Archive for the ‘Out There – Cosmology and all that’ Category

The James Webb Space Telescope

May 10, 2018

Last week I was on holiday in Southern California. Lucky me.

Lucky me indeed. During my visit I had – by extreme good fortune – the opportunity to meet with Jon Arenberg – former engineering director of the James Webb Space Telescope (JWST).

And by even more extreme good fortune I had the opportunity to speak with him while overlooking the JWST itself – held upright in a clean room at the Northrop Grumman campus in Redondo Beach, California.

[Sadly, photography was not allowed, so I will have to paint you a picture in words and use some stock images.]


In case you don’t know, the JWST will be the successor to the Hubble Space Telescope (HST), and has been designed to exceed the operational performance of the HST in two key areas.

  • Firstly, it is designed to gather more light than the HST. This will allow the JWST to see very faint objects.
  • Secondly, it is designed to work better with infrared light than the HST. This will allow the JWST to see objects whose light has been extremely red-shifted from the visible.

A full-size model of the JWST is shown below and it is clear that the design is extraordinary, and at first sight, rather odd-looking. But the structure – and much else besides – is driven by these two requirements.

JWST and people

Requirement#1: Gather more light.

To gather more light, the main light-gathering mirror in the JWST is 6.5 metres across rather than just 2.5 metres in the HST. That means it gathers around 7 times more light than the HST and so can see fainter objects and produce sharper images.


Image courtesy of Wikipedia

But in order to launch a mirror this size from Earth on a rocket, it is necessary to use a  mirror which can be folded for launch. This is why the mirror is made in hexagonal segments.

To cope with the alignment requirements of a folding mirror, the mirror segments have actuators to enable fine-tuning of the shape of the mirror.

To reduce the weight of such a large mirror it had to be made of beryllium – a highly toxic metal which is difficult to machine. It is however 30% less dense than aluminium and also has a much lower coefficient of thermal expansion.

The ‘deployment’ or ‘unfolding’ sequence of the JWST is shown below.

Requirement#2: Improved imaging of infrared light.

The wavelength of visible light varies from roughly 0.000 4 mm for light which elicits the sensation we call violet, to 0.000 7 mm for light which elicits the sensation we call red.

Light with a wavelength longer than 0.000 7 mm does not elicit any visible sensation in humans and is called ‘infrared’ light.

Imaging so-called ‘near’ infrared light (with wavelengths from 0.000 7 mm to 0.005 mm) is relatively easy.

Hubble can ‘see’ at wavelengths as long as 0.002 5 mm. To achieve this, the detector in HST was cooled. But to work at longer wavelengths the entire telescope needs to be cold.

This is because every object emits infrared light and the amount of infrared light it emits is related to its temperature. So a warm telescope ‘glows’ and offers no chance to image dim infrared light from the edge of the universe!

The JWST is designed to ‘see’ at wavelengths as long as 0.029 mm – 10 times longer wavelengths than the HST – and that means that typically the telescope needs to be on the order of 10 times colder.

To cool the entire telescope requires a breathtaking – but logical – design. There were two parts to the solution.

  • The first part involved the design of the satellite itself.
  • The second part involved the positioning the satellite.

Cooling the telescope part#1: design

The telescope and detectors were separated from the rest of the satellite that contains elements such as the thrusters, cryo-coolers, data transmission equipment and solar cells. These parts need to be warm to operate correctly.

The telescope is separated from the ‘operational’ part of the satellite with a sun-shield roughly the size of tennis court. When shielded from the Sun, the telescope is exposed to the chilly universe, and cooled gas from the cryo-coolers cools some of the detectors to just a few degrees above absolute zero.

Cooling the telescope part#2: location

The HST is only 300 miles or so from Earth, and orbits every 97 minutes. It travels in-to and out-of full sunshine on each orbit. This type of orbit is not compatible with keeping a gigantic telescope cold.

So the second part of the cooling strategy is to position the JWST approximately 1 million miles from Earth at a location known as the second Lagrange point L2.

