BBC - Orbit: Earth's Extraordinary Journey

The final post...

2012-03-26T09:00:00Z

The aim of this last post is to essentially thank everyone for participating in our project. We set out, marking our distance through space, every step of the way throughout the year of 2011.

From the early stages of Aonach Mor, bringing you the first video blog from the team on location, to our first call to action for your iwtiness severe weather footage, during the February Scottish storm - several snow storms, tornadoes, monsoon events, tropical storms and aurora's later, we are very grateful for all the footage sent in to help us document Earth's extraordinary journey on this blog.

A selection of the footage can be viewed on the 'severe weather videos' page and remain available to flick through on our 'photography pool' and on the blog. We want to remind you that you can continue to send your up to date severe weather footage and astronomy photos to yourpics@bbc.co.uk where they may form part of future weather and astronomy stories across the BBC.

We also want to thank everyone who joined us on twitter at the beginning with #bbc23degrees and then later with #bbcorbit - the latter hashtag will remain available to you as archive.

For all the comments on the blog posts across the entire production, we thank you for sharing your opinions with us to create an informed series, and raising points worth consideration for future BBC Science projects.

This post as with the three episode posts will remain open for comments until the end of this week, after which commenting on the blog will be closed.

All that is left to say is, Goodbye, and remember that you're hurtling through space at over 100'000 kph.

Orbit: Episode Three

2012-03-18T21:45:00Z

In our journey so far we have explored the impacts of the Earth's Spin and Orbit on the weather and climate.

The final instalment of the series explores the influence of the tilt on the Earth's weather and climate, and how the Earth's relationship with the Sun affects the way we live our lives.

Originally the series was called 23 Degrees, (the angle of the tilt) as we considered this factor extremely significant to the variability in seasons our planet experiences. Although the series is now called Orbit, the tilt of the Earth continued to be an extremely important factor of the series. What do you think?

From the arrival of spring in the Hay river to the affects of the monsoon to the people in India, we wanted to uncover how Nature and culture respond to the variations in the Sun's energy.

Kate takes us through the ancient archeological site Chichen Itza, Yacatan region of Mexico. At its peak, in the 10th century AD it was a thriving city that sprawled over 25 square kilometres and was home to more than 40000 people.

We wanted to explore how ancient civilizations had developed a great understanding of our Earth's journey around the Sun, and Kate takes us there on a significant day; the March Equinox. How significant are sites such as temple of Kukulkan and Stonehenge to us today?

In this episode we also wanted to breakdown the key factors that drive the extremes of weather like the Monsoon, Dust storm and the Tornado.

Helen travels to Kerala, South of India to discover what drives the Monsoon and visits Tornado Alley with atmospheric Scientist Josh Wurman to explain 'What causes a tornado?'

A record six EF-5 tornadoes were confirmed in 2011, the most deadly being Joplin Missouri tornado (158 killed, 14 mile path length.)

What do you think about Episode three? How significant do you think the Earth's tilt is to our climate and weather? How far are we in understanding why one supercell drops a tornado and another doesn't? Has our cultural relationship with the Sun changed over time? Leave your comments on this post.

Orbit: Episode Two

2012-03-11T21:30:00Z

The second instalment of the series follows the Earth's journey from the start of January to the Spring Equinox in March. Available on iplayer. What did you think?

Kate begins the film on a day with a very significant point in our Earth's journey - Perihelion. Kate climbs Aonach Mor mountain, one of the highest mountains in Scotland, which brings her as close to the Sun as she'll ever be for the entire year.

This however is not because of where she is but because of the point the Earth has reached in its orbit around the Sun. In fact we kick started our blog on this day just over a year ago, when we explored the elliptical shape of our planet's orbit and how significant this was to our understanding of Earth's climate.

Later in the film Helen explains how the proximity of the Earth to the Sun doesn't guarantee warmth - which brings us to the tilt of the Earth (23.4 degrees) - a theme we explore in further detail in episode three.

Throughout this episode Kate and Helen explore the increase in solar radiation and how land and ocean respond to it.

Kate drives over a frozen lake in Canada with an ice road trucker in one of the coldest places in that region and learns how important this ice formation is to connecting communities.

