Featured Research

from universities, journals, and other organizations

Liquid spacetime: What if spacetime were a kind of fluid?

Date:
April 23, 2014
Source:
Sissa Medialab
Summary:
What if spacetime were a kind of fluid? This is the question tackled by theoretical physicists working on quantum gravity by creating models attempting to reconcile gravity and quantum mechanics. Some of these models predict that spacetime at the Planck scale is no longer continuous – as held by classical physics – but discrete in nature. Just like the solids or fluids we come into contact with every day, which can be seen as made up of atoms and molecules when observed at sufficient resolution. A structure of this kind generally implies, at very high energies, violations of Einstein’s special relativity (a integral part of general relativity).

What if spacetime were a kind of fluid?
Credit: Deyan Georgiev / Fotolia

What if spacetime were a kind of fluid? This is the question tackled by theoretical physicists working on quantum gravity by creating models attempting to reconcile gravity and quantum mechanics. Some of these models predict that spacetime at the Planck scale (10-33cm) is no longer continuous -- as held by classical physics -- but discrete in nature. Just like the solids or fluids we come into contact with every day, which can be seen as made up of atoms and molecules when observed at sufficient resolution. A structure of this kind generally implies, at very high energies, violations of Einstein's special relativity (a integral part of general relativity).

In this theoretical framework, it has been suggested that spacetime should be treated as a fluid. In this sense, general relativity would be the analogue to fluid hydrodynamics, which describes the behaviour of fluids at a macroscopic level but tells us nothing about the atoms/molecules that compose them. Likewise, according to some models, general relativity says nothing about the "atoms" that make up spacetime but describes the dynamics of spacetime as if it were a "classical" object. Spacetime would therefore be a phenomenon "emerging" from more fundamental constituents, just as water is what we perceive of the mass of H2O molecules that form it.

Stefano Liberati, professor at the International School for Advanced Studies (SISSA) in Trieste, and Luca Maccione, a research scientist at the Ludwig-Maximilian University in Munich, have devised innovative ways of using the tolls of elementary particle physics and high energy astrophysics to describe the effects that should be observed if spacetime were a fluid. Liberati and Maccione also proposed the first observational tests of these phenomena. Their paper has just been published in the journal Physical Review Letters.

Quantum mechanics is able to effectively explain three of the four fundamental forces of the Universe (electromagnetism, weak interaction and strong interaction). But it does not explain gravity, which is currently only accounted for by general relativity, a theory developed in the realm of classical physics. Identifying a plausible model of quantum gravity (that is, a description of gravity within a quantum physics framework) is therefore one of the major challenges physics is facing today. However, despite the many models proposed to date, none has proved satisfactory or, more importantly, amenable to empirical investigation. Studies like the one carried out by Liberati and Maccione provide new instruments for assessing the value of possible scenarios for quantum gravity.

In the past, models considering spacetime as emerging, like a fluid, from more fundamental entities assumed and studied effects that imply changes in the propagation of photons, which would travel at different speeds depending on their energy. But there's more to it: "If we follow up the analogy with fluids it doesn't make sense to expect these types of changes only" explains Liberati. "If spacetime is a kind of fluid, then we must also take into account its viscosity and other dissipative effects, which had never been considered in detail."

Liberati and Maccione catalogued these effects and showed that viscosity tends to rapidly dissipate photons and other particles along their path, "And yet we can see photons travelling from astrophysical objects located millions of light years away!" he continues. "If spacetime is a fluid, then according to our calculations it must necessarily be a superfluid. This means that its viscosity value is extremely low, close to zero."

"We also predicted other weaker dissipative effects, which we might be able to see with future astrophysical observations. Should this happen, we would have a strong clue to support the emergent models of spacetime," concludes Liberati. "With modern astrophysics technology the time has come to bring quantum gravity from a merely speculative view point to a more phenomenological one. One cannot imagine a more exciting time to be working on gravity."


Story Source:

The above story is based on materials provided by Sissa Medialab. Note: Materials may be edited for content and length.


Journal Reference:

  1. Stefano Liberati, Luca Maccione. Astrophysical Constraints on Planck Scale Dissipative Phenomena. Physical Review Letters, 2014; 112 (15) DOI: 10.1103/PhysRevLett.112.151301

Cite This Page:

Sissa Medialab. "Liquid spacetime: What if spacetime were a kind of fluid?." ScienceDaily. ScienceDaily, 23 April 2014. <www.sciencedaily.com/releases/2014/04/140423095208.htm>.
Sissa Medialab. (2014, April 23). Liquid spacetime: What if spacetime were a kind of fluid?. ScienceDaily. Retrieved August 19, 2014 from www.sciencedaily.com/releases/2014/04/140423095208.htm
Sissa Medialab. "Liquid spacetime: What if spacetime were a kind of fluid?." ScienceDaily. www.sciencedaily.com/releases/2014/04/140423095208.htm (accessed August 19, 2014).

Share This




More Space & Time News

Tuesday, August 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Space to Ground: Hello Georges

Space to Ground: Hello Georges

NASA (Aug. 18, 2014) Europe's ATV-5 delivers new science and the crew tests smart SPHERES. Questions or comments? Use #spacetoground to talk to us. Video provided by NASA
Powered by NewsLook.com
Tiny Satellites, Like The One Tossed From ISS, On The Rise

Tiny Satellites, Like The One Tossed From ISS, On The Rise

Newsy (Aug. 18, 2014) The Chasqui I, hand-delivered into orbit by a Russian cosmonaut, is one of hundreds of small satellites set to go up in the next few years. Video provided by Newsy
Powered by NewsLook.com
This Week @ NASA, August 15, 2014

This Week @ NASA, August 15, 2014

NASA (Aug. 15, 2014) Carbon Observatory’s First Data, ATV-5 Delivers Cargo, Cygnus Departs Station and more... Video provided by NASA
Powered by NewsLook.com
Space Shuttle Replica Hoisted for Landmark Exhibit

Space Shuttle Replica Hoisted for Landmark Exhibit

Reuters - US Online Video (Aug. 14, 2014) The space shuttle replica Independence has been hoisted atop Space Center Houston's shuttle carrier aircraft, creating a monument to the shuttle program which will open to the public next year. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins