The Night Sky

[Jack Harrison]

Wiki - as ever - has a good explanation about libration and even mentions diurnal libration which is the effect I had proposed using to produce that 3-D effect.

http://en.wikipedia.org/wiki/Libration

So now all that is needed to test the 3-D effect is a couple of Moon photos taken same phase but at different librations. Adjust size and rotation as required.

Web trawl imminent.

Lets get back to butterflies. Insect eyes are very different in structure from ours, but more significant in terms of stereoscopic vision, they are very close together. Can insects see in 3-D? Have their been any experiments with one eye covered up? There must be little doubt that they would be less efficient going about their everyday business.

There have of course been various areas of research in controlling insect pests, such as making females sterile. I wonder if researchers have considered the possibility of breeding blind or one-eyed insects? (That would make a good April Fool story - maybe I should have left publication of the idea for a couple of months!)

Jack

[Jack Harrison]

This one isn't bad:
http://www.pixheaven.net/geant/0505-060 ... l_moon.jpg

Unfortunately the cross-eyed viewing method produces a concave moon in some instances. But even when I had switched them around with PhotoShop, the effect wasn't that impressive.

Good link:
http://www.fourmilab.ch/earthview/moon_ap_per.html

Get your students working on that equation Guy; indeed why not the whole project?

Jack

[Padfield]

Daybreak in the Alps this morning, seen from my balcony:



Venus is to the left of the picture.

Over the next two days the moon will become a very thin crescent and in two mornings time will be directly below Venus. If the skies are clear it will be a beautiful spectacle.

Guy

[Padfield]

For the record:





Guy

[Jack Harrison]

Nice pictures Guy.

For info (others - not you of course Guy) Venus would only rarely show exactly the same phase as the Moon. In this picture, while the Moon is a crescent, Venus (if seen through a telescope) would show a gibbous phase (between half and full) something like this (actually rotated a little anti-clockwise):

http://2.bp.blogspot.com/_N-36xJMPdm4/S ... +light.gif

Jack

[Jack Harrison]

Just came across this Night Sky forum. The format is familiar.

http://bb.nightskylive.net/asterisk/viewforum.php?f=29

In the meantime my time is currently divided between England v Australia (dismal performance), Andy Murray (not going too well) and this laptop. But there was just a distraction out the window when a Heron went flapping past. Nothing rare about a Heron, but I live some distance from nearest lakes so not a common site here.

Jack

[Jack Harrison]

Astronomy Picture of the Day: http://apod.nasa.gov/apod/ is usually good.

Guy especially will like the picture for 2nd Feb (in the archive after that date).

Jack

[Padfield]

That is simply awesome! I am humbled.

Guy

[Susie]

Jaw droppingly stunning. Made me say "wow" out loud when I saw it, Jack.

[Lee Hurrell]

It didn't quite look real upon first look, it is so good. What a photo.

Lee

[Jack Harrison]

Special Flight to see the Northern Lights:

http://www.bbc.co.uk/news/uk-12396298

I did exactly this years ago when flying a scheduled service from Amsterdam to Aberdeen - and my passengers didn't have to pay extra.

There was superb aurora, so I told the passengers over the PA what was planned. The cabin lights were dimmed, and a few minutes were allowed for them to get used to the dark. Air Traffic Control readily agreed that I could turn left 90 degrees (for the benefit of passengers sitting on the right of the cabin). I held that course for about a minute and then did a 180 to the right for the benefit of those sitting on the left. After a minute I resumed course for Aberdeen. Total time for the exercise about four minutes. The Air Traffic Controller commented: "I'm jealous of you guys. Here I am stuck looking at a radar screen all night!"

My bosses never knew nor do I imagine would they have been particularly censorious if they had. Sure it cost a few extra £££s in fuel, but who can say how many of those passengers might have related the story to friends and drummed up more custom for our airline in the future? I somehow can't image a Ryanair captain getting away with that sort of thing today.

Jack

[Padfield]

Must be wonderful to see them from a plane. You'd need a window seat, I presume...