In this film we also tackle ice ages and how over time, as Earth has repeated it's annual journey, it's climate has changed.

Helen dives under water in Belize to discover how sea levels have risen and fallen over time due to ice age - and explores the three cycles that need to be right in order for another ice age to exist.

What did you think of episode two?

(There are a total of three episodes in this series)

Orbit - Episode One

2012-03-04T22:00:00Z

The first episode of Orbit aired on BBC Two, 4th March 9pm, and is now available to watch on iplayer. What did you think?

In the first episode we travel from July - the height of summer in the Northern Hemisphere - to December, and the darkest days of winter. As well as following the seasonal change from summer to winter, the film explores one of the most everyday but significant aspects of our journey around the Sun - the fact that the Earth is spinning on its axis.

We start just inside the Arctic Circle in northern Norway, on a special day. We wanted to film the day when the Sun set for the first time in more than two months - an evocative moment that captures both the seasonal change from summer to winter, and the importance of the Earth's daily 24 hour cycle.

Through this film we wanted to find events which highlighted the importance of the Earth's spin. So Helen goes hurricane chasing to show how the Earth's spin sets weather systems rotating.

Hurricanes was a great way to highlight spin and last years season provided many events to explore - an Atlantic season which some argued was unusual.

Another way we wanted to explore spin was by visiting a place which has the biggest tides in the world. Kate travels to the Bay of Fundy in Canada to show how tides too are a consequence of the Earth's spin.

Whilst back home, Helen uses the Earth's spin to explain why Britain's winter weather is so unpredictable and changeable.

UPDATE 16:00 5th March: We've had a lot of feedback on twitter with a number of viewers asking why Episode One was not available simultaneously on BBC HD.

The HD Channel tries to promote the best of the portfolio of BBC Channels, but invariably, this can at times lead to clashes in simulcasts - this was the case with the 9pm Sunday slot, where they have been simulcasting the BBC 3 series 'Being Human' for some weeks now. 'Orbit' however has been given a peak repeat slot, on Fridays at 21:00 from the 16th March.

Other comments raised on twitter discussed the set up of having two presenters, and both female at that, which all in all seemed to be well received.

Not everyone was impressed however with all that Episode one had to offer, and, with such a landmark series as this, that was to be expected.

So, what did you make of Episode one? Leave a comment on this post.

(There are a total of three episodes in this series. Episode Two on BBC Two 11th March, 9pm.)

New series title! Orbit: Earth's Extraordinary Journey

2012-02-14T11:30:00Z

We have finally decided on the title of our series. So long '23 Degrees' and hello 'Orbit: Earth's Extraordinary Journey'.

23 Degrees was always the working title and with this change we're just about wrapping up.

Look out for more updates. What do you think about the title?

Day 365: We're on our way back out again

2011-12-31T15:00:00Z

(Phil Plait is an Astronomer and Author who writes the Bad Astronomy blog for Discover Magazine. His blog is dedicated to clearing up public misconceptions about astronomy and space science in the media. After working for ten years with the Hubble Space Telescope team at NASA Goddard Space Flight Center he went on to work on astronomy education. Phil has appeared on numerous TV and online astronomy features. Here Phil celebrates Perihelion which is just a few days away, and the point when 23 Degrees started it's project a year ago. Phil can be reached @badastronomer)

Distance travelled ~ 938'107'200 km

The Earth travels 'round the Sun at the terrifying speed of 30 kilometers per second, making a gigantic circle nearly a billion kilometers in circumference once per year.

That's a fantastic distance, but in one way it's a bit disappointing. After all, a year after you started this high-velocity trip, you're back where you started.

However, the journey isn't actually a perfect circle. It's off by a tiny amount, so slight that you'd never notice if someone didn't tell you. But in fact, this minor deviation can make a big difference: it means that the Earth's distance from the Sun changes over its orbit to the tune of over 5 million kilometers!

That difference amounts to about 3.4% of the average distance to the Sun, which astronomers, for convenience, call an Astronomical Unit, or AU. In real terms, an AU is 149,597,870 km plus a bit. When the Earth is at aphelion - its farthest point from the Sun - it's about 152,141,000 kilometers from our star. At perihelion, that distance shrinks to 147,055,000 kilometers.

Aphelion occurs on one side of the Earth's orbit, and perihelion on the other. It takes the Earth half a year to travel that distance, of course, so in a sense it drops toward the Sun by 5 million kilometers in about 182.5 days - an average velocity of well over 1100 km/hr.

And my teachers told me I'd never go anywhere.

You might expect this change in distance to the Sun would have an effect on the Earth's temperature. It does, in fact, but it's pretty small, only a couple of degrees Celsius. That's swamped by the seasonal change in temperature due to the Earth's tilt, which is what really drives the seasons. Think of it this way: the Earth reaches perihelion in January, which is the dead of winter for the northern hemisphere. While this does make northern winters a tad more clement, the amount is too small to make an appreciable difference.

Oddly, for those in the antipodes of the southern hemisphere, we're closest to the Sun in their summer. You'd expect temperatures then to be higher than average, but in reality they're about the same as their boreal neighbors. Why is that? It's because the southern hemisphere is dominated by the Pacific Ocean, and water is an excellent heat sink. It absorbs the extra heat in the summer, and releases it in the winter, mitigating temperature extremes.

Weather, it turns out, is complicated.

There is one measurable effect, though: the size of the Sun changes by that same 3.4% over the course of half a year. You'd never suspect that by eye - of course, looking at the Sun is not a suggested pastime - but if you carefully take pictures of it over the course of the year you'll see it, as astronomer Anthony Ayiomamitis did in the picture here. Since the change is slow day-by-day it's beneath our notice, but the telescope doesn't lie.

Credit: Anthony Ayiomamitis

So when is the next perihelion? Why, it's January 5, 2012, and it will occur at about 01:00 GMT. At that moment, or thereabouts, the Earth will again be as close to the Sun as it will get all through 2012. The 23 Degrees project started on the day of Perihelion for 2011 and we're already on our way back out, and on July 5, at 04:00 GMT, the Earth will reach the apex of its orbit, and oh so slowly start the fall back toward the Sun.

And it will do this, over and over for the next few billion years, until the Sun swells into a red giant and cooks the Earth like a banger in a blowtorch.

So enjoy the ride while you can.

Day 364: Mt. Rainier's incredible cloud shows make 2011's Seattle rains worth it

2011-12-30T09:00:00Z

(Scott Sistek is a meteorologist and producer for KOMONews.com. He has been producing weather reports for broadcast and the web since 1994 and can be found on the 'Partly to Mostly Bloggin' weather blog. Keep up to date with Scott via @scottSKOMO)

Distance travelled ~ 934'891'200 km

The Pacific Northwest is known for its beauty, from the lush greenery to the tranquil waters to the majestic mountains. But no mountain is as iconic to the Northwest as Mt. Rainier, which stands just over 14,000 feet tall about 70 miles southeast of Seattle.

But while the Seattle area is world famous for its rainy, cloudy weather, at times, Mt. Rainier can act like its own paintbrush and using the sky as its canvas, bring a whole new awe-inspiring level to a "cloudy" sky. Thanks to it's status as the tallest peak around and its unique position to catch the moist jet stream, it flows in off the Pacific Ocean - Mt. Rainier can create its own weather patterns.

Perhaps the most dramatic are its frequent lenticular cloud displays. Seen maybe a dozen times a year, it still looks amazing every time it's showcased.

The cloud is formed when warm, moist air runs into the surface of Mt. Rainier. The mountain's topography forces the air upward, which cools and condenses the air -- turning it into a cloud. As the air sinks back on the other side of the mountain, it dries out and the cloud dissipates. That's why it just hangs over or near the summit area. (Although it looks like it is "hanging" over the mountain, air is continually flowing over the summit.)

Sometimes if the atmospheric set up is just right, you can get layers upon layers of stacked lenticular clouds that combine to make dramatic shapes -- many times mistaken for UFOs years ago.

Image credit: David Embrey

Locals have used this cloud as a sign that rainy weather is on the way -- many locals might think the cloud is the mountain's version of an umbrella? -- as that cloud usually occurs with west or southwesterly flow in the upper atmosphere, a usual precedent to rainy weather. However, that's not always the case -- especially in the summer. Then, it can just be an indication that we have a good westerly, marine flow and that it won't be too hot anytime soon.

