Hi folks, an interesting and topical question: **where is the dark energy responsible for the accelerating universe from?**

First of all, we need to be clear that if** the universe is rapidly expanding, then the energy-momentum tensor of all matter in the Universe is not conserved.** As the energy-momentum tensor must be conserved, **the simplest solution** to this problem **is to introduce a scalar field in Einstein’s equations. This scalar field checks its own equations and makes the energy-momentum tensor including all matter and scalar field conserved.**

**The scalar field is created by the matter itself and its energy-momentum tensor contains four functions. Three of these functions **can be chosen as independent variables and** can be adjusted to observational data of the accelerating expansion of the universe**.

For all this, **the scalar field is responsible for the accelerating expansion of the universe.**

As there is a long range vector field like the electromagnetic and a long range tensor field like the gravitational, there is also a long range scalar field.

Moreover, **this scalar field causes the inertia.**

**All this rigorously detailed in the Appendix of the section “****THE PHYSICS OF TIME TRAVEL****“**