One Moon and another

Typical. The weather front that came in yesterday caused a cloudy night making it impossible to see the total lunar eclipse. The previous night started off badly but improved during the night. The undergraduates got some very nice images of the Orion Nebula (M42) and Saturn. Talking of Saturn, the Cassini-Huygens mission has been taking some nice shots of Titan - a moon of Saturn - while on a fly-by. The images show continent-like structures on the surface of the moon.

The images of Titan also contain doughnut shapes, which conspiracy theorists will probably claim are alien spaceships. They are actually caused by out-of-focus specks of dust in the camera and are imaginatively called dust doughnuts. The easy way to see that they are related to the camera, and not the object being imaged, by comparing two or three different view. The dust doughnuts don't move even though the camera is looking at a different object at a different time. They are usually removed by taking an image called a flat field. A flat field is essentially an image of something very boring and uniform. Usually this will be the inside of the telescope dome or a patch of evening sky before stars become visible. As Cassini is in space, I imagine a flat field image is a little harder to organise. With some knowledge of the camera optics it is even possible to work out where the dust is relative to the CCD chip (the bit of a digital camera that takes the picture).

Posted in astro blog by Stuart on Thursday 28th Oct 2004 (16:21 UTC) | Permalink

Totally Flipped

I'm supposed to be writing my thesis at the moment but while idly browsing through the Sunday Times, I noticed an article by Jeremy Clarkson, which frustrated me. It is a complaint of Denmark's claim on the North Pole combined with a review of Doomsday Just Ahead by Ian Rankin. Now I haven't read the book myself so I only had Jeremy's comments to go on but it seems as though it based on some strange ideas - think of a cross between The Core and The Day After Tomorrow. They are so odd that I can't believe Jeremy Clarkson takes them seriously, even if he does so in a humourous way.

I have only managed to find a review, of the ideas in the book, on Amazon and in (sorry, PDF file) and they seem to be pretty confused. What doesn't help is that Jeremy is even more confused than Ian Rankin as he doesn't make a distinction between the magnetic pole and the geographic pole which Mr Rankin does. The central argument is that if the Earth was to flip its rotational axis every x years, it would cause mass disruption to life on Earth. He even goes so far as to say that this could happen within the next 30 years and would only take about three days. What isn't clear is if the Earth's axis direction moves (like in the precession of the equinoxes which takes 26,000 years) or if the surface moves with respect to the axis of rotation. Jeremy seems to think it is the latter and having the North Pole (NP) in a different place takes up the rest of his article. He also has major problems with his understanding of how seasons work as he associates the NP with cold and ice. There is no reason, in general, for the poles to be the coldest location. They are the coldest places on the Earth because of the low tilt (23.5) with respect to the Sun; the Sun's rays always travel through more atmosphere (compared to at the equator) and are spread over a larger area making them weaker and so it is colder.

There is no disputing that an event such as this would cause massive disruption - an entire planet turning itself on its head does that dort of thing - but it isn't seriously going to happen in the first place. Imagine if your house spontaneously flipped itself upside down for no reason. It that likely? No. He uses the analogy of a spinning beach ball which can easily be turned so that its rotation axis points in a different direction. I agree with that example but you can't compare a beach ball to the Earth. The only similarity is that they are spherical and spinning but that is where it ends. A beach ball is mainly filled with air; that is, all the mass (stuff), is in the thin plastic skin. This is very different to an iron ball which contains rather a lot of 'stuff'. A beach ball is easy to spin compared to an iron ball which takes a lot of effort to get turning and once it is, it takes a lot to change it. The Earth is, in many ways, like the iron ball and would need rather a lot of energy to do anything so dramatic as suggested. A good job really.

It seems that he continues to get all confused about gravity and 'centrifugal forces' and claims that the Sun is orbiting a black hole. Apparently it is the black hole which provides a 'pull' to the Earth and the solar wind gives us a 'push', keeping us in orbit. Hmmm. Perhaps some brushing up on gravity is required here. I should point out that the Sun does actually orbit around a point which isn't at its centre. This point is still within the Sun though so the cover illustration isn't very accurate. Presumably the black hole would be in the Sun then?

What dismays me is that this seems to be another of those books that comes up with dramatic revalations that say 'science' is wrong without any real evidence. They are defended with claims that science classes these people as heretics against the orthodoxy. Science is not religion and doesn't (and shouldn't) work on the basis of belief. Scientists are constantly challenging theories to see if they do or do not work. If a theory is rubbish it is rejected and others are tested. I'll finish with a quote:

It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast. It keeps him young.

Konrad Lorenz

Posted in astro blog by Stuart on Sunday 24th Oct 2004 (15:47 UTC) | Permalink

Light Years Ago

Spotted this in The Times today: Letter reference...

Sir, Mr Martin Morris (letter, October 13) says the light we see from stars is out of date in the sense that it left the object often many light years ago.

A light year is a measure of distance, not time. Stars are often many light years away. I wonder if they have pedantry in space.

Yours faithfully,


80 Mannamead Road,

Plymouth PL3 4SY.

October 13.

Ah well, at least they were brave enough to publish this as a correction.

I was just thinking though - when it comes to the public understanding of science, scientists don't often do themselves any favours; to steal an example from my brother's fiancee, think about a nuclear container. Nuclear fuel is, according to the public perception (and rightfully so to a certain extent) very very dangerous. It needs to be handled and transported very securely and carefully; what do scientists decide to put it in? A flask.

