Watch This Space

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,009
Credit: 80,153,230
RAC: 187,439
Topic 196596

OK, on Nov 14 just after dawn I'll be at Port Douglas ( coastal north Queensland, Australia ) a mere 5km from the centerline of the shadow track of a total eclipse of the Sun! :-)

So stay tuned for uploads of photos etc ... if the weather doesn't stuff it, it will be a magnificent view looking east across the Pacific. Reports suggest the area will be buzzing with 100K + visitors ( usually a sleepy hollow of < 10K ).

Cheers, Mike.

( edit ) ..... the longer range forecasts are very hopeful for excellent clear skies. I do hope I may also see diffraction bands racing across the sea/land-scape like I saw for a total eclipse in Victoria in the mid-1970's .....

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,009
Credit: 80,153,230
RAC: 187,439

Watch This Space

OK, I have landed in Far North Queensland amongst the Flame trees, palms and sugar cane. I had to endure champagne and cheese last night, with Eggs Benny and iced coffee this morning. I think that is why this coastline is described as rugged. :-)

Weather forecast for The Day is clear in the morning with clouds in the afternoon. Excellent. Just testing my camera for stop-motion mode which later ought yield a nice little movie at around 10X 'realtime' speed, with at least twenty minutes worth fitting inside a 16GB card b/4 I have to swap out. With the middle of totality at 6.39am local time I'll thus start 10 minutes earlier to cover that phase. Before and after I'll use minutely snaps on another card. Have two dawns to test it out ....

Cheers, Mike ( FNQ Correspondent )

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,009
Credit: 80,153,230
RAC: 187,439

Down on the beach b/4 dawn

Down on the beach b/4 dawn this morning, testing again. Found I can do over 2500 shots b/4 the battery goes too low. At 100 shots per 38 seconds that gives around 16 minutes. Plenty still, but that makes the battery limiting rather than memory. Which is why I have two! :-)

I wasn't the only one doing much the same, I crossed paths with a guy who has seen many since the early 1970's. He kindly taught me about the different types of total eclipses, they do vary! The main reason is the length of totality, he wasn't referring to one's personal position with respect to the shadow track here, but variation due to the near/far-ness of the moon from the Earth at the time. Closer in is longer, further out is shorter ie. how much angle does the moon subtend compared to the Sun? Now on account of tides and their 'abrasion' upon continents the Moon is steadily moving away at around 3cm per year. Eventually there will be no total eclipses ( relax, that's about 1.5 billion years away ).

The geometry that determines the recurrence of eclipses is interesting. You may know that the plane of the Earth/Moon co-orbit is different from the plane of the Sun/Earth co-orbit ( of course it is a 3+ body system with inevitable wiggling, but it helps to think of things in this way with other stuff, say Jupiter, being a perturbation on that ). So two non-parallel planes will intersect at a line, with two normals to that line placed with their tails at some given point on it ( with each normal projecting into a different plane ) having an angle b/w them. This is about 22 degrees or so and remains pretty fixed in our lifetimes, being determined by the angular momentum vectors ( ~ conservation thereof ) of each co-orbit. I use the term co-orbit to emphasise that neither the centre of the Sun nor the centre of the Earth are really at the 'centre' of the Sun/Earth or the Earth/Moon systems respectively. In any case : as the Earth moves around the Sun the line of those intersecting orbital planes is pointing in some fixed direction with respect to the distant stars. All day, everyday.

Now the question becomes : when will the Earth, Sun and Moon all lie along that line? Thinking of just the Sun and Earth for the moment : this will happen twice per year ie. six months apart, with the Earth and Sun swapping ends ( with respect to distant stars ) each time. So now we need to know if/when will the Moon also be on that line on those occasions? If the Moon is on the line with the Sun on the other side of the Earth at the time - you get a lunar eclipse. If the Moon is on the same side of Earth as the Sun is you have a solar eclipse. This reduces our question to : how many complete Earth/Moon orbits coincide with how many complete Sun/Earth orbits?

For this we may ( partly ) thank a chap called Meton who a long time ago worked out that around every 19 or so years such coindicences ( plus/minus about 8 hours ) ought be close and thus you should get a short run of eclipses of both lunar and solar type in a matter of weeks. The truth is rather more complex and replete with mathematical horror, so the Sun/Moon/Earth may only be nearly in a line and hence partial eclipses. I'm sure someone has attempted a full GR solution .... :-)

Now if you are thinking of what time of day and where on the planet you can find one to see, that means what stage/phase of Earth's own rotation is occurring beneath the Moon's shadow. This eclipse can be seen at least in some degree from the northern island of New Zealand to the Northern Territory within a ~180km band. For the Port Douglas area I'm told the last one was 710AD and the next 2237AD, so plenty of time for advance plans. With 'eclipse fever' now taking firm hold, I easily realise why I had to book over twelve months ago ... :-)

[ Nice kangaroo loin steak and a Mojito ( cocktail, phew!) last night, sitting nearby but not too close to a fig tree heavily frequented by rather well fed fruit bats ]

Cheers, Mike ( FNQ Correspondent )

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,009
Credit: 80,153,230
RAC: 187,439

Amazing who you meet on the

Amazing who you meet on the beach! Chap from Oxford who is involved with the beam lines at their synchrotron. Fascinating. :-)

Poor weather this morning, alot of cloud and smattering of rain - from the East - so I do hope the Pacific sorts itself out in the next 24.

