Saturday 20 December 2014

'oldest cave art

Thursday, 21 June 2012

'oldest cave art'

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Bristol researchers removing samples for dating from Tito Bustillo Cave, Spain Bristol researchers removing samples for dating from Tito Bustillo Cave
Red discs The El Castillo Cave has numerous red discs on its walls. One was dated to 40,800 years ago

Red dot becomes 'oldest cave art'

A look inside the Altamira Cave in northern Spain
  • Earliest music instruments found
  • Remains are 'earliest Europeans'
  • Ancient 'paint factory' unearthed
Red dots, hand stencils and animal figures represent the oldest examples yet found of cave art in Europe.
The symbols on the walls at 11 Spanish locations, including the World Heritage sites of Altamira, El Castillo and Tito Bustillo have long been recognised for their antiquity.
But researchers have now used refined dating techniques to get a more accurate determination of their ages.
One motif - a faint red dot - is said to be more than 40,000 years old.
"In Cantabria, [in] El Castillo, we find hand stencils that are formed by blowing paint against the hands pressed against the wall of a cave," explained Dr Alistair Pike from Bristol University, UK, and the lead author on a scholarly paper published in the journal Science.
"We find one of these to date older than 37,300 years on 'The Panel of Hands', and very nearby there is a red disc made by a very similar technique that dates to older than 40,800 years.
"This now currently is Europe's oldest dated art by at least 4,000 years," he told reporters. It is arguably also the oldest reliably dated cave art anywhere in the world.
The team arrived at the ages by examining the calcium carbonate (calcite) crusts that had formed on top of the paintings.
This material builds up in the exact same way that stalagmites and stalactites form in a cave.
In the process, the calcite incorporates small numbers of naturally occurring radioactive uranium atoms. These atoms decay into thorium at a very precise rate through the ages, and the ratio of the two different elements in any sample can therefore be used as a kind of clock to time the moment when the calcite crust first formed.
Uranium-thorium dating has been around for decades, but the technique has now been so refined that only a tiny sample is required to get a good result.
This enabled the team to take very thin films of deposits from just above the paint pigments; and because the films were on top, the dates they gave were minimum ages - that is, the paintings had to be at least as old as the calcite deposits, and very probably quite a bit older.
The oldest dates coincide with the first known immigration into Europe of modern humans (Homo sapiens). Before about 41,000 years ago, it is their evolutionary cousins, the Neanderthals (Homo neanderthalensis), who dominate the continent.
Dr Pike's and colleagues' work therefore raises some intriguing questions about who might have authored the markings.
If anatomically modern humans were responsible then it means they engaged in the activity almost immediately on their arrival in Europe.
If Neanderthals were the artisans, it adds another layer to our understanding of their capabilities and sophistication.
Hand stencils The Panel of Hands: Produced by blowing paint over a hand pressed against the wall
The great antiquity of the paintings leads co-author Joao Zilhao, a research professor at ICREA, University of Barcelona, to think the Neanderthals produced the motifs. Finding even older paintings than the red dot at El Castillo might confirm that "gut feeling", he said.
"There is a strong chance that these results imply Neanderthal authorship," Prof Zilhao explained.
"But I will not say we have proven it because we haven't, and it cannot be proven at this time.
"What we have to do now is go back, sample more and find out whether we can indeed get dates older than 42, 43, 44,000.
"There is already a sampling programme going on. We have samples from more sites in Spain, from sites in Portugal and from other caves in Western Europe and so eventually we will be able to sort it out."
Tracing the origins of abstract throught and behaviours, and the rate at which they developed, are critical to understanding the human story.
The use of symbolism - the ability to let one thing represent another in the mind - is one of those traits that set our animal species apart from all others.
It is what underpins artistic endeavour and also the use of language.
  • Earliest music instruments found
    25 MAY 2012, SCIENCE & ENVIRONMENT
  • Remains are 'earliest Europeans'
    02 NOVEMBER 2011, SCIENCE & ENVIRONMENT
  • Ancient 'paint factory' unearthed
    13 OCTOBER 2011, SCIENCE & ENVIRONMENT
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  • Colourful ancient art 'is alive'
    28 DECEMBER 2010, SCIENCE & ENVIRONMENT
  • New method used to date cave art
    07 OCTOBER 2008, BRISTOL
  • Neanderthal 'face' found in Loire
    02 DECEMBER 2003, SCI/TECH


