Author: BBC World Service

This week two research groups announced that they have made synthetic mouse embryos that developed brains and beating hearts in the test tube, starting only with embryonic stem cells. No sperm and eggs were involved. Previously, embryos created this way have never got beyond the stage of being a tiny ball of cells. These embryos grew and developed organs through 8 days – more than a third of the way through the gestation period for a mouse. Roland Pease talks to the leader of one of the teams, developmental biologist Magdalena Zernicka-Goetz of Cambridge University and Caltech about how and why they did this, and the ethical issues around this research.

Also in the programme: the latest research on how we spread the SARS-CoV-2 virus when we breathe. Infectious disease researcher Kristen Coleman of the University of Maryland tells us about her experiments that have measured the amounts of virus in the tiny aerosol particles emanating from the airways of recently infected people. The results underscore the value of mask-wearing and effective ventilation in buildings.

We also hear about new approaches to vaccines against the virus – Kevin Ng of the Crick Institute in London talks about the possibility of a universal coronavirus vaccine based on his research, and immunologist Akiko Iwasaki of Yale University extolls the advantages of nasal vaccines against SARS-CoV-2.

From dumping raw sewage into rivers to littering the streets with our trash, humans don’t have a great track record when it comes to dealing with our waste. It’s something that CrowdScience listener and civil engineer Marc has noticed: he wonders if humans are particularly prone to messing up our surroundings, while other species are instinctively more hygienic and well-organised.

Are we, by nature, really less clean and tidy than other animals? Farming and technology have allowed us to live more densely and generate more rubbish - maybe our cleaning instincts just aren’t up to the vast quantities of waste we spew out? CrowdScience digs into the past to see if early human rubbish heaps can turn up any answers. We follow a sewer down to the River Thames to hear about The Great Stink of Victorian London; turn to ants for housekeeping inspiration; and find out how to raise hygiene standards by tapping into our feelings of disgust and our desire to follow rules.

(Image: Stem cell built mouse embryo at 8 days. Credit: Zernicka-Goetz Lab)

From dumping raw sewage into rivers to littering the streets with our trash, humans don’t have a great track record when it comes to dealing with our waste. It’s something that CrowdScience listener and civil engineer Marc has noticed: he wonders if humans are particularly prone to messing up our surroundings, while other species are instinctively more hygienic and well-organised.

Are we, by nature, really less clean and tidy than other animals? Farming and technology have allowed us to live more densely and generate more rubbish - maybe our cleaning instincts just aren’t up to the vast quantities of waste we spew out? CrowdScience digs into the past to see if early human rubbish heaps can turn up any answers. We follow a sewer down to the River Thames to hear about The Great Stink of Victorian London; turn to ants for housekeeping inspiration; and find out how to raise hygiene standards by tapping into our feelings of disgust and our desire to follow rules.

Presented by Marnie Chesterton and produced by Cathy Edwards for the BBC World Service.

[Image: Man on beach with rubbish. Credit: Getty Images]

This week two research groups announced that they have made synthetic mouse embryos that developed brains and beating hearts in the test tube, starting only with embryonic stem cells. No sperm and eggs were involved. Previously, embryos created this way have never got beyond the stage of being a tiny ball of cells. These embryos grew and developed organs through 8 days – more than a third of the way through the gestation period for a mouse. Roland Pease talks to the leader of one of the teams, developmental biologist Magdalena Zernicka-Goetz of Cambridge University and Caltech about how and why they did this, and the ethical issues around this research.

Also in the programme: the latest research on how we spread the SARS-CoV-2 virus when we breathe. Infectious disease researcher Kristen Coleman of the University of Maryland tells us about her experiments that have measured the amounts of virus in the tiny aerosol particles emanating from the airways of recently infected people. The results underscore the value of mask-wearing and effective ventilation in buildings.

We also hear about new approaches to vaccines against the virus – Kevin Ng of the Crick Institute in London talks about the possibility of a universal coronavirus vaccine based on his research, and immunologist Akiko Iwasaki of Yale University extolls the advantages of nasal vaccines against SARS-CoV-2.

(Image: Stem cell built mouse embryo at 8 days. Credit: Zernicka-Goetz Lab)

Presenter: Roland Pease Producer: Andrew Luck-Baker

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