Wednesday, November 11, 2015

Black holes: We explode six myths to prevent you from getting sucked in

Artist's concept of a supermassive black hole, billions of times the mass of our sun, surrounded by an accretion disk where matter flows into the black hole.

By Stuart Gary

Black holes are the stuff of science and sci-fi and the line between fact and fiction can often be blurred. So, here are some common black hole myths that you'll never be sucked into again.

Are black holes portals to other worlds or monsters gobbling up everything in sight? How much of what we see in movies is science fiction and how much is science fact?

"Most people know that a black hole is a very small volume of space with a lot of stuff in it, so that its gravity is so strong nothing can escape from it, not even if it's travelling at the speed of light," said Dr Amanda Bauer, astronomer at the Australian Astronomical Observatory.

But there's a lot more to know about black holes than that.

Myth 1: Our Sun will become a black hole when it dies

No, our Sun isn't massive enough to become a black hole. Instead in about 6 billion years' time, the Sun will expand to become a red giant star with a diameter stretching maybe as far as Earth's orbit.
The Sun will then puff off its outer gaseous envelope, leaving behind its white hot stellar core, and become a white dwarf.

If the Sun was a far more massive star then it would have a more violent death, exploding as a supernova and leaving behind a super-dense object called a neutron star.

"When a star maybe 10 times more massive than the Sun goes supernova, its core collapses beyond the neutron star phase to form an even denser object called a stellar mass black hole," Dr Bauer said.

Myth 2: Black holes aren't real because you can't see them

Black holes can't be seen because light can't escape from them, but that doesn't mean they can't be detected using other means. Astronomers can see the effects of black holes on the space around them.
"While we can't actually see them directly, mathematically we have known about black holes since Albert Einstein's time, since the early 1900s," Dr Bauer said.

With modern telescopes we can see how black holes affect the stars orbiting around them.
"We have something at the centre of our Milky Way galaxy called SgrA* that doesn't produce any light, and we can watch individual stars going around it, not in nice circular orbits, but in highly elliptical, elongated paths," Dr Bauer said.

We can watch maybe a dozen of these stars orbiting around SgrA*, Dr Bauer says, and use very basic physics equations to calculate the mass of any of these stars and the thing they're orbiting around in order to account for the motion of that star.

"And you find that there is something there that's over four million times the mass of our Sun but in a tiny area that produces absolutely no light. There's nothing else we think that it could be other than a black hole."

Myth 3: Black holes will suck up all the matter in the universe like a giant vacuum cleaner

Fortunately, this isn't likely to be true.

This is because you have to be very close to a black hole to feel the strength of its gravity, and gravity gets weaker the further away you get, Dr Bauer said.

"If the Sun could magically turn into a black hole (which as we already pointed out it can't), then all its stuff would get shoved down into a tiny little volume maybe a couple of kilometres across.

"Think about what would happen to Earth, the Sun would still have the same mass if it were a black hole instead of a star. Earth also still has the same mass and still be the same 150 million kilometres away from it, and gravitationally speaking the only things that matter are your mass and how far away you are."

This means gravitationally nothing changes, Earth has no idea that the Sun has suddenly changed into a black hole and so it just continues its orbit. And the same thing happens on the larger scale of the galaxy.

Mind you, things would be a lot darker on Earth.

"Remember at the centre of our galaxy we have SgrA*, we have this supermassive black hole that's there and our Sun just orbits around it with the rest of the galaxy," Dr Bauer said.

"The Sun doesn't care what's there creating that mass. There are also hundreds of billions of stars between us and that black hole, so gravitationally we don't care what it is. You have to be very close to the black hole to get sucked in."

Myth 4: Entering a black hole takes you through a wormhole to another place and time

Mathematically, this is possible. But there are several problems with this possibility, including spaghettification.

"You could potentially have a wormhole that ties you to another place in the universe and maybe you'll pop out of a white hole on the other side," Dr Bauer said.

But these are very delicate solutions. If anything happens to the black hole, if you disturb it by something falling into it, or if the black hole's spinning, then this solution falls apart.
"Mathematically it's possible but it's not very likely," Dr Bauer said.

And it's unlikely that we'll be able to ever find out.

"We are never going to be able to measure this scientifically because if we send something into a black hole we could not get a signal out to tell us what's happening," Dr Bauer said.

