Question

Gravitational force is attractive not repulsive then why our whole universe is expanding with some acceleration and accelerating at a faster rate from the time of Big Bang.Which law of physics is working over here?

Answer 1

Answer on Question #44233, Physics, Astronomy | Astrophysics

Gravitational force is attractive not repulsive then why our whole universe is expanding with some acceleration and accelerating at a faster rate from the time of Big Bang. Which law of physics is working over here?

Solution :

It should be noted that the physical laws is a consequence of observations and very rarely predictions based on other laws. We can only say that the laws are based on observations in one place may not be true elsewhere.

Laws are usually expressed some models that allow to predict the evolution of the parameters of the phenomena that the model describes.

In such models usually use a tried and tested model that describes other natural phenomena.

The metric expansion of space is no exception.

At the end of the early universe's inflationary period, all the matter and energy in the universe was set on an inertial trajectory consistent with the equivalence principle and Einstein's general theory of relativity and this is when the precise and regular form of the universe's expansion had its origin (that is, matter in the universe is separating because it was separating in the past due to the inflation field).

According to measurements, the universe's expansion rate was decelerating until about 5 billion years ago due to the gravitational attraction of the matter content of the universe, after which time the expansion began accelerating. In order to explain the acceleration physicists have postulated the existence of dark energy which appears in the simplest theoretical models as a cosmological constant. According to the simplest extrapolation of the currently-favored cosmological model (known as "ΛCDM"), this acceleration becomes more dominant into the future.

Model constructed on the basis of views was incompatible with experiment. Then introduced an amendment to the model in the form of dark energy and dark matter. Dark energy plays role of repulsive forces.

* http://en.wikipedia.org/wiki/Metric_expansion_of_space

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