Science

The bartender says: “We don’t serve time travellers in here.” A time traveller walks into a bar. OK, yes, I will almost certainly regret starting this article with such a hoary old joke. At some point, most of us have wished we could travel back in time to repair some misstep or faux pas. But it’s impossible, right? Well, not necessarily. Albert Einstein’s general theory of relativity suggests that time travel may indeed be possible. We know that matter can bend space-time, and if you bend it enough, you may be able to create a time loop. Caveats abound, of course, and researchers are yet to announce a working time machine. But that hasn’t put them off exploring the possibilities. Here are five ways that time travel might just be feasible, from science fiction st...

Last month, more than 50,000 people from 200 countries gathered for the 29th U.N. Climate Change Conference of the Parties (COP29) in Baku, Azerbaijan. For two weeks, global leaders, academics, scientists, public citizens, activists and nonprofit organizations from around the world came together to address the growing challenges and potential solutions to climate change.   Similar to previous years, COP29 and its aftermath were met with mixed reactions. While this year’s convention ultimately reached a finance goal—known formally as the New Collective Quantified Goal on Climate Finance (NCQG)—promising $300 billion in annual funding to developing countries by 2035, many nations say this will be inadequate for climate mitigation and adaptation in the coming decade. Delegates also sig...

Unidentified drones have been flying over US military sitesU.S. Navy/Ensign Drew Verbis Mysterious drones have been swarming the night skies above New Jersey and other nearby states for a month. They have been spotted over several US military sites. They have been videoed over houses and apartment buildings. A swarm was seen following a US Coast Guard rescue boat at the same time that New Jersey police reported 50 drones arriving on land from the ocean. But no one seems to know who is piloting them, or whether it is a coordinated effort. The incidents have drawn the attention of state governors and legislators, as well as members of the US Congress, and the FBI has launched an investigation, asking for the public to report sightings. Witnesses describe the drones ...

Entanglement is a key part of quantum computingBartlomiej K. Wroblewski/Alamy While scientists generally try to find sensible explanations for weird phenomena, quantum entanglement has them tied in knots. This link between subatomic particles, in which they appear to instantly influence one another no matter how far apart, defies our understanding of space and time. It famously confounded Albert Einstein, who dubbed it “spooky action at a distance”. And it continues to be a source of mystery today. “These quantum correlations seem to appear somehow from outside space-time, in the sense that there is no story in space and time that explains them,” says Nicolas Gisin at the University of Geneva, Switzerland. But the truth is that, as physicists have come to accept the my...

Ashokan Reservoir, October 2024. Photo: Agnes Laylicha, School of International and Public Affairs and Columbia Climate School Increasing climate variability is threatening the water supply and exposing the fragility of the New York City watershed, which hosts the largest unfiltered water supply in the world. Columbia Climate School students had the opportunity to learn about the history of this critical reservoir system—one that supplies 10 million New Yorkers with over 1 billion gallons of safe drinking water every day—on a recent field trip. The New York City Watershed: From Community Displacement to Collaboration and Climate Adaptation, one of four practicum courses offered annually within the sustainable development program, takes students to the Catskill Mountains to learn fir...