OUR UNIVERSE
‘In order to make an apple pie [or a human] from scratch,
you must first create the Universe.’
Carl Sagan
you must first create the Universe.’
Carl Sagan
NB As I explained in the Introduction (see Web Archive) what follows is my interpretation and summary, as a layperson for other laypeople, of the generally available scientific account. As in the rest of the story, check the Ultimate Websites and relevant Further Reading list for my main sources, and also the Internet (I recommend Wikipedia) for an explanation of unfamiliar terms. Google or Wikipedia will also provide information on the people identified in the relevant Pathfinders List. And if you are not a layperson please don’t hesitate to make suggestions for a more accurate summarized representation of any specialized area. All readers are also invited to suggest additions to my various Lists.
Once upon a time, or what scientists tell us was around 13.7 billion Earth-years ago, our Universe sparked into being in what is generally known as The Big Bang. At its birth it was apparently a glowing sphere of energy - super-hot, super-dense and rapidly inflating. And with it came space and time, as well as endless possibilities.
But in order for the possibility of human beings to be realized the tiny bits of matter that we call atoms would have to emerge, and the forces that clump bits of matter together into larger entities. The one that you are probably most familiar with is gravity.
So how did all this happen?
Almost immediately after the Big Bang the expansion rate of our Universe slowed, and it began to cool. Within minutes it was a cosmic soup made up of quarks, gluons and other things shifting between energy and matter – even smaller than atoms and very volatile.
A few hundred thousand Earth-years later more stable forms of matter appeared: atoms of the simplest chemical elements. These are familiar to us as hydrogen and helium.
And now the atoms began gathering in vast swirling clouds, with denser clumps of hydrogen scattered throughout them. As gravity built up in these clumps they drew even closer together and their centres became hotter. And a few became hot enough to ignite as giant stars, where nuclear reactions in their cores fused hydrogen into helium and then into atoms of new, complex elements that are also familiar to us, like carbon, oxygen and iron.
It took several million years for a giant star to change all of its hydrogen into other elements, and then it exploded in a supernova. (The literal meaning of this word is ‘a very bright new star’, because that is how such an explosion appears to the naked eye on Earth.)
The explosion sent elements from the outer layers of the star into its surroundings, while its core usually compressed into a rapidly spinning neutron star. Some of these sent out pulsing beams of radio-waves. But in a really gigantic star the core collapsed into a stellar black hole, whose intense gravity pulled in everything nearby. Even light couldn’t escape.
Then as the supernova’s remnant clouds of gas and dust cooled, some elements within the clouds joined together, making compounds that are actually more common on Earth than pure elements are. Thus atoms of hydrogen and oxygen formed molecules of water vapour.
But other hydrogen atoms gathered in clumps again, with some igniting as second- generation stars. And in a few cases the debris around the star clumped together in a new kind of matter: orbiting bodies of gases or molten solids not large or hot enough to ignite.
The stars with orbiting bodies were the first solar systems. Meanwhile other stars remained solitary or were grouped together in star-clusters of varying sizes.
The fusion in a second-generation star was less intense, and it took several billion Earth-years for one to run out of fuel. When the hydrogen in its core was gone, it began to fuse the hydrogen in its outer layers, expanding rapidly into a Red Giant. Then when all of its hydrogen was exhausted it collapsed into a White Dwarf, surrounded by clouds of debris.
Scientists say that such stars will finally become Black Dwarfs, with no heat or light at all. But our Universe is not yet old enough for any to have reached this point.
The process of star creation followed by destruction seems to have been going on ever since it began, in a rhythm of occasional sudden, explosive changes in various parts of our Universe, against an overall background of smaller, slowly accumulating ones.
And all the changes are caused by one kind of energy being transformed into another. This was first revealed by Albert Einstein when he identified matter as just another form of energy: e = mc2 (with ‘e’ signifying energy, ‘m’ matter, and ‘c’ the speed of light).
From Earth today, helped by a widening array of very powerful telescopes, we can observe countless entities within our Universe clumping, igniting, scattering, expanding and collapsing, in a panorama extending more than 13 billion years into the past.
