The incident dates back to about 5 billion years ago. It was the time when the universe was breathing its last. The universe was gradually slowing down over a period of billion years, its expansion coming to a halt but then it stopped and reversed course, suddenly deciding to jerk ahead exponentially with the acceleration. Think of it like a car that brakes but then accelerates full tilt, never really stopping in the process. This sudden and deliberate process where larger galaxies got together to make clusters and more left scientists for a long time in a turmoil.
Then it was theorized that the mysterious force that suddenly took over the universe some five billion years ago and made it bend to its will was dark matter. This lay dormant beneath radiation and matter but the moment it let go, it made its presence known almost instantly. Five billion years ago, dark matter announced its presence with an iron will.
Universe And Its Guts
General Relativity or how energy and mass interact is what tells space-time how to move and bend. This in turn governs the movement of celestial objects. It can reveal secrets about specific planets and even dark hole properties. However, the same mathematics that apply to these interactions as well as for GPS satellites cannot tell you everything about how the universe grew and then evolved into what it is today.
What general relativity revealed is that there is a critical density. If this density is exceeded by the universe, then it will crunch to a halt and gradually squeeze back onto itself thus resulting in a Big Crunch. However, if the density of the universe is lower then it will expand always with an exponential rate. But, if it is perfectly equal to the critical density then the universe will expand but at a diminishing rate.
All live measurement reveals that the universe we live in has exactly the same density as that of the critical density as discovered through general relativity. This then suggests that the universe should be slowing down but still expand forever but then why is it accelerating?
What scientists believe is that dark energy is responsible for this. It is believed that dark energy constitutes nearly 69.2 percent of our entire university and that it behaves in odd manners. One peculiar property of dark energy is that its density always stays constant and second is that it always remains in the vacuum of space where nothing else exists.
Basically if you remove everything from space such as matter, regular dark and all kinds of stuff, what you are left with then is pure unadulterated vacuum and it is composed of dark pure energy. Larger the size of this space, more is the dark energy.
Our laws tell us that matter in a specific space will lose half its density if you double the space itself. However, this is not how dark matter functions. And if you are thinking that this observation somehow violates the laws of physics then think again because our laws apply to a static place and not something as dynamic as our universe. And the law of conservation of energy also holds true except it isn’t how you would expect it to be.