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solstice

Winter solstice as seen from Stonehenge

Winter solstice at Stonehenge.
Winter solstice at Stonehenge.
At Stonehenge in England on the northern winter solstice, people watch the sunrise and sunset. Learn more and see photos here.
Many travel each year to Stonehenge in England – perhaps the most famous of the ancient astronomical monuments found around the world – to be present on the day of the northern winter solstice. (The 2014 December solstice occurs on December 21 at 23:03 UTC). Most who travel to Stonehenge visit the site early in the morning, to watch as the sun rises above the stones. In 2013, according to the BBC, about 3,500 people visited Stonehenge on the morning of the winter solstice. That’s fewer than the BBC reported in 2012 (that year, they said, there were 5,000 visits, which is about the maximum the area can hold for winter solstice festivities, due to winter parking concerns).
Winter solstice visits to Stonehenge apparently always bring fewer visitors than at the summer solstice, when parking can be provided in fields around the site, and when 20,000 to 30,000 people typically turn up for the celebration.
EarthSky Facebook friend Buddy Puckhaber of South Carolina took this photo of Stonehenge in the early morning, while visiting. He said,
EarthSky Facebook friend Buddy Puckhaber of South Carolina took this photo of Stonehenge in the early morning, while visiting. He said, “My wife and I were among the first visitors of the day.” Thank you, Buddy!
Another beautiful shot of Stonehenge from our friend Buddy Puckhaber. Thank you, Buddy.
Another beautiful shot of Stonehenge from our friend Buddy Puckhaber. Thank you, Buddy.
Stonehenge is carefully aligned on a sight-line that points to the winter solstice sunset (opposed to New Grange, which points to the winter solstice sunrise, and the Goseck circle, which is aligned to both the sunset and sunrise).
It is thought that the winter solstice was actually more important to the people who constructed Stonehenge than the summer solstice. The winter solstice was a time when most cattle were slaughtered (so they would not have to be fed during the winter) and the majority of wine and beer was finally fermented.
Winter solstice sunset at Stonehenge in the mid-1980s. Image via Wikimedia Commons.
What is special about the winter solstice sunrise and sunset? For the Northern Hemisphere, the December solstice marks the sun’s most southerly point on the celestial sphere, the imaginary sphere of stars surrounding Earth. It is sun’s southernmost sunset and thus marksa turning of the year, from decreasing daylight to increasing daylight, for us at northerly latitudes.
This Stonehenge monument – built in 3,000 to 2,000 BC – shows how carefully our ancestors watched the sun. Astronomical observations such as these surely controlled human activities such as the mating of animals, the sowing of crops and the metering of winter reserves between harvests.
When Stonehenge was first opened to the public it was possible to walk among the stones – even climb on them.
The stones were roped off in 1977 as a result of serious erosion. Today, visitors to the monument are not permitted to touch the stones, but, if you go, you will be able to walk around the monument from a short distance away.
Visitors can also make special bookings to access the stones throughout the year.
Comet PANSTARRS above the Stonehenge monument in March, 2013. Image via Simon Banton
Comet PANSTARRS above the Stonehenge monument in March, 2013. Image via Simon Banton
Bottom line: The Stonehenge monument in England is a popular winter (and summer) solstice sunrise gathering place. In 2014, the winter solstice happens on December 21 at 23:03 UTC).
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Friday 6 June 2014

e formed the Moon

Traces of another world found on the Moon

Pallab GhoshBy Pallab GhoshScience correspondent, BBC News
Out of media player. Press enter to return or tab to continDr Caroline Smith of the Natural History Museum in London explains the indications of the planet believed to havn

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Researchers have found evidence of the world that crashed into the Earth billions of years ago to form the Moon.
Analysis of lunar rock brought back by Apollo astronauts shows traces of the "planet" called Theia.
The researchers claim that their discovery confirms the theory that the Moon was created by just such a cataclysmic collision.
The study has been published in the journal Science.

“Start Quote

It was getting to the stage where some people were suggesting that the collision had not taken place”
Dr Daniel HerwartzUniversity of Cologne
The accepted theory since the 1980s is that the Moon arose as a result of a collision between the Earth and Theia 4.5 billion years ago.
Theia was named after a goddess in Greek mythology who was said to be the mother of Selene, goddess of the Moon. It is thought to have disintegrated on impact with the resulting debris mingling with that from the Earth and coalescing into the Moon.
It is the simplest explanation, and fits in well with computer simulations. The main drawback with the theory is that no-one had found any evidence of Theia in lunar rock samples.
Earlier analyses had shown Moon rock to have originated entirely from the Earth whereas computer simulations had shown that the Moon ought to have been mostly derived from Theia.
Alien origin
Now a more refined analysis of Moon rock has found evidence of material thought to have an alien origin.
MoonOne mystery replaced by another: Traces of Theia have been found on the Moon but its composition is very similar to that of the Earth
According to the lead researcher, Dr Daniel Herwartz, from the University of Goettingen, no-one has found definitive evidence for the collision theory, until now.
"It was getting to the stage where some people were suggesting that the collision had not taken place," he told BBC News.
"But we have now discovered small differences between the Earth and the Moon. This confirms the giant impact hypothesis."