Because most of this ongoing process of transformational change is so slow, the only evidence of it is in the various stages of star development on display for us. But now and then we see the sudden burst of a supernova, the most famous one probably being the first to be recorded in 1987, aptly if unimaginatively called 1987a.
Over time billions of large and small galaxies have emerged from the original vast swirling clouds of gases. Each galaxy has stars of different sizes, in different groupings, and at different stages in their life cycles, and each of the largest ones has billions of stars.
Most observed galaxies are in the form of a spiral, at the centre of which is evidently a super-massive black hole, hidden by the glow of the surrounding stars being pulled in to it.
Around this black hole the galaxy circles in a similar way to a solar system. Basically the gravitational force of the centre pulls orbiting matter in, and a not quite equivalent centrifugal force pushes it away.
The galaxies are arranged in groups or clusters of varying sizes, and scientists say that the only way that they can be held together is by some kind of invisible matter that altogether makes up 20% of our Universe’s total mass. Their name for this force, which includes black holes, is Dark Matter. The galaxies within a group or cluster pull on each other according to their individual masses, and sooner or later they merge to form larger galaxies.
Our galaxy seems to be a merged galaxy, with four spiralling arms and about 400 billion stars. It takes 100,000 Earth-years for light from one point on its rim to reach the opposite point. As we look across its dense central area it seems like a white path in the sky. Hence its name: The Milky Way Galaxy.
It is in a small group called The Local Group and is pulling in two smaller galaxies, The Magellanic Clouds. A larger galaxy in the group, Andromeda, is 2.1 million light years away, but apparently it will also eventually merge with ours.
The Magellanic Clouds and Andromeda are the only heavenly bodies outside our own galaxy that are visible to the naked eye (and the Magellanic Clouds are visible only from the Southern Hemisphere). This is because, while activity is going on within the clusters of galaxies, our Universe keeps on expanding in the otherwise dormant spaces between them.
Scientists theorize that it is driven by a mysterious invisible force that acts in an opposite way to gravity, pushing out rather than pulling in, and growing stronger with distance. The further it stretches, the closer it gets to the speed of light. From Earth it looks as if our Local Group is at the centre and the other galaxies are moving away from us. But actually every clump of galaxies is moving away from every other clump.
Edwin Hubble, who discovered the phenomenon, likened it to spots on a balloon that grow further apart as it expands, although in this case the spots would have to be inside the balloon as well as on its surface. More recently it has been likened to sultanas in an expanding yeasty fruit-loaf. But any Earth-bound analogy is bound to be inadequate.
One way to think of the expansion is to imagine a night sky that is just one long twilight. Without it the other galaxies would still be close by, lighting up almost all the dark spaces.
Scientists call the paradoxical expansionary force Dark Energy, and calculate that it makes up a further 70% of our Universe’s mass. This means that what is visible to us with the most powerful telescopes is astoundingly less than 10% of the total!
When all the clumps of hydrogen in its galaxies have progressively ignited to form new stars our Universe may keep expanding indefinitely, growing colder and darker as all the existing stars one by one collapse, cool and go out. Or it may reach some tipping point and begin rushing in again until it implodes in A Big Crunch. Then there may even be a bounce back into a brand new expanding Universe.
The more we explore this world of ours the more mysterious it becomes!
All that the experts agree on is that the long-term existence of our Universe seems to depend on a dynamic balance between clumping and splitting apart, with galaxy clusters, galaxies and solar systems all based on the same precarious balance.
In this process, however, as matter clumps in a certain locality (as a galaxy cluster, a galaxy or a solar system) it begins to take on its own unique features, thus adding to a trend towards increasing diversity and complexity within the whole.
Mathematicians call this a dynamic fractal pattern, a branching process repeated at larger and smaller orders of magnitude but never quite the same. To some it suggests that our Universe is a self-ordering system following a potentially discernible course, both as a whole and in each of its parts as well.