"The signal will travel at the speed of light, and that's not fast enough to escape the gravity of a black hole."

Also, any object falling into a black hole would experience huge amounts of gravitational force as it fell closer to the event horizon, the point beyond which light can no longer escape a black hole's gravity.

For example, a clock falling into a black hole would feel a far stronger gravitational pull on the side nearest the black hole than the part further away from the black hole, so the clock would slowly start to elongate and be pulled apart.

"We have a word for this. We call it spaghettification, as you get stripped down to your individual atoms as you get pulled into the black hole," Dr Bauer said.

If somehow the clock magically survived spaghettification and you were able to see it ticking, you would see the ticking appear to slow down as it fell towards the event horizon. This is because time slows down as you get closer to a massive body, like a black hole.

"But from the clock's perspective time is still ticking at the same rate it actually doesn't seem like anything happened," Dr Bauer said.

Myth 5: Supermassive black holes form when a massive star dies

There are supermassive black holes in the centres of most galaxies — but the way they form is more uncertain.

"One possibility is that the very first generation of stars which were made out of almost pure hydrogen and helium from the Big Bang 13.8 billion years ago were bigger than today's stars, maybe hundreds of times the mass of our Sun," Dr Bauer said.

These stars were so hot and huge that they burned through their nuclear fuel supplies in just a few million years before going supernova and forming primordial black holes.

Formed in regions where lots of gas was collecting and forming the first galaxies, these primordial black holes probably sank to the centre and grew over time, eventually forming supermassive black holes, Dr Bauer said.

"Another possibility is nearby black holes merged to create progressively bigger black holes, so you get this merging of black holes, which over time form supermassive black holes.

"The big challenge is that we haven't seen any intermediate-sized black holes, we haven't seen anything between stellar mass and supermassive black holes, so we're not sure yet whether this is the formation process, but it's a good theory."

Myth 6: The universe will be consumed by black holes

Feel free to breathe a sigh of relief because this is not likely to happen.

"The universe does go through various transitions in its future but this is over trillions of trillions of years in the future," Dr Bauer said.

"Eventually stars won't be able to form any more, but black holes are very long-lived and will continue to absorb material becoming more massive, but they don't last forever."

Black holes slowly evaporate through a process called Hawking radiation, but this will take trillions of years.

"So in this scenario of the fate of the universe, all the stars will slowly burn out, no new stars will form, and you'll be left with a black hole epoch, dominated by these supermassive black holes which will slowly evaporate," Dr Bauer said.

"In the end what we're left with is a big, huge, vast space with lots of tiny little elementary particles floating around but nothing really to bump into, and with no more stars it's very cold and dark."


Lenticular 'UFO' clouds over Cape Town and other weird cloud formations

Lenticular clouds over Cape Town on November 8, 2015.

South Africans have been treated to an eerie cloud formation known as lenticular clouds.
The so-called "UFO clouds" appeared in the sky over the weekend in the city of Cape Town.

Lenticular clouds form when high winds blow over rough terrain, such as mountains and valleys.

Take a look at some of the photos from social media, as well as other weird formations clouds can take.

The unusual meteorological sighting happened on November 8 and citizens in the South African city rushed to the streets to gaze up at the natural spectacular.

'The aliens have been moniting [sic] cape town for years now,' Instagram user monre44 said.

However, keen to dispel rumors that the formation was an out-of-this-world visit, CNN meteorologist Derek Van Dam said they are 'common clouds' known scientifically as 'stratocumulus standing lenticularis'. 

They are saucer- or lens-shaped clouds, which are typically stationary in nature.

On account of their typical shapes, lenticular clouds have been mistakenly identified as Unidentified Flying Objects (UFOs) in the past.

Social media users were eager to photograph the beautiful daytime cloud formations and post their images online. 

'Right now above my head! The strangest most amazing UFO shaped clouds,' wrote amazed Instagram user called Arthur Albert. 

Shocked Twitter user Monique Jackson added: 'Weird UFO clouds over Cape Town.'

While impressed Di Brown posted on Instagram: 'The cloud looks like a tornado in pause mode.

Really very weird skies today.

Tuesday, October 20, 2015

Ancient crystals reveal life could be millions of years older than first thought, international scientists say

The zircon crystals - including one which scientists say contains the signature of life within it - were found at Jack Hills.

