A mysterious force, known as dark matter, has baffled scientists for decades. Many scientists think dark matter is responsible for the accelerating growth of the universe. However, a new study purports that dark matter might just be an illusion.
If it does indeed exist, it is estimated that dark energy would make up roughly 68% of the energy that we can currently observe. Despite this large percentage, it is only 10 to the negative-27th kilograms per square meter...which makes it near impossible to see in the laboratory. Furthermore, the idea of dark energy helps us to explain things, for example the overall shape of the Universe and even the patterns of matter that we can see in space but can't quite explain.
And, although it is currently assumed to be correct...it hasn't been wholly proven. However, it is not without it's potential and it is fundamental to our understanding of the universe. In fact, it was Einstein himself who proposed the cosmological constant as a way to explain exactly why all the mass scattered throughout the Universe..."wasn't pulling back together under the attraction of its own gravity." But, like I said, there isn't a whole lot of concrete proof...it's just a theory that fits into our understanding of the observable universe. A theory that was later disproved by Hubble, who was able to prove that the universe was expanding.
So why even mention the cosmological constant? Well, in this piece from early 2017 it was proven that, while the universe WAS expanding...it's expansion rate is starting to speed up. Now, back to the dark matter. Dark matter + the cosmological constant we get the Lambda Cold Dark Matter (ΛCDM) model, which aims to explain how the universe evolved.
The ΛCDM model, in this case, assumes a uniform expansion that progressively gets faster and faster. Why? Well, because of an increasing push of dark energy that works to overcome the pull of other matter that is distributed, more or less, evenly throughout space.
Now, NASA released a new study putting all these big ideas together in this release. Researchers used these theories, along with new data, and have argued that previous approximations of what the universe consists of have largely ignored influences of large scale structures within the Universe.
Dr László Dobos, co-author of the paper "Explaining the accelerating expansion of the universe without dark energy" says, "Our findings rely on a mathematical conjecture which permits the differential expansion of space, consistent with general relativity, and they show how the formation of complex structures of matter affects the expansion..These issues were previously swept under the rug but taking them into account can explain the acceleration without the need for dark energy."
Though, it should also be pointed out, the proposed model is not without its faults. The model Dobos and her partner created makes its own necessary assumptions. But, if it is in fact able to stand up to further scrutiny it could become incredibly important in proving how the Universe's expansion is accelerating without the need for negative pressure.
The argument for dark matter, at this point in time, is still largely up in the air.
the above image is from flickr user Katie187 and is liscensed under creative commons 2.0.