Since Einstein there is an increasing number of theories that make a connection between expansion, gravitation and relativity. Some theories may look crazy, some ingenious. What is gravitation?
In spite of all precise measuring and formulas gravitation is still a remarkable physic phenomenon. Gravitation is a force that we all know too well: all our actions have been based on that force. So just because of our familiarity with this force we have the risk to stand on it not really knowing on what force we stand.
“It is very odd that the theory of gravity, originated by Newton and completed by Einstein, should stand now in majestic isolation, a Taj Mahal of science, having little if anything to do with the rapid developments in other branches of physics…. Einstein’s Theory of Relativity, and the Special Theory was based on the theory of the electromagnetic field formulated in the last century by the British physicist James Clerk Maxwell (1831-79). But in spite of many attempts, Einstein and those who have followed him have failed to establish any contact with Maxwell’s electrodynamics. Einstein’s theory of gravitation was more or less contemporary with quantum theory’, but in the forty-five years since they appeared the two theories have had quite different rates of development. Proposed by Max Planck and carried forward by the work of Niels Bohr, Louis de Broglie, Erwin Schrodinger, Werner Heisenberg, and others, quantum theory has made colossal progress and evolved into a broad discipline that explains in detail the inner structures of atoms and their nuclei. On the other hand, Einstein’s theory of gravity remains to this day essentially as it was when he formulated it half a century ago. While hundreds, even thousands, of scientists study the various branches of quantum theory and apply it in many, many fields of experimental research, only a few persist in devoting their time and passion to further development in the study of gravitation. Can it be that empty space is simpler than material bodies?”
George Gamow.

Let ‘s think about it.