At L2 the gravitational attraction of the Sun is approximately 30 times greater than the gravitational attraction of the Earth and Moon.

At L2 the satellite orbits the Sun in a period of one year – and so stays in the same position relative to the Earth.

  • The advantage of orbiting at L2 is that the satellite can maintain the same orientation with respect to the Sun for long periods. And so the sun-shade can shield the telescope very effectively, allowing it to stay cool.
  • The disadvantage of orbiting at L2 is that it is beyond the orbit of the moon and no manned space-craft has ever travelled so far from Earth. So once launched, there is absolutely no possibility of a rescue mission.

The most expensive object on Earth?

I love the concept of the JWST. At an estimated cost of $8 billion, if this is not the most expensive single object on Earth, then I would be interested to know what is.

But it has not been created to make money or as an act of aggression.

Instead, it has been created to answer the simple question

I wonder what we would see if we looked into deep space at infrared wavelengths.”. 

Ultimately, we just don’t know until we look.

In a year or two, engineers will place the JWST on top of an Ariane rocket and fire it into space. And the most expensive object on Earth will then – hopefully – become the most expensive object in space.

Personally I find the mere existence of such an enterprise a bastion of hope in a world full of worry.


Many thanks to Jon Arenberg  and Stephanie Sandor-Leahy for the opportunity to see this apogee of science and engineering.


Breathtaking photographs are available in galleries linked to from this page


Gravity Wave Detector#2

July 15, 2017

GEO600 One arm


After presenting a paper at the European Society of Precision Engineering and Nanotechnology (EUSPEN) in Hannover back in May, I was offered the chance to visit a Gravity Wave Detector. Wow! I jumped at the opportunity!

The visiting delegation were driven in a three-minibus convoy for about 30 minutes, ending up in the middle of a field of cabbages.

After artfully turning around and re-tracing our steps, we found a long, straight, gated track running off the cabbage-field track.

Near the gate was a shed, and alongside the road ran some corrugated sheet covering what looked like a drainage ditch.

These were the only clues that we were approaching one of the most sensitive devices that human beings have ever built: the GEO600 gravity-wave detector(Wikipedia or GEO600 home page)

Even as we drove down the road, the device in ‘the ditch’ was looking for length changes in the 600 metre road of less than one thousandth the diameter of a single proton.

Nothing about how to achieve such sensitivity is obvious. And as my previous article made clear, there have been many false steps along the way.

But even the phenomenal sensitivity of this detector turns out be not quite good enough to detect the gravity waves from colliding black holes.

In order to detect recent events GEO600 would have to have been between 3 and 10 times more sensitive.

The measuring principle

The GEO600 device as it appears above ground is illustrated in the drone movie above.

It consists of a series of huts and an underground laboratory at the intersection of two 600 metre long ‘arms’.

In the central laboratory, a powerful (30 watt) laser shines light of a single wavelength onto a beam-splitter: a piece of glass with a thin metal coating.

The beam-splitter reflects half the light and transmits the other other half, creating two beams which travel at 90° to each other along the two arms of the device.

At the end of the arms, a mirror reflects the light back to the beam-splitter and onto a light detector where the beams re-combine.

Aside from the laser, all the optical components are suspended from anti-vibration mountings inside vacuum tubes about 50 cm in diameter.

When set up optimally, the light traversing the two arms interferes destructively, giving almost zero light signal at the detector.

But a motion of one mirror by half of a wavelength of light (~0.0005 millimetres), will result in a signal going from nearly zero watts (when there is destructive interference) to roughly 30 watts (when there is constructive interference).

So this device – which is called a Michelson Interferometer – senses tiny differences in the path of light in the two arms. These differences might be due to the motion of one of the mirrors, or due to light in one arm being delayed with respect to light in the other arm.


The basic sensitivity to motion can be calculated (roughly) as follows.

Shifting one mirror by one half a wavelength (roughly 0.0005 millimetres) results in an optical signal increasing from near zero to roughly 30 watts, a sensitivity of around 60,000 watts per millimetre.

Modern silicon detectors can detect perhaps a pico-watt (10-12 watt) of light.

