Another year has come to an end, so it's time to look back at the scientific breakthroughs and inventions that excited us this year. From innovative new materials that open the door to more advanced tools and products, to discoveries that continue to push the borders of human knowledge, 2018 didn't fail to deliver. The inspirational scientific stories were offset somewhat by the flood of bad news regarding the climate, but maybe science can be a source of hope there, too.

Climate sirens sound

If you turned on the news in 2018 there was a good chance you saw a story on an extreme weather event taking place somewhere around the world. In 2018, study after scary study pointed to the reasons for this and painted an increasingly grim picture of the precarious plight of the planet's climate.

At the start of 2018, NASA and the National Oceanic and Atmospheric Administration (NOAA) both released reports looking back at the previous year, revealing 2017 as one of the hottest years since records began in 1880, with the five hottest years all occurring since 2010. The World Meteorological Organization's (WMO) provisional Statement on the State of the Climate in 2018, which only takes into account the first 10 months of the year, suggests things won't be much better this year.

Even the White House's release of the Fourth National Climate Assessment (NCA4) report on Black Friday couldn't hide how badly climate change will affect not just the environment, but society and the economy. Meanwhile, another report outlined how the percentage of the world's population exposed to deadly heatwaves will continue to rise – since 2000 the number has already risen by 157 million people.

But it was the Intergovernmental Panel on Climate Change's (IPCCs) Special Report on Global Warming of 1.5° C, put together by 91 scientists from 40 countries, that really drove things home, cautioning that "unprecedented changes in all aspects of society" are needed if we're to avoid the worst effects of climate change. That's something that won't be possible if we continue on the path indicated by a UN report that revealed global carbon emissions were once again on the rise and reached a record high in 2017 after stabilizing the three previous years.

On the upside, we saw numerous technologies that could help us tackle the problem, such as a couple of direct air capture (DAC) pilot systems – one from Canadian company Carbon Engineering and another from Swiss company Climeworks – designed to capture CO2 from the atmosphere, and the announcement of the 10 finalists in the Carbon XPrize that is offering a US$20 million incentive for the development of technologies that transform CO2 into valuable products.

Energy

Fusion

One of the biggest problems we'll have to address if we're to tackle climate change is our reliance on fossil fuels, and there were a few encouraging developments on that front in 2018. Nuclear fusion, seen as the holy grail of clean energy production, came a couple of steps closer to reality with the experimental Wendelstein 7-X nuclear fusion reactor setting a record for so-called "fusion product" before achieving the highest energy density and longest plasma discharge times for a device of its type.

In June, UK company Tokamak Energy reported its ST40 device had reached temperatures similar to those found at the center of the Sun (15 million degrees Celsius), but China's "artificial sun", the Experimental Advanced Superconducting Tokamak (EAST) left that in the shade, reaching a core plasma temperature of over 100 million degrees Celsius, as well as a heating power of 10 MW, furthering the study of a number of aspects of practical nuclear fusion.

Solar

But there's one fusion reactor we can already harness and we saw numerous advances that could help us make better use of our friend the Sun in the future, many of which involved building on current solar cell technology.

A case in point is a new conversion efficiency record of 25.2 percent for a solar cell that combines silicon and perovskite in one device. Another combination solar cell, this time one that harnesses both solar and triboelectric energy, was developed to generate power when the sun don't shine – specifically, when it's raining. The proof-of-concept device operates as a traditional solar cell when the sun's shining, and harvests energy from the impact of raindrops on its surface when the weather's more inclement.

And the hybrid devices kept coming with researchers at Stanford creating a prototype rooftop device that combines a solar panel and a radiative cooling system to both generate electricity and cool the building, while another team from Berkeley Lab and the Joint Center for Artificial Photosynthesis (JCAP) designed a hybrid cell that uses the power of the sun to split water into water and hydrogen, with some of the excess energy also used to generate electricity.

Meanwhile, researchers at the University of British Columbia turned to additives of a different sort, using bacteria to create a "biogenic" solar cell that can generate electricity even on overcast days.

A material world

Graphene may be the two-dimensional wonder material du jour, but a few new materials sidled up to it on the 2D plane in 2018. A 2D form of soft metal gallium dubbed gallenene, which could find application as super-efficient, thin metal contacts in electronic devices joined the club, as did hematene, a 2D material made up of sheets of iron just three atoms thick. Scientists also proved the existence of a predicted fifth form, or allotrope, of phosphorous called blue phosphorous. They found that the phosphorous atoms form a honeycomb pattern similar to graphene, but the lattice buckles, giving it different properties to black phosphorous.

Things were just as interesting in the third dimension, with a high strength and lightweight alloy called Allite Super Magnesium set to find its way into consumer products after being the reserve of military and aerospace applications. While on the subject of alloys, researchers at Sandia Labs combined gold and platinum to develop what they claim is the most durable alloy ever created – and it even makes its own lubricant. But if it's strength you're after, you can't do better than the strongest material in the universe? With the tasty moniker of "nuclear pasta", this material is formed inside neutron stars, so we won't be building anything out of it anytime soon.

