All posts tagged: Spacetime

Physicists rewrite Einstein’s equations to define spacetime evolution

Physicists rewrite Einstein’s equations to define spacetime evolution

Spacetime is often described as the stage on which the universe unfolds, a four-dimensional blend of space and time that bends, stretches and shifts as matter and energy move through it. However, despite more than a century of work since Einstein introduced general relativity, physicists still struggle to describe how that stage evolves when gravity becomes violent, nonlinear and hard to predict. A new theoretical study points to a different way of looking at the problem. Instead of treating spacetime only as geometry, researchers found that some of its structures may behave more like features in an electrically conducting fluid. In this view, these structures stay connected as spacetime changes. That idea comes from researchers at Adolfo Ibáñez University in Chile and Columbia University, whose work was published in Physical Review Letters. Using tools borrowed from electrodynamics and plasma physics, they argue that spacetime can contain what they call gravitational field connections. Additionally, they describe conserved quantities that place topological limits on how curved spacetime can evolve. In plain terms, topology deals with what stays …

Black hole GW190521 may be a wormhole from another universe

Black hole GW190521 may be a wormhole from another universe

For just one-tenth of a second in May 2019, the universe delivered a signal that did not fit the usual script. LIGO and Virgo recorded a gravitational wave from GW190521, but unlike the familiar rising chirps from orbiting black holes spiraling together, this one arrived more like a crack, brief, blunt, and missing a clear inspiral phase. That made it an oddity from the start. The LIGO-Virgo-KAGRA collaboration interpreted it as the merger of two black holes, one about 85 times the Sun’s mass and the other about 66 times, which then formed a remnant black hole of about 142 solar masses. In that reading, GW190521 became the first observed example of an intermediate-mass black hole. Even so, the event has never sat comfortably within standard expectations. The source black holes fell into a mass range that the article describes as being in tension with established models of stellar evolution, a region often discussed as the “forbidden gap.” That tension has helped keep GW190521 near the center of debate, even as the broader catalog of …

Light can travel for billions of years yet experience no time

Light can travel for billions of years yet experience no time

A photon emitted from a star a billion light-years away arrives at a telescope having experienced no time whatsoever. Not very little time. None. That result is not a loose approximation or a poetic way of speaking. It falls directly out of the mathematics of special relativity, and it points toward something genuinely strange about the structure of the universe: time is not a fixed backdrop against which events unfold. It is something that changes depending on how fast you move through space. Two Clocks, One Disagreement The cleanest entry point into this problem is a thought experiment, though it has since become a laboratory result. Imagine two identical atomic clocks, synchronized and placed side by side. One remains stationary. The other is carried aboard a fast-moving aircraft and brought back. When the traveling clock returns, it shows slightly less elapsed time than the one that stayed behind. This effect has been confirmed experimentally, most famously in a 1971 experiment by physicists Joseph Hafele and Richard Keating, who flew cesium clocks around the world and …

Scientists Say: Spacetime

Scientists Say: Spacetime

astronaut: Someone trained to travel into space for research and exploration. black hole: A region of space having a gravitational field so intense that no matter or radiation (including light) can escape. cosmos: (adj. cosmic) A term that refers to the universe and everything within it. dimension: Descriptive features of something that can be measured, such as length, width or time. engineer: A person who uses science and math to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need. fabric: Any flexible material that is woven, knitted or can be fused into a sheet by heat or compression and drying. force: Some outside influence that can change the motion of an object, hold objects close to one another, or produce motion or stress in a stationary object. gravity: The force that attracts anything with mass, or bulk, toward any other thing with mass. The more mass that something has, the greater its gravity. interstellar: Between stars. literally: An adjective indicating that …