Planetary confusion: why astronomers keep changing what it means to be a planet

Christopher Palma, Pennsylvania State University As an astronomer, the question I hear the most is why isn’t Pluto a planet anymore? More than 10 years ago, astronomers famously voted to change Pluto’s classification. But the question still comes up.

What are lost continents, and why are we discovering so many?

Maria Seton, University of Sydney; Joanne Whittaker, University of Tasmania, and Simon Williams, University of Sydney For most people, continents are Earth’s seven main large landmasses. But geoscientists have a different take on this. They look at the type of rock a feature is made of, rather than how much of its surface is above …

Were other humans the first victims of the sixth mass extinction?

Nick Longrich, University of Bath Nine human species walked the Earth 300,000 years ago. Now there is just one. The Neanderthals, Homo neanderthalensis, were stocky hunters adapted to Europe’s cold steppes. The related Denisovans inhabited Asia, while the more primitive Homo erectus lived in Indonesia, and Homo rhodesiensis in central Africa. Several short, small-brained species …

Climate explained: why Mars is cold despite an atmosphere of mostly carbon dioxide

Paulo de Souza, Griffith University Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

Humanity’s birthplace: why everyone alive today can call northern Botswana home

Vanessa Hayes, University of Sydney Where was the evolutionary birthplace of modern humans? The East African Great Rift Valley has long been the favoured contender – until today. Our new research has used DNA to trace humanity’s earliest footsteps to a prehistoric wetland called Makgadikgadi-Okavango, south of the Great Zambezi River. Our analysis, published in …

Evolution tells us we might be the only intelligent life in the universe

Are we alone in the universe? It comes down to whether intelligence is a probable outcome of natural selection or an improbable fluke. By definition, probable events occur frequently, improbable events occur rarely – or once. Our evolutionary history shows that many key adaptations – not just intelligence, but complex animals, complex cells, photosynthesis, and …

Animals are disappearing from forests, with grave consequences for the fight against climate breakdown – new research

It’s tempting to think that our forests would be fine if we could simply stop trees from being felled or burnt. But forests – particularly tropical ones – are more than just trees. They’re also the animals that skulk and swoop among them. Worryingly, these furry and feathered companions are rapidly disappearing – and our …

Wandering Earth: rocket scientist explains how we could move our planet

In the Chinese science fiction film The Wandering Earth, recently released on Netflix, humanity attempts to change the Earth’s orbit using enormous thrusters in order to escape the expanding sun – and prevent a collision with Jupiter. The scenario may one day come true. In five billion years, the sun will run out of fuel …

What Earth’s changing climate can teach us about altering the surface of Mars

In a rare instance of environmental success, the United Nations has just announced it believes the damage to the Earth’s protective ozone layer will be fully restored by the year 2050. This stands in stark contrast to the increasing alarm over the climate emergency, caused by an increasing greenhouse effect. Gareth Dorrian, University of Birmingham …