But there are a couple of new wood-based materials we could be making use of in the not-too-distant future, including a "super wood" that is as strong and tough as steel, a wood/metal foam that could be used for insulation, and a new wood nanofiber that knock spider silk off its perch as the world's strongest biomaterial. But that doesn't mean spider silk isn't still attractive to all kinds of industries – if only we could get our hands on enough of the stuff. Researchers made that a possibility by engineering bacteria to produce biosynthetic spider silk that is claimed to be as good as the real stuff.

Physics

The bible-derived idiom says there's nothing new under the sun, but scientists have long been proving that wrong, and 2018 is no different. In February, a team of researchers reported the creation of a new form of matter they dubbed a Rydberg polaron, which is a "giant atom" stuffed with smaller atoms that could aid in investigating the physics of ultracold atoms.

Meanwhile, in a discovery that could have applications in quantum computing, scientists created a new form of light in which groups of photons can be made to interact with each other, slow down and gain mass. While we're on the subject of light, astronomers managed to calculate the total number of photons emitted by all the stars in the observable universe in the past 13 billion years. Unsurprisingly, it's a very big number – a four followed by 84 zeroes.

Time itself was the subject of another notable advance this year – specifically the accuracy of the experimental atomic clocks tested at the National Institute of Standards and Technology (NIST). Setting new records for systematic uncertainty, stability and reproducibility, the clocks could help more precisely measure the Earth's gravity and aid in the search for dark matter.

For the first time, scientists also managed to create rare and elusive quantum ball lightning in the lab. In addition to shedding light on this strange phenomenon, this could help in the development of more stable fusion reactors.

Last month, scientists voted in a new definition for the kilogram that relies on the Planck constant rather than a lump of metal in a vault in France. You won't notice the change on your bathroom scales, so unfortunately it doesn't mean you can indulge in an extra helping of desert.

Biology

Like the changing climate of the planet, there was also plenty of worrying news for the lifeforms that live on it in 2018. A WWF report found a 60 percent decline in animal populations since 1970, with the number of vertebrates falling by more than half between 1970 and 2012. Another report by the Wildlife Conservation Society revealed a big part of the problem is the dramatic decrease in wilderness regions, with just 23 percent of the planet's landmass remaining in a near natural state.

Such news doesn't bode well for the survival of a multitude of species, but scientists provided a glimmer of hope for keeping functionally extinct species from disappearing completely by producing first-of-a-kind test tube embryos of the northern white rhino, of which no males remain.

And providing more proof of just how much we still don't know about the organisms we share our planet with, scientists uncovered the first life form that doesn't adhere to a "universal rule" of DNA and continued to uncover new species that span from the depths of the Atacama Trench to the high altitudes of the atmosphere. And if your interest lies with old instead of new animals, how about the worms found frozen in the Siberian permafrost that were thawed out and revived after 40,000 years.

Going back even further, scientists used what is known as a "molecular clock" to create a rough timeline of all life on Earth that traced the first organisms on the planet to around 4.5 billion years ago.

Fossils

This year saw the declaration of a new geological age – the official updating of the International Chronostratigraphic Chart means we are now living in the Meghalayan age, which began 4,200 years ago. And although we're still living in the Holocene epoch, which began 11,700 ago, some scientists are arguing a new geological epoch called the Anthropocene should be declared to reflect the impact of human activity on the planet.

Genetic studies also provided direct evidence of interbreeding between early humans, while an extraordinarily well-preserved corpse found frozen in the Eastern Italian Alps revealed what was on the menu 5,300 years ago. Additionally, the discovery of what may be the oldest human drawings ever found reveal just how far back our artistic side goes, while studies of ancient stone mortars showed our love of beer and cheese might be older than previously thought.

Human remains are all well and good, but nothing beats a good dinosaur fossil. And there were plenty of finds that kept paleontologists busy in 2018, including the remains of what would have been the world's largest land animal almost 200 million years ago, the first giant dinosaur, the first known bird beak, and a new species of ichthyosaur that could rival the Blue Whale in terms of size. Fossilized footprints also proved a treasure trove, with the smallest and largest dinosaur footprints ever found, along with what may have been a "dinosaur superhighway" in Alaska that connected Asia to North America, and evidence of early mammals and dinosaurs living side-by-side.

Vale Stephen Hawking

Finally, the scientific world, and the world at large, suffered a huge loss in March when Stephen Hawking passed away at the age of 76. He was diagnosed with motor neurone disease at 21 when doctors gave him just two years to live, but he proved them wrong and went on to become the most famous theoretical physicist since Einstein – maintaining a sense of humor along the way. He built on Einstein's work with a theory of cosmology that explained a union between Einstein's general theory of relativity and quantum mechanics, while in 1976 he set out the theoretical argument for black holes releasing a form of radiation that now bears his name. His list of accomplishments are long and his impact on science massive and ongoing. The world is a poorer place without him but a better place for having had him in it.

This is hardly a comprehensive list of the remarkable goings on in the world of science in 2018, so if your favorite science story doesn't appear above, be sure to jog our memories in the comments. Also, some of the biggest science news took place in space and medicine, which we've covered in dedicated roundups here (space) and here (medicine). And if your interests lean towards the weird as well as the wonderful, check out our look back at the weirdest science stories of 2018.

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