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Nasa ’should follow Columbus’

Professor Stephen Hawking has called for a new era of space conquest akin to Christopher Columbus’ discovery of the new world.

In a speech honouring Nasa’s 50th anniversary, the 66-year-old astrophysicist said the situation we face “is like Europe before 1492″.

“People might well have argued it was a waste of money to send Columbus on a wild goose chase,” he mused.

“Yet the discovery of the new world made profound difference to the old.”

And then he quipped: “Just think, we would not have a Big Mac or KFC (Kentucky Fried Chicken).

“Spreading out into space will have an even greater effect,” he told an audience assembled at George Washington University, Washington DC.

“It will completely change the future of the human race and maybe determine whether we have any future at all.”

Earth focus

Professor Hawking envisions a long-term space exploration project that would include building an experimental base on the Moon within 30 years.

He said scientists must devise a new propulsion system to take us on a planetary hunt outside our Solar System in 200-500 years.

“If the human race is to continue for another million years, we will have to boldly go where no one has gone before,” argued the theoretician, who is known for his works in cosmology and quantum gravity.

“It will not solve any of our immediate problems on planet Earth, but it will give us a new perspective on them and… Hopefully, it will unite us to face a common challenge.”

The Oxford-born scientist suffers from amyotrophic lateral sclerosis (ALS), a degenerative motor neurone disorder, which has left him almost completely paralysed.

However, a year ago, he was able to get out of his wheelchair and float about in a special plane that simulates the weightless conditions of space.

Rocket ride

He hopes to repeat the experience in space, above the atmosphere, aboard the maiden, suborbital flight of British billionaire Richard Branson’s Virgin Galactic rocket plane. The vehicle is expected to start commercial flights before the decade’s end.

During his speech in Washington, the Cambridge University professor told his audience that he had been thinking a lot about the cosmic question, “Are we alone?”

The answer, he concludes, is probably not. But if there is life elsewhere in the Universe, he asked, why has humanity not stumbled onto some alien broadcasts in space, maybe something like “alien quiz shows?”

One possible reason is that there is no life elsewhere. Or maybe there is intelligent life, but when it gets smart enough to send signals into space, it also is smart enough to make destructive nuclear weapons, he said.

But Professor Hawking prefers a third option: “Primitive life is very common and intelligent life is fairly rare,” he said, before quickly adding: “Some would say it has yet to occur on Earth.”

Mokslas

Čia aš pabandysiu surinkti ir suklasifikuoti man įdomius straipsnius.

Ion engine enters space race

Engineer Neil Wallace peers into a huge vacuum chamber designed to replicate – as far as possible – the conditions of space.

Cryogenic pumps can be heard in the background, whistling away like tiny steam engines.

Using helium gas as a coolant, they can bring down the temperature in the vacuum chamber to an incredibly chilly 20 Kelvin (-253C). The pressure, meanwhile, can drop to a millionth of an atmosphere.

This laboratory in a leafy part of Hampshire is where defence and security firm Qinetiq develops and tests its ion engines – a technology that will take spacecraft to the planets, powered by the Sun.

Ion engines are an “electric propulsion system”. They make use of the fact that a current flowing across a magnetic field creates an electric field directed sideways to the current.

This is used to accelerate a beam of ions (charged atoms) of xenon away from the spacecraft, thereby providing thrust.

Neil Wallace, technical lead of the electrical propulsion team at Qinetiq, winds open the door of the testing chamber.

The most exciting time for us will be when that space craft comes over the horizon Neil Wallace, Qinetiq

He points to some large metal blocks at the bottom of the chamber.

“These are the xenon pumps and these are cooled down by the helium compressors to approximately 20 degrees Kelvin,” he explains.

“So any gas atoms that strike those panels, they freeze. After you’ve been running the engines for a number of hours you can see a frost – it looks like snow – which is actually frozen air and xenon.”

During testing, the engine fires ions towards the opposite end of the chamber, which has a protective coating of graphite.

“The ions are travelling very fast, at approximately 50km a second,” he says.

“When they strike the other end of the chamber, they actually knock atoms off the surfaces they strike; it’s analogous to sand-blasting on an atomic level.”

