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30 July 2012

Frogs rescued from killer fungus have 'massive' brood

Mother mountain chicken frog in nest with eggs The female mountain chicken frog lays its eggs into a special self-made foamy nest
Rare tropical frogs rescued from a killer fungus in the Caribbean have produced a bumper brood in the UK.
The two female mountain chicken frogs responsible for the 76 new additions are part of an attempt to rescue the species from extinction.
All 12 frogs in the UK breeding programme came from Montserrat, where the chytrid fungus has ravaged the population.
"We're absolutely chuffed to bits," said herpetologist, Dr Ian Stephen.
The frogs, simply known as mountain chickens, were rescued as part of the conservation efforts led by the Zoological Society of London (ZSL) and the Durrell Wildlife Conservation Trust (DWCT).

Frog-killer fungus

Dead frog
  • The chytrid disease is caused by the fungus Batrachochytrium dendrobatidis
  • It penetrates the skin of many amphibian species causing lesions which prevent the animals from taking in oxygen, effectively suffocating them
  • According to the Global Bd Mapping Project conducted by Imperial College London, over 500 species have now been recorded as affected by the disease
"The first challenge was getting them out of the Caribbean in to Europe safely," said Dr Ian Stephen, ZSL's Curator of Herpetology.
The frogs were transported in temperature-controlled boxes to protect them and minimise stress on the long and hazardous journey.
"Although the mountain chicken is one of the biggest frogs in the world they're still a small animal so they're incredibly sensitive to temperature fluctuations and that tends to be the thing that would kill a frog during transportation."
"It's obviously quite a hairy moment when you open up the boxes," he said.
The 50 airlifted frogs were split into three groups and housed at ZSL London Zoo, the DWCT in Jersey and at Parken Zoo in Sweden in the hope of growing a healthy population of the species.
Since their arrival, the 12 UK frogs have been living in a bio-secure breeding unit at the zoo, where the eggs were laid.
Mountain chicken females produce a special foam nest into which they lay their eggs. The tadpoles then feed on deliberately unfertilised eggs laid by the female.
Dr Stephen hopes that most of the 76 will survive to adulthood and make a return trip to the Caribbean.
"Because a mountain chicken wouldn't lay hundreds or thousands of eggs like a common frog would in England, for the ones that make it to metamorphosis, you'd hope for a very high success rate."
Tadpoles feeding on unfertilised eggs The mountain chicken tadpoles were fed unfertilised eggs every few days
On Montserrat, mountain chicken frogs face threats from volcanic activity and predation but the biggest threat remains the chytrid fungus.
"It's an incredibly important disease because it's probably the first time where a disease is affecting an entire class of animals."
"It's moving towards driving the extinction of most of the amphibian species across the globe," Dr Stephen told BBC Nature.
The chytrid fungus was spread around the world mainly by people and it is the fear of creating a new epidemic that means in situ programmes tend to be more common these days, Dr Stephen told the BBC.
That is why the frogs are being kept in a bio-secure facility with keepers wearing full paper suits, masks and gloves "like in ET".
"Basically you're trying to prevent any new pathogens coming in to that population," he said.

25 July 2012

‘Stop obscuring the night sky’


Each week a global thinker from the worlds of philosophy, science, psychology or the arts is given a minute to put forward a radical, inspiring or controversial idea – no matter how improbable – that they believe would change the world.
This week the UK's Public Astronomer, Marek Kukula
“If I rule the world I would replace old inefficient street lights all over the planet with modern efficient designs that only put the light where it is needed – down on the streets.
Instead of wasting it by shining it up into the sky where all it does is blot out the stars – that orange glow that mean city dwellers never see a dark sky.
Think of the difference that this would make. We would still have safe, well lit streets, but for the first time in decades people in towns and cities would be able to look up and see the wonder of the night sky. And it would not just would-be stargazers that would benefit. Less wasted light, means less waster electricity, less wasted money and a reduced carbon footprint.
Migrating birds and animals would also benefit – they would be able to navigate more easily using the moon and stars and there is even some benefit that human health would benefit from a more natural cycle of light and dark in urban areas.
So we would see many practical benefits and a natural wonder that should belong to everyone would be restored. I think this would make the world a better place because everyone would have a chance to see the stars and appreciate our place in the Universe.”

