'Planck' puts Einstein to the test

March 5, 2015
Artist's impression of the Planck spacecraft. Credit: ESA/AOES Medialab

Researchers, including physicists from Heidelberg University, have gained new insights into dark energy and the theory of gravitation by analysing data from the "Planck" satellite mission of the European Space Agency (ESA). Their results demonstrate that the standard model of cosmology remains an excellent description of the universe. Yet when the Planck data is combined with other astronomical observations, several deviations emerge. Further studies must determine whether these anomalies are due to measurement uncertainties or undiscovered physical correlations, which would also challenge Einstein's theory of gravitation. Thus, the analysis of the Planck data gives major impetus for research during future space missions.

From 2009 to 2013, the ESA's Planck satellite took measurements of the so-called cosmic microwave background (CMB). The CMB is radiation that originated approx. 13 billion years ago, about 380,000 years after the Big Bang. Due to the expansion of the universe, this light is still observable today at microwave wavelengths across the entire sky. Between 2009 and 2013, Planck surveyed the sky to map this ancient light in unprecedented detail. Now several research articles on the Planck data have been published. The Cosmology research group of the Institute for Theoretical Physics (ITP) at Heidelberg University participated in one of these studies.

"Precise measurements of cosmic microwave radiation reveal minute differences in temperature. On a celestial map, these temperature fluctuations look like small specks. Every speck is a region of somewhat higher or lower temperature," explains Dr. Valeria Pettorino, junior research group leader at the ITP. Prior findings point to only six parameters that describe the development of the universe after the Big Bang with relative accuracy, using what is known as the of cosmology. The temperature differences of the cosmic microwave background have allowed researchers to identify these parameters with extreme accuracy. One of them accounts for so-called dark energy, which comprises about 70 per cent of the total energy of the universe and is responsible for its accelerated expansion.

Research into dark energy is still in its infancy. Even though the data from the shows that dark energy is required, its composition remains unclear. Using the latest satellite data, the Planck researchers have put various theories to the test that take dark energy into account and are based on modified gravitation – and hence also call into question the theory of gravitation postulated in Albert Einstein's theory of relativity. They employed a broad spectrum of methods and other measurement data, including Baryonic Acoustic Oscillations, which are density waves from the early universe, local measurements of the Hubble constant, which specifies the universe's rate of expansion at the present day, as well as a certain group of supernovae or exploding stars.

From the Planck data the scientists were able to determine just how much dark energy existed in the past. "Surprisingly, the amount of early dark energy was significantly less than we expected. So far, it had been assumed that dark energy comprised a maximum of one per cent of all energy at the time the microwave background radiation was released. But the new Planck results indicate that it could have been no more than 0.4 per cent," explains Dr. Pettorino. "That's a big problem for the theoretical models of dark energy which predicted a considerably higher amount of energy for the early universe," adds Dr. Matteo Martinelli, postdoc at the ITP.

Furthermore, the analysis of the Planck data also revealed small disruptions in gravity itself that are not completely consistent with the standard model of cosmology. Even though these deviations are tiny and vary depending on the dataset studied, they call for further testing and investigation with other sets of data. "Further study might enable us to find out whether we are really dealing with deviations from Einstein's law of gravity that require a return to the drawing board," says Valeria Pettorino. According to the physicist, the analyses are of key importance to cosmological research on and gravitation. They can give invaluable impetus to upcoming satellite missions, such as the 2020 Euclid mission planned by the ESA and NASA. The astronomical institutes of Heidelberg University will again be major participants in this mission.