Cruise control

The ion engine developed by Qinetiq, the T5, will be flown for the first time on the European Space Agency’s Goce spacecraft. The mission will fly just 200-300km above the Earth, mapping the tiny variations in its gravity field.

GOCE – EUROPE’S GRAVITY EXPLORER 1. The 1,100kg Goce is built from rigid materials and carries fixed solar wings. The gravity data must be clear of spacecraft ‘noise’ 2. Solar cells produce 1,300W and cover the Sun-facing side of Goce; the near side (as shown) radiates heat to keep it cool 3. The 5m-by-1m frame incorporates fins to stabilise the spacecraft as it flies through the residual air in the thermosphere 4. Goce’s accelerometers measure accelerations that are as small as 1 part in 10,000,000,000,000 of the gravity experienced on Earth 5. The UK-built engine ejects xenon ions at velocities exceeding 40,000m/s; Goce’s mission will end when the 40kg fuel tank empties 6. S Band antenna: Data downloads to the Kiruna (Sweden) ground station. Processing, archiving is done at Esa’s centre in Frascati, Italy 7. GPS antennas: Precise positioning of Goce is required, but GPS data in itself can also provide some gravity field information ‘Space arrow’ to map Earth’s tug

A replica of the T5 engine sits in the test facility at Qinetiq. It is tiny – weighing 3kg, and looks rather like the oil filter of a car.

Yet despite this humble appearance, it took 20 to 30 years to develop, at a cost of tens of millions of pounds.

In space, ion engines will draw electric power from solar panels, generating a thrust equivalent to the weight of a postcard.

This incredibly gentle thrust could, in theory, take a spacecraft beyond our Solar System, if sustained for long enough.

Goce is staying very close to Earth, flying in an ultra-low orbit, where it will encounter wisps of air.

The benefit of an ion engine on this mission is to provide drag compensation, or cruise control.

“This spacecraft is [travelling] at a speed of about eight and a half kilometres per second,” says Neil Wallace.

“As it travels around the Earth, it’s going through the upper atmosphere and it experiences a buffeting.

“They need to compensate that buffeting very accurately and that’s what we’re doing, so we’re actually providing cruise control for that spacecraft.”

Real flight

Various types of ion engine have been used before on only a handful of space missions, including Smart-1, the European mission to the Moon, and Nasa’s Deep Space 1, which flew by a comet.

The T5 ion engine being tested

Future Esa missions such as BepiColombo, bound for the innermost planet, Mercury, will also use the technology.

Qinetiq gets to test its T5 engine for real this summer, when Goce is launched from the Russian space port of Plesetsk. It will go up on the same type of rocket that failed three years ago, destroying Europe’s Cryosat ice mission.

Neil Wallace says the nature of the space business makes watching any launch a dramatic event.

“You spend 10 years working on a mission, treating the components and equipment like a newborn baby. You never take it out of the clean room, and then you put in on the top of 100 tonnes of high explosive and set light to it,” he says, laughing nervously.

“But no, the most exciting time for us will be when that spacecraft comes over the horizon and the ground station picks it up, and you can see the engines are doing what we’ve always said they will do.”

Hear more about Goce and its ion engines in Science In Action on the BBC World Service this Friday, 18 April, at 0930 GMT. (Check World Service schedules for alternative broadcast times)

More doubt on cosmic climate link

Research has thrown further doubt on the notion that cosmic rays are a major influence on the Earth’s climate.

The idea that modern global warming is due to changes in cloudiness caused by solar influences on cosmic rays is popular with “climate sceptics”.

But scientists found changes in cosmic ray flux do not affect cloud formation – the second such report in a month.

Separately, other researchers have found that particles from space may affect temperatures at the poles.

Both pieces of research were presented here at the European Geosciences Union (EGU) meeting.

Cosmic rays, hugely energetic particles coming from space, smash into the top of the Earth’s atmosphere, creating a cascade of charged particles lower down.

These particles may help water droplets to coalesce, and so aid the formation of clouds.

The proposed link to climate change is that cosmic rays can be partially blocked by the Sun’s solar wind.

