2017 has been a big year for science.
From exploding neutron stars to a crashing spacecraft, huge icebergs breaking away from Antarctica to genetically modified skin.
The Australian Science Media Centre, an independent, not-for-profit service for the news media, has picked what it sees as the best science stories of the year:
Trump dumped Paris
In June, recently-elected US President Donald Trump announced he would pull the US out of the Paris Agreement, the international deal thrashed out in 2016 to tackle man-made global warming.
The withdrawal was widely criticised in a year which saw 2017 declared one of the hottest on record and global emissions from fossil fuels begin to rise again after levelling out for several years.
The US is the only functioning country that isn’t signed up — even North Korea is on board.
However, the withdrawal process takes four years, so the US will remain in the agreement until November 2020, one day after its next presidential election.
There’s gold in exploding neutron stars
Scientists for the first time measured via gravitational waves the violent death of two neutron stars and saw the subsequent fireball.
When detectors first picked up the gravitational waves, a burst of gamma rays in the sky alerted scientists, sending astronomers scurrying for their telescopes, and ushering in a new era of astronomy.
Australian scientists played key roles, and were the first to detect radio waves from the explosion.
Analysing the stars also revealed that distant neutron star explosions are likely to be the source of all the gold, platinum and uranium on Earth.
Human history got a rewind
In June, the discovery of five ancient Moroccan fossilised skulls revealed that humans have been around for longer than thought. About 100,000 years longer.
Humans were previously believed to have originated in southern Africa 200,000 years ago but these skulls, teeth and bones show it’s been at least 300,000 years.
And the fact that these skulls were unearthed in Morocco hints that Homo sapiens may be even older than that.
Australian scientists used a pair of modern dating techniques to pinpoint the time these ancient humans lived.
A huge iceberg broke free
One of the largest icebergs on record, known as A68, broke away from Antarctica in July.
The trillion tonne iceberg was more than twice the size of the ACT at 5,800 square km.
The rift has been visible in satellite images since the 1980s, so the breakup was a long time coming, and it is thought to have been a naturally-occurring event rather than one caused by man-made climate change.
However, scientists warned that the iceberg’s departure may mean newly exposed glaciers will melt faster, potentially accelerating sea level rises.
Cassini slammed into Saturn
After 20 long years hurtling through space, 13 of which were spent orbiting Saturn, we farewelled the Cassini spacecraft in September.
The craft, a collaboration between NASA, the European Space Agency, and the Italian Space Agency, was deliberately sent to a fiery end, burning up in Saturn’s atmosphere to avoid contaminating any of the gas giant’s moons with bacteria of Earth origin.
During its mission, Cassini sent back rafts of data on Saturn via CSIRO’s team at the Canberra Deep Space Communication Complex, revealing a surprisingly changeable ring system and the birth of a new moon.
And it wasn’t just Saturn. Cassini also took in Venus, Earth, Jupiter and a passing asteroid en route to the gas giant.
The first Australians arrived even earlier
In July, Australian scientists announced that Aboriginal artifacts at a rock shelter called Madjedbebe in NT had revealed that the first Australians arrived here around 65,000 years ago, 5,000 years earlier than thought.
This suggests indigenous Australians arrived before the extinction of the megafauna, the giant animals that once roamed this land.
Among the finds were the oldest ground-edge stone axe technology in the world, the oldest known seed-grinding tools in Australia and evidence of stone spear tips.
The scientists also found a Tasmanian tiger jaw painted with red pigment.
Genetically modified skin saved a boy’s life
In November, a seven-year-old Syrian boy was saved from a lethal condition called Junctional Epidermolysis Bullosa (JEB) that gradually eats away at the outer layer of the skin.
When he arrived at hospital, the boy had lost around two-thirds of his skin and doctors were convinced he would die.
But Italian scientists grew him a new skin using cells taken from his own body, which they genetically modified (GM) to remove the disease-causing genes.
Then, in a series of operations, they successfully grafted the GM skin to 80% of his body. And 21 months after the operations, the boy’s skin is stable and self-healing.
The fight against killer robots
In August, 116 robotics and artificial intelligence (AI) company heads signed a letter penned by an Australian scientist urging the UN to ban lethal autonomous weapons, or killer robots.
They warned that robots could lead to war on a scale never before seen.
The letter was similar to one signed by thousands of scientists in 2015, but this was the first time robotics and AI company bosses, including Tesla and SpaceX boss Elon Musk, had come together.
Their warning came in a year when AI came on leaps and bounds; Google’s AlphaGo Zero program taught itself to play the tricky Chinese game of Go, taking just three days to trump thousands of years of human knowledge, and another AI called DeepStack thrashed human opponents at poker.
A global sperm count showed a 50% drop
The fact that sperm counts have fallen dramatically in men in the Western world has been known for years, but in July scientists confirmed and quantified that drop by analysing all the existing studies of male sperm counts.
They found sperm counts in Australia, Europe and North America have dropped by 52.4% in just 40 years.
The reasons for plummeting sperm numbers remains a mystery, although the scientists suggest that Western men’s exposure to modern commercial chemicals could be a factor.
They found that dropping sperm numbers aren’t stabilising — the decline is ongoing — which could push more men into infertility.
In March and again in August, scientists announced that they’d successfully kept premature lambs alive in artificial wombs for longer than ever before.
In the first study, US scientists kept lambs alive for four weeks, and said they developed normally, even opening their eyes and growing wool. In the other, Australian study, lambs were kept alive for a week.
The artificial wombs were essentially plastic bags filled with high-tech amniotic fluid and fitted with artificial placentas and umbilical cords.
The technology could be particularly useful for very premature babies whose lungs haven’t fully developed when they’re born, said the scientists. It would allow them to continue in amniotic fluid until their lungs are ready to breathe air.
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