So the device can detect a motion of just

10-12 watts ÷ 60000 watts per millimetre

or roughly 2 x 10-17 mm which is 10-20 metres. Or one hundred thousandth the diameter of a proton!

If the beam paths are each 600 metres long then the ability to detect displacements is equivalent to a fractional strain of roughly 10-23 in one beam path over the other.

So GEO600 could, in principle, detect a change in length of one arm compared to the other by a fraction:

0.000 000 000 000 000 000 000 01

There are lots of reasons why this sensitivity is not fully realised, but that is the basic operating principle of the interferometer.

The ‘trick’ is isolation

The scientists running the experiment think that a gravity wave passing through the detector will cause tiny, fluctuating changes in the length of one arm of GEO600 compared with the other arm.

The changes they expect are tiny which is why they made GEO600 so sensitive.

But in the same way that a super-sensitive microphone in a noisy room would just makes the noise appear louder, so GEO600 is useless unless it can be isolated from noise and vibrations.

So the ‘trick’ is to place this extraordinarily sensitive ‘microphone’ into an extraordinarily ‘quiet’ environment. This is very difficult.

If one sits in a quiet room, one can slowly become aware of all kinds of noises which were previously present, but of which one was unaware:

  • the sound of the flow of blood in our ears:
  • the sound of the house ‘creaking’
  • other ‘hums’ of indeterminate origin.

Similarly GEO600, can ‘hear’ previously unimaginably ‘quiet’ sounds:

  • the ground vibrations of Atlantic waves crashing on the shores of Europe:
  • the atom-by-atom ‘creeping’ of the suspension holding the mirrors


So during an experiment, the components of GEO600 sit in a vacuum and the mirrors and optical components are suspended from silica (glass) fibres, which are themselves suspended from the end of a spring-on-a-spring-on-a-spring!

In the photograph below, the stainless steel vacuum vessels containing the key components can be seen in the underground ‘hub’ at the intersection of the two arms.

GEO600 Beam Splitter

They are as isolated from the ‘local’ environment as possible.

The output of the detector – the brightness of the light on the detector is shown live on one of the many screens in the control ‘hut’.

GEO 600 Control Centre

But instead of a graph of ‘brightness versus time, the signal is shown as a graph of the frequencies of vibration detected by the silicon detector.


The picture below shows a graph of the strain – the difference in length of the two arms – detected at different frequencies.

[Please note the graph is what scientists call ‘logarithmic’. This means that a given distance on either axis corresponds to a constant multiplier. So the each group of horizontal lines corresponds to a change in strain by a factor 10, and the maximum strain shown on the vertical 10,000 times larger than the smallest strain shown.]

Sensitivity Curve

The picture above shows two traces, which both have three key features:

  • The blue curve showed the signal being detected as we watched. The red curve was the best performance of the detector. So the detector was performing close to its optimal performance.
  • Both curves are large at low frequencies, have a minimum close to 600 Hz, and then rise slowly. This is the background noise of the detector. Ideally they would like this to be about 10 times lower, particularly at low frequencies.
  • Close to the minimum is a large cluster of spikes: these are the natural frequencies of vibration of the mirror suspensions and the other optical components.
  • There are lots of spikes caused by specific noise sources in the environment.

If a gravity wave passed by…

…it would appear as a sudden spike at a particular frequency, and this frequency would then increase, and finally the spike would disappear.

It would be over in less than a second.

And how could they tell it was a gravity wave and not just random noise? Well that’s the second trick: gravity wave detectors hunt in pairs.

The signal from this detector is analysed alongside signals from other gravity wave detectors located thousands of kilometres away.

If the signal came from a gravity wave, then they would expect to see a similar signal in the second detector either just before or just afterwards – within a ‘time window’ consistent with a wave travelling at the speed of light.


Because powerful lasers were in use, visitors were obliged to wear laser google!

Because powerful lasers were in use, visitors were obliged to wear laser goggles!

This was the second gravity wave detector I have seen that has never detected a gravity wave.

