NASA telescopes set limits on space-time quantum 'foam'

May 28, 2015
A new study combining data from NASA's Chandra X-ray Observatory and Fermi Gamma-ray Telescope, and the Very Energetic Radiation Imaging Telescope Array (VERITAS) in Arizona is helping scientists set limits on the quantum nature of space-time on extremely tiny scales. Credit: NASA/CXC/FIT/E.Perlman et al, Illustration: NASA/CXC/M.Weiss

A team of scientists has used X-ray and gamma-ray observations of some of the most distant objects in the universe to better understand the nature of space and time. Their results set limits on the quantum nature, or "foaminess," of spacetime at extremely tiny scales.

This study combines data from NASA's Chandra X-ray Observatory and Fermi Gamma-ray Space Telescope along with ground-based gamma-ray observations from the Very Energetic Radiation Imaging Telescope Array (VERITAS).

At the smallest scales of distance and duration that we can measure, spacetime—that is, the three dimensions of space plus time—appears to be smooth and structureless. However, certain aspects of quantum mechanics, the highly successful theory scientists have developed to explain the physics of atoms and subatomic particles, predict that spacetime would not be smooth. Rather, it would have a foamy, jittery nature and would consist of many small, ever-changing, regions for which space and time are no longer definite, but fluctuate.

"One way to think of spacetime foam is if you are flying over the ocean in the airplane, it looks completely smooth. However, if you get low enough you see the waves, and closer still, foam, with tiny bubbles that are constantly fluctuating" said lead author Eric Perlman of the Florida Institute of Technology in Melbourne. "Even stranger, the bubbles are so tiny that even on atomic scales we're trying to observe them from a very high-flying airplane."

The predicted scale of spacetime foam is about ten times a billionth of the diameter of a hydrogen atom's nucleus, so it cannot be detected directly. However, If spacetime does have a foamy structure there are limitations on the accuracy with which distances can be measured because the size of the many quantum bubbles through which light travels will fluctuate. Depending on what model of spacetime is used, these distance uncertainties should accumulate at different rates as light travels over the large cosmic distances.

The researchers used observations of X-rays and gamma-rays from very distant quasars—luminous sources produced by matter falling towards supermassive black holes—to test models of spacetime foam. The authors predicted that the accumulation of distance uncertainties for light traveling across billions of light-years would cause the image quality to degrade so much that the objects would become undetectable. The wavelength where the image disappears should depend on the model of spacetime foam used.

Chandra's X-ray detection of quasars at distances of billions of light-years rules out one model, according to which photons diffuse randomly through spacetime foam in a manner similar to light diffusing through fog. Detections of distant quasars at shorter, gamma-ray wavelengths with Fermi and even shorter wavelengths with VERITAS demonstrate that a second, so-called holographic model with less diffusion does not work.

"We find that our data can rule out two different models for spacetime foam," said co-author Jack Ng of the University of North Carolina in Chapel Hill. "We can conclude that spacetime is less foamy that some models predict."

The X-ray and gamma-ray data show that spacetime is smooth down to distances 1,000 times smaller than the nucleus of a hydrogen atom.

These results appear in the May 20th issue of The Astrophysical Journal.

Explore further: Spacetime: A smoother brew than we knew

More information: "New Constraints on Quantum Gravity from X-Ray and Gamma-Ray Observations," Eric S. Perlman et al., 2015 May 20, Astrophysical Journal, Vol. 805, No. 1, 10 dx.doi.org/10.1088/0004-637X/805/1/10 , Preprint: arxiv.org/abs/1411.7262

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SciTechdude
3 / 5 (4) May 28, 2015
If the effect is so small that we can still see billions of light years away, I don't think this is really a big issue for science at present. Maybe in a few thousand years they might have to figure it out, if we get some kind of light speed drive. And even then...
rufusgwarren
3.7 / 5 (3) May 28, 2015
What if you are wrong?
Tuxford
1.1 / 5 (7) May 28, 2015
The underlying etheric elementals (what ever that is), of which their are likely at least seven distinct types that interact under proper diffusive mixture to form a sub-atomic particle of our universe, are thus quite small. There is no hope of ever detecting them from our universe made of entirely much larger structures. But when conditions are right, such as deep in the core of massive stars, matter springs into our universe. Hence, the growing core stars at the center of all galaxies.
Disproselyte
not rated yet May 28, 2015
First is stated "The predicted scale of spacetime foam is about ten times a billionth of the diameter of a hydrogen atom's nucleus".

Then the conclusion is: "The X-ray and gamma-ray data show that spacetime is smooth down to distances 1,000 times smaller than the nucleus of a hydrogen atom".

Am I missing something here?
Returners
2 / 5 (3) May 28, 2015
The X-ray and gamma-ray data show that spacetime is smooth down to distances 1,000 times smaller than the nucleus of a hydrogen atom.


Do you mean there's an actual change at that scale, or do you mean you just can't measure any smaller scale to see where any change happens?!

I don't think this is a problem, because if this effect was happening there would be diffuse radiation seemingly coming from "everywhere" at those wavelengths, which there isn't. That is to say, every path that you can imagine for a stream of photons from a distant object would itself be emitting photons as some of them would "leak" from the quantum foam, having been redirected heavily enough to escape the path predicted in relativity.