Explore further: With new data, Planck satellite brings early universe into focus

More information: Planck 2015 results. XIV. Dark energy and modified gravity, www.cosmos.esa.int/documents/3 … ergy_Mod_Gravity.pdf

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19 comments

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indio007
2.1 / 5 (7) Mar 05, 2015
WTF is "Einstein's Law of Gravity" ???
rufusgwarren
1 / 5 (10) Mar 05, 2015
Are we talking about the focal point of reality or the focus of somebodies idea?
rufusgwarren
1 / 5 (12) Mar 05, 2015
Simple, Einstein's idea implies that momentum, no matter how measured, is a function of displacement. So maybe, you don't understand his relationship with Newton. Juz, say'n.
rufusgwarren
1 / 5 (12) Mar 05, 2015
A better picture is the relationship Newton has with Maxwell. But, wait relationship, mass & charge? Ah! no mass needed! Then, no charge needed, e is a constant. It only about the location of the singularities and the relative EM field. The wave-fronts, may have any velocity. We do not understand, the "permanence" of a simple distribution of charge that define everything! A child can see this. You can show them with games the creation of the world, from any point in time from within this space. The beauty is when you see it in 4 dimensions, the singularities disappear.
rufusgwarren
1 / 5 (12) Mar 05, 2015
Simply the thought that God exist and the creation of light, might have been mis-understood.
rufusgwarren
1 / 5 (11) Mar 05, 2015
Just think about it, you could stuff everything you see above the singularity in scale and stuff it into the volume of 0 from any point of view in 4D, time and space, every point "with no place to start, no place to end"
rufusgwarren
1 / 5 (11) Mar 05, 2015
The time derivatives of mass and position!

Next try charge, position, relative to each other and time. Think we need a better understanding of the boundary conditions.
SHREEKANT
1 / 5 (9) Mar 05, 2015
SINCE 2013 I HAVE BEEN WRITING ABOUT THE ROLE OF DARK ENERGY IN GRAVITATION
http://swarajgrou...-in.html
http://swarajgrou...-to.html

GENERAL RELATIVITY AND GRAVITATION [submitted on 17th,aug'2013]

"GRAVITY"- a PUSHING FORCE [-a "Layman concept of Unified Dark Energy"]

Full Title: "GRAVITY"- a PUSHING FORCE [-a "Layman concept of Unified Dark Energy"]

Article Type: Original Research
Corresponding Author: Shree kant, M.Sc.,M.B.A

Abstract: 'Gravity' is an 'Effect', which is PULLING by nature, but its CAUSE is certainly not a PULLING FORCE as it has been assumed, claimed & proved time and again. The cause of gravity is the "PUSHING FORCE"- the SINGLE FORCE of the UNIVERSE that governs all the phenomenon of the universe. It is the reason of expansion of Universe ..

http://swarajgrou...est.html
24volts
1.8 / 5 (4) Mar 06, 2015
Why did there have to be more? It seems to expand right along with the universe...Maybe dark energy is the energy that actually supplies particles popping in and out of space all the time. If dark energy is like regular energy and wants to reach it's lowest level it would have to expand I think. Probably wrong but it makes sense in a way.
Torbjorn_Larsson_OM
4.3 / 5 (7) Mar 06, 2015
Funny how the WMAP team, with its scantier data, could show how "anomalies" were few and likely statistical in nature. While the Plack team actively chase shadows, when each of their data releases suppress even more of earlier data anomalies as their instrument and their models becomes better understood.

Indeed, the reference shows that LCDM fits without the described tension. It is the "modified gravity" schemes that comes into tension. With early low DE, as opposed to perturbations, "The background is then forced to be very close to ΛCDM". [p26]

Beside the effects getting weaker, the Planck team has had more time for data fishing and turns up ever fewer anomalies. So their chase is in turn hunted from both sides. =D
Torbjorn_Larsson_OM
4.3 / 5 (6) Mar 06, 2015
Ah, now I get it: ""That's a big problem for the theoretical models of dark energy which predicted a considerably higher amount of energy for the early universe,"".

I.e. it is quintessence that is in dire straits.

@Indio: An analog to Newton's law at a guess, i.e. referring to general relativity and noting that it replaced Newton in these applications.
Torbjorn_Larsson_OM
4.5 / 5 (8) Mar 06, 2015
@24volts: Why there is increasing DE over time?

