Does it take 15,000 litres of water to produce a kilogram of beef?

Does it take 15,000 litres of water to produce a kilogram of beef?

If you spend much time on social media, and we don’t necessarily recommend it, then you’ve probably come across a strange fascination with water consumption. Mainly, this is people telling you that using AI is terrible for the planet because of how much water it uses. We’ve already made a couple of programmes about the numbers in those arguments and, long story short, they probably aren’t saying what you think they’re saying. But on platforms like X, BlueSky, and TikTok, an opportunity to keep an argument going is rarely missed And one of the numbers that’s been enlisted in that glorious cause concerns the water that’s used for a seemingly unrelated past-time - eating beef. Here’s an example from a user on X: “A kilogram of beef requires over 15,000 litres of water to produce,” they wrote. “A vegan who uses ChatGPT every day is living a more sustainable lifestyle than someone who regularly eats beef while boycotting AI.” Ignoring the AI part, is that true? Does it actually take 15,000 litres of water to produce a kilogram of beef? It turns out that the number isn’t wrong, but it probably isn’t saying what you think it’s saying. If you’ve seen a number you think we should take a look at, email the More or Less team: moreorless@bbc.co.uk CONTRIBUTORS: Mesfin Mekonnen, Assistant Professor at the University of Alabama Mark Mulligan, Professor of Physical and Environmental Geography at King's College London Tim Hess, Professor of Water and Food Systems at Cranfield University CREDITS: Presenter: Charlotte McDonald Producer: Mhairi MacKenzie Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound mix: Emma Harth Editor: Richard Vadon

Have RFK and MAHA really changed American views on vaccines?

Vaccine policy in the US is something of an ideological battleground. Health Secretary Robert F Kennedy Jr is a vaccine sceptic, and since taking office he has attempted to remake US vaccine policy. In March a judge blocked his proposal to cut the number of jabs that are recommended for kids. At the same time, last year saw the worst measles outbreak in the US in decades. There were more than 2000 cases last year, and three people died. There have been more than 1500 cases so far in 2026. There’s a lot going on, so it’s possible the public’s views on vaccination are shifting. A new poll published by online news site Politico added a big claim into the mix. According to the headline “more Americans doubt vaccine safety than trust it”. But is that what the survey actually found? Dr David Higgins, a paediatrician and public health assistant professor who writes a Substack called Community Immunity, explains why he believes the headline is misleading. If you've seen a number in the news you think we should take a look at, email moreorless@bbc.co.uk Presenter: Charlotte McDonald Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound mix: Neil Churchill Editor: Richard Vadon

Is Trump right that wind turbines are killing millions of birds?

US president Donald Trump is no fan of wind turbines, or windmills as he calls them. Not only does he think they ruin the view from a golf course he owns in Scotland, but they are also deadly to birds. “If you love birds, you’d never want to walk under a windmill,” he said in 2019. “It’s a very sad, sad sight. It’s like a cemetery. We put a little statue for the poor birds.” Earlier this year he posted on Truth Social saying that wind turbines were killing “millions” of birds. But is that true? We speak to Dr Hannah Ritchie, Deputy Editor at Our World in Data and senior researcher at the University of Oxford, who has dug into the numbers on bird mortality and wind turbines. Credits: Presenter: Charlotte McDonald Producer: Mhairi MacKenzie Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound mix: Sue Maillot Editor: Richard Vadon

Dr Spock’s dangerous advice on baby sleep

Sometimes it is obvious to everyone when an idea is harmful, or a piece of advice is damaging. But not always. Occasionally bad ideas and terrible advice end up being accepted in society and supported by people in authority. In such circumstances, one of the most powerful tools for changing people's minds is evidence – scientific studies that show beyond doubt that the bad idea is, indeed, a bad idea. That's the subject of a new book by Helen Pearson, titled Beyond Belief: How Evidence Shows What Really Works. An editor at the scientific journal Nature in her day job, the book chronicles those determined individuals who shake up the status quo by gathering just the right kind of evidence. One story in that book stood out to us on More or Less as it shows just what happens when you don't have the evidence you need to challenge a dangerous way of doing things. It's the story of a piece of advice from childcare expert Dr Benjamin Spock. In a 1958 revision of his bestselling parenting guide Baby and Childcare he made a small change to his advice on sleeping position – advising parents to put their babies to sleep on their front. It eventually became clear that this sleeping position was associated with a significant increase in the risk of sudden infant death, or cot death. CREDITS: Presenter: Charlotte McDonald Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound mix: Rod Farquhar Editor: Richard Vadon

How likely is ‘likely’?

When you’re listening to the news, you will often hear words that are meant to communicate the probability of something happening.   A terrorist attack is “a realistic possibility”, the spread of a certain strain of virus is “highly likely", the relegation of your favourite football team is “possible”. But when you hear these terms, do you really know what kind of probabilities they’re trying to convey? Do you know how likely “likely” is? Or what probability “probable” is meant to get across? In some cases, it seems you probably don't. Professor Adam Kucharski, author of Proof, the Uncertain Science of Certainty, designed a quiz to work out the actual probabilities of the language we use to convey risks. The data he got back shows how sometimes these words mean very different things to different people. If you want to try the quiz for yourself, head over to https://probability.kucharski.io/ Email the More or Less team: moreorless@bbc.co.uk CREDITS: Presenter: Charlotte McDonald Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound mix: Gareth Jones Editor: Richard Vadon