Found the use of the hook below the tripod centre ie. hang a bag of sand from it so it jams the legs firmly into the sand. Also discovered the high tide line.

Now there's something we can thank the Moon for. Tides. Ancient understanding did attribute it to the Moon, but with only one cycle a day. The real trick, which Newton shone rational light upon, was that in an orbiting system of two bodies the centre about which they orbit is not the centre of either body : it is somewhere b/w the two. With the Earth being the more massive of the two that point lies closer to the Earth.

So in a simple sense the water nearer the Moon would be attracted and 'rise' toward it. However on the other side of the Earth away from the Moon the water is pulled less by the Moon than the nearside, as that farside water is in an 'orbit' further from the common orbital centre and thus the Moon too. It gets less of a tug from the Moon while having an arc of wider radius to traverse. It is 'thrown outwards' so to speak and hence a tidal bulge of water there also. The Sun also gives an effect depending on it's position. The upshot is that around a New Moon ( which is when solar eclipses occur! ) these effects compound to give a larger tidal variation than otherwise.

A key point is that there is a lag in this. A line passing through the high point of each tidal bulge and the Earth's centre will not be parallel to the line from Earth to Moon. In fact it 'leads' in the sense of pointing to where the Moon will be a short time later. The nett effect here is that the Moon is pulled with a component in the direction along it's instantaneous velocity, which wants to make the Moon go faster, so to speak. But it doesn't, as what actually happens is that the Moon goes into a 'higher' orbit and that is slower. So the energy boost from tidal effects goes into pushing it uphill in the gravity well of the Earth.

Back on Earth the water pushes against the continents to slow the Earth's rotation much like a brake shoe on a brake disc. This is because most of the water's tidal motion is not 'up and down' ie. along a radius from the centre of the Earth, but transverse to that ie. going 'around' along the curvature of the Earth. That hits continental edges and applies a braking effect as the Earth is rotating around it's own axis in the same sense that the Moon is orbiting the Earth.

So the Moon retards the Earth's rotation, the Moon moves into a higher orbit and slows. Angular momentum is conserved, outside of other influences, but energy of nett motion is lost to other forms : heat generated by distorting things, eroding continental edges etc. Interestingly the LIGO inteferometers have to account for distortions in the Earth's shape as it's solid components distort as well as the liquid bits.

The Moon's own rotation around it's own axis is currently a month, this is because over a long period of time it too suffered tidal braking or acceleration such that they match. Which is why we now see only one face of the Moon. While 'The Dark Side of The Moon' is a great work by Pink Floyd, it is a common myth. If we were on the side not visible from Earth it would get recurrent sunshine with it's sunlit period being one half of one month. So a day on the Moon is one month long as it were. All this is known as 'tidal locking', which is a whole other story ... ;-)

'Tidal forces' have a more general meaning in the context of a body which has a variation in the strength of gravity across it. A star coming in towards a close shave with a black hole, say, will be dismembered into a distinctly non spherical smear as it's bits go their own ways without much 'cohesion' to prevent it. If I were to fall inwards to a black hole ( or other highly dense body ) feet first then my feet would have a greater acceleration than my head. My left arm would be following a non-parallel course with respect to the right one - both converging radially toward the centre of the hole. I will become long and thin, and eventually so on smaller scales too : my individual molecules, then atoms, then nuclei etc. This is called 'spaghettification'. I'm serious, it's an actual technical term, though some think of noodles instead! You could demonstrate this at home by whirling around a balloon full of water, as you go faster the balloon will progressively distort outwards until, well, I suppose you get told off for doing that. There's Einstein's Principle of Equivalence right there, as any acceleration ( at least for short intervals of space and time ) mimics gravity. :-)

Cheers, Mike ( FNQ Correspondent )

( edit ) Sharp punters will note that the Moon gets a pull from both tidal bulges. The nearside gives a pull component in the direction of the Moon's instantaneous velocity, the farside in a direction against that vector. But the farside retardation is less, that bulge being further away. So the nett in the direction of the Moon's motion is still a plus.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

ML1
ML1
Joined: 20 Feb 05
Posts: 334
Credit: 51,121,693
RAC: 40,309

Good reporting

Good reporting there...

