The first galaxies at the universe's dawn

In the last week, teams of astronomers have rushed to report ever deeper views of the universe thanks to the James Webb Space Telescope. These are galaxies of stars more than 13.5 billion light years from us and we see them as they were when the universe was in its infancy, less than 300 million years after the Big Bang. As University of Texas astronomer Steve Finkelstein tell us, there are some real surprises in these glimpses of the cosmic dawn. The super-distant galaxy that Steve's group has identified is named after his daughter Maisie.

Also in the programme: a 550 million year old fossil which is much the oldest representative of a large group of animals still with us today. The early jellyfish relative lived at a time known as the Ediacaran period when all other known complex organisms were weird, alien-looking lifeforms with no surviving descendants. Roland Pease talks palaeontologist Frankie Dunn at the University of Oxford who's led the study of Auroralumina attenboroughii.

Did the cultural invention of romantic kissing five thousand years ago lead to the spread of today's dominant strain of the cold sore virus (Herpes simplex 1) across Europe and Asia? That's the hypothesis of a team of virologists and ancient DNA experts who've been studying viral DNA remnants extracted from four very old teeth. Cambridge University's Charlotte Houldcroft explains the reasoning.

And, if a tree falls in a forest and no-one is there to hear it, does it make a sound? This is an age-old debate that listener Richard and his family have been arguing about for years. Can CrowdScience settle it once and for all?

Caroline Steel speaks to experts in hearing, biology, philosophy, physics and sound design, which takes her to some unexpected places.

Professor Stefan Bleek is an expert in psychoacoustics who says that sounds only exist in our heads. Dr Eleanor Knox and Dr Bryan Roberts are philosophers that make her question if anything exists outside our own perception. Professor Lilach Hadany wonders if it’s limited to humans and animals - could other plants hear the falling tree too? And Mat Eric Hart is a sound designer who says that sound is subjective – it’s always tangled up with our own interpretations.

Things get truly weird as we delve into the strange implications of quantum physics. If there is such a thing as reality, doesn’t it change when we’re there to observe it? Does the tree even fall if we aren’t there?

Image: Maisie's Galaxy aka CEERSJ141946.35-525632.8. Credit: CEERS Collaboration