What you're getting wrong about hydration (and how much is really enough)

As storm season begins, America's weather service is still reeling from sweeping cuts. And the consequences could be fatal

Myopia is booming. Can we stop the epidemic of short-sightedness?

Meeting new people, making conversation, keeping up appearances – it all takes energy. Here's how to make it easier

At this point in time, black holes feel… inescapable. I’m not talking about their gravitational pull, but rather how every week seems to bring the publication of a new paper about these cosmic monsters. For such enigmatic objects, we hear an awful lot about them. This is mostly thanks to the discovery, made a little over 10 years ago, that we could detect and measure gravitational waves. When this happened, we found a new way to look at the Universe. Until then, we had relied on various types of sensors to collect light (X-rays, visible light, radio waves and so on) or particles, such as cosmic rays, to examine the Universe. All of which, famously, tell us almost nothing about black holes. But then, on 14 September 2015, we picked up the signal created by two black holes spiralling around each other and merging. The event didn’t create a flash or a bang; instead, it created a ripple in spacetime that surged towards us at the speed of light. Here on Earth, the Laser Interferometer Gravitational-wave Observatory (LIGO) picked up this vibration in the fabric of spacetime and, in doing so, gave us a new way to probe the Universe – and a means to investigate the behaviour of black holes. Fast forward to today, and LIGO and its new partners – the Virgo interferometer in Italy and the Kamioka Gravitational Wave Detector (KAGRA) in Japan – have become black hole hunters, tracking 300 mergers between them. The signals received and the measurements taken are slowly disrobing black holes of their secrecy. By analysing these signals, scientists can determine how a black hole formed, its mass and spin, its energy output and much more. We’ve discovered black holes are much bigger and much more common than we thought, and that there might be different generations spread throughout the Universe. And yet, we still haven’t been able to peer inside one. That final frontier still remains… or does it? Read this issue to find out.

The healthcare system wasn’t built for women. Here’s why that needs to change

Neuroscience may have finally uncovered the secrets of self-belief

An almost invisible galaxy could crack open one of the biggest questions in cosmology

Known for its massive retractable jaw, the spooky footage shows the goblin shark lurking deep in the Pacific Ocean