Tag

General Relativity

All articles tagged with #general relativity

physics12 days ago•20 min saved

Australian Physicist Claims Gravity Alters Light Speed, Challenging Einstein's Core Principle

Enbang Li, a physicist at the University of Wollongong in Australia, has proposed that the speed of light is not constant but is instead influenced by local gravity. Using a device built within an elevator shaft on the university campus, Li claims to have detected changes in light speed as it traverses Earth's surface. These findings suggest that gravity can speed up light, potentially contradicting the foundational assumption of special relativity that light travels at a constant rate in a vacuum. If validated, this discovery could impact Earth science applications, including climate monitoring and mineral resource exploration, by providing new methods to measure local gravitational variations.

via zmescience.com|

#enbang-li #general-relativity #gravitational-variation

space19 days ago•44 min saved

Laser-powered nanocraft could reach a nearby black hole within a century to test gravity

A speculative concept by Cosimo Bambi envisions gram‑scale, laser‑driven nanocrafts accelerated by Earth‑based lasers to roughly one‑third light speed, potentially reaching a nearby black hole 20–25 light‑years away in 60–75 years, with data returning 20–25 years later. The mission could involve two probes to test Einstein’s general relativity near the Kerr metric, investigate the event horizon, and probe fundamental constants in strong gravity. However, no suitable nearby black hole is known (Gaia BH1 is too distant), the approach requires a massive, costly laser system (on the order of a trillion euros with current tech), and significant navigation and propulsion challenges remain, so the concept is a roadmap, not a ready-to-build mission.

via The Brighter Side of News|

#black-holes #general-relativity #interstellar-mission

science28 days ago•10 min saved

The Silent Disco Ball That Maps Earth from Space

Launched in 1976, LAGEOS-1 is a nearly passive spherical satellite with no onboard instrumentation, electronics, power, or propulsion. It uses corner-cube retroreflectors to bounce laser pulses back to Earth, providing a stable reference frame for ultra-precise geodesy and tests of general relativity, and is expected to orbit for millions of years.

via Hackaday|

#general-relativity #lageos-1 #laser-ranging

science1 month ago•12 min saved

Evolving warp bubble reveals instability: caustics create multivalued flow

A 2026 study allowed an Alcubierre‑like warp field to evolve rather than enforcing a fixed bubble profile; under an inertial‑motion setup, neighboring trajectories cross to form caustics, producing a multivalued velocity at some locations and destroying a smooth, single‑valued field. The result shows that simply prescribing a bubble shape is not the same as explaining how such a field forms or persists, and stabilizing it would require additional physical dynamics (e.g., a material model with a suitable equation of state). The work does not present a working warp drive, but highlights the need for concrete stabilization mechanisms beyond the initial profile.

via Space Daily|

#alcubierre #caustics #general-relativity

science1 month ago•136 min saved

Gravity Goes Quantum: First Quantum-Scale Test Nudges Toward Unifying Physics

Scientists used the Quantum Galileo Interferometer to split a cloud of rubidium atoms into two paths—one falling under gravity and the other held in place—then recombined the waves to measure gravity’s effect on a quantum phase. The observed interference shows Einstein’s equivalence principle holds at the quantum scale and represents the first quantum‑scale hint of how gravity and quantum mechanics might be unified, though it is not a full quantum gravity demonstration; the work appeared in Science Advances.

via Space|

#atom-interferometry #equivalence-principle #general-relativity

space1 month ago•45 min saved

Cosmic Glitch Suggests Gravity Fades at the Universe’s Largest Scales

Researchers from the University of Waterloo and University of British Columbia propose a minimal modification to gravity—a 'cosmic glitch'—where gravity is about 1% weaker on cosmological scales (billions of light-years) than predicted by general relativity, captured by the parameter Ωg. Analyses of Planck 2018 data yield Ωg ≈ -0.0087 ± 0.0046 and a Hubble constant near 68.6 km/s/Mpc; in some data combinations this can lessen the Hubble tension, but the improvement isn't universal across all datasets. The model preserves GR on smaller scales and could be tested by future CMB and large-scale structure surveys (DESI, Euclid). If confirmed, it would hint at physics beyond general relativity at cosmic distances.

via The Brighter Side of News|

#cosmic-glitch-in-gravity #general-relativity #gravity

science1 month ago•12 min saved

The 1919 Eclipse That Made Einstein Famous

During the May 29, 1919 total solar eclipse, astronomers photographed star positions near the Sun to test Einstein’s prediction that light bending by the Sun’s gravity would amount to about 1.75 arcseconds. Two expeditions—Sobral, Brazil, and Príncipe—produced measurements with mixed data quality, but the best results (notably from Sobral’s four‑inch telescope) aligned with Einstein’s value and disagreed with Newton. After careful reductions and later reanalyses, the evidence favored Einstein, boosting his fame and cementing relativity. The episode also foreshadowed modern gravitational lensing research; today, more precise methods continue to test gravity, but the 1919 plates remain a landmark in scientific history.

