The Universe is expanding. But what is fuelling this expansion? Gravity is holding the Universe together but, dark energy, an invisible force, is pushing the Universe apart.
Welcome to very new picture of the universe. But even the experts can hardly believe it’s real. The most famous force in physics has met its match – because the entire universe is defying gravity.
Anthony Aguirre “This was saying that there was something that fills the universe, and causes an anti-gravity force. Something that was causing everything to push everything else apart, and to make universe bigger and bigger in an accelerated way.”
Gravity acts as a brake – pulling back on the expansion of the universe. But we now know there is another, more mysterious force – with its foot on the gas.
Anthony Aguirre “What’s doing the pushing? What’s that force that’s forcing everything apart? Well, we don’t know, but we did work out what to call it. We have a name for it. We call it dark energy.”
Cosmologists don’t know what dark energy is. They only know what it does. Where gravity pulls – dark energy pushes.
Anthony Aguirre “You don’t see this stuff. You don’t see it doing anything, it just does one thing, it causes an anti-gravity force. We don’t have any other handle on it.”
Dark energy is dark matter’s dark adversary. A shadow on the entire universe.
Anthony Aguirre “There’s invisible energy in the galaxy. There is invisible energy, here on earth. The invisible energy passing through it right now. We are filled with this dark energy. We don’t see it – we don’t feel it. But it’s everywhere. It’s kind of just a uniform colouration to our map.”
73% of universe is dark energy, but you’d never know.
Anthony Aguirre “In everyday life, this stuff is just hard to detect. Now, it’s true that between my two fingers, there’s an anti-gravity force, right now. But that anti–gravity force is so incredibly miniscule, that I never ever notice it. It’s only when you get to really large scales, that you really see the effect of this stuff. If I could move my fingers, all the way across the universe, then they’d feel is tremendous push apart, due to this invisible force.”
In the really big scheme of things, dark matter is fighting a losing battle… Because there’s only so much of it all round.
Anthony Aguirre “If you add more space, if you give more place for those little pieces of matter to be, then, the density of them goes down. You just see less of it – it gets diluted.”
As the universe expands, dark matter spreads out until it can no longer compete with dark energy.
Anthony Aguirre “The really crucial thing about how this dark energy behaves, is that it doesn’t dilute. When the universe doubles in size, you’ve got twice as much dark energy. You make it four times as big, you just get four times as much dark energy. Once you get to this cosmological scale, the biggest possible scale, it becomes the biggest game in town. It becomes the prime player.”
Dark energy is on the map. But cosmologists can’t explain it.
Anthony Aguirre “Depressing, or exciting? I think it’s exciting. As a map maker, this is a strange thing. We go out, we make this map, we discover this land, we’ve mapped it out, and we still don’t know what it is.”
Dark Energy – Wikipedia Page