Dr Chris van Tulleken has been at the forefront of the campaign to change our food system and better regulate the sale of ultra-processed foods (UPF). This year he will be giving the Royal Institution Christmas lectures, Britain’s most prestigious public science lectures, in which he’ll be investigating how food has fundamentally shaped human evolution, the importance of our microbiome – as the extra ‘organ’ we didn’t know we had – and how we can all eat better in future, for the sake of our own health and the health of the planet. Nicola Davis sat down with Van Tulleken to discuss the lectures, the challenge of understanding the impact of UPFs on our health, and his top tip for Christmas dinner. Madeleine Finlay hears from them both in this Christmas special edition of Science Weekly. Help support our independent journalism at theguardian.com/sciencepod

For the past 10 years cosmologists have been left scratching their heads over why two methods for measuring the universe’s rate of expansion provide totally different results. There are two possible solutions to the puzzle, known as the Hubble tension: either something is wrong with the measurements or something is wrong with our model of the universe. It was hoped that observations from the James Webb space telescope might shed some light on the problem, but instead results published last week have continued to muddy the waters. To understand why the expansion rate of the universe remains a mystery, and what might be needed to finally pin it down, Madeleine Finlay speaks to Catherine Heymans, the astronomer royal for Scotland and a professor of astrophysics at the University of Edinburgh. Help support our independent journalism at theguardian.com/sciencepod

On Monday Google unveiled its Willow quantum computing chip. The new chip takes just five minutes to complete tasks that would take 10 septillion years for some of the world’s fastest conventional computers to complete. But despite its impressive power, it’s not clear the chip has any practical applications. So does it bring quantum computing any closer? To find out Ian Sample speaks to Winfried Hensinger, professor of quantum technologies at the University of Sussex. Because of industrial action taking place by members of the National Union of Journalists at the Guardian and Observer this week, you may notice some disruption to the availability of new episodes in your Guardian podcast feeds in the coming days. All the work on this episode was done before the strike action began. For more information please head to theguardian.com. Help support our independent journalism at theguardian.com/sciencepod

Madeleine Finlay speaks to Sophie Scott, a professor of cognitive neuroscience at University College London, to dig into the science of laughter. Sophie explains what exactly laughter is, the many different purposes it serves for humans and animals, and how prioritising it could make us all feel a little better. Help support our independent journalism at theguardian.com/sciencepod

Ian Sample speaks to colorectal surgeon and researcher James Kinross about the miraculous world of our gut microbiome, how modern life is impacting it, and what we can do to look after it Because of industrial action taking place by members of the National Union of Journalists at the Guardian and Observer this week, we are re-running an episode from earlier in the year. For more information please head to theguardian.com. We’ll be back with new episodes soon.. Help support our independent journalism at theguardian.com/sciencepod

What if you could take a pill or a shot that could reduce your blood alcohol level and make you feel better in the morning? That’s the promise of a range of wellness products aiming to be the next big hangover antidote. But what exactly are hangovers, and which methods of preventing them are backed by science? Madeleine Finlay speaks to Dr Sally Adams, an alcohol researcher and associate professor of psychology at the University of Birmingham. Help support our independent journalism at theguardian.com/sciencepod

The conversation about fluoride’s health benefits has exploded recently after a US federal toxicology report, court ruling and independent scientific review all called for updated risk-benefit analysis. Ian Sample hears from Catherine Carstairs, professor of history at the University of Guelph in Canada, about how attitudes to fluoridation have evolved, and Oliver Jones, professor of chemistry at RMIT University in Australia, about where the science stands today. Help support our independent journalism at theguardian.com/sciencepod

Madeleine Finlay hears from the Guardian’s environment editor, Damian Carrington, about the controversial climate finance deal that brought Cop29 negotiations to a close in the early hours on Sunday morning in Baku, Azerbaijan. Developing countries asked rich countries to provide them with $1.3tn a year to help them decarbonise their economies and cope with the effects of the climate crisis. But the final deal set a pledge of just $300bn annually, with $1.3tn only a target. Damian tells Madeleine how negotiations unfolded, and what we can expect from next year’s conference in Brazil. Help support our independent journalism at theguardian.com/sciencepod

Science editor Ian Sample joins host Madeleine Finlay to discuss some of the most intriguing science stories of the week. From a study finding that fat cells ‘remembering’ past obesity drives yo-yo dieting, to concerning developments in the bird flu virus, and research pinpointing which parts of the UK are best at spotting fake accents. Help support our independent journalism at theguardian.com/sciencepod

It’s a dream for many children, but what does it actually take to become an astronaut? Science correspondent Hannah Devlin tells Ian Sample about her trip on a zero gravity flight with the European Space Agency (Esa). Back on solid ground she also got to speak to Rosemary Coogan, one of Esa’s newest recruits, about the rigorous process that led to her being chosen from more than 20,000 applicants, to become an astronaut, and what she hopes to achieve in her role. Help support our independent journalism at theguardian.com/sciencepod