In other words I think those findings mean there simply is not Quantum Foam. If it effects the small scale eventually that would effect all scales, so no evidence of it existing down to 1000 times smaller than a nucleus is pretty much evidence of non-existence.
Returners
3.3 / 5 (3) May 28, 2015
First is stated "The predicted scale of spacetime foam is about ten times a billionth of the diameter of a hydrogen atom's nucleus".

Then the conclusion is: "The X-ray and gamma-ray data show that spacetime is smooth down to distances 1,000 times smaller than the nucleus of a hydrogen atom".

Am I missing something here?


No.

It just means they cannot measure at the scale predicted, but the smallest scale they've managed to measure shows no evidence of foam.
TabulaMentis
5 / 5 (2) May 29, 2015
From article:

"Detections demonstrate that a second, so-called holographic model with less diffusion does not work."

Are the scientists saying there needs to be more diffusion? If so, a strange conclusion, but even then at those scales how would they know besides just guessing?

"The X-ray and gamma-ray data show that spacetime is smooth down to distances 1,000 times smaller than the nucleus of a hydrogen atom."

The Holographic Principle is based on one Planck length per unit.

"The Planck length is 20 powers of 10 smaller than the diameter of a hydrogen nucleus, and it is suspected to be the level at which the 'foam' of space-time is built." *

* Source: http://www.fromqu...-length/
AmritSorli
5 / 5 (1) May 29, 2015
would be better to talk abot "quantum vacuum" than space-time foam.
We show that curvature of space ij GR has origin in density of quantum vacuum
http://www.degruy...rmat=INT
EnsignFlandry
5 / 5 (2) May 29, 2015
First is stated "The predicted scale of spacetime foam is about ten times a billionth of the diameter of a hydrogen atom's nucleus".

Then the conclusion is: "The X-ray and gamma-ray data show that spacetime is smooth down to distances 1,000 times smaller than the nucleus of a hydrogen atom".

Am I missing something here?


No. One is a prediction, the other is observation.
EnsignFlandry
5 / 5 (4) May 29, 2015
The underlying etheric elementals (what ever that is), of which their are likely at least seven distinct types that interact under proper diffusive mixture to form a sub-atomic particle of our universe, are thus quite small. There is no hope of ever detecting them from our universe made of entirely much larger structures. But when conditions are right, such as deep in the core of massive stars, matter springs into our universe. Hence, the growing core stars at the center of all galaxies.


This makes no sense at all.
viko_mx
1 / 5 (3) May 29, 2015
This sounds me similar to the ancient hypothesis for the flat Earth carried on the back of four turtles. Of course in this times scientiеs did not have super computres to confirm their imagination.
TimLong2001
1 / 5 (1) May 29, 2015
Quantum "foam" is merely a remnant of the probabilistic statistics used to describe Sub-Planck dimensions, and really doesn't describe the deterministic charge interactions and processes of the sub-quantal scale.
docile
May 29, 2015
This comment has been removed by a moderator.
Tuxford
1 / 5 (1) May 29, 2015
This makes no sense at all.


A fish on the line? OK for those with little appreciation of autonomous system dynamics, imagine a simple analogy:

Our universe is composed only of the dissolved salt in the ocean. So everything detectable is just salt by detectors made of salt. But there is so much more in the ocean! When sufficient chloride and sodium ions gather in sufficient concentration, they combine into salt, thereby becoming a component of our universe.

There may be no way to detect the individual ions using salt molecules. Still they exist in the ocean. The underlying elementals combine into an autonomous self-sustaining reaction when gathered in the proper concentration, becoming a sub-atomic particle of our universe propagating through the ocean of elementals.
Disproselyte
not rated yet May 29, 2015
Thanks for the clarification.
Nevertheless do I have doubts on the relevance of experimental results, several orders of magnitude away from the predictions: this thus proves very little and looks waste of precious time.
But the statement "We find that our data can rule out two different models for spacetime foam" seems to contradict at least one of the two formerly cited statements?
Urgelt
5 / 5 (4) May 30, 2015
docile wrote, "The CMBR noise is an analogy of Brownian noise at the water surface. If we would observe the sky in microwave spectrum, we would see it flickering like the air above camp fire."

We *do* observe CMBR in microwave. That's what CMBR *is.*

CMBR radiation is too diffuse to form sharp images. We are not capable of obtaining data about quantum foam from CMBR observations because we don't know where each photon has been, what path it took, how far away it was emitted.

With partially-diffuse photons from identifiable objects to which we can obtain distance measurements, we have a shot at quantifying quantum diffusion. When diffusion is all but total, as with CMBR, we can't get much use out of the data to help us understand quantum foam's effects on photons.
Urgelt
5 / 5 (6) May 30, 2015
Tuxford wrote, "The underlying etheric elementals (what ever that is), of which their are likely at least seven distinct types..."

Be nicer to your nurse. I think she's shorting your meds.
richardwenzel987
not rated yet May 30, 2015
It sounds to me as though the quantum nature of space-time would only appear if we were trying to "resolve" it, let's say by making measurements of the position of a test particle with increasing precision. With unlimited amounts of energy available you could get arbitrary precision. I think you would lose the test particle but we are only talking about the instant of measurement. But detecting a photon that has traveled through space to your detector does not seem to be that sort of measurement, and as far as the detector is concerned, the photon has traveled through a perfectly continuous space. Or am I missing something here? I think I am asking whether a region of space needs to exhibit quantum characteristics if you are not pumping energy/making measurements in that region of space?

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