Dark matter + dark energy = fluid with negative mass?

Physicists introduced the concept of dark matter after they determined that, among other things, galaxies didn’t have enough mass to explain their rotation. Dark energy with its strange properties is needed to explain, for example, the evolution of the universe during its early childhood when it must have experienced a sudden, tremendous growth spurt. Both concepts are incorporated into the current model of the universe called Lambda-CDM.

This model, however, has a small disadvantage: it says nothing about what dark matter and dark energy are made from. Experimental physicists haven’t gotten any closer to an answer to this question in recent years. New physics would be needed, but everything that experiments have so far yielded has been a confirmation of our current physical knowledge.

That could actually be good news, if it didn’t leave a bad aftertaste and unresolved questions. This is because the universe appears to behave slightly differently than our physics would predict. Maybe a new model would help? Physicists from the University of Oxford have now presented one such model in the journal Astronomy and Astrophysics. Their model unifies dark matter and dark energy into a new substance that has the properties of a fluid with negative mass and thus also generates a negative gravitational effect, that is, it repels everything around it.

According to this theory, this negative mass is being created continuously as the universe expands, mimicking the effect of dark energy. At the same time, however, the negative mass would also generate the rotation of the galaxies observed in practice and would thus replace dark matter. In this new model, positive mass floats, so to speak, on a giant sea of negative mass, at whose bottom there is a source through which more and more negative mass is coming in.

This new theory would probably be able to be tested with a new international radio telescope, the Square Kilometre Array.

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