This week three experts explain why more people are thinking about leaving Hong Kong after China's clampdown on dissent – and the choices they face about where to go. And we hear about a new way to speed up the hunt for one of the universe's most elusive enigmas: dark matter. Welcome to episode 4 of The Conversation Weekly, the world explained by experts.

Since China imposed a new National Security Law on Hong Kong in mid-2020, the situation for protesters has become much more dangerous. Many of those involved in recent pro-democracy protests are being rounded up and arrested. Some Hong Kongers are now thinking about leaving – and in this episode we hear from experts researching what is influencing these decisions. Sui Ting Kong, assistant professor in sociology at Durham University, tells us what her interviews with Hong Kongers is revealing about the different ways they describe their decision to leave. Peter William Walsh, a researcher at the Migration Observatory at the University of Oxford, explains the details of a new visa route the UK government has opened up those Hong Kongers who hold British National Overseas status. And Tsungyi Michelle Huang, professor of geography at National Taiwan University, talks about her research on migration from Hong Kong to Taiwan, and how Taiwan has become a more attractive destination.

In our second story, we're joined by Benjamin Brubaker, a physicist at the University of Colorado, Boulder, who is on the hunt for dark matter. Dark matter is invisible – but it accounts for 85% of the matter in the universe. He explains how he and his colleagues used technology from the quantum computing world to speed up the search.

And Luthfi Dzulfikar, associate editor at The Conversation in Jakarta, recommends a couple of recent stories by academics in Indonesia. 

The Conversation Weekly is hosted by Gemma Ware and Dan Merino. The show is co-produced by Mend Mariwany and Gemma Ware, with sound design by Eloise Stevens. Our theme music is by Neeta Sarl. Visit The Conversation for full credits.

Further reading:

• Hong Kong: China crackdown is likely to boost migration to UK, by Peter William Walsh, Researcher at the Migration Observatory, University of Oxford
• With mass arrests, running for office in Hong Kong is now not only futile, it can be criminal, by Brendan Clift, Teaching Fellow and PhD Candidate, University of Melbourne
• Hong Kong: does British offer of citizenship to Hongkongers violate Thatcher’s deal with China? by Chi-Kwan Mark, Senior Lecturer in International History, Royal Holloway, University of London  
• The search for dark matter gets a speed boost from quantum technology, by Benjamin Brubaker, Postdoctoral Fellow in Quantum Physics, University of Colorado Boulder
• Ignoring aspirations and threatening arrest: these 5 things show that the Jokowi administration does not accept criticism from its citizens, (in Bahasa Indonesian), by Herlambang P Wiratraman, Lecturer of Constitutional Law at Universitas Airlangga and Juwita Hayyuning Prastiwi, Lecturer in Political Science at Universitas Brawijaya
• Single people in Indonesia look for happiness on the internet - but fail to find it, (in Bahasa Indonesian), by Karel Karsten Himawan, Lecturer of Psychology, Universitas Pelita Harapan