future

  Our galaxy formed its original disk 2 billion years before its stellar halo The Milky Way arches over the Large Sky Area Multi-Object Fiber Spectroscopic Telescope in China, one of the observatories whose data has revealed that our galaxy began forming a disk of stars surprisingly fast after the Big Bang. YINGWEI CHEN A new analysis of nearly a quarter million stars puts firm ages on the most momentous pages from our galaxy’s life story. Far grander than most of its neighbors, the Milky Way arose long ago, as lesser galaxies smashed together. Its thick disk — a pancake-shaped population of old stars —  originated remarkably soon after the big bang and well before most of the stellar halo that envelops the galaxy’s disk, astronomers report March 23 in  Nature . “We are now able to provide a very clear timeline of what happened in the earliest time of our Milky Way,” says astronomer Maosheng Xiang. He and Hans-Walter Rix, both at the Max Planck Institute for Astronomy in Heidelberg, Ge

 Nasa's first spacecraft built to explore the deep interior of another world streaked toward a landing scheduled for Monday on a vast, barren plain on Mars, carrying instruments to detect planetary heat and seismic rumblings never measured anywhere but Earth. After sailing 301 million miles (548 million km) on a six-month voyage through deep space, the robotic lander InSight was due to touch down on the dusty, rock-strewn surface of the Red Planet at about 8 pm GMT. If all goes according to plan, InSight will hurtle through the top of the thin Martian atmosphere at 12,000 miles per hour (19,310 kilometers per hour). Slowed by friction, deployment of a giant parachute and retro rockets, InSight will descend 77 miles through pink Martian skies to the surface in 6 1/2 minutes, traveling a mere 5 mph (8 kph) by the time it lands. The stationary probe, launched in May from California, will then pause for 16 minutes for the dust to settle, literally, around its landing site, before disc-

  According to theoretical physicist Carlo Rovelli, time is an illusion: our naive perception of its flow doesn’t correspond to physical reality. Indeed, as Rovelli argues in  The Order of Time , much more is illusory, including Isaac Newton’s picture of a universally ticking clock. Even Albert Einstein’s relativistic space-time — an elastic manifold that contorts so that local times differ depending on one’s relative speed or proximity to a mass — is just an effective simplification. So what does Rovelli think is really going on? He posits that reality is just a complex network of events onto which we project sequences of past, present and future. The whole Universe obeys the laws of quantum mechanics and thermodynamics, out of which time emerges. Rovelli is one of the creators and champions of loop quantum gravity theory, one of several ongoing attempts to marry quantum mechanics with general relativity. In contrast to the better-known string theory, loop quantum gravity does not att

  A   blockchain   is a growing list of  records  , called   blocks , that are linked together using  cryptography  .   Each block contains a  cryptographic hash   of the previous block, a  timestamp , and transaction data (generally represented as a  Merkle tree ). The timestamp proves that the transaction data existed when the block was published to get into its hash. As blocks each contain information about the block previous to it, they form a chain, with each additional block reinforcing the ones before it. Therefore, blockchains are resistant to modification of their data because once recorded, the data in any given block cannot be altered retroactively without altering all subsequent blocks. Blockchains are typically managed by a peer-to-peer network for use as a publicly distributed   ledger, where nodes collectively adhere to a protocol  to communicate and validate new blocks. Although blockchain records are not unalterable as forks are possible, blockchains may be considered