By Sarah Taillier

Ancient crystals unearthed in Western Australia may contain evidence that life existed hundreds of millions of years earlier than previously thought.

The multi-billion-year-old zircon crystals were found at Jack Hills, about 600 kilometres north-east of Perth, a site well known for the mineral grain, which is so far the oldest known material ever identified on dry land.

Scientists from Stanford University and the University of California recently examined rocks from the area and believe they have found one with the signature of life within it.

The crystal contains a carbon deposit, which the scientists believe could be about 4.1 billion years old, suggesting that life may have appeared on the planet 300 million years earlier than previously thought.

But some Australian-based academics are sceptical about the find.

Curtin University School of Mines associate professor Alexander Nemchin said the research highlights the possibility of ancient life but it is not a definite discovery.

"It is significant because it states the possibility, but whether it gives us 100 per cent confidence ... probably not," he said.

Geology not a 'precise science'

Professor Nemchin, who is a geochemist, suggested that the life-like features in the carbon deposit found by US scientists could be "achieved without involving living organisms".

"Geology really isn't ... a precise science, so what we base our conclusion on is observation, and the more observations [that] are made coming from different sites, the more confidence we get in what we believe is happening," he said.

University of New South Wales professor Martin Van Kranendonk, an expert on early earth studies and the formation of the planet's crust, said he was underwhelmed by the US scientists' findings.
"It's a discovery of carbon in very ancient crystals and the carbon is fractionated," he said.

"And these guys have gone off to say, 'oh this is the signature of life and that it's older than anything'.

"This is an interesting little observation and discovery, any discovery in old materials is of interest, but is it a life signature?

"Do I get excited? Not really."

Professor Nemchin said he believes the scientists did the best they could with the current "development of our understanding and analytical methods".

"To some extent it confirms the idea that life probably existed very early, almost from the beginning of the planet itself and the solar system itself and probably not really restricted to our planet," he said.
"Probably all over the universe and probably other places in other solar systems."

The ABC has contacted Stanford University for comment. 

Thursday, October 15, 2015

Big-Toothed Fossil May Be Primitive New Human

Penghu 1 mandible. Its morphology suggests the presence of a robust, primitive type of hominin so far unrecognised in the Pleistocene Asian fossil record (Y Kaifu)

Photos: Faces of Our Ancestors

The first known prehistoric human from Taiwan has been identified and may represent an entirely new species that lived as recently as 10,000 years ago, according to a new study.

The newly discovered big-toothed human, "Penghu 1," strengthens the growing body of evidence that Homo sapiens was not the only species from our genus living in Europe and Asia between 200,000 and 10,000 years ago.

Anthropologists have learned that Neanderthals, Denisovans and Homo floresiensis (a.k.a. the "Hobbit Human") lived in Europe and Asia within that time frame. Penghu 1, which is described in the latest issue of Nature Communications, adds to that already impressive list and might have co-existed -- and even interbred -- with our species.

"The available evidence at least does not exclude the possibility that they survived until the appearance of Homo sapiens in the region, and it is tempting to speculate about their possible contact," co-author Yousuke Kaifu, who is an associate professor in the Department of Biological Sciences at The University of Tokyo, told Discovery News.

Kaifu, lead author Chun-Hsiang Chang, and their team studied the remains of the new human, which is represented by a jawbone with big teeth still in it. Chang explained that fishermen dredged up the jawbone off the coast of Taiwan in Penghu Channel. The fishermen sold it to a local antique shop, where collector Kun-Yu Tsai purchased it. Tsai donated his collection to the National Museum of Natural Science in Taiwan, where Chang works in the Department of Geology.

Chang and his team recognized the importance of Penghu 1, which they theorize could represent a new human species or a regional group of Homo erectus, a.k.a. "Upright Man."

"Penghu 1 is a national treasure in Taiwan and is well preserved at my museum with high security," Chang said.

He and his colleagues believe that, due to its size, the jawbone came from an adult individual and possibly a senior, "because its teeth are worn severely," Chang said.

The jawbone's size further reveals that Penghu 1 was not a dwarf, unlike tiny Homo floresiensis, which lived on the island of Flores, Indonesia, where other animals were also smaller than usual.
Penghu 1 instead lived on what was then mainland Asia in an ecosystem that included many other animals.

