Relativity of rotational motion confirmed

It has been one hundred years since the publication of Einstein's general theory of relativity in May 1916. In a paper recently published in EPJ Plus, Norwegian physicist Øyvind Grøn from the Oslo and Akershus University College of Applied Sciences and his co-author Torkild Jemterud demonstrate that the rotational motion in the universe is also subject to the theory of relativity.

Imagine a person at the North pole who doesn't believe the Earth rotates. As she holds a and can observe the stars in her telescope, she remarks that the swinging plane of the pendulum and the stars rotate together. Newton, who saw the world as a classical physicist, would have pointed out that it is the Earth that rotates. However, if we assume the general principle of is valid, the Earth can be considered as being at rest while the swinging plane of the pendulum and the night sky are rotating.

In fact, the rotating mass of the observable part of the universe causes the river of space—which is made up of free particles following the universe's expansion—to rotate together with the stars in the sky. And the swinging plane of the pendulum moves together with the river of space.

Until now, no-one has considered a possible connection between the general principle of relativity and the amount of dark energy in the universe, which is associated with the acceleration of the expansion of the universe, discovered in 1998. This connection can be established, Grøn argues, by using the phenomenon of inertial dragging.

When formalised in mathematical terms, the condition for inertial dragging yields an equation for calculating the amount of dark energy. The solution of that equation is that 73.7 % of the present content of the is in the form of . This prediction, derived from the theory of general relativity, is remarkably close to the values arrived at by different types of observations.

More information: Øyvind Grøn et al. An interesting consequence of the general principle of relativity, The European Physical Journal Plus (2016). DOI: 10.1140/epjp/i2016-16091-9 , dx.doi.org/10.1140/epjp/i2016-16091-9
Provided by Springer

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May 12, 2016
An interesting title of the paper:

"An interesting consequence of the general principle of relativity".

[ http://www.epj.or...91-9.pdf ]

Our universe isn't a black hole.

But they may be on to something. If they put back their cc value in the real FRW geometry, they get our universe, flat and everything, And the toy model obey the important criteria of being constant energy.

[tbctd]

May 12, 2016
[ctd]

The toy model is also a manifestly *not* a weak field approximation to GR.

Coincidence? We still doesn't know why the universe is flat.

But perhaps the toy model considered give a hint: a toy model universe would be ruled by GR, like ours. There may be a connection here.

May 12, 2016
OFFS! The incompetent phys.org editor just cut off lines in my 1st comment, so here it is again:

An interesting title of the paper:

"An interesting consequence of the general principle of relativity".

[ http://www.epj.or...91-9.pdf ]

It *is* interesting, but there is a problem with the paper. The problem is that they assume a Schwarzschild solution to GR, i.e. that the universe is a black hole and - with flat space - it will be close to the critical density.

But it isn't, precisely because of dark energy, so the current radius of the observable universe is >> the Schwarzschild radius. [ http://physics.st...ht-years ]

Our universe isn't a black hole.

May 12, 2016
@torbjorn, the editor has trouble with more than one link in a post. It does weird stuff between the links.

May 12, 2016
@torbjorn_b_g_larsson, & Da Schneib, must admit the picture is suggestive of a BH without even reading the article and confused me a bit because that picture does not look like how I imagine the universe (or at least, been conditioned by current science and observations). However, I do remember having read somewhere that certain 'units' of the Sch. metric had a similarity with certain cosmological models and wonder if that is why the Sch. equation is used here. (Ha! might be from my copy of 'Gravitation' which coincidentally is falling apart under it's own weight.) As a layman I would respect your probable corrections to my memory.

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