19 July 2012

Iceberg breaks off from Greenland's Petermann Glacier

Petermann Glacier
1/3

An iceberg twice the size of Manhattan has broken away from the Petermann Glacier in northern Greenland.
Images from a Nasa satellite show the island breaking off a tongue of ice that extends at the end of the glacier.
In 2010 an ice island measuring 250 square km (100 square miles) broke off the same glacier.
The process that spawns icebergs - known as calving - is a natural, periodic process affecting all glaciers that terminate at the ocean.
A previous calving event at the same glacier in 2010 created an iceberg twice the size of this one.
Scientists have raised concerns in recent years about the Greenland ice shelf, saying that it is thinning extensively amid warm temperatures.
No single event of this type can be ascribed to changes in the climate.
But some experts say they are surprised by the extent of the changes to the Petermann Glacier in recent years.
"It is not a collapse but it is certainly a significant event," Eric Rignot from Nasa said in a statement.
Some other observers have gone further. "It's dramatic. It's disturbing," University of Delaware's Andreas Muenchow told the Associated Press.
"We have data for 150 years and we see changes that we have not seen before," Mr Muenchow added.
The calving is not expected have an impact on sea levels as the ice was already floating.
Icebergs from the Petermann Glacier sometimes reach the waters off Newfoundland in Canada, posing a danger to shipping and navigation, according to the Canadian Ice Service.

13 July 2012

What happened to Hilton’s ‘hotel on the Moon’?

