The end of the world: Five to seven billion years from now, the Sun will loom in our sky as a blazing 'red giant'.
Credit: Photolibrary
The outer planets in our Solar System will fare somewhat better. Mars, for example, will become distinctly more hospitable over the next few billion years. In about six billion years, Adams says, the Red Planet will absorb about as much sunlight as the Earth does today. Will the next chapter in human history unfold on the fourth rock from the Sun?
Our planet, by this time devoid of life, will linger a bit longer. Although Earth will have moved to a wider orbit, Adams explains that it will meet with more resistance as it passes through matter from the Sun. This will ultimately cause Earth's orbit to decay, dragging the planet closer to the Sun, where it will meet its demise. In his paper, Adams describes the end of planet Earth in two terrifyingly concise sentences: "Earth is thus evaporated, with its legacy being a small addition to the heavy element supply of the solar photosphere. This point in future history, approximately seven billion years from now, marks the end of our planet."
Happily, this billion-year time scale is inconceivably long compared to the 200,000 years or so that our species has been around, let alone the few millennia in which we've been using technology. So perhaps we can dare to imagine that we will have spread out across the galaxy – or at least beyond our doomed planet – before the Earth's demise. So let us turn, then, to the long-term prospects for the universe itself.
ISAAC NEWTON IMAGINED a static cosmos of infinite space and time. In such a universe, it would be reasonable to conceive of an infinite future for our species or its remote descendants. But the discoveries of 20th century physics changed that picture, and after the Big Bang model began to solidify, astronomy textbooks typically described two possible fates for our universe.
First, if the average density of the universe were great enough, the universe would be 'closed': gravity would eventually halt its expansion and the universe would start to contract, ultimately collapsing in a kind of reverse Big Bang, or 'Big Crunch'.
Alternatively, if its average density were lower than this threshold, the universe would be 'open': it would expand forever and all processes in the universe would gradually cease, in accordance with the second law of thermodynamics (which says, essentially, that the amount of disorder in the universe must always increase, and that systems tend towards equilibrium). The universe would become ever darker, colder and less hospitable to life.
The 20th century American poet Robert Frost captured the essence of the two possibilities in 1923 with a famous poem 'Fire and Ice': "Some say the world will end in fire | Some say in ice". Until the final decades of the 2oth century, this was the best we could do: the universe would suffer one of these fates, but we could not say which one.
But the universe had more surprises in store, and as the century drew to a close, it delivered a whopper. In the late 1990s, astronomers were studying the properties of distant supernovae when they found something remarkable: the universe wasn't just expanding – the rate of expansion was accelerating. The rate of expansion had been decelerating until sometime around seven billion years ago, at which time we entered a new era of ever-faster expansion.
What could possibly be causing the expansion of the universe to accelerate? The Big Bang explosion would have given everything an outward push – but astronomers and physicists thought that the force of gravity ought to be slowing that expansion. They concluded that there must be some kind of intangible energy that works against gravity– some energy that is literally pushing all of the galaxies away from each other. No one knows exactly what that entity is; for now it has been labelled 'dark energy'.
Early Days - End Of Days - Wrong Conclusions
QUOTE:
"Krauss has said that astronomers living at that time will be misled by their observations: "It will lead them to the wrong conclusion about what the universe is doing," he said in a recent interview."
Doesn't the same apply to the science and astronomy of today?
What we are currently observing of the universe might also be incorrect... because of the limitations of light speed we can only "see" up to 13.6 billion years ago, what happened before that we can never truly see... and our assumptions can therefore only be exactly that - assumptions.
All the same, a nice thought provoking article.
So the universe is only a one-time event it seems, much like life on earth, but then a new life (universe) coming into being is still a possibility - it might be very far away from where we are right now, and incredibly far into the future, but a possibility, also just like the birth of early life forms, where the birth of one primitive cell, where it's position and time-line might be so far removed from it's nearest neighbouring cell - that one cell would not know of the existence of the other.
Wonderful stuff, thank you Cosmos Magazine.