This is a series that I've been thinking about for a while. I'm not sure why. It's really meant to be a survey of life on earth, how it originated and how it developed, but I felt like I should start at the beginning.
The most widely accepted theory of the origins of the universe at this point is the Big Bang Theory: there was a point of very high density and very high temperature which developed an instability and exploded, creating the universe, about 13.8 billion years ago. It wasn't really the universe as we know it at that point, because it was very, very hot, but eventually it cooled enough to allow the formation of things like subatomic particles. Then gravity and the other major forces took over, and we have, first, atoms, then stars. Our sun was one of those stars. Here's what seems to be a pretty accurate exposition of the theory, at Wikipedia. And as you can see from this video, it wasn't really all that straightforward.
If you want more detail, here's a series from Space.com.
By the way, the Big Bang Theory has not gone unchallenged:
I sort of like this idea -- considering that most of the world's religious traditions assume that the earth and the universe are cyclic, with no beginning and no end . . . well, food for thought, at the very least.
At any rate, starting about 13.5 billion years ago, we have stars. The sun was one of those stars, formed about 4.5-5 billion years ago in a cloud of molecules -- mostly hydrogen, with a little helium and some heavier elements thrown in for fun. Some of those molecules began to attract each other -- gravity again -- and as the group got bigger, the pull became stronger, pulling in more molecules until, finally, we had ignition. At the core of the sun the pressure and temperature are so intense that we have, in effect, a really, really big fusion reactor.
Now, there was still a lot of dust and gas around the sun, mostly forming a big disc, which contained not only hydrogen and helium, but also heavier elements -- remember, other fusion reactors -- stars -- had been burning merrily along for 8 or 9 billion years, and some had exploded after converting the lighter elements into heavier elements -- carbon, oxygen, iron, nickel, all the way up to uranium: the building blocks of planets.
The creation of the earth was undoubtedly a lot more spectacular than the creation of the sun -- lots of crashing and explosions as actual rocks collided and stuck together.
Here's Neil deGrasse Tyson with a description of the process:
Pretty neat, huh?
So, now we have a sun and a planet -- a whole solar system, actually (well, OK, a whole universe, but for this we're keeping it local) -- so where do we go from here? Well, life, of course. After all, that's what we're most interested in. But we need to wait about a billion years, for things to calm down a little bit, so that's for next time.
The most widely accepted theory of the origins of the universe at this point is the Big Bang Theory: there was a point of very high density and very high temperature which developed an instability and exploded, creating the universe, about 13.8 billion years ago. It wasn't really the universe as we know it at that point, because it was very, very hot, but eventually it cooled enough to allow the formation of things like subatomic particles. Then gravity and the other major forces took over, and we have, first, atoms, then stars. Our sun was one of those stars. Here's what seems to be a pretty accurate exposition of the theory, at Wikipedia. And as you can see from this video, it wasn't really all that straightforward.
If you want more detail, here's a series from Space.com.
By the way, the Big Bang Theory has not gone unchallenged:
In Einstein's formulation, the laws of physics actually break before the singularity is reached. But scientists extrapolate backward as if the physics equations still hold, said Robert Brandenberger, a theoretical cosmologist at McGill University in Montreal, who was not involved in the study.
"So when we say that the universe begins with a big bang, we really have no right to say that," Brandenberger told Live Science.
There are other problems brewing in physics — namely, that the two most dominant theories, quantum mechanics and general relativity, can't be reconciled.
Quantum mechanics says that the behavior of tiny subatomic particles is fundamentally uncertain. This is at odds with Einstein's general relativity, which is deterministic, meaning that once all the natural laws are known, the future is completely predetermined by the past, Das said.
And neither theory explains what dark matter, an invisible form of matter that exerts a gravitational pull on ordinary matter but cannot be detected by most telescopes, is made of.
I sort of like this idea -- considering that most of the world's religious traditions assume that the earth and the universe are cyclic, with no beginning and no end . . . well, food for thought, at the very least.
Now, there was still a lot of dust and gas around the sun, mostly forming a big disc, which contained not only hydrogen and helium, but also heavier elements -- remember, other fusion reactors -- stars -- had been burning merrily along for 8 or 9 billion years, and some had exploded after converting the lighter elements into heavier elements -- carbon, oxygen, iron, nickel, all the way up to uranium: the building blocks of planets.
The creation of the earth was undoubtedly a lot more spectacular than the creation of the sun -- lots of crashing and explosions as actual rocks collided and stuck together.
Here's Neil deGrasse Tyson with a description of the process:
Pretty neat, huh?
So, now we have a sun and a planet -- a whole solar system, actually (well, OK, a whole universe, but for this we're keeping it local) -- so where do we go from here? Well, life, of course. After all, that's what we're most interested in. But we need to wait about a billion years, for things to calm down a little bit, so that's for next time.
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