Hope you get good clear skies and no wet feet from the extra high tides ;-)

Cheers,
Martin

(Over on the dark side of the Earth!)

Powered by: Mageia5
See & try out your OS Freedom! Linux Voice
The Future is what We all make IT [url=http://www.gnu.org/copyleft/gpl.html](GPLv3

Bikeman (Heinz-Bernd Eggenstein)
Bikeman (Heinz-...
Moderator
Joined: 28 Aug 06
Posts: 3,515
Credit: 408,031,677
RAC: 59,493

Yup, good luck with the

Yup, good luck with the weather!! The only total solar eclipse I have witnessed so far was a complete disaster: perfect cloud cover :-(, standing in the middle of a disappointed crowd somewhere in southern Germany.

Cheers
HB

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,009
Credit: 80,153,230
RAC: 187,439

Well we had intermittent

Well we had intermittent cloud cover low down and misty high level cirrus, and I only got three halfway decent shots at totality. So the time-lapse/stop-motion idea fell right over. But I did way better than many as 20km north or south was solid cloud and rain - so I'll take today as a win ! :-)

This one is just moments before showing sunlight streaming past lunar limb features of valleys and peaks ( Baily's Beads ) :

.... same shot but color inverted shows three stars ( near and far at 10 o'clock, far at 4 o'clock ) :

.... here's that corona we all hear about but never see everyday ( that's about two million degrees! )

.... here's a shot a few moments later color inverted :

.... and this one just looks nice :

It was a hoot none-the-less, got up real early and walked several km to a spot I'd picked out earlier on the beach, above the high tide line ( which arrived about an hour later post totality ). Totality is unreal - the wind dies, the birds go quiet, spookin' a bit etc - mainly because all of a sudden the Sun/Moon combo actually looks 3D !! Some trick of our vision interpretation lobes I reckon, I experienced the same thing with a lunar eclipse some years ago.

I'll post more later when I've gone through all of them. :-)

Cheers, Mike ( FNQ Correspondent )

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Rod
Rod
Joined: 3 Jan 06
Posts: 4,396
Credit: 811,266
RAC: 0

Great Shots Mike! A Solar

Great Shots Mike!

A Solar Eclipse is Spooky for all species :-)

There are some who can live without wild things and some who cannot. - Aldo Leopold

Rod
Rod
Joined: 3 Jan 06
Posts: 4,396
Credit: 811,266
RAC: 0

I should have added, that a

I should have added, that a eclipse whether lunar or solar, puts you in your place in the universe, in regard to the 3D effect.

I hope I don't sound to hippy:-)

There are some who can live without wild things and some who cannot. - Aldo Leopold

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,009
Credit: 80,153,230
RAC: 187,439

RE: I should have added,

Quote:

I should have added, that a eclipse whether lunar or solar, puts you in your place in the universe, in regard to the 3D effect.

I hope I don't sound to hippy:-)


Not at all! :-)

If you see an eclipse and are not moved to profound thought then you have no heart/soul. Such perspectives ought be felt more frequently. :-)

Actually that made me think of what any of us would think if we didn't know the 'correct technical' explanation ( assuming that reassures ). Probably scared for starters. I'm sure that all cultures have experienced eclipses enough to make them memorable across generations. Even if eclipses over any given area are decades or more apart, it would be viewed by many and certainly remembered to become part of at least oral tradition.

Now the special reason I wanted catch some stars in the frame was on account of the famous 1919 eclipse that confirmed Einstein's general relativity and propelled him to worldwide fame. Starlight grazing nearby the Sun will deflect inwards ( just like any massive body ) and thus appear to be at a wider angle from a point in the sky that the centre of the Sun overlies, than it would be in the absence of the Sun. Now I won't be doing any measurements myself, plenty will be up to that I expect. I just wanted to see for myself if you could see stars nearby the Sun during an eclipse. You can !! :-)

Cheers, Mike ( FNQ Correspondent )

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
Mike Hewson
Moderator
Joined: 1 Dec 05
Posts: 6,009
Credit: 80,153,230
RAC: 187,439

Here's a shot in false color

Here's a shot in false color of the Moon just starting to take a bite on the upper right edge, like a flat spot on a race tyre, between two cloud banks ( about the only clear shot free of cloud the whole morning ) :

.... while this is a plain weird one of partial eclipse. I interpret as a direct shine-through-cloud image on the top left, but a displaced/diffused shadow on the lower level cloud to the bottom right.

[ Barramundi with Moet&Chandon today. What a struggle it is to do science DownUnda ! Ahem .... :-) ]

Cheers, Mike ( FNQ Correspondent )

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.