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This week’s new questions

Why is tea more likely than coffee to leave a stain in the cup? And how exactly does one entangle two photons? Can it be done at home?

5 March 2025

Âé¶¹´«Ã½. Science news and long reads from expert journalists, covering developments in science, technology, health and the environment on the website and the magazine.

Dimitri Otis/Getty Images

Why is tea more likely than coffee to leave a stain in the cup?

Wolf Kirchmeir,

Blind River, Ontario, Canada

RAT1RK Experiment with red laser in optics lab

For submit/Alamy

Quantum physicists talk a lot about entanglement. How exactly does one entangle two photons? And can I try it at home?

John Healey,

Adelaide, South Australia

To answer this question – or ask a new one – email lastword@newscientist.com.

Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.

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