Darkness. It has often been portrayed to us as a symbol of fear, evil or just plain emptiness. But surprisingly, darkness is also essential, especially when our universe is concerned. Everything that we can see – including ourselves – is part of “normal” matter. But there is also a dark side, composed of two things: dark matter and dark energy. Simply put, dark matter has influenced the history of the universe, and dark energy may decide the future of it.
Let’s start with dark matter, which we cannot see because it does not absorb or give off light. So how do we know that it exists? Simply put, there is not enough normal matter in the universe to account for all the matter that astronomers know is out there, with the aid of mathematical equations. However, in the midst of all this darkness, they have found indirect ways of measuring dark matter. Surprisingly, it is six times more abundant than normal matter. But what exactly is it? That question is largely unanswered. One idea suggests that molecular hydrogen gas is part of dark matter. Measurements have shown that there are small “clumps” where hydrogen is known to exist. This is important because astronomers have predicted that dark matter is just that – clumpy.
In fact, dark matter’s clumpy nature is responsible for forming our universe! Without dark matter at the beginning of time, our universe would be much too uniform for galaxies to exist. All of the hot atomic gas floating around soon after the Big Bang eventually cooled and “attached” to clumps of dark matter. This eventually created galaxies, including our own. Clearly, dark matter is important, but another component of the darkness within may be even more important: dark energy.
Recent research has shown that dark energy has become the dominant component in the structure of our universe. Both matter and energy are responsible for the universe’s “shape” and even taking into account dark matter, there is still a discrepancy between astronomers’ calculations of “shape” and their observations. That’s where dark energy comes into play. Since it is self-repulsive, it “pushes” outward, and is responsible for the accelerated expansion of our universe today. Dark energy resembles a driver with his foot continuously on the gas pedal – the car not only accelerates, but it accelerates ever faster. Although we are in no immediate danger of crashing, such research poses interesting questions on the exact boundaries of the universe.
This work on dark matter and dark energy is relatively new, but it shows us the importance of unseen things. Dark matter is responsible for creating us, and dark energy may decide where we will go. In this case, darkness is not merely an empty thing, but full of consequences for the past, present and future.
The darkness within – how our universe relies on dark forces
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