Or on rare occasions, the mountain can have the opposite effect, as seen here:

Image credit: John Meadows

This time, the mountain caused some turbulence that created some sinking air in the vicinity of the mountain peak. Sinking air dries as it does so, in essence "eating" away a hole in the cloud!

Finally, when the mountain isn't creating or destroying clouds, it can just put on a show using the clouds that are already there.

In the autumn and early winter in the Seattle area, the Sun's position on the horizon during sunrise is just in the exact right spot to where Mt. Rainier will cast a shadow against a cloud layer!

Image courtesy of Nick Lippert/YouNews

So while yes, it rains a lot around here, there are plenty of advantages to living in an area with such unique terrain and meteorology!

Day 363: Two things have stood out this year

2011-12-29T09:00:00Z

Distance travelled ~ 932'318'400 km

It’s very liberating to be completely and utterly soaked by a rainstorm, especially when what’s falling out of the sky are raindrops the size of large peas.

I tried to explain this to the director and crew who were huddled beneath enormous umbrellas, missing out on all the fun. They were not convinced. They had not come to India during the monsoon to get wet. That was my job.

The thing is, weather is fun. We are brought up to hide from it a bit, to carry on (usually with a British stiff upper lip) in spite of it. But it’s not going away, so I think that we might as well appreciate it. As long as it’s not giving you hypothermia or sunburn, why not just play with whatever the atmosphere is doing today?

For 23 degrees, we’ve been lucky enough to travel to some fantastic places in our global weather patterns. Different parts of the planet receive different amounts of energy from the Sun, and this is just the start. That energy is carried around the planet by the ocean and atmosphere, and the result is a giant pattern of hot and cold air, dry and moist air and huge swirling wind systems. The pattern is never exactly the same from one year to the next, but there are features that are present all the time (tropical thunderstorms and the jet stream), or that return every year (spring showers and hurricanes).

Two things have stood out for me. The first is how little we appreciate the depth of the atmosphere. I realized this properly while looking at the tornado we found in June.

It’s almost certainly the biggest thing I’ve seen whose scale I’ve been able to understand. We know that the clouds are high up, but until you see a single thing joining the clouds to the ground, you have no idea what “high up” means. The atmosphere is big, vertically as well as horizontally.

The second thing is how little we actually look at the sky, especially in Britain. We’re too busy getting on with things on the ground, and anyway there are lots of buildings and trees in the way. Above us thousands of tonnes of nitrogen and oxygen are flowing around, carrying water and energy, and all we do is complain about it when it gets uncomfortable down here. But if you look up, you can usually see some of the structure of the atmosphere, and that gives you a hint about the larger scale patterns that cover our continent and our planet. Next time you look up at the sky, imagine how all this is connected to the weather over Iceland and Morocco and Costa Rica.

The last day of filming for this series was on the south coast of England, near Beachy Head. We haven’t done that many days filming in the UK, and it was as though the weather was determined to prove that it shouldn’t have been neglected.

As the day went on, we had incredibly hard rain followed by hail, very strong winds and occasional spells of sunshine. My boots filled up with water and at the end of the day I felt as though I’d been in a giant washing machine for a few hours. It was impossible not to be impressed by what the atmosphere was up to, even on our own doorstep.

Day 362: Global perspective

2011-12-28T09:00:00Z

(Peter Gibbs is a BBC weather forecaster and appears as an expert meteorologist on "The Weather Show" for the BBC News channel. He started his first guest blog post for 23 degrees with 'What would happen if the Earth spun the other way' and provided much food for thought with his post on 'Abundance in fruits indicator to past British weather'. His post on 'What's in a name' cleared some misunderstandings that where flying around the web as remnants of hurricane Katia stirred it's way to the UK, and he provided us with a breakdown of the difference between cyclones, typhoons and hurricanes with his post on Cyclone Yasi. Keep up to date with Peter Gibbs - @peterg_weather)

Distance travelled ~ 929'745'600 km

It may seem surprising, but weather forecasters need to take a rather parochial view of the world. At an airport, the forecaster has to predict cloud base, visibility, wind speed and direction in great detail over a few hours for a very specific location. Even a forecaster with a national brief will tend to concentrate only on the weather systems moving across that country and give no more than a passing glance to the storm spiralling across neighbouring areas.