“Start Quote

What you are looking for is a much bigger difference, because that is what the rest of the solar system looks like”
Prof Alex HallidayOxford University
But the difference, some say, could be explained by material absorbed by the Earth after the Moon formed.
And Prof Alex Halliday of Oxford University, is among many scientists who are surprised that the difference between the Theian material found in the Moon rock and the Earth is so small.
"What you are looking for is a much bigger difference, because that is what the rest of the Solar System looks like based on meteorite measurements," he said.
Dr Herwartz measured the difference in what is called the isotopic composition of the oxygen contained in rocks on Earth and Moon rock. This is the ratio of different forms of oxygen.
Studies of meteorites from Mars and the outer solar system show that these ratios are markedly different - rather like a fingerprint. So Prof Halliday and others are puzzled by the fact that the fingerprints of Earth and Theia seem almost identical.
Similar composition
One possibility is that Theia was formed very close to the Earth and so had a similar composition. If that was the case, it raises the possibility that the assumption that each planet in the current Solar System has a markedly different fingerprint needs to be revisited, according to Prof Halliday.
"It raises the question of how well the meteorites from Mars and the asteroid belt in the outer Solar System are representative of the inner Solar System? We do not have samples from Mercury or Venus.
"They may well be similar to the Earth. If that is the case then all the arguments over the similarities of the Earth and the Moon fall away," he told BBC News.
Astronaut on MoonRock and roll: it's taken more than 40 years to discover traces of Theia in samples collected by the Apollo astronauts
Dr Mahesh Anand from the Open University described the research as "exciting" but noted that the data was from just three lunar rock samples.
"We have to be cautious about the representativeness of these rocks of the entire Moon, and so further analysis of a variety of lunar rocks is required for further confirmation," he said.
Other theories have been proposedto explain why the composition of the Earth and Moon are so similar: one is that the Earth spun much faster before impact, another is that Theia was much larger than current models suggest.
An alternative, controversial, theory proposed by Prof Rob de Meijer of Groningen University in the Netherlands is that the Earth's crust and mantle was blown into space by an accumulation of nuclear material 2,900km (1,800 miles) below the surface. It was this debris that clumped together to form the Moon.
He told BBC News that the new finding - demonstrating that there was a difference in the composition of the Earth and the Moon - did not change his view.
"The difference is too small," he said. "We don't know how the Moon was formed. What we need are manned missions to the Moon and a search for rocks deeper under the lunar surface, that have not been polluted by meteorite impacts and the solar wind."
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Monday 17 February 2014

jet stream

Wavier jet stream 'may drive weather shift'

Pallab GhoshBy Pallab GhoshScience correspondent, BBC News, Chicago
Pallab Ghosh: "We may have to get used to winters where spells of weather go on for weeks - or even months"

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The main system that helps determine the weather over Northern Europe and North America may be changing, research suggests.
The study shows that the so-called jet stream has increasingly taken a longer, meandering path.
This has resulted in weather remaining the same for more prolonged periods.
The work was presented at the annual meeting of the American Association for the Advancement of Science (AAAS) in Chicago.
The observation could be as a result of the recent warming of the Arctic. Temperatures there have been rising two to three times faster than the rest of the globe.
According to Prof Jennifer Francis of Rutgers University in New Jersey: "This does seem to suggest that weather patterns are changing and people are noticing that the weather in their area is not what it used to be."

“Start Quote

We can expect more of the same and we can expect it to happen more frequently”
Prof Jennifer FrancisRutgers University
The meandering jet stream has accounted for the recent stormy weather over the UK and the bitter winter weather in the US Mid-West remaining longer than it otherwise would have.
"We can expect more of the same and we can expect it to happen more frequently," says Prof Francis
The jet stream, as its name suggests, is a high-speed air current in the atmosphere that brings with it the weather.
It is fuelled partly by the temperature differential between the Arctic and the mid-latitudes.
If the differential is large then the jet stream speeds up, and like a river flowing down a steep hill, it ploughs through any obstacles - such as areas of high pressure that might be in its way.
If the temperature differential reduces because of a warming Arctic then the jet stream weakens and, again, like a river on a flat bed, it will meander every time it comes across an obstacle.
This results in weather patterns tending to becoming stuck over areas for weeks on end. It also drives cold weather further south and warm weather further north. Examples of the latter are Alaska and parts of Scandinavia, which have had exceptionally warm conditions this winter.
In the UK, storm after storm has rolled across the countryIn the UK, storm after storm has rolled across the country
With the UK, the US and Australia experiencing prolonged, extreme weather, the question has been raised as to whether recent patterns are due to simple natural variations or the result of manmade climate change? According to Prof Francis, it is too soon to tell.
"The Arctic has been warming rapidly only for the past 15 years," she says.
"Our data to look at this effect is very short and so it is hard to get a very clear signal.
"But as we have more data I do think we will start to see the influence of climate change."
Prof Francis was taking part in a session on Arctic change involving Mark Serreze, the director of the US National Snow and Ice Data Center in Colorado.
He said the idea that changes in the polar north could influence the weather in middle latitudes - so-called "Santa's revenge" - was a new and lively area of research and somewhat controversial, with arguments for and against.
"Fundamentally, the strong warming that might drive this is tied in with the loss of sea-ice cover that we're seeing, because the sea-ice cover acts as this lid that separates the ocean from a colder atmosphere," Dr Serreze explained.
"If we remove that lid, we pump all this heat up into the atmosphere. That is a good part of the signal of warming that we're now seeing, and that could be driving some of these changes."
Chicago 6 JanuaryChicago is now warming after being gripped by frigid polar air in January

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