The ratio of energy content of the universe is a relative measure, and matter is diluted over time as the volume of the late universe expands exponentially.

A large part of a basic cosmology course describes how inflation, then radiation, then matter, now dark energy dominates depending on the phase changes of the universe and how that couple to expansion rates. [See e.g. Susskind's Stanford University youtube lectures.]

You have the quantum field physics backwards, it is the fields that make the particle interactions - and particle creation/destruction can work even in the vacuum due to the uncertainty principle. However, there is a lowest energy for a field configuration, the so called "vacuum energy" and this is tied to dark energy behavior. See here: "Everything You Always Wanted To Know About The Cosmological Constant Problem (But Were Afraid To Ask)", Jerome Martin ; http://arxiv.org/abs/1205.3365 .
bla
4.2 / 5 (5) Mar 06, 2015
@indio007

WTF is "Einstein's Law of Gravity" ???

Also known as General Relativity ;)
david_gold
5 / 5 (1) Mar 06, 2015
Very interesting article.

"...and hence also call into question the theory of gravitation postulated in Albert Einstein's theory of relativity."

This challenge is also presented in http://www.scienc...ale.pdf. In Einstein's General Theory of Relativity the underlying principle of gravitational attraction is attributed to the bending of space-time by mass. This equates to a 'fictional' gravitational force (where there is no actual force) and appears relevant to the root cause in its irreconcilability with quantum theory. And, likewise, would be reaffirmed by any Quantum Theory of Gravity where a 'non-fictional' gravitational force arises from mediation by gravitons.

An explanation for dark energy is forwarded in http://www.scienc...ces.pdf.
24volts
5 / 5 (1) Mar 06, 2015
@24volts: Why there is increasing DE over time?


It was just an idea...thanks for that link I have to admit though, the math in that one is a bit beyond me.

Shootist
not rated yet Mar 07, 2015


George Smoot, eat your heart out.
richardwenzel987
not rated yet Mar 07, 2015
Something to consider: thinking in terms of the simple Heisenberg uncertainty we might ask what region of space we might be able to resolve, in something like a hadron collider, if we had all of the energy in the visible universe available to put into the hypothetical experiment? If the dimensions were on the order of the Planck length, we might suppose that the entire visible universe emerged from a region with those dimensions. If we used ALL of the energy available in principle, but not in practice, from even the unseen parts of the universe, and resolved a region smaller than the Planck length, could we suppose that ALL the universe emerged from a region so small that we can't give any meaning to the dimensions-- as what could be smaller than the Planck length? I'm just trying to give a cosmological spin to a basic and widely accepted component of quantum theory.
Da Schneib
not rated yet Apr 12, 2015
Why did there have to be more? It seems to expand right along with the universe...Maybe dark energy is the energy that actually supplies particles popping in and out of space all the time. If dark energy is like regular energy and wants to reach it's lowest level it would have to expand I think. Probably wrong but it makes sense in a way.
You're actually quite close; you just missed a couple points.

The main theory of dark energy is that it is the energy of empty spacetime, which is, as Torbjorn points out, expanding. And that is, yes, the energy that manifests as vacuum pair creation and annihilation, and in the laboratory as the Casimir effect. And the Casimir effect is a physical, measurable force; the force of spacetime. In other words, dark energy.

Because it's a property of spacetime itself, as space expands, so does the total dark energy of the universe. On the other hand, matter (dark or not) and ordinary energy are conserved, and cannot vary.
Da Schneib
not rated yet Apr 12, 2015
Thus, as space expands, gravity (from the matter and energy in the universe) becomes weaker and weaker due to the inverse square law as the matter and energy get farther and farther apart, but dark energy becomes stronger and stronger, because there is more and more space, and dark energy is an intrinsic property of space. And that's why dark energy causes accelerating expansion.

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