And this course seems to be based on the three principles referred to in this scene: transformational change; a dynamic balance between splitting apart and clumping together; and increasing diversity and complexity. As our story continues we’ll encounter more examples of these underlying principles, in increasingly familiar contexts.
Once upon a time, or what scientists tell us was around 13.7 billion Earth-years ago, our Universe sparked into being in what is generally known as The Big Bang. At its birth it was apparently a glowing sphere of energy - super-hot, super-dense and rapidly inflating. And with it came space and time, as well as endless possibilities.
But in order for the possibility of human beings to be realized the tiny bits of matter that we call atoms would have to emerge, and the forces that clump bits of matter together into larger entities. The one that you are probably most familiar with is gravity.
So how did all this happen?
Almost immediately after the Big Bang the expansion rate of our Universe slowed, and it began to cool. Within minutes it was a cosmic soup made up of quarks, gluons and other things shifting between energy and matter – even smaller than atoms and very volatile.
A few hundred thousand Earth-years later more stable forms of matter appeared: atoms of the simplest chemical elements. These are familiar to us as hydrogen and helium.
And now the atoms began gathering in vast swirling clouds, with denser clumps of hydrogen scattered throughout them. As gravity built up in these clumps they drew even closer together and their centres became hotter. And a few became hot enough to ignite as giant stars, where nuclear reactions in their cores fused hydrogen into helium and then into atoms of new, complex elements that are also familiar to us, like carbon, oxygen and iron.
It took several million years for a giant star to change all of its hydrogen into other elements, and then it exploded in a supernova. (The literal meaning of this word is ‘a very bright new star’, because that is how such an explosion appears to the naked eye on Earth.)
The explosion sent elements from the outer layers of the star into its surroundings, while its core usually compressed into a rapidly spinning neutron star. Some of these sent out pulsing beams of radio-waves. But in a really gigantic star the core collapsed into a stellar black hole, whose intense gravity pulled in everything nearby. Even light couldn’t escape.
Then as the supernova’s remnant clouds of gas and dust cooled, some elements within the clouds joined together, making compounds that are actually more common on Earth than pure elements are. Thus atoms of hydrogen and oxygen formed molecules of water vapour.
But other hydrogen atoms gathered in clumps again, with some igniting as second- generation stars. And in a few cases the debris around the star clumped together in a new kind of matter: orbiting bodies of gases or molten solids not large or hot enough to ignite.
The stars with orbiting bodies were the first solar systems. Meanwhile other stars remained solitary or were grouped together in star-clusters of varying sizes.
The fusion in a second-generation star was less intense, and it took several billion Earth-years for one to run out of fuel. When the hydrogen in its core was gone, it began to fuse the hydrogen in its outer layers, expanding rapidly into a Red Giant. Then when all of its hydrogen was exhausted it collapsed into a White Dwarf, surrounded by clouds of debris.
Scientists say that such stars will finally become Black Dwarfs, with no heat or light at all. But our Universe is not yet old enough for any to have reached this point.
The process of star creation followed by destruction seems to have been going on ever since it began, in a rhythm of occasional sudden, explosive changes in various parts of our Universe, against an overall background of smaller, slowly accumulating ones.
And all the changes are caused by one kind of energy being transformed into another. This was first revealed by Albert Einstein when he identified matter as just another form of energy: e = mc2 (with ‘e’ signifying energy, ‘m’ matter, and ‘c’ the speed of light).
From Earth today, helped by a widening array of very powerful telescopes, we can observe countless entities within our Universe clumping, igniting, scattering, expanding and collapsing, in a panorama extending more than 13 billion years into the past.
Because most of this ongoing process of transformational change is so slow, the only evidence of it is in the various stages of star development on display for us. But now and then we see the sudden burst of a supernova, the most famous one probably being the first to be recorded in 1987, aptly if unimaginatively called 1987a.
Over time billions of large and small galaxies have emerged from the original vast swirling clouds of gases. Each galaxy has stars of different sizes, in different groupings, and at different stages in their life cycles, and each of the largest ones has billions of stars.