In 1958 the Boulevard Room at the swanky Conrad Hilton Hotel in downtown Chicago offered delicious steaks, a lavish stage show, and a curious peek at the future.
At the front of the grand hall was what was billed as the “largest hotel ice rink in the country”, on which troops of tutu-wearing girls danced for the crowds of diners. It was here, in the summer heat of August that black-tie wearing customers were given the first teaser of a legend that survives to this day: Hilton Hotels was going to the Moon.
On stage, the final scene for the dancers was called “out of this world”. Although details of the performance are scarce, a Chicago-area newspaper called the Suburbanite Economist wrote that it was set in a “plush” hotel called the Lunar Hilton. The lavish show caught the writers’ imagination and he took it to its logical conclusion. As the 27 August 1958 edition put it: “this could mean that the Hilton chain is dickering with the idea of opening the first hotel on the Moon.”
Fast forward to 2009 and an episode of the popular TV series Mad Men features the louche Don Draper and his team creating a fictional ad campaign for a Hilton Hotel on the Moon. “I want a Hilton on the Moon; that’s where we are headed,” says “Connie” Hilton at one point. Although the series is fiction, it got me wondering: had Hilton hotels ever really planned to go into space?
When the writers of Mad Men were researching the programme, their go-to man was Dr Mark Young, who oversees the hotel founder’s archive at the University of Houston. He seemed like an obvious person to shed light on the story.
According to Dr Young, there’s no evidence that Conrad Hilton was behind the vision of a hotel on the Moon. “[The writers of Mad Men] contacted me to learn about Conrad Hilton so I talked with them, but when I watched it this Moon thing came out of nowhere and I thought, ‘wait a minute, that’s not Conrad Hilton at all’.”
In fact, he says, it was one of Conrad Hilton’s sons, Barron Hilton, who appears to have been the true evangelist for a Hilton on the Moon.  “He, like everyone else was very captivated by the space age,” says Dr Young.
‘Earth view’
Barron was elected as vice-president of Hilton Hotels in 1954, serving behind his father. Just four years later the Suburbanite Economist article appeared – the earliest reference to the idea I can find. I expect it will be difficult to find anything much earlier. That was the beginning of space fever in the United States, as the Russians had launched Sputnik in October of 1957, kicking off the Space Age - a period of tremendous fear and wide-eyed hope for what was to come.
Throughout later years, the idea appears again and again in popular culture. In the 28 October 1962 episode of The Jetsons, The Good Little Scouts, George brings Elroy’s scout troop to the Moon and in a quick, fleeting shot we see the Moonhattan Tilton, a clear reference to the Manhattan Hilton hotel. And in  Stanley Kubrick’s classic 1968 film “2001: A Space Odyssey” there is an office marked “Hilton Space Station 5” on the glass exterior, where people could presumably make reservations for the Hilton hotel on the film’s orbiting space station.
Though it wasn’t Conrad’s idea he certainly didn’t discourage the idea of a hotel on the Moon. The March 1963 issue of Cosmopolitan magazine ran a long and glowing profile on Conrad Hilton as the hard-nosed businessman who understood what people wanted and would stop at nothing to give it to them. Though not a quote from “Connie” himself, the article nonetheless ends with a space age promise from the writer: “it won’t be very long before our astronauts land on the Moon and immediately behind them will be Connie Hilton with his plans for his Lunar Hilton Hotel.”
Those plans began to take off in 1967. Barron, who was then president of Hilton, told the Wall Street Journal that he was planning to cut the ribbon at an opening ceremony for a Lunar Hilton hotel within his lifetime. He described the Lunar Hilton as a 100-room hotel that would be built below the surface. Guests would gather around a piano bar in an observation dome that allowed them to gaze back at earth.
Barron’s desire to build a Hilton on the Moon - whether it was merely clever PR or something more sincere - struck a chord with people all over the world. The hotel group even printed promotional “reservations cards” for customers to reserve a hotel room on the Moon. “In the [Hilton] archive we’ve got hundreds, if not thousands, of letters of people writing in to him,” says Dr Young. “They’d seen the picture of the reservation form and they wanted to get their name on there.
“You read the letters, from all around the world - I always remember the one from Pakistan for some reason it stands out in my mind -- but people really wanted to know that sometime in [their] lifetime we’ll have hotels on the Moon.”
‘Freeze-dried steak’
The archive that Dr. Young oversees in Texas also contains promotional Lunar Hilton hotel keys which were distributed as promotional item in hotels. “The idea that we’d have a plastic key card like we do today was - I guess - just way too far out for ‘67, ‘68. And so [the Lunar Hilton key] looks like an old fashioned hotel room key, except it’s sleek,” Dr. Young said.
Just days before the first Moon landings in 1969, the Hilton lunar vision reappeared. Never one to miss an opportunity to sell the idea (or at least the hotel chain), Barron addressed the American Astronomical Society where he once again pressed that Hilton would soon be on the Moon. “I firmly believe that we are going to have hotels in outer space, perhaps even soon enough for me to officiate at the formal opening of the first,” he told the assembled crowd.
With the world gripped by Moon fever, it was an obvious story for newspapers recorded every twist and turn of the space race. For example, an article in the 15 July Lowell Sun in Lowell, Massachusetts picked up on the speech and painted a picture of the hotel of the future. Their story relies heavily on images of food and alcohol pills, an idea we examined here a few months back.
“Imagine yourself in the Galaxy Lounge of the Lunar Hilton - the first hotel on the Moon. In place of a ceiling, a transparent dome allows you to view the heavens as you never could see them from beneath the thick atmosphere covering Earth, Mars looks bigger and redder, the star do not twinkle, and you are just in time to watch an Earth-set,” it reads. “You order a martini. The bartender pushes a button and out comes a pre-measured, pre-cooled mixture of pure ethyl alcohol and distilled water -- 80 proof. Into the mixture he droops a gin and vermouth tablet. As you sip the result, the huge bright-blue Earth slips below the stark, brown horizon and you begin to think about a freeze-dried steak for dinner.”
Clearly, Barron’s vision has yet come to pass, but the idea has never fully gone away. In the late 1990s, the firm backed plans for a private orbiting space station whilst in a separate plan, British architect Peter Inston was commissioned to draw up a plan for a 5,000-room domed structure on the Moon for the hotel chain. As the plans were shown off, the then president of the firm – Peter George – reportedly repeated the hotel’s maxim: “One day soon, there will be hotels on the Moon. The Hilton wants to be the first.”
It’s difficult to know whether successive Hilton bosses actually believe this message or whether, as is perhaps more likely, they have simply hit on perhaps one of the longest and most imaginative marketing campaigns in history. Certainly, Conrad Hilton’s grandson, Steve Hilton, has suggested that it was an idea that was never meant to be taken seriously. Instead, he said in a 2009 interview following the Mad Men episode, that he thought it was meant to be “symbolic”.
Certainly the idea seems to have disappeared in recent years. But the recent surge of commercial activity in space means that perhaps it could soon return. If, and when it does, Hilton may have to compete with another hotelier in the race to the Moon.
In 2006, Robert Bigelow, the former owner of the Budget Suites of America chain, launched an inflatable habitat capsule into space. In 2007 another followed, and his company – Bigelow aerospace – has begun working on a full scale capsule which could, he has said, form the basis of a Moon habitat.
Whether the plan is anything more than an idea worthy of Don Draper, only time will tell.

