my spot on the surface of the earth. Therefore, is how I'm visualizing the angles in the sky wrong?



When the moon orbits 45 degrees around the earth, is that a much greater distance than the distance I see from overhead to halfway to the horizon?

But... as can be seen in the diagram, the larger you draw the earth, the closer the 45 degrees gets to one's visible horizon, and it would eventually even pass below the horizon. Yet I've been able to see the moon in the mornings, and the distance between it and the sun hasn't seemed such a large angle. So surely the above diagram can't be right.

(Update #2, 2017/08/20: I've figured it out. The diagram is basically correct, but my assumption about the 45 degree line eventually passing below the horizon was wrong (just because I don't draw the horizon line to infinity, doesn't mean it doesn't go to infinity). If the angle to the moon as measured from the center of the earth is 45 degrees (from directly overhead), then the angle as measured from the surface of the earth would be more than 45 degrees. But because the distance to the moon is so large in comparison to the size of the earth, the angle is only slightly more. See follow-up post.)

On the same topic, I got to wondering how much of the sky / celestial sphere am I actually capable of observing from a point on the earth, at any moment in time. Ie. if I turn all the way around, looking towards the horizon, and up above me, how much of the sphere of the sky which surrounds the earth, am I seeing?

Based on the diagram, the amount of sky seen would not be half the sphere, as I've previously assumed. Yet again, the larger one draws the earth, the less of the sky one would seem to see. Surely that can't be right?

Based on these answers, it sounds like you should be able to see half of the sky at any time. But I don't understand the formulas and calculations listed.


Update (afternoon of 2017/08/19):

Today, the morning of 8/19, around 7:40am and again at 10:20am, I wasn't able to find the moon in the sky, even though it was clear with no clouds. So as of 2 days before new moon, the crescent must be too small and faint to see in the daytime. Perhaps a clear sky being so much brighter than a partially cloudy sky, also makes it harder to see.

MoonCalc.org - shows you the current position of the moon in the sky, and moonrise/moonset directions, for any position you select on the map.

Sun Locator Lite - a free app which lets you find the sun and moon by pointing the phone at the sky (as long as the phone has an internal compass/magnetometer - mine doesn't, but Qiao's does). The Pro version lets you get information for any day and time of the year.

Today, 2 days before the eclipse, the moon should be about 2 * 13 = 26 degrees from the sun. I used the above Sun Locator app to find the position of the moon and compare it to the sun's position, and estimated the angle between them. If anything, it seemed less than 26 degrees, not more. So that indicates that there's something wrong with my thinking in terms of the above diagram. But where have I gone wrong? I still haven't figured that out.
(And even with the app to show me its exact location, I still can't see the crescent moon in the afternoon sky.)

But I did have an epiphany on how much of the sky is visible from a point on earth at a single moment in time. It depends on what I'm calling the "sky". I think of the sky as a sphere centered around the earth, upon which I see moon, sun, stars, clouds, etc. But there are many such possible spheres around the earth, different distances from the center of the earth.

How much of the sky is seen depends on which of those spheres one considers. If one considers a sphere which is say, 10 kilometers above sea level, you can calculate the surface area of that sphere. The earth's diameter is 12,742 km. So the sphere's diameter would be 12,752 km, its radius (r) would be 6376 km, and it's surface area would be 4*pi*r^2.

[ another interesting thought... For an infinitely thin sphere, the size of the inside and outside surface areas should be the same, right? But how can that be? I can't visualize them being the same size. ]

Imagine that we cut a small slice, 10 km deep, from the top of that sphere. We can then calculate the surface area of that slice (with some formula, which I would have to look up.) That would tell us how much of the whole sphere we can see at a single moment, and it would be a fairly small portion.

But now, consider a sky-sphere with a much larger radius of 5 light-years - reaching the nearest stars - or even larger. At such distances, the diameter of the earth is minute in comparison - it can be considered negligible. A plane which touches the surface of the earth at one point is practically the same as another parallel plane which intersects both the center of the earth and the sphere. Either way, half of the sphere is above the plane, and half below. So the person can see half of that sky-sphere.

Now, what about a sphere with radius of 150 million km (about the distance from the earth to the sun)? In comparison to that distance, the earth's diameter is roughly 0.01%.* So again, it's basically negligible, and we can see practically half of the sphere at any moment in time.

..

Other interesting tidbits:

How far away is the horizon? Short answer: About 4 to 5 kilometers away, at standing eye-level for an average-height adult.

I see the moon: introducing our nearest neighbour - has several good diagrams/images.
Per this page, the moon's orbital plane is tilted 5 degrees from the ecliptic. That's not as much as I imagined. But when you add in the 23.5 angle of the earth's axis, the moon can orbit up to 29 degrees above or below the earth's equator.

Lunar Orbital Libration
Libration definition: "a real or apparent oscillatory motion, especially of the moon."

Altitude and Azimuth

* A lot of these numbers are rough calculations I've done, and they may have errors. Please don't rely on any numbers I've posted, without verifying them. If you find an error, please let me know so that I can correct it.

[Ω] Juxtaposition

Aug. 18th, 2017 11:44 pm
siderea: (Default)
[personal profile] siderea
(h/t [personal profile] fiddlingfrog)

UrsulaV bats it out of the park:

https://twitter.com/UrsulaV/status/898201836800364547/photo/1

(Note, this requires clicking through to see two images.)

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