Imagine you're a member of the public. Your perception of a 'flask' is a vacuum flask that you keep your tea warm in. Not the most robust thing you've got to keep things in - in fact, one of the more fragile things! So why on earth are nuclear fuels transported in them?

Physicists/scientists in general need better communications skills - and to think about things like this!

Posted in astro blog by Peter on Friday 22nd Oct 2004 (17:45 UTC) | Permalink

Total Eclipse

Having mentioned the Moon earlier today, I should point out that there will be a total lunar eclipse on 28th October. It will occur from midnight onwards as the Moon moves into the shadow cast by the Earth. Of course some people will be on the wrong side of the Earth to see it but they can always watch a live webcast of the event. Unfortunately here in Manchester, although we should be well placed to see the eclipse, we have to rely on the weather. If it conspires against us we will have to wait until 2007 to see the next one.

Posted in astro blog by Stuart on Saturday 16th Oct 2004 (12:59 UTC) | Permalink

Once in a Blue Moon

People always seem to be ringing Jodrell with astronomy questions, strange sightings or crazy claims. A few weeks ago, someone called asking what defined a blue Moon. My superviser had answered the call but didn't know the answer without the aid of Google. When he came back to the tea room and told us the question, I was surprised that nobody else in the tea room knew the answer. However it seems that I have been using an incorrect definition anyway.

I had thought it referred to a second full moon in a calendar month. As the average time between full moons is 29.5 days and the average calendar month is 30.4 days, once in a while there will be two full Moons in a month. However, it seems that this definition was mistakenly published by the distinguished Sky and Telescope in 1946. It seems that the original definition comes from the Maine Farmers' Almanac which states that it is the third full Moon in a season with four full Moons. That isn't quite the end of the story though as the Almanac uses the dynamical mean Sun - rather than the actual position of the Sun - which gives the seasons an equal length. So, using the 1946 Sky and Telescope definition, there was a blue moon at the end of July - probably what prompted the caller to ring - but using the Almanac method, there won't be one until August 19th 2005.

Incidentally, although the phrase 'blue Moon' doesn't refer to the actual colour of the Moon, the Moon did appear blue and even green after the Indonesian volcano, Krakatoa, exploded in 1883.

Posted in astro blog by Stuart on Saturday 16th Oct 2004 (02:30 UTC) | Permalink

Anti Astrology

It is amazing what you find on the hyperinternetwebgrid sometimes. After a fairly random walk, I discovered the AntiAstrology blog which aims to bring "science to the astrologer's doorstep". It was set up by Prashant Mullick (the AntiAstrologer?) and Selvakumar Ganesan partly in response to an Indian Supreme Court ruling. The ruling dismissed a petition by scientists against a University Grants Commission directive to introduce courses in Vedic Astrology in the university curriculum.

So it may now be possible to do a degree in astrology? Does that mean that my title as the most qualified astrologer in the world may be under threat? I should explain that statement before we go any further. When I graduated from university, my old high school sent me a letter congratulating me on my degree in 'Physics with Astrology'. Oh how I laughed that morning. I thought it was quite funny as it meant I was more qualified than Russell Grant. Another example was the University of Manchester exam timetable, last year, which listed an exam in 'Introductory Astrology' much to the amusement of the lecturer. As a one off, these mix-ups can be quite funny, but they seem to be all to frequent. Interestingly, I can't think of an occasion when it has happened the other way around. It annoys me because there is quite a lot of difference between astrology and astronomy (or astrophysics); one is a bit of fun and the other is a lot of fun!

Astrology and astronomy have common origins but they parted some time ago when astronomy decided to use scientific principles and astrology didn't. There isn't much love lost between the two camps these days and you will be hard pushed to find an astronomer that defends astrology on a scientific basis. I should point out that all astronomers agree that astronomical bodies and phenomena have effects on our everyday lives. Just look at the fact we have day and night, tides and disturbance to communications caused by the solar wind not to mention the sheer thrill of seeing the Saturn with a small telescope. However, they aren't likely to make you meet a tall, dark, hansome stranger. Answering personal ads in the newspaper will be much more successful at that sort of thing.

I will no doubt have further things to say about astrology in the future when I am less tired than I am now.

Posted in astro blog by Stuart on Tuesday 12th Oct 2004 (00:34 UTC) | Permalink

'Security' Lighting

The Campaign for Dark Skies (CfDS) have a good page with details of how to install a floodlight. They have an interactive image that shows the effect of the tilt of the light. In case you haven't already worked it out, the light works better if tilted down rather than up! They also point out that domestic security lighting can contain 500 Watt bulbs. This is in comparison to the bulbs used by lighthouses; around 1000 Watts. And finally, here is a quote from Lisa Simpson:

"Springfield! Turn off your lights! Nobody likes sickly orange barf glow!"

Posted in astro blog by Stuart on Monday 11th Oct 2004 (23:09 UTC) | Permalink

Lovell at Night

For the last few days, the evening sky has been very clear and I kept wishing I had taken my camera with me to Jodrell. Today I made sure that I packed my camera and tripod in my rucksac so that I could take some shots if the weather turned out to be fine. Luckily, it did clear up and I was able to get some nice pictures shortly after sunset and even some stars as it got darker. I also took some pictures of the Lovell Telescope with the Plough in the background; the red light on the focus box stands out well.

Posted in astro blog by Stuart on Saturday 09th Oct 2004 (00:32 UTC) | Permalink
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