10 July 2012

Nature's big picture: Rarest snake

The Saint Lucia racer, the rarest snake in the world Conservationists confirm that the Saint Lucia racer is the world's rarest species of snake, with fewer than 18 surviving in the wild. Populations of the small, non-venomous snake suffered rapid declines after mongooses were introduced from India in the late 19th Century. They were actually declared extinct in 1936 but an individual was discovered in 1973. To fully understand the state of the population, an international team of researchers undertook a five month study on the Caribbean island nation. They micro-chipped 11 snakes and are now investigating how to protect the species. "It was a huge relief to confirm that a population of the racer still survives," said Matthew Morton, Eastern Caribbean Programme Manager for Durrell Wildlife Conservation Trust who were involved in the research, "but that relief is tempered by the knowledge of how close we still are to losing it forever."

07 July 2012

Palau: Is it the world's cannabis capital?

Palau
A small group of Pacific islands with the population of a small town has been named as the country with the highest consumption of beer and cannabis. Is that really true?
The United Nations' 2012 World Drugs Report, published in June, contains at least one surprising number - the nation with the highest level of cannabis use among adults is Palau.
This tiny island nation in the western Pacific Ocean is home to just 21,000 people, where - according to the UN - a quarter of adults use cannabis.
Not only are Palauans ahead of everyone else on this measure, they're ahead by a long way. The country with the next highest rate of cannabis use is Italy, where - the report says - some 15% of adults use the drug.
If the idea that Palau is some sort of hedonist's retreat sounds familiar, that may be because the island topped a 2011 World Health Organisation chart examining another vice.
According to the WHO's global status report on alcohol and health, Palauans drink more beer per capita than any other nation in the world.
Beer Cannabis
Source: World Health Organisation, United Nations
Beer - litres of alcohol consumed annually per capita aged 15+
Cannabis - prevalence of use as % of population, 15-64, countries only
Palau
8.68
Palau
24.2
Czech Republic
8.51
Italy
14.6
Seychelles
7.15
New Zealand
14.6
Irish Republic
7.04
Nigeria
14.3
Lithuania
5.60
USA
14.1
So what on earth is going on in Palau? Is it really an island of beer-swilling cannabis smokers?
Let's look at beer drinking first. The WHO report was published in 2011 but it compared data from 2005.

Republic of Palau

President Johnson Toribiong
  • Area: 508 sq km (196 sq miles) of more than 200 volcanic and coral islands
  • Capital: Melekeok
  • Politics: Became independent in 1994 after being run by the US
  • Leader: President Johnson Toribiong (above)
  • Economics: Heavily dependent on US aid. Some tourism. Fishing by foreign fleets contributes to national income
  • International: One of few countries to recognise Taiwan
That's important because, for some reason, Palauans appear to have gone on a drinking spree that year. They simply drank more beer than usual in 2005. In other years, they slide down the chart.
More importantly, perhaps, while Palauans seem to drink a lot of beer, they don't drink much of anything else.
If one looks at the total amount of alcohol consumed - rather than just beer - Palau slips down to 42nd place out of 188. On that measure, the Czech Republic has the dubious honour of occupying the top spot.
The UN's 2012 figures on cannabis use in Palau are more problematic than the WHO's data on beer drinking.
The report's authors could not obtain survey data for adults in Palau. So they used a survey of cannabis use among state high school pupils and extrapolated those results to estimate a figure for the whole adult population.
There is one state high school in Palau, with a student population of 742. The surveyors found that about 60% of the 565 respondents in that school had used cannabis at least once and almost 40% said they had used cannabis in the last month.
Not so much a high school, then, as a really high school. For comparison, a similar survey of schoolchildren carried out in the US found 23% of students say they used cannabis in the last month.
But although the numbers from the Palauan school survey are striking, it is clearly a very small sample, as well as being unrepresentative of the wider population (one might reasonably expect Palauan teenagers to smoke a lot more cannabis than, say, their middle-aged parents).
Map of Palau Koror is one of the most populous islands
Emery Wenty, a director for the Ministry of Education in Palau, simply does not believe the UN's figures.
"Palau is a very small island. If cannabis use is as prevalent as the UN claims," he says, "you would see it and smell it everywhere. You don't.
"You sort of know just about everybody. It's inconceivable that a quarter of the population uses cannabis."
Wenty accepts that cannabis use may be a problem in the Palauan state high school but he points that there are about 500 other high school children in Palau studying in private - and mostly religious - institutions.
He suspects that the data from the state high school is not even representative of all Palauan teenagers, let alone the entire adult population.

