Concerns raised that some people may be cancelling their second AstraZeneca dose hoping to obtain a shot of Pfizer insteadFollow our Covid live blog for the latest updatesHotspots: NSW; Vic; QldVaccine rollout tracker; get our free news app; get our morning email briefingThe evidence is strongest for receiving two doses of the same Covid-19 vaccine, rather than mixing different types, medical...

Seán Boyle suspects that the Gaelicised spelling of ‘craic’ may be a more recent ploy to attract touristsAndrew Poole (Letters, 26 August) is of course correct that “crack” has a long history in Scots and north-eastern English. But it also existed in Ireland well before its late 20th-century emergence as “craic”. Growing up in south Ulster, it was in regular use by young and old –...

There is scant evidence that ivermectin can treat or prevent Covid - but that hasn’t stopped rightwing pundits and conservative politicians from promoting itYou are not a horse. You are not a cow. You are, I’m afraid, a homo sapiens living in a world so deranged that people would rather poison themselves with worm medicine meant for farm animals than take a vaccine meant for human beings....

The long-running series in which readers answer other readers’ questions on subjects ranging from trivial flights of fancy to profound scientific and philosophical conceptsWhat evolutionary advantage comes from women having considerably less body hair than men? Mal Jones, CardiffPost your answers (and new questions) below or send them to nq@theguardian.com. A selection will be published on...

They can go on research missions in stormy weather, dive to 150 metres and could soon be ‘singing’ signals. These penguin-like devices are helping to explain the eddies that are key to all lifeIf it looks like a penguin and swims like a penguin – but it’s actually a robot – then it must be the latest advance in marine sensory equipment.The Quadroin is an autonomous underwater vehicle...

Food and water were thought to be the main ways humans are exposed to PFAS, but study points to risk of breathing them inToxic PFAS compounds are contaminating the air inside homes, classrooms and stores at alarming levels, a new study has found.Researchers with the University of Rhode Island and Green Science Policy Institute tested indoor air at 20 sites and detected the “forever chemicals”...

Country to press ahead with school openings as it encourages all over-12s to get third jabCoronavirus – latest updatesSee all our coronavirus coverageIsrael has recorded its highest daily number of coronavirus cases with nearly 11,000 new infections, amid a surge caused by the highly transmissible Delta variant as schools prepare to re-open.The previous high came on 18 January, with 10,118...

It is time to evaluate how much transformational control we give billionaires over our societies, and our livesA few weeks ago, Elon Musk announced that his company, Tesla, plans to have a humanoid robot prototype ready next year. The intention is to create a 56kg machine that isn’t “super expensive” to retail. Oh, yes: the commercial application of the planned robot is absolutely to replace...

In an era of divisions over the climate breakdown, tree planting seems to bring everyone together. But are there situations where tree planting can cause more harm than good? And how much can it help us counteract global heating? Patrick Greenfield leads you through the science and controversy behind the decisions we’re making and how those decisions could shape our future environment. He and...