But I have seen this in the new era where we now know these waves exist.

People have been actively searching for these waves for roughly 50 years and I am filled with admiration for the nobility of the researchers who spent their careers fruitlessly searching and failing to find gravity waves.

But the collective effect of these decades of ‘failure’ is a collective success: we now know how to the ‘listen’ to the Universe in a new way which will probably revolutionise how we look at the Universe in the coming centuries.

A 12-minute Documentary

Gravity Wave Detector#1

July 6, 2017
Me and Albert Einstein

Not Charlie Chaplin: That’s me and Albert Einstein. A special moment for me. Not so much for him.

I belong to an exclusive club! I have visited two gravity wave detectors in my life.

Neither of the detectors have ever detected gravity waves, but nonetheless, both of them filled me with admiration for their inventors.

Bristol, 1987 

In 1987, the buzz of the discovery of high-temperature superconductors was still intense.

I was in my first post-doctoral appointment at the University of Bristol and I spent many late late nights ‘cooking’ up compounds and carrying out experiments.

As I wandered around the H. H. Wills Physics department late at night I opened a door and discovered a secret corridor underneath the main corridor.

Stretching for perhaps 50 metres along the subterranean hideout was a high-tech arrangement of vacuum tubing, separated every 10 metres or so by a ‘castle’ of vacuum apparatus.

It lay dormant and dusty and silent in the stillness of the night.

The next day I asked about the apparatus at morning tea – a ritual amongst the low-temperature physicists.

It was Peter Aplin who smiled wryly and claimed ownership. Peter was a kindly antipodean physicist, a generalist – and an expert in electronics.

New Scientist article from 1975

New Scientist article from 1975

He explained that it was his new idea for a gravity wave detector.

In each of the ‘castles’ was a mass suspended in vacuum from a spring made of quartz.

He had calculated that by detecting ‘ringing’ in multiple masses, rather than in a single mass, he could make a detector whose sensitivity scaled as its Length2 rather than as its Length.

He had devised the theory; built the apparatus; done the experiment; and written the paper announcing that gravity waves had not been detected with a new limit of sensitivity.

He then submitted the paper to Physical Review. It was at this point that a referee had reminded him that:

When a term in L2 is taken from the left-hand side of the equation to the right-hand side, it changes sign. You will thus find that in your Equation 13, the term in L2 will cancel.

And so his detector was not any more sensitive than anyone else’s.

And so…

If it had been me, I think I might have cried.

But as Peter recounted this tale, he did not cry. He smiled and put it down to experience.

Peter was – and perhaps still is – a brilliant physicist. And amongst the kindest and most helpful people I have ever met.

And I felt inspired by his screw up. Or rather I was inspired by his ability to openly acknowledge his mistake. Smile. And move on.

30 years later…

…I visited Geo 600. And I will describe this dramatically scaled-up experiment in my next article.

P.S. (Aplin)

Peter S Aplin wrote a review of gravitational wave experiments in 1972 and had a paper at a conference called “A novel gravitational wave antenna“. Sadly, I don’t have easy access to either of these sources.


How would you take a dinosaur’s temperature?

March 15, 2017
A tooth from a tyrannosaurus rex.

A tooth from a tyrannosaurus rex.

Were dinosaurs warm-blooded or cold-blooded?

That is an interesting question. And one might imagine that we could infer an answer by looking at fossil skeletons and drawing inferences from analogies with modern animals.

But with dinosaurs all being dead these last 66 million years or so, a direct temperature measurement is obviously impossible.

Or so I thought until earlier today when I visited the isotope facilities at the Scottish Universities Environmental Research Centre in East Kilbride.

There they have a plan to make direct physical measurements on dinosaur remains, and from these measurements work out the temperature of the dinosaur during its life.

