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The Universe is expanding and this expansion is accelerating over time. Both of these facts have been well established by observation, but we do not know what is causing this expansion. This seems to be a mysterious and unknown energy that acts as the opposite of gravity.
We call this hypothetical energy "dark energy", and it has been calculated to represent about 72% of all that constitutes the Universe. We do not know what it really is. But a new experience has just allowed us to dismiss one last thing it is not: a new force.
"This experiment, which links atomic physics with cosmology, has allowed us to eliminate a wide range of proposed models for explaining the nature of dark energy, and will allow us to constrain many other models of physics." 39, black energy, "said physicist Ed Copeland of the University of Nottingham.
The Universe is a huge and complicated place, but as far as we know, it is governed by only four fundamental forces. This is the strong nuclear force, the weak nuclear force, the electromagnetic force and the gravitational force.
But there are certain observation anomalies that do not fit well into existing theories or models of the functioning of the Universe. The hypothetical "fifth force" is the practical basket used by scientists to highlight these anomalies.
Like dark energy, we do not really know what this force is, but these observation anomalies allowed to impose constraints on the fifth force. In turn, this allowed the formation of theoretical alternatives to general relativity, with the aim of explaining the accelerated expansion of the Universe. Among these alternatives are the theory of chameleons and symmetry theory, for example.
Some physicists have also proposed that dark energy be the fifth force. And that's the premise that researchers have tried to test here.
If there existed in the Universe a force representing nearly three quarters of its mass density, one would think that it would be quite easy to spot. But if it is the opposite of gravity – a force of repulsion, rather than attractive – it is also logical to think that it is the weakest where gravity is the strongest.
Where would it be? Around objects of a large mass. For example, a planet – therefore, the force would be too weak to be detected on Earth, or in an experiment using two heavyweights. But it would be much stronger in the void of space.
The team therefore designed an experiment to see if they could observe this force of opposite gravity. In a sealed vacuum chamber, they placed a larger weight (an aluminum sphere the size of a marble) and a much smaller weight (a single atom of rubidium-87), and used the # 39, atomic interferometry to measure the acceleration of the atom to the largest mass. .
If there was a fifth force acting between the sphere and the atom, the atom would deviate slightly from its path past the sphere.
But this deviation was not observed, indicating that there was no unknown force at play in the room.
This does not mean that there is no fifth force at all. But this means that constraints can be imposed on the nature of this fifth force and dark energy – which, in turn, means that constraints can be imposed on theories of chameleons and symmetons.
It's like a cosmic game of Guess who?: determine the right questions to ask, then how to ask them, to reduce the number of suspects.
And as noted by physicist Ed Hinds of Imperial College London: "It's very exciting to be able to discover something about the evolution of the Universe using a tabletop experience in a London basement.
The search was published in Letters of physical examination.
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