The same size as Palau (roughly)

  • Buxton, Derbyshire, UK
  • West Pensacola, Florida, US
  • Alcala, Andalucia, Spain
  • Husum, Schleswig-Holstein, Germany
  • Wenquan Town, Guangdong, China
  • Broken Hill, New South Wales, Australia
Angela Me, a UN statistician who works on the World Drugs Report, accepts some of Mr Wenty's criticisms.
There is a particular problem, she says, with collecting data from very small populations, because a small number of people changing their behaviour can create large swings in the statistics.
She points out, however, that their data - whatever its shortcomings - does suggest there is a relatively high prevalence of drug use in a number of Pacific island nations.
"We are going to have a meeting in the Pacific islands," she says, "where we hope to collect more information and also reduce the margin of error."
It would be wise to wait for the UN to complete its collection of more and better data from the Pacific islands before concluding that Palau really is the booze and drugs capital of the world.

06 July 2012

Whales to gain Panama Canal traffic protection

Humpback whale breaching Satellite-tagged humpbacks show just how often whales cross paths with ships

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Shipping lanes into and out of the Panama Canal are likely to be constrained in order to protect whales.
Humpback whales breed around Las Perlas archipelago 60km (40 miles) from the canal's southern entrance, and are disturbed and even killed by shipping.
Panamanian officials and scientists have developed a plan that would corral vessels into narrow lanes.
They plan to present it for discussion and maybe adoption by the International Maritime Organisation (IMO) next year.
Details of the proposal were presented at the International Whaling Commission (IWC) annual meeting in Panama City.
Hector Guzman from the Smithsonian Tropical Research Institute drew up the plans following research comparing movements of ships with those of 15 humpback whales fitted with satellite tags.
Maps show the whales swimming throughout the Gulf of Panama, which lies outside the canal entrance on the Pacific Ocean side, repeatedly crossing the ships' tracks.
"We recorded 98 interactions between whales and ships during an 11-day period," he told BBC News.
"Just over half of the whales had encounters; one particular whale had 45 encounters in just four days."
An "interaction" was defined as approaching within a distance of 200m - though the area has seen 13 whale deaths in the last two and a half years, some of which were probably as a result of being hit by a ship.
Watching brief Humpbacks migrate northwards from their summer feeding grounds around Antarctica, arriving in the region around late June.
They breed in the fertile Las Perlas waters, where an upwelling of nutrient-rich water produces an annual plankton bloom.
Altogether, about 900 animals are thought to be involved. There are also visitors from a Northern Hemisphere humpback population.
Some 17,000 large ships pass through Panamanian waters each year, the majority international cargo vessels using the canal.
Data shows one particular vessel routinely passing right through the Las Perlas protected area in order to excavate sand from the sea bed and bring it to land for construction.
Panama whales map
Las Perlas is becoming an important area for tourists, with whale-watching trips one of the attractions on offer.
Tomas Guardia, director-general for international organisations with the Ministry of Foreign Affairs and Panama's commissioner to the IWC, said the changes were stimulated both by economic factors and a burgeoning environmental awareness.
"The New York Times selected Panama as their number one tourist destination for 2012; so when you add on an additional activity such as whale-watching, it all helps to promote Panama outside the country," he said.
"Also, many Panamanians were previously not aware of the resource we have close to our city, and in fact one of the reasons for hosting the IWC was to raise awareness of our marine environment."
Channel solutions The government proposes funnelling ships into parallel lanes 65 nautical miles long, one approaching the canal entrance and one leaving it, separated by distance of about 2-3 nautical miles.
Dr Guzman calculates this would reduce the total area of sea where the whales would be at risk of collision by about 95%.
During the whale breeding season, ships would also be obliged to slow down to 10 knots on their way in and out.
Panama shipping lanes infograhic
Similar schemes have been implemented in several US ports, and the IMO has produced an advisory booklet based on the US experiences.
Vessels travelling west along the coast would be constrained into a couple of further corridor sections.
This would push them further offshore than they currently tend to travel, reducing the chance of collision with fishing boats.
"You can imagine; you have these small artisanal fishing boats and these huge vessels - it's just chaos, the way they come in and out of the country," said Dr Guzman.
"So [under the new scheme] they'll have their vessels, they'll be apart from the heavy traffic lanes - more important still is we're increasing the buffer of protection between the mainland and the shipping lanes in a region where we have five different protected areas including World Heritage Sites."
On the northern side of the country on the Atlantic Ocean side, where there is no significant presence of whales, the government is proposing a system involving three separate corridors leading in different directions.
Panama took over ownership of the canal from the US in 1999. The lock system is currently being upgraded, which will see vessels larger than the current 300m-long limit able to pass through.

