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Category: physics – Page 66

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The rate at which the universe is currently expanding is known as the Hubble Rate. In recent years, different measurements have given different results for the Hubble rate, a discrepancy between theory and observation that’s been called the “Hubble tension”. Now, a team of astrophysicists claims the Hubble tension is gone and it’s the fault of supernovae data. Let’s have a look.

Paper: https://iopscience.iop.org/article/10…

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#science #sciencenews #cosmology

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Our is capable of demonstrating high spectral resolution and accurate reconstruction of full-Stokes polarization states in both theoretical and experimental settings. Precision detection of high-dimensional information by our photodetector, such as a two-color laser field with different polarization states or broadband reflection from a gold interface exhibiting varying states, is achieved beyond the capabilities of commercial polarimeter and spectrometer.

Additionally, this approach can be extended to imaging applications by sandwiching the film with a commercial microlens array and sensor array to realize ultra-compact high-dimensional imager, said Assistant Professor Chunqi Jin from the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences.

Looking ahead, Prof. Wei Li envisions that ultra-broadband detection can be achieved by integrating broadband commercial photodetectors; the detection resolution can be further improved by using , metasurfaces, and two-dimensional materials instead of existing thin film schemes; and the detection capability can be stepped up in higher dimensions by integrating functionalities such as , and distance measurement.

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New discoveries about Jupiter could lead to a better understanding of Earth’s own space environment and influence a long-running scientific debate about the solar system’s largest planet. “By exploring a larger space such as Jupiter, we can better understand the fundamental physics governing Earth’s magnetosphere and thereby improve our space weather forecasting,” said Peter Delamere, a professor at the UAF Geophysical Institute and the UAF College of Natural Science and Mathematics.

“We are one big space weather event from losing communication satellites, our power grid assets, or both,” he said.

Space weather refers to disturbances in the Earth’s magnetosphere caused by interactions between the solar wind and the Earth’s magnetic field. These are generally associated with solar storms and the sun’s coronal mass ejections, which can lead to magnetic fluctuations and disruptions in power grids, pipelines and communication systems.

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While tantalizing, Alcubierre’s design has a fatal flaw. To provide the necessary distortions of spacetime, the spacecraft must contain some form of exotic matter, typically regarded as matter with negative mass. Negative mass has some conceptual problems that seem to defy our understanding of physics, like the possibility that if you kick a ball that weighs negative 5 kilograms, it will go flying backwards, violating conservation of momentum. Plus, nobody has ever seen any object with negative mass existing in the real universe, ever.

These problems with negative mass have led physicists to propose various versions of “energy conditions” as supplements to general relativity. These aren’t baked into relativity itself, but add-ons needed because general relativity allows things like negative mass that don’t appear to exist in our universe—these energy conditions keep them out of relativity’s equations. They’re scientists’ response to the unsettling fact that vanilla GR allows for things like superluminal motion, but the rest of the universe doesn’t seem to agree.

The energy conditions aren’t experimentally or observationally proven, but they are statements that concord with all observations of the universe, so most physicists take them rather seriously. And until recently, physicists have viewed those energy conditions as making it absolutely 100 percent clear that you can’t build a warp drive, even if you really wanted to.

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Life appears to require at least some instability. This fact should be considered a biological universality, proposes University of Southern California molecular biologist John Tower.

Biological laws are thought to be rare and describe patterns or organizing principles that appear to be generally ubiquitous. While they can be squishier than the absolutes of math or physics, such rules in biology nevertheless help us better understand the complex processes that govern life.

Most examples we’ve found so far seem to concern themselves with the conservation of materials or energy, and therefore life’s tendency towards stability.

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The future of space-based UV/optical/IR astronomy requires ever larger telescopes. The highest priority astrophysics targets, including Earth-like exoplanets, first generation stars, and early galaxies, are all extremely faint, which presents an ongoing challenge for current missions and is the opportunity space for next generation telescopes: larger telescopes are the primary way to address this issue.

With mission costs depending strongly on aperture diameter, scaling current space telescope technologies to aperture sizes beyond 10 m does not appear economically viable. Without a breakthrough in scalable technologies for large telescopes, future advances in astrophysics may slow down or even completely stall. Thus, there is a need for cost-effective solutions to scale space telescopes to larger sizes.

The FLUTE project aims to overcome the limitations of current approaches by paving a path towards space observatories with large aperture, unsegmented liquid primary mirrors, suitable for a variety of astronomical applications. Such mirrors would be created in space via a novel approach based on fluidic shaping in microgravity, which has already been successfully demonstrated in a laboratory neutral buoyancy environment, in parabolic microgravity flights, and aboard the International Space Station (ISS).

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