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At this point, most people have heard the accepted wisdom that you need 8 hours sleep every night, especially for a healthy brain. But what if we’ve got it all wrong? If you lie awake at night worrying about getting enough sleep, you may be in luck. A reminder that correlation is not causation, and some surprising new research into how our brains respond to lower amounts of sleep.

In space news, NASA’s Lucy spacecraft has just completed a fly-by of a ‘nearby’ asteroid, in preparation for a much bigger excursion out into the solar system. Lucy’s next mission takes it to Jupiter, where it’ll be exploring the asteroids that follow in the gas giant’s orbit, and which may be fragments from early planetary formation. Also, unusual dense spots buried deep within Earth’s mantle may actually be remains of an ancient planet that collided with ours. What buried bits of ‘Theia’ might tell us about Earth’s cosmological history and the creation of our moon.

The UK’s first summit to discuss the safety and security of AI and its role in society has now drawn to a close. Prime Minister Rishi Sunak brought together more than 100 delegates from 28 countries, including tech CEOs such as Elon Musk. Amid frustrations over transparency, and a lacklustre policy result, what did the summit actually achieve?

Can you find the head on a starfish? Researchers investigating the animal’s genes are finding that starfish are actually just heads, and perhaps nothing else, crawling around on their lips. What this finding tells us about the way ecology and natural selection shape animal evolution.

Plus: Why some flatworms are great at sex, while others can regrow their heads – and why they can’t do both at the same time. How a desert plant is adapting to low moisture environments with salty sweat. And why chimps seek out high ground to spy on their rivals.

Hosts Timothy Revell and Christie Taylor discuss all of this with guests Clare Wilson, Leah Crane, Matt Sparkes and Claire Ainsworth. To read more about these stories, visit newscientist.com.

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Weekly: Do you really need 8 hours of sleep?; The ancient planet buried inside Earth; Starfish are just heads

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