Their cunning three-step plan goes like this:

  1. Find some dinosaur remains: They have chosen to study the teeth from tyrannosaurs because it transpires that there are plenty of these available and so museums will let them carry out experiments on samples.
  2. Analyse the isotopic composition of carbonate compounds in the teeth. It turns out that the detailed isotopic composition of carbonates changes systematically with the temperature at which the carbonate was formed. Studying the isotopic composition of the carbon dioxide gas given off when the teeth are dissolved reveals that subtle change in carbonate composition, and hence the temperature at which the carbonate was formed.
  3. Study the ‘formation temperature’ of the carbonate in dinosaur teeth discovered in a range of different climates. If dinosaurs were cold-blooded, (i.e. unable to control their own body temperature) then the temperature ought to vary systematically with climate. But if dinosaurs were warm-blooded, then the formation temperature should be the same no matter where they lived (in the same way that human body temperature doesn’t vary with latitude).
A 'paleo-thermometer'

A ‘paleo-thermometer’

I have written out the three step plan above, and I hope it sort of made sense.

So contrary to what I said at the start of this article, it is possible – at least in principle – to measure the temperature of a dinosaur that died at least 66 million years ago.

But in fact work like this is right on the edge of ‘the possible’. It ought to work. And the people doing the work think it will work.

But the complexities of the measurement in Step 2 appeared to me to be so many that it must be possible that it won’t work. Or not as well as hoped.

However I don’t say that as a criticism: I say it with admiration.

To be able to even imagine making such a measurement seems to me to be on a par with measuring the cosmic microwave background, or gravitational waves.

It involves stretching everything we can do to its limits and then studying the faint structures and patterns that we detect. Ghosts from the past, whispering to us through time.

I was inspired.


Thanks to Adrian Boyce and Darren Mark for their time today, and apologies to them both if I have mangled this story!

SI Superheroes

January 12, 2016

Somehow this episode of SI Superheroes came out last May (2015) and I didn’t notice!

If anything, this is even better than the first episode – perhaps because it’s more focussed on a single theme without the need to introduce all the characters.

In case you are unfamiliar with the work of NIST, the US National Institute for Standards and Technology, they are basically the US version of NPL and are a very serious organisation. In my recollection, this is only the second output from NIST that has featured laugh-out-loud moments (which I will not reveal!).

I can foresee great things for these characters.

Remember that Superman, Batman and their friends and foes inhabited a (DC) universe of paper comics for decades.

Then they became TV cartoon characters.

And only relatively recently have they become the stars of the current genre of all action, computer-graphic laden movies.

I wonder if they will be recruiting for a male with slightly older looks to play Dr. Kelvin…


Incidentally, the number 9,192,631,770 displayed on the side of the cartoon satellite is the number of oscillations a Caesium atom that defines what we mean by the passage of one second.

At places like NPL and NIST we can make clocks based on Caesium atoms that very perfectly realise this definition.

The atoms in these super-clocks vibrate at  9,192,631,770.000 000 ± 0.000 001 oscillations per second and form the basis of Universal Coordinated Time (UTC)  that is used throughout the world.

One of the difficulties which Major Uncertainty may have tried to exploit is that the number of oscillations per second changes very slightly with changes in the physical environment of the atom.

Some of the environmental parameters that matter for clocks mounted in space are:

  • the strength of the gravitational field,
  • any accelerations that the atom experiences,
  • the  speed of the clock with respect to the person (often on the ground)  counting the oscillations,
  • the temperature of the walls surrounding the atoms.

Anyway – all is well now that the League of SI Superheroes has done their job again.

How Apollo Flew to the Moon

September 6, 2015
The Moon photographed above some beach grass in Northumberland

The Moon photographed above some beach grass in Northumberland

On my recent holiday in Northumberland, I both photographed the moon, and read about how almost 50 years ago, human beings landed on its surface.

This article is a review of the book I read: ‘How Apollo Flew to the Moon‘ by W. David Woods.

Staring at the moon and considering what we now know about its distance from Earth, its size, and its inhospitable surface, is an exercise in bridging emotional and intellectual understanding.

I have long-considered that the Apollo programme of manned spaceflights to the Moon to have been an exemplar of the power of human intellect, and overall one of humanity’s exceptional achievements.

The enormous cost of the programme (4% of the US Federal budget in 1967) was – in my opinion – well justified by the cultural shift it engendered.