One of the advantages of working as a weather broadcaster on BBC World is that I get to see the whole picture and can begin to understand the interactions of the global weather system with its regular seasonal pulse. A group of thunderstorms produces newsworthy rainfall as it tracks westwards across equatorial Africa, grows into a hurricane over the tropical Atlantic to threaten east coast America, then gets caught up by the jetstream and races across the north Atlantic to bring rain and gales to northwest Europe, passing through several forecast jurisdictions en route.

Other rhythms overlay the annual one. Swings from El Nino to La Nina take place over periods of several years and enhance or diminish normal seasonal features, especially rainfall. 2011 has been mostly a La Nina year,

with unusually warm water washing into the western side of the Pacific. The extra atmospheric moisture this provided was the likely cause of January deluges in Sri Lanka and the Philippines, as well as the extraordinary flooding in Queensland where an area the size of France and Germany was underwater for a time.

Continental landmasses tend to produce the biggest temperature contrasts and hence the most violent weather, especially during the transitional periods of spring and autumn. April 2011 was a record month for tornadoes in the USA with an estimated 600, smashing the previous April record of 257 and even beating the all time monthly record of 542, set in May 2003. Arctic air pushed further south than usual, meeting air from the exceptionally warm waters of the Gulf of Mexico and combining with a jetstream pushed unusually far south by La Nina.

As the Atlantic warmed, an active hurricane season was expected and the predictions were spot-on with a total of 19 named storms, of which seven became hurricanes including three major hurricanes of category 3 or above. Surprising then, that we had to wait for a record eight tropical storms to come and go before our first hurricane. But once formed, hurricane Irene made the biggest impact, passing through the islands of the northern Caribbean before becoming the first landfalling hurricane in the USA since 2008.

La Nina was in the dock again as the likely culprit when weeks of heavy rain produced some of the worst floods on record in Thailand. The monsoon season started early and finished late, meaning there were even greater volumes of water than usual flowing from the mountainous north to the low-lying plains of the south.

Having a global perspective makes me even more appreciative of our UK climate. The British Isles are at the crossroads of European weather. Atlantic winds are a moderating influence, while the proximity of continental Europe can provide bigger swings from hot to cold. Last December found me gliding on Nordic skis across the snowfields of Berkshire, while this December the Christmas journeys to friends and family will be easier on roads kept clear of snow and ice by mild westerlies. There is the excitement of the occasional mid-latitude depression or summer thunderstorm, but without the devastation of hurricanes and monster tornadoes.

Meteorological variety without the jeopardy. If you have to be a parochial forecaster, the UK isn't such a bad place to be.

Day 361: An extreme year for the United States

2011-12-27T09:00:00Z

(Jason Samenow is the Washington Post's weather editor. He founded Capitalweather.com in early 2004, the first weather blog on the web which was absorbed by the Post in 2008. He can be reached via @capitalweather)

Distance travelled ~ 927'172'800 km

A strong case can be made that 2011 was the most extreme weather year on record in the U.S. In addition to the record of at least 12 weather events that produced more than $1 billion (U.S.) in damages (totaling more than $52 billion), never has a larger percent of the country dealt with either extreme drought or abnormally heavy precipitation.

The U.S. contended with virtually every kind of weather hazard including mega snowstorms in the Midwest and Northeast, historic flooding of the Mississippi and Missouri rivers, devastating wind and flood damage from tropical weather systems (Irene and Lee) in the East, and one of the worst spring tornado seasons in memory. The tornado outbreaks that ravaged the central and southern U.S. between April and June resulted in more than 500 deaths, tied second most on record. Several exceptionally strong tornadoes struck densely populated areas including Birmingham and Tuscaloosa in Alabama as well as Joplin, Missouri.

Perhaps the most notable weather to afflict the U.S. was the devastating combination of extreme heat, drought, and wildfires in the South Central U.S. Texas was particularly hard hit. Exceptional drought gripped almost the entire state and groundwater, lake, and reservoir dropped to historic lows. The state suffered its worst wildfire season, with more than 4 million acres burned. In July, neighboring Oklahoma's average temperature was the hottest of any state in 130 years of U.S. weather records, a searing 88.9 degrees.

