So, last week I dealt with dark matter. This week we'll be talking about dark energy. Let's just have a recap on dark matter and visible matter. The visible universe is made up of ordinary matter - that includes our Earth, the Sun, stars and other galaxies. It makes up less than 5% of mass in the universe. The rest of the universe is made up of dark matter (25% of the universe's mass) that's difficult (some say impossible) to detect. And there's also a force present in our universe that repels gravity - this is known as dark energy (and accounts for 70% of the universe's mass). And our universe is expanding - that's an important point too. But first... What's the difference between dark matter and dark energy?Dark matter produces the attractive force of gravity, but dark energy produces a repulsive force - commonly referred to as anti-gravity. That's the difference. Dark matter attracts, but dark energy repels. Remember I said that the universe is expanding? Well, two teams of scientists tried to measure the rate of that expansion in the 1990s. They were shocked to discover that the universe isn't just expanding - it's accelerating. Scientists had previously assumed that gravity would eventually slow down the expansion of the universe. They were wrong. More baffling still, this repulsive force gets stronger as the universe expands. It's a bit like Ironman throwing his helmet in the air and, instead of it falling back to Earth, it accelerates away from him. What's causing this accelerated expansion?No one really knows. The term "dark energy" was coined for this mysterious force and that's all dark energy really is at this stage - a name. But theories do exist. One is that dark energy is a fifth fundamental and unknown force called quintessence that only exists when the universe is a certain size. Under quintessence, dark energy could eventually disappear and our universe will stop accelerating. Another idea is that dark energy is consistent with a cosmological constant. In other words, dark energy is constant and our universe will continue to accelerate in its expansion. Alternatively, dark energy could result from the weird behaviour seen for the physics of the incredibly small - aka quantum mechanics. On such tiny scales, energy and matter can appear out of nothing for the tiniest of instants. The constant appearance and disappearance of matter could produce dark energy. But every possible explanation still does not explain why dark energy exists in the first place. Extra reading and watchingIf you Google "dark energy", there are a myriad of articles and videos out there. It's a big topic. The most up-to-date and accessible article I could find is by Adrian Cho - Is dark energy an illusion? It discusses some of the challenges in the dark energy space right now (no pun intended). And this video is a great round-up of dark energy: What is Sunday Science?Hello. I’m the freelance writer who gets tech. I have two degrees in Physics and, during my studies, I became increasingly frustrated with the complicated language used to describe some outstanding scientific principles. Language should aid our understanding — in science, it often feels like a barrier.
So, I want to simplify these science sayings and this blog series “Sunday Science” gives a quick, no-nonsense definition of the complex-sounding scientific terms you often hear, but may not completely understand. If there’s a scientific term or topic you’d like me to tackle in my next post, fire an email to [email protected] or leave a comment below. If you want to sign up to our weekly newsletter, click here.
1 Comment
I completely agree about nomenclature and language in science often being somewhat ridicules. My take on all of this is composite Dark Matter "transparent matter" is almost a certainty at this point, but it’s hard to say how long it will take science to fully realize that. The result is a pseudo or shadow 5th dimension, but that doesn't preclude other types of dark matter or even up to 11 dimensions of composite dark matter at different quantum phases and interactions with our reality, most noticeable with gravity. Beyond that, other parallel universes could occupy the same space without any interaction with our reality whatsoever. As for Dark Energy, laboratory tests have demonstrated quantum gases at sub-absolute zero temperatures result in a negative gravity, so composite dark matter gases could easily explain dark energy too. I've written several papers on this, some are available online, others are available in a collection of papers called the Grand Unification of Dark Matters: The Dark Universe Revealed at Amazon: http://www.amazon.com/dp/1520306318
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