I saw the Northern Lights in Norway, where I often used to teach privately. We were living in an isolated house in the mountains. One night, after I had gone to bed, the father of my student ran in and told me to put some clothes on and come outside. The sky was draped in luminous green curtains - a truly wonderful sight.

I'm sure you never tired of it, Jack.

Guy

[Jack Harrison]

You'd need a window seat, I presume...

Yes the best view from an office window anywhere in the world.

Jack

[Pete Eeles]

I once saw the Northern Lights when traveling from Los Angeles to Heathrow. The lights were dimmed in the cabin (since it was an overnight flight) and I opened the blind to take a peek (we were asked to close them so that we didn't wake up fellow passengers as the sun came up). The lights were distant, but really did look like someone was drawing the curtains as they shimmered in the darkness! I so wanted to tell everyone to look out of the left side of the plane but they were, of course, mostly asleep. Their loss! Such natural phenomena are just awesome.

Cheers,

- Pete

[Jack Harrison]

Pete once:

saw the Northern Lights when traveling from Los Angeles to Heathrow

Many people when looking a a map might imagine that the flight would be much too far south to see the northern lights. In fact the shortest distance over the earth's surface (a great circle) would take the aircraft over quite high latitudes (circa 60 degs north) such as Hudson Bay Canada and southern Greenland.

It really is quite easy to understand as this equation shows:

equation.jpg (4.27 KiB) Viewed 379 times

Guy. What do you reckon? I think it should be dt /ge p NOT dt /ge r

Jack

[Padfield]

The inequality seems OK to me, if you make certain assumptions, which you evilly didn't make clear!!

Consider two points, p and q. Take spherical polar coordinates from one of them as origin, so theta is angular separation along a line of longitude from the pole. Any arbitrary curve between the points will of necessity be of greater length or equal to the total distance covered longitudinally on the curve (represented by the central integral, summing the infinitesimal changes in theta as the parameter t varies from a to b, but ignoring changes along a line of latitude, and multiplying this angle in radians by the radius of the earth), which must of necessity be greater than or equal to the distance along a line of longitude (remembering that one point has been taken arbitrarily to be the pole).

I.e., if one point is considered to be the pole, the shortest curve is a line of longitude from that pole to any other point.

But it is nearly midnight here, and I have a beer or two in my tummy, so I might have missed something!

Guy

[Pete Eeles]

What Guy said

LA at the top, Britain at the bottom. Follow a straight line between them

Cheers,

- Pete

[Lee Hurrell]

Consider two points, p and q. Take spherical polar coordinates from one of them as origin, so theta is angular separation along a line of longitude from the pole. Any arbitrary curve between the points will of necessity be of greater length or equal to the total distance covered longitudinally on the curve (represented by the central integral, summing the infinitesimal changes in theta as the parameter t varies from a to b, but ignoring changes along a line of latitude, and multiplying this angle in radians by the radius of the earth), which must of necessity be greater than or equal to the distance along a line of longitude (remembering that one point has been taken arbitrarily to be the pole).

Pardon?

I haven't seen the northern lights but would love to.

Cheers

Lee

[Padfield]

But it is nearly midnight here, and I have a beer or two in my tummy, so I might have missed something!

Mmm... What I missed is that Jack was taking the p***.

Sorry Lee - I was only trying to be helpful!

Guy

[Jack Harrison]

Padfield:

Mmm... What I missed is that Jack was taking the p***.

As if I would ever do that. Tut, tut.

The origin of that coarse expression "taking the p***" is worth a wiki search.

I digress - as always (apologies if you have heard this before).

When I was doing my flying training in the RAF, we were joined on our course by a Jordanian officer. Mr.Hussain (yes, that was his real name) who quickly picked up the English language including the vernacular. One day, he confessed to being confused:

"If you say that Jack HAS pi**ed off you mean that he has gone away somewhere. But if you say Jack IS pi**ed off you mean that he is fed up.
Are you chaps taking the p***? What has this to do with pi**ing anyway?"

Jack