Undoubtedly, the moderate La Nina pattern set the stage for the unusually volatile weather conditions across the U.S. It helped fuel the powerful jet stream slicing through the middle of the country, bringing the onslaught of stormy weather. But to the south and southwest of that jet stream, a stifling heat dome blossomed and the moisture abruptly shutoff leading to historic drought.

Although global warming should not be blamed as the root cause of this punishing set of weather conditions, it very likely amplified the sharp contrasts in this pattern. The added heat in the atmosphere presumably juiced up the wet extremes by making more water vapor available, while speeding up evaporation and drying in drought areas.

Day 360: What a year it has been...

2011-12-26T09:00:00Z

Distance travelled ~ 924'600'000 km

23 Degrees is coming to an end, but what a journey it has been and what a year.

Coming into this project we didn't have any expectations, well I didn't anyway. I think we all appreciate that it's hard to predict the weather. The most extreme tornadoes in the US mid West, huge cyclones like Yasi hitting Australia, record snows in the US and the UK. Our mission when we set out on 3rd january 2011 (the day of Perihelion) was to tell the story of Earth's annual journey around the Sun.

So what has this year's weather shown us?. That's a really difficult question.

Making 23 Degrees has had a huge impact on me, I have learnt how our climate and our weather is all generated by our orbit around the Sun. It's all interconnected. It really does feel like a huge single organism where everything is linked to create our extraordinary world. I have always liked James Lovelock's idea of Gaia, the Earth as a single organism and seeing how land , sea and atmosphere all interact powered by the Sun has made me want to look into Gaia more.

It has been a real privilege to work on this series and get a glimpse of our incredible planet's annual journey. I just hope we humans step closer to more action in limiting the affects we have on our climate.

It would be great to hear which weather events of 2011 stand out for you?

(Keep updated - The series will transmit early 2012)

New Moon on Christmas Eve

2011-12-24T12:00:00Z

Distance travelled ~ 919'776'000 km

Ever wondered why the Moon seems to look different at varying times of the month and sometimes, like today, seems to have totally vanished?

(SORRY SANTA NO FULL MOON TONIGHT...)

(Image courtesy of Dry Icons - http://dryicons.com)

These are questions that perplexed mankind for centuries but the answer is actually not all that complicated.

Image credit: US Naval Observatory/Astronomical Applications Department. What does the Moon look like now?

The first thing to understand is that we see the Moon because it reflects sunlight; turn the Sun off and the Moon would to all intents disappear from view.

While the Earth is spinning and orbiting around the Sun, the Moon is orbiting around the Earth, completing one orbit in 27.3 days. Its actually more accurate to say that the Moon AND Earth orbit a common centre of gravity called the barycentre which lies inside the Earth but not at its centre. Because the Moon orbits the Earth, and the Earth orbits the Sun its easy to see that the actual angle between the three objects varies throughout the lunar orbit and its this variation that leads to the 'appearance' of the phases of the Moon.

At the start of this blog, I stated that we see the Moon because it reflects sunlight. If the Moon lies opposite the Sun in the sky then we see the fully illuminated portion of the Moon and see a full Moon. If on the other hand, the Moon is between us and the Sun then we see the non-illuminated portion and see a new Moon. Then at various points between we see a varying amount of dark and light portions as the phases change from full to new and back again. Today the Moon is at its new phase which means its in line with the Sun and can't easily be seen without sophisticated equipment.

You might expect that during either a full or new Moon, we should experience a lunar or solar eclipse every month (the Moon blocks sunlight reaching Earth during a solar eclipse and the Earth blocks sunlight reaching the Moon during lunar eclipses) but it turns out that the orbit of the Moon is tilted by about 5 degrees to the orbit of the Earth around the Sun. On most occasions at full or new Moon, the Moon is either just above or just below the Sun or shadow cast by the Earth, making eclipses a little more rare.

Interestingly if you measure the time it takes from one full Moon to the next it takes 29.5 days instead of 27.3! This strange effect is seen because the Earth is independently orbiting the Sun and the Moon has to travel a little further to get back to exactly the same angle as the previous full Moon.

