However, somebody might maintain the following supposition;
As the Cosmos had been expanding at the velocity of light, the Cosmic radius was smaller in the past.
Therefore, the radius of the Local Group must have been smaller, too.
In such a situation, intergalactic gravity had to increase to result inevitably in faster movements of galaxies.
Consequently, though they are moving slowly at the moment, they must have revolved many times already while the Cosmic radius was much smaller than now.
This sounds plausible.
But let's see the reality, not the deduction.
Astronomers have observed that the Cosmic structure is uniform as far as 100 billion light-years.
This means that galaxies in the Group systems have not revolved once during at least 100 billion years.
Now, let's think about the future this time.
The Cosmos is expanding in the viewpoint of the Big Bang theory.
Therefore, if the Cosmic radius becomes double the present radius, the extent of the Local Group will also be double the present radius.
After 15 billion years when the Cosmos has expanded to 30 billion light-years in radius, the extent of the Local Group should be 5 million light-years.
By then, the Andromeda galaxy may be reaching the position where Our Galaxy is presently located.
However, the Andromeda galaxy would not be able to reach there because the extent of the Local Group will become wider and wider while it travels and, to the contrary, its travelling speed will become slower and slower with the decrement of the gravitational interaction.
Though the Andromeda galaxy has reached the position where Our Galaxy was once located, Andromedans will never be able to finish a revolution around the Local Group.
That is because it will take another 30 billion years or longer to carry out another half of their itinerary.
We can tell this story at any point in the future.
Therefore, we may conclude that the Andromeda galaxy can never complete a revolution in the future as long as the Cosmos expands.
Now, we have obtained two definite points in case we regarded the Big Bang theory as true; one is that galaxies in the Group systems have not revolved once during at least 10 billion years in the past, and another is that they will never be able to carry out a revolution in the future.
Therefore, the conclusion seems to me that galaxies are not revolving.
Galaxies can not revolve if the Cosmos is ruled by the Big Bang theory.
However, it is in contradiction to reality.
The reality is that galaxies are combined by gravity and they are revolving around the whole gravitational center of the Group.
This is a reality that astronomers have concluded through observations.
Those two contradictory conclusions can not be true at same time.
So, we have to choose one of them.
We have to choose one between the reality and the deduction.
I would like to choose reality, because I think no theory can surpass reality.
As the Big Bang theory failed to explain the time factor of Cosmic phenomenons, so it might be said to be untrue.
Now we might consider the Fractal Cosmology.