Ancient teeth point to earliest modern humans in southern China

47 human teeth found in the Fuyan Cave in Daoxian in China are between 80,000 - 120,000 years old.

Map of where teeth were found.

Modern humans may have occupied southern China at least 30,000 years earlier than previously thought.

Archaeologists have found 47 Homo sapiens teeth closely resembling our own, dated from 80,000-120,000 years old, in a cave in Hunan province, according to a letter published today in Nature.

The discovery adds a new chapter to the story of modern human migration, suggesting that our genetic ancestors were not the first H. sapiens to populate east Asia.

Until now, the earliest fossil evidence of H. sapiens further east than the Arabian Peninsula was been dated at 40,000-50,000 years ago, from Northern China, Borneo, and Lake Mungo in southwest New South Wales.

While the researchers did not find any other human bones or stone tools at the Hunan province site, they did uncover a large number of teeth from other animals, including five extinct large mammals such as an ancient elephant and an ancestor of the giant panda.

Researchers said the discovery also showed modern humans were living in southern China 30,000-70,000 years earlier than they were found in Europe.

They suggested the slower migration of H. sapiens into Europe may have been the result of competition with Neanderthals, which ultimately led to extinction of Neanderthals and the dominance of modern humans.

Lead researcher, Dr Wu Liu of the Chinese Academy of Sciences in Beijing said the team was planning to undertake a genetic analysis on the teeth in the hope that this would answer questions about possible genetic links between these ancient H. sapiens and us.

Unlikely these humans are genetically related to us
Human evolution expert Associate Professor Darren Curnoe from UNSW Australia said it was unlikely these earlier H. sapiens were genetically related to us.

Although the find is "very clear evidence" of an early migration of modern humans out of Africa, it "predates the genetic signal for the peopling of the planet," Professor Curnoe added.

Analysis of the rate of genetic change over time - the 'genetic clock' - tells us that our ancestors arrived in east Asia around 30,000-50,000 years ago, he said.

"If we assume that the genetic clock is right, then ... the teeth that have been found would represent a population that probably didn't contribute genetically to living people in east Asia today."
These earlier H. sapiens were probably replaced by a later wave of migration from Africa that gave rise to contemporary human populations, he said.

This is not the first discovery of its kind for the region; an analysis by Professor Curnoe's team of teeth found 30 years ago in a neighbouring province suggested they could be 60,000-80,000 years old, and another group found similarly modern teeth from another cave in southern China.

"So we've now got three sites from south-west China - this one being the most comprehensively studied and the best example - [so] this is not likely to be an anomaly, this is likely to be correct," he said.

What is now needed is DNA or more fossil evidence, particularly skulls or jaws, to help determine the relationship between these earlier H. sapiens and our direct ancestors, said Professor Curnoe.

Monday, September 21, 2015

Pentecopterus decorahensis: Ancient Giant Sea Scorpion Unearthed in Iowa

This is an artist’s rendering of Pentecopterus decorahensis. Image credit: Patrick Lynch / Yale University

The fossil of a previously unknown species of eurypterid that lived 460 million years ago (Middle Ordovician period) has been discovered in Iowa.

The creature, Pentecopterus decorahensis, is the oldest known species of eurypterid (sea scorpion) – a group of aquatic arthropods that are ancestors of modern spiders, lobsters, and ticks. The discovery published in the journal BMC Evolutionary Biology was made by paleontologists from Yale University and the University of Iowa.

“This shows that eurypterids evolved some 10 million years earlier than we thought, and the relationship of the new animal to other eurypterids shows that they must have been very diverse during this early time of their evolution, even though they are very rare in the fossil record,” said lead author Dr James Lamsdell of Yale University.

Dr Lamsdell and co-authors named the ancient monster after the ‘penteconter’ – an ancient Greek warship that the species resembles in outline and parallels in its predatory behavior.

Pentecopterus decorahensis is large and predatory, and eurypterids must have been important predators in early Palaeozoic ecosystems,” Dr Lamsdell said.

The creature had a long head shield, a narrow body, and large, grasping limbs for trapping prey.
Pentecopterus decorahensis is incredibly bizarre. The shape of the paddle – the leg which it would use to swim – is unique, as is the shape of the head. It’s also big – over 6 feet (1.5 m) long,” Dr Lamsdell added.