When the Sun is forceful, there are fewer cosmic rays arriving in the atmosphere, so fewer clouds form, which has a net heating effect on the Earth.

f the mechanism has an impact today, several scientists have hypothesised, it should be possible to spot a link between the intensity of cosmic rays and the formation of clouds.

Jon Egill Kristjansson from the University of Oslo is one; and he unveiled his new results at the EGU meeting.

Human trails

Over the southern Atlantic, Pacific and Indian oceans, where air is much cleaner than in more urbanised regions of the world, particles from ship’s chimneys change the properties of clouds in a way that is clearly visible to the Modis instruments (Moderate-resolution Imaging Spectroradiometers) onboard Nasa’s Aqua and Terra satellites.

The particles are stimulating the formation of water droplets.

If cosmic rays play a significant role in cloud formation, Dr Kristjansson reasoned, sudden changes in cosmic ray intensity should also show up, producing increases in cloud cover, changes in the size of droplets, and possibly in the total amount of water carried in the clouds.

“We have short-term changes called ‘Forbush decreases’, caused by eruptions on the Sun, where cosmic ray flux can decrease dramatically over one or two days and then gradually recover,” he told BBC News.

“The cosmic ray signature on clouds, if there is one, should show up here.”

He identified 13 Forbush events between 2000 and 2005 and looked for evidence in Modis data of concurrent changes in could properties.

Although some of the events were followed by a decrease in cloud cover or changes in the size of cloud droplets, others preceded an increase in cloud cover, or no change at all.

Overall, the results essentially appeared random; abrupt dips in cosmic ray intensity did not produce any discernible pattern of changes in clouds, either immediately or in the four days following the Forbush decrease.

“This is a careful piece of work by Jon Egill Kristjansson that appears to find no evidence for the reputed link between cosmic rays and clouds,” commented Joanna Haigh from Imperial College London, who is also attending the EGU meeting and has also studied possible links between solar variability and modern-day climate change.

“It’s supporting other recent work that also found no relationship,” she added, referring to a research paper published two weeks ago by a UK team which, using different sets of data and different means of analysis, also found no discernible influence of cosmic rays on cloud cover.

“I think that as a factor in climate change, it’s pretty clear that we don’t have any indication at this point that this is important at all,” added Dr Kristjansson.

“Whereas global mean temperatures have been rising steadily over the last 30 years, we see that the cosmic ray flux has been steady.”

Local change

The EGU meeting also saw the first presentation of other research that could perhaps help to explain temperature variations seen between different regions of the Arctic and Antarctic.

Computer models have predicted that energetic particles hitting the top of the atmosphere in polar regions may change temperatures by stimulating the production of nitrous oxides (NOx).

“The energetic particles induce NOx production, and the NOx is then transported down to the stratosphere,” explained Annika Seppala, who led the project from the Finnish Meteorological Institute and also works with the British Antarctic Survey.

“NOx destroys ozone in catalytic reaction cycles; and when you change ozone in the stratosphere, that… can then feed down to surface temperatures,” she told BBC News.

Dr Seppala’s observations appear to bear out the models’ predictions, at least in winter in the polar regions.

In periods of relatively intense particle activity, some areas of the Earth’s surface in both the Arctic and Antarctic are warmer while others become colder, showing differences of up to 2C or 3C compared to the long-term averages.

In periods of unusually low particle activity, the patterns are reversed.

The mechanism appears to be redistributing heat across the polar regions; there is no evidence for any overall warming or cooling, Dr Seppala added, nor that the scale of the effect has changed over time.

“The results were amazing, and I think it’s something significant that we have to take into account,” commented Katje Matthes from the Free University of Berlin, who chaired the EGU session which saw the new data presented.

“I think it’s rather a local effect,” she added, “and I don’t think it has a big impact on global temperatures.”

The Antarctic picture is particular fascinating. High particle flux places a big red patch, indicating warmth, over the Antarctic Peninsula, an area that is feeling the impacts of climate change faster than most other parts of the planet.

The heating and cooling from this mechanism might be short-term; but scientists studying the loss of ice from this region of Antarctica will surely want to understand whether the short-term natural highs and lows combine with the overall warming trend in a way that speeds melting.