We went to the Moon and discovered the Earth‘ is a truth expressed by many, including several of the early astronauts.

However this book is not about the cultural impact of the programme, but about how the journey was made. For anyone with a technical disposition the book will fascinate.

I took all 500 pages of the book on holiday with me and self-indulgently read it slowly from cover to cover: it was enormously enjoyable.

After an overview, the book follows the Apollo 11 mission through all its stages, sprinkling in astronaut comments and explaining the differences between earlier and later missions.

There are many fascinating details, but what came through to me above everything was NASA’s pervasive mindset of constantly, painstakingly, meticulously and expensively planning for failure.

The philosophy of not just being aware that an operation may fail, but making detailed plans for what you will do when it does is a lesson for anyone who wants a complex plan to succeed.

And not only were there back-up plans for failure, there were plans for failure of the back-up plans! Only at one or two key points in the entire mission were there operations which simply had to work.

So, for example, when their spacecraft fired a rocket engine to leave Earth’s orbit and head towards the Moon –  or rather where the Moon was going to be in three days time – the rocket burn placed them into a so-called ‘free-return trajectory‘.

Thus if something went wrong on the voyage, or the rocket engine failed to fire – the spacecraft would sail around the Moon and head straight back to Earth.

When launched towards the Moon, the Apollo spacecraft was placed in a “Circumlunar-free-return-trajectory” . This meant that unless they did something positive to enter the Moon’s orbit, they would return to the Earth. Picture by NickFr Licensed under Public Domain via Wikipedia

Overall, the book is a great read for the technically minded. And in addition to the narrative there are occasional superlatives – like ‘vista-points’ on a highway – where you can stop and simply wonder.

  • The total mechanical output power of five first stage rockets was 60 GW. This is equivalent to peak electrical supply of the entire United Kingdom.
  • On its return from the moon, its speed just before entry into the Earth’s atmosphere was more than 11 kilometres per second.
  • Since Apollo 17 returned in 1972. no human being has been more than 500 miles from Earth’s surface.

The days of our lives

September 30, 2014
MIchael de Podesta is 20,000 days old today.

Michael de Podesta is 20,000 days old today.

Today, 30th September 2014 is a special day: I am 54 years, 9 months and 2 days old!

Special? Yes, because today I am 20,000 days old!

It is natural to mark the passage of time since our birth.

Traditionally we do this by counting the number of times the Earth has orbited the Sun (years) since the day we were born.

We then celebrate when this number reaches a multiple of 10, the number of fingers and thumbs on our hands.

Is it any less arbitrary to count the number of rotations of the Earth about its axis (days) since we were born?

And then celebrate when this number reaches a multiple of 10. Or 100. Or 1000, Or in my advanced case, 10,000.

I don’t expect to see my 30,000th day on Earth (15th February 2042), but I am looking forward to 15th May 2023.

If I am alive, then sometime during that day I will pass my 2 billionth second on Earth! Wow!

On reflection, I realise it is arbitrary to pick any particular unit for counting our age – we should just follow the local convention.

But make sure that we celebrate every second of every minute of every hour of every day of every year. They all pass so quickly.

Happy Whatever 🙂


You can plan the dates for your own celebrations using this excellent web site.

The hours of our days

September 8, 2014
The chart shows the number of hours between sunrise and sunset in London for each day of the year. In the spring and autumn day length changes by more than 3.5 minutes each day - or 25 minutes each week.

The chart shows the number of hours between sunrise and sunset in London for each day of the year. In the spring and autumn day length changes by more than 3.5 minutes each day – or 25 minutes each week.

It is around this time of year that I begin to feel the nights closing in, encroaching on my evenings and generally making me feel that the summer is slipping away.

The change in the number of hours of daylight in the UK is dramatic, falling from a peak of over 16.5 hours to less than 8 hours. If it wasn’t so familiar we would be amazed.

At this time of year ‘day length’, the difference between sunrise (when the Sun just pops over the horizon) and sunset (when it just disappears from view) changes by more than 3.5 minutes each day – or 25 minutes each week.

