載入中...
相關課程

登入觀看
⇐ Use this menu to view and help create subtitles for this video in many different languages.
You'll probably want to hide YouTube's captions if using these subtitles.
Chronometric Revolution : Discussion of the relatively recent changes in our ability as a species to shine light on our deep past
相關課程
0 / 750
- If we want to understand where we come from
- the stories that have led us to our present condition
- if we want to understand our history
- one of the prerequisites is to have a good sense of
- chronometry. Chronometry is a fancy word
- but its really just the science of the passage of time
- chrono relating to time
- metry, time measurement
- and we take many things forgranted these days
- we assume we know what happen the last fifty years
- the last hundred years
- and now we're starting to assume what happened
- to ten thousand years ago
- or what happened to our planet a hundred million years ago
- or a billion years ago
- but these are all very very new phenomena
- this ability to kind of shine a light on the past
- and even the traditional notions of history
- the traditional stories of what lead to what
- the political nations that formed the migrations of people
- and when they happened
- that tradition notion of history is fairly new
- when you think about just the scope of how long
- humans have been on this planet
- and that first traditional notion of history
- you can kind of view as the first chronometric revolution
- and that first chronometric revolution that gives us
- this kind of tradition notion of history really just
- come out of humanities ability to write
- so writing gives us our first chronometric revolution
- because this was the first time
- even through we think that humans or human like creatures
- have been around for hundreds or hundreds of years
- at this point
- they weren't able to keep their stories in a very exact way
- they might have had an oral tradition
- that might have gone from one generation to another
- but those oral traditions things would get lost
- and the most important information that would get lost
- is how long ago did these stories stories start up
- and we weren't able as a species to understand
- when things happened and how long ago things happened
- until writing became mainstream
- and until writing became permanent
- and our best sense of when this happened
- the first time is by the sumarians with cuneiform
- and this happened right around the third millenia b.c.
- so around five thousand years before the present time
- and this is what some of the writing looked like
- this is actually a letter from a king
- and you can see its just highly symbolic carvings
- this is what we more traditionally associate with cuneiform
- and it was symbolic based as opposed to now
- most of our language most of our language
- is based on phonetics which has fewer symbols
- so you can have more meanings
- but this was a huge technological revolution for humanity
- because now with the advent of cuneiform you had writing
- that someone could look at a thousand years later
- two thousand years later
- and if they can decipher the cuneiform
- they can get a written testimony of what was
- happening at that time
- and they didn't have to rely on an oral story
- or guess when that oral story started
- but writing since it only happened five thousand
- years ago
- so this is five thousand years before the present
- or you could say three thousand B.C.
- that was a start but this only gave us stories about
- five thousand years old
- but even then it was a very spotty historical record
- we didn't get really deep, depending on where you are
- in the world until really the last few thousand years
- but it was a start
- this was the first chronometric revolution
- but what you may, or may not, realize is that frankly
- we are I believe at the start of another chonometric
- revolution that has really just begun to accelerate
- in the last fifty, sixty, seventy years
- and this second chonometric revolution
- 2nd chonometric revolution
- I should write revolution up here too
- this was a revolution, it allowed us to keep time in a
- permanent way to understand things
- to not have to talk to the people to whom something
- happened we can see their written testimony of it
- but the second revolution really comes out of our
- understanding of modern science
- so in the late eighteen hundreds you have radio activity
- discovered by Marie Curie
- so this is nineteen hundred here
- so this is relatively recent here
- remember we're talking about a species that has been
- around for several hundreds of thousands of years
- and proto-humans have been around for millions of years
- and now only five thousand years ago
- at least as far as we know was the first writing
- and then only a little over a hundred years ago
- was the discovery of radio-activity, so radio-activity
- and then the ability to use radio activity
- so radio activity is interesting
- its the idea that elements can change
- from one variation to another variation over a long
- periods of time through radio activity
- they become kind of this natural clock
- no one had to go there and set up a time piece for it
- that luckily there are these things that decay at a very
- predictable rate
- so we discover radio activity a little over a hundred
- years ago and then over the course of the twentieth century
- we got better and better, more sophisticated
- at understanding radio activity to be able
- to use it to measure the times of things
- and if you fast forward to second half of the twentieth
- century, so now we're at 1950, this is where
- the second chronomentric revolution really took hold
- where we started to understand carbon-14 dating
- we started to understand other techniques that we
- talk as we can start to date older and older things
- and I want to be clear, radio activity, the understanding of
- radio activity was just the beginning of the second
- chronometric revolution, the second chronometric revolution
- which frankly we're still a part of isn't just radio activity
- its also understanding the expansion of the universe
- the constancy, the speed limit of light, that allows us
- to figure out that, wow, that background radiation that
- we're getting that must have be traveling for
- 13.7 billion years ago, so now we can look at evidence
- from our environment and our environment isnt just
- earth it's self its radion bombarding us from space
- that allows us to make -- that gives us clues as to not just
- the age of us, the age of species, the age of the planet
- but the age of the universe it's self, so it isn't just about
- radio activity, radio activity is a big part of the chronometric
- revolution, this is what allowed us for the first time
- if we have layers on the earth
- people have known for a long time that if we assume
- these layers haven't been jostled
- that something at a lower layer down here is probably
- going to be older than an upper layer
- because year after year you have deposits
- if it hasn't been messed up in some way
- but no one knew, they said ok
- well this is relative dating this is older, this is younger
- but we had no way of knowing is this a hundred years old
- is this a billion years old
- but now with radio activity we can start to say hey
- we can date some of the rocks here that are a 150 million
- years old and some of the rocks here are 100 million
- years old
- so maybe this fossil of a fish we're finding
- or this primitive fish like creature over here would be
- between 100 - 150 million years old
- and the only way we're able to do this is with being able
- to date things using radio activity
- but radio acitivity is just the start as I mentioned
- we're getting better and better understanding of cosmology
- we're getting better measurements of the universe it's self
- we're understanding physics and a deeper level
- now we can start to look at the genome
- and think about how the genome diverges