Dr Seppala’s team now intends to investigate what happens in the other seasons of the year, which will give a better understanding of the importance of this newly confirmed process.

Richard.Black-INTERNET@bbc.co.uk

Visata dvynė prieš Didįjį sprogimą?

Jeigu paklausite fiziko, kas įvyko prieš arba per Didįjį sprogimą, jis greičiausiai nesileis į ilgas diskusijas ir atsakys, kad tai priklauso nuo kiekvieno žmogaus vaizduotės. Bendroji reliatyvumo teorija šiuo atveju yra bejėgė – esant nuliniam tūriui, mes gauname tik krūvą nulių ir begalybių.

Tačiau per pastaruosius kelerius metus atsirado nauja teorija, pavadinta kilpine kvantine gravitacija (LQG). Pagal šią teoriją, mūsų Visata gimė „kvantinio atšokimo“ metu kolapsavus ankstesniai visatai. Fizikus labiausiai domina, kaip galėjo atrodyti mūsų Visatos protėvė.

Alechandras Koričis (Alejandro Corichi) iš Meksikos universiteto bei Parampritas Sinhas (Parampreet Singh) iš Ontarijo Teorinės fizikos perimetro instituto išplėtojo supaprastintą LQG teorijos variantą, kuris pateikia įdomų atsakymą: ankstesnioji visata galėjo būti daug kuo panaši į mūsiškę. Mokslininkų darbas bus išspausdintas kitame „Physical Review Letters“ numeryje.

„Ši idėja svarbi tuo, jog ji padeda mums atsakyti, kas atsitiko visatai prieš Didįjį sprogimą, – pasakoja P. Sinhas. – Teoriniai modeliai, kurie gali susitvarkyti su Didžiojo sprogimo singuliarumu, nieko nepasako, koks galėjo prieš tai egzistuoti erdvėlaikis. Mūsų skaičiavimai rodo, kad ankstesnė visata primena mūsiškę“.

Pernai Pensilvanijos universiteto fizikos profesorius Martinas Bojovaldas (Martin Bojowald) panaudojo supaprastintą LQG teorijos variantą, kad įrodytų visatos egzistavimą prieš Didįjį atšokimą. Nors matematinis modelio aparatas nesusidūrė su problemomis, tačiau paaiškėjo, kad stebėdami dabartinę Visatą mes ničnieko negalėsime pasakyti apie ankstesniąją. M. Bojovaldas šį reiškinį pavadino „kosminiu užmaršumu“.

A. Koričis ir P. Sinhas žengė toliau. Aproksimavę pagrindinę lygtį, mokslininkai parodė, kad tam tikros ankstesnės visatos tūrio ir judesio kiekio fliuktuacijos sugebėjo išlikti per Didįjį atšokimą.

„Tai reiškia, jog visatoje dvynėje galiojo tie patys fizikos dėsniai“, – teigia P. Sinhas.

Galima sakyti, kad mūsų Visata, praėjus maždaug 13,7 mlrd. metų po atšokimo, turėtų būti labai panaši į ankstesniąją visatą, kai šiai buvo likę 13,7 mlrd. metų iki atšokimo. Kitaip tariant, mūsų Visata yra veidrodinis savęs pačios atspindys, o Didysis sprogimas (arba atšokimas) yra tarsi visatas skiriantis veidrodis.

„Ankstesnėje visatoje turėjo galioti tos pačios dinamikos ir Einšteino lygtys,– toliau tęsia fizikas. – Pagal mūsų modelį, mums įprasti dėsniai turi pasireikšti 100 kartų viršijus Planko skalę. Toliau medžiagos struktūra bus tokia pati, ir evoliucija vyks identiškai“.

Tyrėjai aiškina, kad visata dvynė nebūtinai turi būti visiškai identiška savo „sesutei“. Pavyzdžiui, tai nereiškia, kad ankstesnėje visatoje egzistavo ankstesnis jūs – žmogus, jau nugyvenęs savo (jūsų) gyvenimą.

„Jeigu sugebėtume itin galingu mikroskopu žvilgtelėti į tam tikras Planko skalės savybes, išvystume skirtumų, lygiai taip pat, kaip jų turi tikri dvyniai, pavyzdžiui, piršto antspaudus“, – tvirtina P. Sinhas.

