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What does “equals” mean? For mathematicians, this simple question has more than one answer, which is causing big issues. Plus: gene therapy enables five children who were born deaf to hear.

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What does ‘equals’ mean?

When you see “2 + 2 = 4”, what does “=” mean? It turns out that’s a complicated question, because mathematicians can’t agree on the definition of what makes two things equal. While this argument has been quietly simmering for decades, a recent push to make mathematical proofs checkable by computer programs, called formalisation, has given the argument new significance. Read more.

Hearing for the first time

Five children in China who were born deaf can now hear with both ears after getting gene therapy to provide a normal copy of a mutated gene. The degree of hearing varies from child to child, but all can now hear voices at a conversational volume and locate the source of sounds. Read more.

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Have a great Thursday!

Chris Simms

Assistant news editor, New Scientist

Email me at [email protected]

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