A team of scientists believe ‘grabby aliens’ are needed to explain why we humans have appeared so soon after the big bang, and that our descendants could encounter them in roughly a billion years’ time.
To calculate such numbers, four researchers, led by Professor Robin Hanson from George Mason University, USA, and including a Durham University PHD student, have built a simple model. A model they say is far more than just speculation, as all its parameters are set by relevant cosmological data. In particular: the current age of the universe, the fact we humans have yet to see aliens in our sky, and the timing of key events in Earth’s history.
The research can be read in full in their paper, accepted for publication in the Astrophysical Journal.
Durham University PhD student Daniel Martin, a co-author who helped to illustrate the model, said: “We think there are other civilisations within the universe that have developed more than humans, and the only reason they do not appear in our sky is because their light has not yet reached us.
“My illustration of this model shows many cones within a particular area of the universe. Each cone represents one civilisation, which expands rapidly in space until it meets others.
“Perhaps only a very few intelligent civilizations can survive for a long period of time or will choose to expand rapidly. But our model says that those few exceptions will eventually fill and remake the universe. A once lifeless universe will soon be filled with intelligent life.”
They estimate that such aliens appear once per million galaxies, that they now occupy about half the space in the universe, and that our descendants would encounter them in roughly a billion years.
Lead researcher Professor Robin Hanson added: “I called these civilisations ‘grabby aliens’ because they last long, expand fast, and change the spaces they enter to meet their needs.
“But this doesn’t mean that such civilizations are aggressive and fight when they meet. Our analysis actually doesn’t say what happens if these ‘grabby’ civilisations were to meet another.”
The team states the existence of grabby aliens provides an answer to the puzzle of why humans have appeared so soon after the big bang.
They continue to explain that while our current date is late compared to when most stars formed, it is early considering how long most stars will last. The team believe we are even earlier when you consider the simple statistical model introduced in the 1980s by the physicist Brandon Carter, that describes what happens when a number of difficult stages (hard steps) must be endured before civilization can appear on a planet.
Earth has overcome those hard steps long before when a typical civilization would, if the universe would sit and wait empty for such civilizations to appear.
Daniel added: “Our hypothesis offers an explanation as to why humans have evolved so quickly. If ‘grabby aliens’ will at some point occupy all of the universe, it’s like a deadline had been set for human civilisation to appear, if it’s not to arrive within a grabby-controlled environment.”
Robin added: “Our account says that if humanity kills itself, that thankfully isn’t the end of life and civilization in the universe. But our account does suggest an aspiration for humanity: if we can avoid extinction, then we can expect to eventually meet and learn of hundreds of grabby civilizations. Let us work so that, when they learn of us, they will find something about us worthy of admiration and emulation.”