05 July 2012

Antarctic moss lives on ancient penguin poo

Aerial view of Antarctica's moss Antarctica's moss viewed from above

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Moss plants that survive the freezing conditions of Antarctica have an unusual food source, scientists say.
The vibrant green plants take nutrients from the poo left behind by penguins that lived in the same area thousands of years ago.
Scientists made their discovery whilst testing the plants to find out how they manage to survive in the icy landscape.
The findings were presented at the Society for Experimental Biology's annual meeting in Salzburg, Austria.

Big chill

Frozen sea surrounding Antarctica
  • The cold, dry desert of Antarctica holds the record for the lowest temperatures on Earth
  • To cope with the cold plants dry to a crisp to protect themselves in winter, rehydrating again in the summer
  • Most mammals and birds choose only to visit for the relatively warmer summer months
  • Between October and February Adelie penguin pairs take turns to heat their eggs on nests constructed from stones
Prof Sharon Robinson, from the University of Wollongong in Australia, has been studying Antarctica's plants for 16 years.
She explained that she was interested in where the plants get their nutrients, because the Antarctic soil on which they grow is so poor.
"Plants need water, sunlight and nutrients; there's plenty of sunlight in the summer and as long as the ice melts there's water," she told BBC Nature.
"But the soil is basically sand and gravel."
To find out where the plants were getting the food they needed to grow, Prof Robinson and her team used a technique that allowed them to see all of the chemicals that made up a moss plant.
This "chemical signature" revealed nitrogen that had passed through a marine predator.
"Nitrogen that's gone through algae, krill and fish and then penguins has a characteristic 'seabird signature'," Prof Robinson told BBC Nature.
Since no penguins live on the elevated lakeside site in East Antarctica, the researchers had to work out where the mysterious seabird poo came from.
They realised that their moss beds were growing on the site of an ancient penguin colony.
"Between 3,000 and 8,000 years ago, on the site where the moss is now growing, there used to be [Adelie] penguins," said Prof Robinson.
"There's fossil evidence to support that, and the little pebbles that the penguins use to make their nests are actually still there.
"The other thing that's still there is the penguin poo.
Antarctic moss Six different species of moss live on the islands of East Antarctica studied by the scientists
"And because Antarctica is so cold, those nutrients have just stayed frozen in the soil; they're now feeding this moss."
Prof Robinson said that the hardy plants, which grow just 2-3mm per year, create "luxuriant green beds" that are home to some of the insects and other miniature creatures that manage to live in this frozen desert.
Prof Robinson hopes to learn exactly how they adapt to this extreme environment.
The mosses are able to "freeze-dry" in order to survive the winter and produce sunscreen compounds to protect themselves from UV rays.
"It's amazing that the plants can do [these things], but it's also interesting to know which compounds they use," said Prof Robinson.
Learning the molecular mechanisms behind plants' abilities to dry out but remain viable could help researchers to develop ways to store food or even medicines for long periods.

02 July 2012

Dark energy

Galaxy cluster Abell 2029

About Dark energy

In physical cosmology and astronomy, dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain observations since the 1990s that indicate that the universe is expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for 73% of the total mass-energy of the universe.
Two proposed forms for dark energy are the cosmological constant, a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli, dynamic quantities whose energy density can vary in time and space. Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant is physically equivalent to vacuum energy. Scalar fields which do change in space can be difficult to distinguish from a cosmological constant because the change may be extremely slow.
High-precision measurements of the expansion of the universe are required to understand how the expansion rate changes over time. In general relativity, the evolution of the expansion rate is parameterized by the cosmological equation of state (the relationship between temperature, pressure, and combined matter, energy, and vacuum energy density for any region of space). Measuring the equation of state for dark energy is one of the biggest efforts in observational cosmology today.
Adding the cosmological constant to cosmology's standard FLRW metric leads to the Lambda-CDM model, which has been referred to as the "standard model" of cosmology because of its precise agreement with observations. Dark energy has been used as a crucial ingredient in a recent attempt to formulate a cyclic model for the universe.
Read more at Wikipedia