But of course it does not get dark immediately after the the sun sets. Even when it is below the horizon the sun illuminates the sky which scatters light downwards giving rise to ‘twilight’.

Google poetically informs me that twilight is:

the soft glowing light from the sky when the sun is below the horizon, caused by the reflection of the sun’s rays from the atmosphere.

Wikipedia tells me there are three definitions of twilight based on how far the Sun is below the horizon.

  • Civil‘ twilight is defined by the time that the Sun is less than 6º below the horizon.
    • Wikipedia describes this as “the limit at which twilight illumination is sufficient, under clear weather conditions, for terrestrial objects to be clearly distinguished
  • Nautical‘ twilight is defined by the time that the Sun is less than 12º below the horizon
    • Wikipedia describes this as “when there is a visible horizon (at sea) for reference“.
  • Astronomical‘ twilight is defined by the time that the Sun is less than 18º below the horizon.
    • Wikipedia describes this as “when the dimmest stars ever visible to the naked eye become visible”.

The chart below shows the times of Sunrise, Sunset and the three twilight times compiled from data on this wonderful web site.

Graph showing the time of sunrise (red line) and sunset (blue line) for each day of the year. Also shown are times of 'civil'. 'nautical' and 'astronomical' twilight.

Graph showing the time of sunrise (red line) and sunset (blue line) for each day of the year. Also shown are times of ‘civil’. ‘nautical’ and ‘astronomical’ twilight.

This chart tells us what we already knew, that in the winter, not only is the day length shorter, but so is twilight.

In the chart above I have removed the anomaly of British Summer Time and so all the times shown are Greenwich Mean Time.

If we leave in this anomaly, then (looking only at sunset and sunrise) the effect of changing to British Summer Time can be seen below.

The time of sunrise (red line) and sunset (blue line) for each day of the year. The solid line shows the 'clock' time in the UK and has a jump when we switch to British Summer Time. The coloured dotted lines shows the 'summer time' in Greenwich Mean Time.

The time of sunrise (red line) and sunset (blue line) for each day of the year. The solid line shows the ‘clock’ time in the UK and has a jump when we switch to British Summer Time. The coloured dotted lines shows the ‘summer time’ in Greenwich Mean Time. The Black dotted lines 8:30 a.m. and 4:00 p.m. typical times for going to and coming from schools.

This shows that when we switch the clocks, instead of giving ourselves extra hours of daylight early in the morning, we choose to give ourselves an extra hour of daylight during summer evenings.

I think this makes sense. Alternatively, we could all just choose to get up a little earlier? Mmmmm.

Sun Spotted in Teddington

January 9, 2014
A picture of the Sun taken on 9th January 2014 from Teddington UK

A picture of the Sun taken on 9th January 2014 from Teddington UK. Click for more detail. Image is courtesy of Peter Woolliams 2014.

The Sun – as you know well – shines night and day, but direct visibility of the Sun has been in short supply in Teddington these last two weeks.

But at break this morning I caught two of NPL’s astronomical gurus sipping lemon tea and enjoying the sunshine streaming through the windows. I sat with them and it felt so good.

We chatted about telescopes and things, and I must have said something amazing because later in the day Peter Woolliams sent me an e-mail with the picture above.

“Michael, inspired by you (and the unusual presence of the sun) I dashed back home at lunchtime to grab the first bit of solar image data for a few months, just caught the sun before the clouds rolled in… and the netbook battery expired…Rapid processing, see attached….”

I was astonished. First of all at the beauty of the image and second at the rapidity with which Peter had got to work. Another colleague joined in a discussion and she sent a me a link to the astonishing Helioviewer site.

At Helioviewer you can look at satellite images of the Sun for any particular moment in the last few years and create your own movies such as the one below. The movie below shows 6 hours of images (not much happens) but it is astounding nonetheless – especially when you notice the scale image of the Earth in the lower left corner.

And so I found myself wondering which image to be more moved by: the breathtaking Helioviewer with its movies and whizzy interface, or Peter’s astonishing image – surely the most astounding image produced in Teddington today.

