Dark matter and dark energy are two separate and unique phenomena. The word ‘dark’ is used because the scientific infrastructure do not yet know what the causes are. I am a layman in this field and learned much of the information I know about these two subjects through personal research. This article will be open to anyone with an interest in the subject and my goal is to try and explain these phenomena from a non-expert standpoint so that everyone can internalize this information and be able to define the distinction.
Dark matter is a form of matter which attempts to describe what our universe is made of. To give an understanding why this might be a big deal consider the following. All of the matter that we know about out there in the universe at large consists of particles and forces which form what is more commonly known as the ‘standard model‘ of particle physics. The standard model comprises most of the things we know about in our everyday reality. Matter makes up the physical world and forces cause matter to interact. The standard model comprises 5% of the matter distribution budget of the known universe. 26% goes to dark matter. The remaining 69% goes to dark energy. These numbers attempt to simplify the matter/energy budget of the universe while also attempting to keep this article from getting too technical and outside my realm of expertise. When scientists shine their light out there on the universe to see what it’s made of, it’s only that 5% humanity has discovered so far. Scientists know there’s an additional 26% of matter out there but have yet to discover what it is. Dark matter does not interact with light so when light is shined on it you see nothing. How then do the scientists know that it even exists? Many years ago a couple scientists by the name of Fritz Zwicky and Vera Rubin noticed there was a discrepancy in galaxy rotational curves. Normally when matter is spinning you should see faster ‘spinning’ near the center of the galaxy and as you move out to the edges the matter should be moving slower. Imagine a record player. The concentric circles closest to the center of the record will have a shorter distance to rotate than the outside edge of the record. What Fritz Zwicky and Vera Rubin noticed was that the galaxies in the universe did not follow this seemingly common sense law. The stars on the outer edges of galaxies were simply moving too fast. Faster than what a normal rotational curve should look like. Looking at several galaxies throughout the universe they discovered this was true of most if not all galaxies. The only way this could be true was if there was more matter/mass in the galaxy as you move out from the center of the galaxy than they could see. Hence, dark matter.
Dark energy on the other hand is the phenomena which describes the mysterious force that’s causing our universe to accelerate over time. If you were unaware of it our universe is expanding. It’s been expanding outward since the ‘big bang’ and the common thought was that over the 14 billion years of the universes history it was assumed that as the galaxy spread outward it must be slowing down. Another case where common sense might lead you to believe this would be the outcome. It was only in the late 1980’s to mid 1990’s did we have the technology to actually measure this ‘expansion rate’ and when the results finally came in, it was discovered that in fact the universe was expanding. This came as a shock to the entire scientific community as the common thought was the universe expansion must be slowing down. This spurred the scientific community to come up with a solution or reason as to what could be causing this speed up. As mentioned above dark energy comprises approximately 69% of what is known of the universe and as of this time it is unknown why the galaxy is expanding at an ever increasing rate. Hence, dark energy.
Energy and matter are two generic items which make up the world we live in. Since the dawn of time man has been on an unending search for what our universe is and why we are here. These are ultimately a couple of questions for which we may never have answers. Having these ‘dark’ items is definitely no help towards that end. However efforts at bettering humanity pulled us out of the dark ages and into enlightenment and dark energy and dark matter research are of couple of efforts to further that end.