1. On 11 February, researchers announced that they had finally sensed the ripples in the structure of space-time known as gravitational waves — capping a decades-long quest.
  2. A tumultuous US presidential campaign ended in a surprise victory for Republican businessman Donald Trump in November. Researchers struggled to understand how a Trump administration would treat science — in part, because it did not feature prominently on the campaign trail.
  3. In March, the Japan Aerospace Exploration Agency’s flagship Hitomi X-ray astronomy satellite failed just weeks after launch. Investigators determined that a software error had caused the spacecraft to rotate out of control and break apart. In July, NASA’s Juno probe arrived at Jupiter, but problems with its main engine delayed the rocket firing that would have shrunk its orbit into a tighter ellipse around the planet.
  4. The development of new applications for the genome-editing tool CRISPR–Cas9 continued apace. On 28 October, a patient with lung cancer at West China Hospital in Chengdu became the first person to be treated with cells edited using CRISPR–Cas9. As part of a clinical trial, researchers disabled a gene that normally holds a cell’s immune system in check, in the hope that the edited cells would mount an immune response against the cancer.
  5. Representatives of a record 174 countries and the European Union gathered on Earth Day, 22 April, to sign the international climate agreement forged in Paris in December 2015.
  6. In February, the World Health Organization (WHO) declared that clusters of birth defects linked to outbreaks of Zika virus in Brazil constituted a global public-health emergency.
  7. In January, a computer program beat a world-class human player at the ancient game of Go for the first time. But the ultimate showdown was in March, when the artificial intelligence (AI), called AlphaGo, trounced Lee Sedol — one of the world’s top players.
  8. In September, researchers working in a Mexican clinic reported the birth of the first healthy baby conceived through assisted-reproduction techniques that mix DNA from three people. A baby in China was also reportedly born using the same technique. And in October, a clinic in Ukraine announced that two previously infertile women had conceived through a similar procedure. On 15 December, following scientists’ advice, the United Kingdom’s Human Fertilisation and Embryology Authority said that the technique was ready for clinical use, which could start as soon as 2017.

To read more, click Science Events of the Year.