The cause of gravity is the sum of contracted space that  a certain amount of elementary particles  have spun together.

The particles twists their energy into space and space absorbs this energy. The natural result is a culmination shortly followed by liberation of the absorbed energy by space. This process will repeat itself and continue in an endless cycle by virtue of the interaction between particle and antiparticle. This means that the interaction (the strong nuclear force) arises as a consequence of the particles’ collective spin: As soon as a particle liberates contracted space, another particle will immediately use this for the opposite action, i.e. contracting space as this will save energy (the expression that the particles exchange “a virtual particle” means that they exchange ”compressed space”). Therefore, the strong interaction is a result of gravity, i.e. the force keeping space contracted (read the chapter on quantum physics).

The cause of the Big Bang was most likely a Big Crunch. The elementary particles were already existing before the Big Bang.

During a Big Crunch, space is gradually being contracted as the Universe gets smaller. This means that the strong interaction (the strong nuclear force) increasingly will compete with the resistance of space in being contracted. A point will finally be reached where the total energy of the particles cannot contract space any further, resulting in a new Big Bang.

Therefore, the Big Bang is basically an “explosion of gravity”. - Shortly after the Big Bang, the strong nuclear force will occur again and space will start locally contracting again. But even though local gravitation/difference in density is occurring locally in the Universe some time during the process, it will be much too weak to stop the Big Bang. You could say that the Big Bang has a lead before the universe begins to contract again.

All galaxy clusters which are being created will easily be “emptied” of contracted space - (so-called) dark matter will be converted to (so-called) dark energy before the Big Bang is out of breath. The strongly concentrated gravity of the galaxies will maybe be capable of resisting the Big Bang and avoid being torn apart. When the (so-called) dark matter of the last galaxy cluster has been converted to (so-called) dark energy, a new Big Crunch will maybe begin.

When contracted space is locked into the space of a galaxy cluster we refer to it as dark matter. As soon as a cluster splits up the contracted space is released, this is known as dark energy.

Measurements from the satellite XMM Newton have shown that younger clusters of galaxies (those which formed 10 Billion years ago) where bigger than clusters of galaxies formed later. This was concluded because younger clusters of galaxies emit less x-ray radiation. Measurements also show that in the past there were fewer clusters of galaxies than today. Read More

These observations came as a shock for older theories, but can easily be explained by applying our contraction of space theory.  

The facts give us reason to ask: How is the universe pulling apart?  - The force driving the expansion of the universe affects space from all sites simultaneously.

Now imagine 6 small galaxy clusters (illustration above) united in a greater cluster. This will help you to imagine, on a grander scale, thousands of small clusters of galaxy bound by a common field of gravity.  

The force behind the expansion of the universe, has increased the volume of very huge cluster of galaxies that existed in the younger days of our universe.

It may sound strange, but we have reason to believe that our universe was initially split into a few very large parts, and like a nuclear chain reaction split into smaller parts, and likely continues to do so.

In the young universe, when huge clusters were split huge empty holes were left in the middle of where these galaxy clusters once were. This is exactly what has happened. >

We have very good reason to believe that our Universe was initially split into a few huge parts just like a nuclear chain reaction splits into smaller parts – and it is likely to continue to do so.

The reason that the very huge clusters in the young universe split must have been that they were the strongest dominating gravitational fields, and therefore 'first in line'.

Hence the weaker gravitational fields (e.g. galaxies and astronomical bodies) are the last to realise contracted space (dark matter) and transform it to dark energy. 

This also means that the expansion of the Universe can only happen with a certain maximum velocity.

In other words, the force responsible for the continuation of the expansion of the Universe is increasingly powered by even smaller gravitational fields. This also includes the Earth.

We already have evidence that for a couple of hundred million years, the Earth has contributed increasingly to the expansion of the Universe by releasing contracted space (dark matter / energy). This will be further covered in the chapter 'Background Gravity)