“Perhaps most surprising is the fantastic way it is preserved – the exoskeleton is compressed on the rock but can be peeled off and studied under a microscope.”

“This shows an amazing amount of detail, such as the patterns of small hairs on the legs.”
“At times it seems like you are studying the shed skin of a modern animal – an incredibly exciting opportunity for any paleontologist.”
James C. Lamsdell et al. 2015. The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa. BMC Evolutionary Biology 15: 169; doi: 10.1186/s12862-015-0443-9

Friday, September 11, 2015

New species of human relative, Homo naledi, found in underground graveyard in Cradle of Humankind in South Africa

The fossilised bones of 15 bodies from a previously unknown human species have been unearthed from the depths of an underground graveyard, in a discovery scientists say could change the history of humankind.

About 1,500 fossils were found deep in a cave system outside Johannesburg, hidden in a deep underground chamber only accessible via several steep climbs and rock crevasses.

Experts are uncertain how the Homo naledi remains came to be inside the cave, or even how old they are, but the discovery may help fill a crucial gap in the fossil record and shed light on how humans evolved from apes.

The bones were first discovered in 2013 by Witwatersrand University (WU) scientists and volunteer cavers in the Cradle of Humankind, a UNESCO World Heritage Site.

"I am pleased to introduce you to a new species of human ancestor," Lee Berger, a research professor at the WU in Johannesburg, told reporters at the site.

Ancient human remains have been found in the area since excavations begun in the 1920s.

The Rising Star expedition was led by Professor Berger, who is also a National Geographic explorer.

It involved an international team of scientists, including six "underground astronauts", who weaved their way through narrow walls and chambers of the cave to reach the mass of human remains.

Donning hard hats and some very creative ways of carrying technology, the team wedged themselves through the narrow gaps and down a vertical, dark, 17-centimetre-wide passage to reach the ancient graveyard.

Most fossil discoveries of human relatives consist of just a handful of bones. But down in this hidden chamber, the team uncovered an unprecedented trove.

"The discovery of so many fossils belonging to at least 15 individuals is remarkable," said Professor Chris Stringer from the Natural History Museum in London, one of the lead analysts on the discovery.

He said the find highlighted "the complexity of the human family tree and the need for further research to understand the history and ultimate origins of our species".

Scientists from Queensland's James Cook University (JCU) were involved in the expedition.
Professor Paul Dirks said the remains were found at the end of a narrow passage in a section where sunlight has never reached, known to scientists as the "dark zone".

The team believed the chamber could be an intentional disposal site — a graveyard of sorts.

Testing at JCU and the University of Johannesburg shows sediments in the chamber did not come from external sources, ruling out the possibility of flash flooding or other catastrophic events leading to the fossils getting into the chamber.

"The deep cave location where the bones were found suggests that they may have been deposited there by other humans, indicating surprisingly complex behaviour for a 'primitive' human species," Professor Stringer said.

Professor Dirks said the features of Homo naledi were similar to other early hominids, combining a human-like face, feet and hands, but with a short, ape-like torso and a very small brain.

"It is a mixture of primitive features and evolved features," he said.

"It shows there were different species of hominids alive at different times that combined all sorts of different features — nature was experimenting."

Homo naledi stood approximately 1.5 metres tall and weighed about 45 kilograms.

Almost every part of skeleton was retrieved which allowed the scientists to piece together the mysterious part of human history.

But it was not an easy feat.

Video from the expedition showed the emotional side of the epic and intricate venture, as the underground astronauts enter the cave and re-emerge exhausted, but excited by their efforts.

JCU's Dr Eric Roberts was one of the people to head inside the tight chamber.

"You crawl several hundred metres into the cave system through some very narrow squeezes," he said.

"Then that final drop into the chamber is very intimidating. It requires a technical rock climb and you hyperventilate a bit going down."

Scientists believe there has never been an alternative, easier route into the chamber.

The University of the Witwatersrand, National Geographic Society and the South African National Research Foundation unveiled their discovery on Thursday September 10.

Their findings are described in two papers published in the journal eLife and the story features on the cover of the October edition of National Geographic.

Study of the fossil site will likely continue for decades.