Most observed galaxies are in the form of a spiral, at the centre of which is evidently a super-massive black hole, hidden by the glow of the surrounding stars being pulled in to it.
Around this black hole the galaxy circles in a similar way to a solar system. Basically the gravitational force of the centre pulls orbiting matter in, and a not quite equivalent centrifugal force pushes it away.
The galaxies are arranged in groups or clusters of varying sizes, and scientists say that the only way that they can be held together is by some kind of invisible matter that altogether makes up 20% of our Universe’s total mass. Their name for this force, which includes black holes, is Dark Matter. The galaxies within a group or cluster pull on each other according to their individual masses, and sooner or later they merge to form larger galaxies.
Our galaxy seems to be a merged galaxy, with four spiralling arms and about 400 billion stars. It takes 100,000 Earth-years for light from one point on its rim to reach the opposite point. As we look across its dense central area it seems like a white path in the sky. Hence its name: The Milky Way Galaxy.
It is in a small group called The Local Group and is pulling in two smaller galaxies, The Magellanic Clouds. A larger galaxy in the group, Andromeda, is 2.1 million light years away, but apparently it will also eventually merge with ours.
The Magellanic Clouds and Andromeda are the only heavenly bodies outside our own galaxy that are visible to the naked eye (and the Magellanic Clouds are visible only from the Southern Hemisphere). This is because, while activity is going on within the clusters of galaxies, our Universe keeps on expanding in the otherwise dormant spaces between them.
Scientists theorize that it is driven by a mysterious invisible force that acts in an opposite way to gravity, pushing out rather than pulling in, and growing stronger with distance. The further it stretches, the closer it gets to the speed of light. From Earth it looks as if our Local Group is at the centre and the other galaxies are moving away from us. But actually every clump of galaxies is moving away from every other clump.
Edwin Hubble, who discovered the phenomenon, likened it to spots on a balloon that grow further apart as it expands, although in this case the spots would have to be inside the balloon as well as on its surface. More recently it has been likened to sultanas in an expanding yeasty fruit-loaf. But any Earth-bound analogy is bound to be inadequate.
One way to think of the expansion is to imagine a night sky that is just one long twilight. Without it the other galaxies would still be close by, lighting up almost all the dark spaces.
Scientists call the paradoxical expansionary force Dark Energy, and calculate that it makes up a further 70% of our Universe’s mass. This means that what is visible to us with the most powerful telescopes is astoundingly less than 10% of the total!
When all the clumps of hydrogen in its galaxies have progressively ignited to form new stars our Universe may keep expanding indefinitely, growing colder and darker as all the existing stars one by one collapse, cool and go out. Or it may reach some tipping point and begin rushing in again until it implodes in A Big Crunch. Then there may even be a bounce back into a brand new expanding Universe.
The more we explore this world of ours the more mysterious it becomes!
All that the experts agree on is that the long-term existence of our Universe seems to depend on a dynamic balance between clumping and splitting apart, with galaxy clusters, galaxies and solar systems all based on the same precarious balance.
In this process, however, as matter clumps in a certain locality (as a galaxy cluster, a galaxy or a solar system) it begins to take on its own unique features, thus adding to a trend towards increasing diversity and complexity within the whole.
Mathematicians call this a dynamic fractal pattern, a branching process repeated at larger and smaller orders of magnitude but never quite the same. To some it suggests that our Universe is a self-ordering system following a potentially discernible course, both as a whole and in each of its parts as well.
And this course seems to be based on the three principles referred to in this scene: transformational change; a dynamic balance between splitting apart and clumping together; and increasing diversity and complexity. As our story continues we’ll encounter more examples of these underlying principles, in increasingly familiar contexts.
* * * * * * *
(click on image to enlarge it)These remnants of a supernova explosion,
seen by us as as they were 1.3 million years ago,
are in the area of the double star "Ori", the (faint) head of Orion.
Orion is one of our most recognizable constellations,
although in Australia we see it upside down (and in Summer),
and usually call Orion's belt The Saucepan.
The pink points are infant stars.
(Just one example of the stunning images available from NASA)
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