Between the two I would vote for Peter’s, but the winning image of the day is one I can’t share with you: it exists only in my mind.

Inspired by Peter and Andrea Sella I looked out the skylight at Jupiter. Using first binoculars, then a small telescope, and then finally the telescope I bought for Maxwell I saw Jupiter’s disc and its 4 Galilean moons perfectly arranged in a line.

Seeing the image of Jupiter and its satellites which had astonished Galileo, and provided crucial evidence for Newton’s theory of Universal Gravitation, I felt in touch not only with vastness of the universe, not only with my family who I dragged upstairs to see it, but with history too.


How did Peter create the image above?

“Images taken during my lunchbreak (just before the sun vanished behind cloud where it has been for the past few months!). 80mm William Optics refractor with Lunt B600 CaK filter onto a DMK41 mono camera. 600frame stacks processed in Autostakkert, post processed in Registax6 (wavelets and gamma stretch), Microsoft ICE (to stitch the disk together from 2 images) and GIMP to colorize. AR1944 is very complex and generated an X class flare yesterday. The sun is very low in the sky so higher magnification images were impossible, it’s nice to see the sun putting on a good show given all the warnings of it being past Solar Maximum!”

Telescope for Christmas?

January 3, 2014
Did you buy a telescope like this for Christmas? Well please don't expect to ever see images like the ones shown.

Did you buy a telescope like this for Christmas? Well please don’t expect to ever see images like the ones shown.

A few years ago I bought a telescope for my son: Sorry Maxwell, it wasn’t Santa Claus.

I bought a decent model, a Meade ETX-80, which had a mount that could automatically track stars and conveniently packed away into a special back-pack. It cost about £300.

It was easily the most expensive piece of optics I had ever bought, costing even more than my spectacles. But despite all my knowledge, and all the reviews I read, I really didn’t have any idea what I would be able to see.

Looking at terrestrial targets – distant chimney pots and the like – the telescope was astounding. It was easy to see insects on bricks 100 metres away. But it was all much harder trying to find an astronomical target.

With help from an expert colleague, Maxwell and I managed to attach a web-cam and after many hours we got some nice pictures of the moon. We were really pleased.

But viewing ‘deep space’ objects such as the galaxies shown in the advertisement was impossible. Actually it was possible to just about detect and get a sense of these galaxies. But it was impossible to see these object in anything resembling the detail shown.

It was not really a matter of magnification: it is a matter of faintness. The telescopes just don’t capture enough light, and our eyes are not sensitive enough.

I received the advert on an e-mail from a well-known camera shop, and I imagined such telescopes being bought for children who would then be disappointed. So I just thought I would mention it.

Seeing astronomical objects with your own eyes through a telescope is a transformatively positive experience: I remember buying a £40 telescope from pedlars in Greece a few years ago and watching the moons of Jupiter changing from one evening to the next: I was astounded. And the fact that the light wave which reached my eyes was the same light wave that had left Jupiter a few hours previously was part of the wonder. Seeing it on a screen would not have been the same.

But failing to see astronomical astronomical objects can have a similarly powerful negative experience: confirming one’s anxieties about the difficulty of ‘science’.

My top tip is to buy an astronomy magazine and attend a local astronomy club. In my experience you will find the people a bit ‘odd’: but they will be delighted to let you see what their years of experience have achieved.

Update: For my Birthday, I was given a book on the history of telescopes – An Acre of Glass by J B Zirker. To be honest, it’s not a very well-written book, but I do find the subject interesting and it has many fascinating details which a better-written book might have left out.

The book makes it clear that the last 50 years has seen astonishing progress in astronomical imaging, and this is likely to continue for many decades to come.

But I fear the perfect images of the cosmos which can now be produced routinely have spoiled us. They are beautiful and mysterious, to be sure. But in the same way that an unobtainable super-model can make one’s actual partner seem ordinary, somehow the perfect images which can never be seen directly, make the glimpses of distant galaxies viewed from Teddington seem less astonishing than they should be.

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