via Fstoppers|

#1919-eclipse #eddington #einstein

space1 month ago•2 min saved

S301: Milky Way’s Fastest Star Skims the Central Black Hole

Astronomers have found S301, the Milky Way’s fastest star, zooming around the central black hole Sagittarius A* at about 25,000 km/s on a tight 8.7-year orbit, coming within roughly 12 AU of the hole. Its extreme proximity could enable a direct measurement of the black hole’s spin and a stringent test of Einstein’s general relativity, using the ESO Very Large Telescope Interferometer to track the orbit back to 2017 and observe the 2031 pericentre passage; spin measurements could come within a decade.

via The Guardian|

#black-hole-spin #general-relativity #s301

science2 months ago•53 min saved

Relativity's Road to Time Travel: From Time Dilation to Timelike Loops

Einstein’s special and general relativity show time is not fixed: moving clocks run slower and strong gravity slows time, enabling travel into the future. Some solutions to Einstein’s equations—such as Kerr spacetime around rotating masses—mathematically permit backward time travel via closed timelike curves, but these regions are inherently unstable and no practical method of time travel exists.

via Yahoo|

#closed-timelike-curves #general-relativity #relativity

science2 months ago•7 min saved

Black Hole Singularity Might Be a 3D Surface, Not a Point

A forthcoming Physical Review D paper argues that Schwarzschild (and likely Kerr) singularities are better described as flat, three-dimensional spacelike surfaces rather than points. This means two observers falling in from opposite directions cannot converge on the same spacetime event, a result that could reshape how general relativity breaks down inside black holes and redefine the starting point for quantum gravity research.

via ScienceAlert|

#black-hole #general-relativity #quantum-gravity

science2 months ago•11 min saved

Star S2's relativistic whirl around Milky Way's black hole tests Einstein's gravity

For nearly 30 years, astronomers tracked the star S2 as it orbits the Milky Way’s center around Sagittarius A*, a supermassive black hole about 4 million solar masses. At its closest approach it reaches ~7,650 km/s (~0.025c), enabling precise tests of general relativity in strong gravity via relativistic effects like gravitational redshift, transverse Doppler shift, and Schwarzschild precession. The findings—made with ESO's GRAVITY and Keck, by Genzel and Ghez’s teams—helped secure the Nobel Prize in Physics 2020 and complement the Event Horizon Telescope’s 2022 image of the black hole’s shadow.

via Space Daily|

#astronomy #black-hole #general-relativity

science-space2 months ago•11 min saved

Time Slows to a Standstill at Black Hole Edges, Then Crosses the Horizon

Black holes warp time as well as space: near the event horizon, a distant observer sees infalling matter slow and freeze at the edge due to gravitational time dilation, while the object itself experiences finite proper time to cross the horizon. This freezing is a coordinate effect, not a literal halt in the falling object’s reality. Gravitational time dilation has been measured on Earth and in GPS systems, confirming relativity beyond black holes. Observations like the Event Horizon Telescope and LIGO support horizon physics but do not show a literal frozen image, and quantum-gravity effects (e.g., Hawking radiation) remain unobserved and unresolved.

via Space Daily|

#black-hole #event-horizon #general-relativity

space2 months ago•15 min saved

Moon drifting away at 3.8 cm per year, confirmed by millimetre-precision laser ranging

Laser pulses bounced off Moon retroreflectors left by Apollo and Lunokhod missions measure the Moon’s recession from Earth at about 3.8 cm per year with millimetre accuracy, a result that tests general relativity and informs Earth–Moon dynamics; the rate depends on ocean tides and continental layout, and future reflectors from Artemis missions will enable sharper measurements.

via Space Daily|

#apollo-reflectors #general-relativity #lunar-laser-ranging

science3 months ago•27 min saved

LARES-2 tightens Earth's frame-dragging test to ~0.1% accuracy

The LARES-2 laser-ranging satellite, combined with LAGEOS and GRACE data, delivers the most precise measurement of Earth's frame-dragging to about one part in a thousand, providing a stringent confirmation of general relativity in the near-Earth environment and placing tight limits on alternative gravity models such as Chern–Simons gravity, while also improving the understanding of Earth tides through high-precision satellite analysis with GEODYN/UTOPIA and ILRS data.

via Nature|

#chern-simons-gravity #frame-dragging #general-relativity

science3 months ago•5 min saved

First Magnetar Birth Seen in Chirping Supernova

Astronomers monitored SN 2024afav for about 200 days and observed four distinct brightness bumps—the object's light curve chirp—best explained by a newborn magnetar with a tilted accretion disk that undergoes Lense-Thirring precession, a relativistic effect that modulates emitted light. This provides the first direct evidence that magnetars power some superluminous supernovae, supporting Dan Kasen's 2010 theory; the magnetar spins ~4.2 milliseconds with a magnetic field around 3×10^14 gauss. The discovery, published in Nature, confirms GR's role in a stellar explosion and suggests future surveys (e.g., Rubin Observatory) will uncover many more chirping events.

via ScienceDaily|

#general-relativity #lense-thirring #magnetar