Make your submissions by the end of the year

2011-12-23T17:30:00Z

Distance travelled ~ 917'792'800 km

Who would have thought we'd be closing the submissions for the Flickr group so soon. It's only been a year, right? But that's what it's always been about. Our annual round trip. And sad to say, but 2012 is looking mighty close.

To all who have submitted photos to the pool, the team say a huge thank you! Over two thousand weather and astronomy images have been submitted by a selection of great photographers - photos that will continue to be available to view long after the production ends.

The date you want to remember for the photography pool is 31st December 2011 - as if you'd forget new years eve :-). Submissions after this date will not be able to be made.

I'll leave you with images of the Aurora Australis, acquired by astronauts on board the International Space Station September 11, 2011 as the ISS orbit pass descended over eastern Australia. Magnificent.

Wishing you all a Merry xmas!

The short and long of it - December Solstice

2011-12-22T04:00:00Z

Image credit Stu.bloggs/Flickr

Distance travelled ~ 913'772'800 km

Today sees the shortest day in the northern hemisphere and for southern hemisphere dwellers, the longest day! A peculiar idea to get your head round perhaps but it's all actually pretty straightforward. The cause of the changing length of the 'day' (and by this I mean the hours of sunlight, not a 24 hour period) is the same thing that causes the changing of the seasons and we can look to the orbit of the Earth around the Sun for the answer.

Surprisingly perhaps, its not the Earth's distance from the Sun which brings the colder months to the northern hemisphere in fact, the Earth is closer to the Sun during December than it is in July. We need to look at the axis of the Earth's rotation to understand why we experience seasons and changing quantities of sunlight.

The Earth spins once on its axis every day, to be precise once in 23hours, 56minutes and 4seconds which is why stars seem to rise about 4 minutes earlier every day. The axis that the Earth spins around is tilted with respect to its orbital plane around the Sun by just over 23 degrees. During a northern winter, the northern hemisphere is pointing away from the Sun and during the northern summer it's pointing toward it. The opposite is true for the southern hemisphere. This all means that during the northern hemisphere winter, there are less hours when the Sun is above the horizon, indeed around the north pole, there are 6 months of it while the southern pole is basking in 6 months of sunlight.

The exact amount of sunlight we receive at any place on Earth is determined by its latitude. The further away from the equator, the less light is experienced during winter. Even small differences in latitude make a big difference to number of daylight hours for example, London will today experience just 7 hours 49 minutes of sunlight whereas the north of Scotland will experience 6 hours 35 minutes, over an hour of difference. What this means astronomically is that the Sun reaches its southernmost point in the sky today which we call the Winter Solstice, more precisely at 05:30 GMT (or UT - Universal Time). This corresponds to the Sun being overhead at local noon at the Tropic of Capricorn in the Southern Hemisphere.

System in Atlantic rapidly develops - Scotland braced for 90mph gusts

2011-12-07T15:30:00Z

Distance travelled ~ 876'413'600 km

The depression is expected to bring gales and heavy rain from the west for Thursday.

Snow is likely for a time on Thursday morning across parts of central and northern Scotland, particularly affecting higher ground, but with some slushy deposits locally to lower levels, and all parts of the UK will have heavy rain for a time during the day.

But the main feature of this depression is the gale to storm force winds it will bring. Gusts of 60 to 70 mph likely to become quite widespread across northern and central Britain, but 70 to 80 mph are expected across much of Scotland with 90mph gusts are possible in exposed places, particularly central and southern Scotland. Elsewhere across England and Wales the wind will gusts of 50-60 mph. (Warnings issued by the Met Office)

As the storm passes through and moves away to the east of the UK on Friday north-westerly winds will bring in cold air which will see a drop in temperatures. This is expected to bring snow to northern and western parts of the UK, giving accumulations to low levels in the north. Accumulations will tend to be confined to higher ground across north Wales and much of northwest England. Untreated surfaces will also become icy at times. Other parts of the country will see a cold night on Friday with widespread frost.

The forecast for the rest of the month is for the unsettled weather to continue, with spells of wet and windy weather interspersed with brighter, colder periods when we can expect to see frost and snow showers - the heaviest of any snowfalls are expected across higher ground from North Wales northwards, but we could occasionally see some snow cover at lower levels as well.