Svarbu atsakyti į klausimą, ar kai kurios savybės galėjo išlikti, jeigu būtų nagrinėjamas sudėtingesnis atvejis. Pavyzdžiui, būtų įdomu sužinoti, ar ankstesnės visatos galaktikos negalėjo dabartinėje mūsų Visatoje palikti pėdsakų, kurie lemtų identišką arba panašų galaktikų formavimąsi.

Visai įmanoma, kad A. Koričio ir P. Sinho teorija netgi numatys, kaip turėtų atrodyti mūsų Visata ateityje. Priklausomai nuo dabartinio plėtimosi greičio, apibendrintasis mokslininkų modelis gali parodyti, jog mūsiškės Visatos laukia kolapsas.

Stars born in galactic wilderness

Baby stars have been discovered spawning in the otherwise barren outskirts of a galaxy.

The finding has surprised astronomers because the galactic periphery was assumed to lack high concentrations of ingredients needed to form stars.

The stars can be seen in a new image of the Southern Pinwheel galaxy, or M83, obtained by a Nasa space telescope and a ground-based observatory.

They are forming more than 100,000 light-years from M83’s bustling centre.

Nasa’s Galaxy Evolution Explorer (Galex) satellite spotted bright features in the long “arms” of the galaxy – coloured red in the image – which astronomers think are large clusters of stars.

“Every little pixel we see probably represents hundreds to thousands of stars. But we view them as a single blob,” said Mark Seibert from the Carnegie Observatories in California.

“It would add up to quite a good number of stars out there.”

Galex is equipped with a 50cm (19.7-inch) -diameter telescope to sweep the sky in search of ultraviolet light sources. But it cannot see individual stars because the design trades fine resolution for a large field of view.

Dr Seibert told BBC News: “A telescope with finer resolution would wash out a bit in the background. But the lower resolution of Galex actually improves detection of these features.”

‘Stunning’ find

To better understand how stars could form in such unexpected territory, the astronomers used the Very Large Array (VLA) in New Mexico to carry out radio observations of the galaxy.

“It is absolutely stunning that we find such an enormous number of young stars up to 140,000 light-years away from the center of M83,” said lead author Frank Bigiel from the Max Planck Institute for Astronomy in Germany.

Light emitted in the radio portion of the electromagnetic spectrum can be used to locate gaseous hydrogen atoms. These are seen as a good sign that the molecular form of the gas is also present. And it is from this molecular gas that stars are born.

When the astronomers combined the radio and the Galex data, they found that they matched up.

“Clearly, the basic ingredients for star formation are out in those regions,” said Dr Seibert.

Close distribution

Co-author Fabian Walter, also of the Max Planck Institute for Astronomy, said: “The degree to which the ultraviolet emission and therefore the distribution of young stars follows the distribution of the atomic hydrogen gas out to the largest distances is absolutely remarkable.”

Dr Seibert said that about 20% of the galaxies he had looked at showed ultraviolet emission in their outer regions.

In the case of some galaxies, stars on the outskirts could have been scooped away from another galaxy that came too close. But this seems unlikely for M83. It appears to be too symmetrical – lacking the uneven appearance of a galaxy that has collided with another.

The astronomers speculate that the young stars seen in far-flung regions of M83 could have formed under conditions resembling those of the early Universe, a time when space was not yet enriched with dust and heavier elements.

But this process is not well understood.

M83 is located 15 million light-years away in the southern constellation Hydra.

Paul.Rincon-INTERNET@bbc.co.uk

Egzaminai

Užvakar, tai yra balandžio 17 dieną, labai aiškiai pasijuto, kad egzaminai artėja: buvo užsienio kalbų įskaita. Visai nesvarbu, kad aš jos nelaikiau, bet tai yra labai ryški egzaminų pradžia.

Spektrai

Šį pavasarį pastebėjau smagų reiškinį: saulės šviesos dispersija akvariume.

O čia iš arčiau:

Pradedam

Na va, manau, kad šito blogo pradžia galima laikyti būtent šia akimirką: 2008-04-18 21:55.

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