Subscribe to our free daily newsletters
. 24/7 Space News .

Subscribe to our free daily newsletters

Russian scientists have found flaws in popular theories of gravity
by Staff Writers
Yekaterinburg, Russia (SPX) Oct 27, 2017

File image of gravity at work.

Taking black holes (as a real object) as a test material, scientists from the Ural Federal university (UrFU, Yekaterinburg) found out that a popular theory of gravity which had seemed to work perfectly at the cosmological level (a subclass of Horndeski theory) is hardly applicable to the real world. They presented their study in the Classical and Quantum Gravity journal.

At the moment, according to the authors of the paper, black holes are believed to be existing rather than hypothetical objects. The gravitational-wave signal received in 2015 and marked by the Nobel Prize in physics in 2017 confirmed this fact again. Black holes exist, and this is one of the proofs that the general theory of relativity (GR) is correct.

However, modern physics has accumulated a lot of prerequisites for the revision of general relativity, for example, the accelerated expansion of the universe, the presence of dark matter and, finally, the impossibility to renormalize gravity. All the fundamental interactions known to science have already been described in quantum language, except for gravitation.

These small inconsistencies indicate that the theory of relativity is not the final theory of gravitation, but only one of the approximations to it (a similar story occurred with Newton's theory). Theoretical physicists constantly formulate and propose extended theories of gravity, and we need to check these models and compare them with observations.

One of the simplest versions of such an extended theory appears under the assumption that the gravitational constant (a fundamental physical quantity that is the same in time and at all points in the universe) is not a constant, but a field that can vary in time and space. Scientists cannot measure this slowly changing field at current level of accuracy and only therefore perceive it as a constant.

If we accept this hypothesis, then there appears gravity with a scalar field (given only one number at each point). This is how the first and simplest theory of gravity with a scalar field, the Brans-Dicke theory, was formulated. Today the class of gravity theories with a scalar field is very wide. Such theories are considered to be one of the most promising ways of expanding the general relativity.

In his work, DariaTretyakova, PhD from UrFU, together with her colleague from the University of Tokyo explored one of the theories of this class - the so-called Horndeski theory. Horndeski framework gives the most general theory of gravity with a scalar field, without instabilities and containing "healthy" physics, that is, no unusual parameters of matter(for example, negative or imaginary mass) occur.

At the cosmological level (the scale at which the universe can be viewed as a single object of study), a subclass of Horndeski models, which are symmetric with respect to the shift of the scalar field in space and time, have proved themselves well and helped scientists describe the accelerated expansion of the universe without resorting to additional theories.

These models were chosen for rigorous and comprehensive testing. The authors of the paper "moved" the Horndeski models to the astrophysical scale (the scale of individual objects of the universe) and found out that black holes (as real objects) turn out to be unstable in the models which previously successfully proved themselves in cosmology.

Consequently, these models are hardly suitable for describing the real universe, because today black holes are believed to exist in space as stable objects. The situation, however, is not hopeless: the scientists proposed a way to construct Horndeski models that ensure black holes stability.

The paper is a next step to a new theory of gravity that will meet all the requirements of modern physics. Now the authors are planning to subject the newly proposed models to standard tests: to check their adequacy at the cosmological and astrophysical scale.

NASA Challenges Students to Design Microgravity Experiments
Cleveland OH (SPX) Oct 24, 2017
Do you have what it takes to think like a scientist? Well, put on your lab coats and thinking caps because NASA is challenging U.S. high school students to participate in research related to the International Space Station as part of its 2018 Drop Tower Challenge. Students are asked to design and build objects that sink in water in normal gravity, but will be expelled as far as possible fr ... read more

Related Links
Ural Federal University
The Physics of Time and Space

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once

credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly

paypal only

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Pope asks spacemen life's big questions in ISS live chat

Saudi Arabia to invest $1 billion in Virgin Galactic

Plants and psychological well-being in space

Spacewalkers fix robotic arm in time to grab next cargo ship

Thruster for Mars mission breaks records

Draper and Sierra Nevada Corporation announce new agreement for space missions

Aerojet Rocketdyne breaks ground on advanced manufacturing center in Huntsville

New solid rocket motor development facility completed at Spaceport America

Mars Rover Mission Progresses Toward Resumed Drilling

Solar eruptions could electrify Martian moons

MAVEN finds Mars has a twisted tail

Mine craft for Mars

Space will see Communist loyalty: Chinese astronaut

China launches three satellites

Mars probe to carry 13 types of payload on 2020 mission

UN official commends China's role in space cooperation

Myanmar to launch own satellite system-2 in 2019: vice president

Eutelsat's Airbus-built full electric EUTELSAT 172B satellite reaches geostationary orbit

Turkey, Russia to Enhance Cooperation in the Field of Space Technologies

SpaceX launches 10 satellites for Iridium mobile network

High field magnet at BER II offers Insights into a hidden order

Solid or liquid? Researcher proposes a new definition of glass

New evidence for dark matter makes it even more exotic

Using space to study ultra-cold materials

Astronomers discover sunscreen snow falling on hot exoplanet

Comet mission reveals 'missing link' in our understanding of planet formation

Marine microbes living beneath seabed resort to cannibalism

New NASA study improves search for habitable worlds

Haumea, the most peculiar of Pluto companions, has a ring around it

Ring around a dwarf planet detected

Helicopter test for Jupiter icy moons radar

Solving the Mystery of Pluto's Giant Blades of Ice

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement