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Archive for the ‘physics’ category: Page 142

May 29, 2022

Scientists Finally Calculated The Speed of Gravity

Posted by in categories: physics, space

Recently, scientists made groundbreaking detections that allowed them that gravity does not act instantaneously as Newton thought, instead it propagates at the speed of light.

Neil Cornish, a physicist at Montana State University said, “The speed of gravity, like the speed of light, is one of the fundamental constants in the Universe. Until the advent of gravitational wave astronomy, we had no way to directly measure the speed of gravity.”

In the course of recent months, physicists have gained exceptionally fast ground in bouncing the speed of gravity utilizing gravitational wave perceptions. Earlier, the first LIGO detections of gravitational waves constrained the speed of gravity suggests 50% of the speed of light.

May 28, 2022

Projection: a mechanism for human-like reasoning in Artificial Intelligence

Posted by in categories: physics, robotics/AI, transportation

(2022). Journal of Experimental & Theoretical Artificial Intelligence. Ahead of Print.


AI has for decades attempted to code commonsense concepts, e.g., in knowledge bases, but struggled to generalise the coded concepts to all the situations a human would naturally generalise them to, and struggled to understand the natural and obvious consequences of what it has been told. This led to brittle systems that did not cope well with situations beyond what their designers envisaged. John McCarthy (1968) said ‘a program has common sense if it automatically deduces for itself a sufficiently wide class of immediate consequences of anything it is told and what it already knows’; that is a problem that has still not been solved. Dreifus (1998) estimated that ‘Common sense is knowing maybe 30 or 50 million things about the world and having them represented so that when something happens, you can make analogies with others’. Minsky presciently noted that common sense would require the capability to make analogical matches between knowledge and events in the world, and furthermore that a special representation of knowledge would be required to facilitate those analogies. We can see the importance of analogies for common sense in the way that basic concepts are borrowed, e.g., the tail of an animal, or the tail of a capital ‘Q’, or the tail-end of a temporally extended event (see also examples of ‘contain’, ‘on’, in Sec. 5.3.1). More than this, for known facts, such as ‘a string can pull but not push an object’, an AI system needs to automatically deduce (by analogy) that a cloth, sheet, or ribbon, can behave analogously to the string. For the fact ‘a stone can break a window’, the system must deduce that any similarly heavy and hard object is likely to break any similarly fragile material. Using the language of Sec. 5.2.1, each of these known facts needs to be treated as a schema,14 and then applied by analogy to new cases.

Projection is a mechanism that can find analogies (see Sec. 5.3.1) and hence could bridge the gap between models of commonsense concepts (i.e., not the entangled knowledge in word embeddings learnt from language corpora) and text or visual or sensorimotor input. To facilitate this, concepts should be represented by hierarchical compositional models, with higher levels describing relations among elements in the lower-level components (for reasons discussed in Sec. 6.1). There needs to be an explicit symbolic handle on these subcomponents; i.e., they cannot be entangled in a complex network. For visual object recognition, a concept can simply be a set of spatial relations among component features, but higher concepts require a complex model involving multiple types of relations, partial physics theories, and causality. Secs. 5.2 and 5.3 give a hint of what these concepts may look like, but a full example requires a further paper.

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May 26, 2022

New calculations of solar spectrum resolve decade-long controversy about the sun’s chemical composition

Posted by in categories: chemistry, cosmology, mapping, physics

What do you do when a tried-and-true method for determining the sun’s chemical composition appears to be at odds with an innovative, precise technique for mapping the sun’s inner structure? That was the situation facing astronomers studying the sun—until new calculations that have now been published by Ekaterina Magg, Maria Bergemann and colleagues, and that resolve the apparent contradiction.

The decade-long solar abundance crisis is the conflict between the internal structure of the sun as determined from solar oscillations (helioseismology) and the structure derived from the fundamental theory of stellar evolution, which in turn relies on measurements of the present-day sun’s . The new calculations of the physics of the sun’s atmosphere yield updated results for abundances of different chemical elements, which resolve the conflict. Notably, the sun contains more oxygen, silicon and neon than previously thought. The methods employed also promise considerably more accurate estimates of the chemical compositions of stars in general.

May 24, 2022

Metamaterials Control the Shape of Water Waves

Posted by in categories: materials, physics

A water wave incident on a grooved wall is shown to be analogous to electromagnetic waves called surface plasmon polaritons.

The ability of metamaterials to steer light has enabled amazing inventions from superresolution microscopes to “invisiblity” cloaks. But the physics underlying these structures also applies to other waves, such as acoustic, seismic, and water waves. Huanyang Chen and his colleagues at Xiamen University in China have demonstrated a structure that can change the propagation of surface water waves, making a localized wave that is analogous to an electromagnetic excitation called a surface plasmon polariton [1].

Surface plasmon polaritons occur at the interface between a dielectric and a negative-permittivity material such as a metal. Generating an equivalent excitation in surface water waves requires a similar sort of interface, such as that between water and a vertical barrier. In this case, the water’s parameter that is analogous to a metal’s permittivity is its depth. Of course, it’s impossible for water to have negative depth, but using metamaterials, Chen and his colleagues engineered the boundary conditions of the waves to achieve the same effect.

May 22, 2022

Could an advanced civilization change the laws of physics?

Posted by in category: physics

Do the laws of physics place a hard limit on how far technology can develop, or could an advanced civilization re-write those laws?

May 22, 2022

Researchers explain how auroras are formed on Mars without a global magnetic field

Posted by in categories: physics, space

May 22, 2022

Far-UVC light zaps airborne pathogens in realistic conditions

Posted by in category: physics

Technology could make indoor areas as safe as outdoors, say physicists.

May 22, 2022

#Innovation

Posted by in categories: nuclear energy, physics

Today is the opening of The CAPT.(DR.) IDAHOSA WELLS OKUNBO STEM AND INNOVATION CENTER in the rural area of Iyara, warri, delta state, Nigeria.aa.

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21 post reach.

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May 22, 2022

Scientists Say There May Be a “Mirror World” to Our Own

Posted by in categories: physics, space

Three researchers published their findings this week in the journal Physical Review Letters and say their hypothesis is based on problems with the Hubble Constant, the rate at which the universe expands. Yesterday’s SciTechDaily report on the study says predictions for that constant are a lot slower than what we’ve measured in reality, and scientists are trying to figure out what’s causing the discrepancy. They say the cause could be a mirror world we can’t yet see.

“This might provide a way to understand why there appears to be a discrepancy between different measurements of the Universe’s expansion rate,” researchers said in a statement about their findings.

Scientists have long built models of the cosmos. Now the task is to create one that doesn’t violate any of the rules cosmological rules we’ve learned so far. The researchers say that if the universe is somehow exploiting what we know about its physics and symmetry there could be an invisible mirror world very similar to ours but invisible except through gravitational impact on our world.

May 21, 2022

Remains of a slamming between two galaxies could shed light upon dark matter

Posted by in categories: cosmology, physics