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If we want to understand where we come from

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the stories that have led us to our present condition

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if we want to understand our history

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one of the prerequisites is to have a good sense of

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chronometry. Chronometry is a fancy word

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but its really just the science of the passage of time

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chrono relating to time

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metry, time measurement

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and we take many things forgranted these days

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we assume we know what happen the last fifty years

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the last hundred years

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and now we're starting to assume what happened

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to ten thousand years ago

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or what happened to our planet a hundred million years ago

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or a billion years ago

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but these are all very very new phenomena

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this ability to kind of shine a light on the past

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and even the traditional notions of history

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the traditional stories of what lead to what

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the political nations that formed the migrations of people

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and when they happened

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that tradition notion of history is fairly new

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when you think about just the scope of how long

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humans have been on this planet

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and that first traditional notion of history

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you can kind of view as the first chronometric revolution

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and that first chronometric revolution that gives us

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this kind of tradition notion of history really just

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come out of humanities ability to write

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so writing gives us our first chronometric revolution

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because this was the first time

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even through we think that humans or human like creatures

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have been around for hundreds or hundreds of years

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at this point

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they weren't able to keep their stories in a very exact way

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they might have had an oral tradition

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that might have gone from one generation to another

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but those oral traditions things would get lost

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and the most important information that would get lost

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is how long ago did these stories stories start up

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and we weren't able as a species to understand

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when things happened and how long ago things happened

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until writing became mainstream

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and until writing became permanent

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and our best sense of when this happened

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the first time is by the sumarians with cuneiform

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and this happened right around the third millenia b.c.

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so around five thousand years before the present time

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and this is what some of the writing looked like

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this is actually a letter from a king

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and you can see its just highly symbolic carvings

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this is what we more traditionally associate with cuneiform

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and it was symbolic based as opposed to now

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most of our language most of our language

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is based on phonetics which has fewer symbols

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so you can have more meanings

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but this was a huge technological revolution for humanity

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because now with the advent of cuneiform you had writing

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that someone could look at a thousand years later

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two thousand years later

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and if they can decipher the cuneiform

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they can get a written testimony of what was

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happening at that time

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and they didn't have to rely on an oral story

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or guess when that oral story started

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but writing since it only happened five thousand

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years ago

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so this is five thousand years before the present

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or you could say three thousand B.C.

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that was a start but this only gave us stories about

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five thousand years old

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but even then it was a very spotty historical record

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we didn't get really deep, depending on where you are

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in the world until really the last few thousand years

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but it was a start

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this was the first chronometric revolution

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but what you may, or may not, realize is that frankly

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we are I believe at the start of another chonometric

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revolution that has really just begun to accelerate

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in the last fifty, sixty, seventy years

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and this second chonometric revolution

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2nd chonometric revolution

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I should write revolution up here too

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this was a revolution, it allowed us to keep time in a

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permanent way to understand things

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to not have to talk to the people to whom something

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happened we can see their written testimony of it

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but the second revolution really comes out of our

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understanding of modern science

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so in the late eighteen hundreds you have radio activity

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discovered by Marie Curie

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so this is nineteen hundred here

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so this is relatively recent here

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remember we're talking about a species that has been

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around for several hundreds of thousands of years

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and proto-humans have been around for millions of years

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and now only five thousand years ago

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at least as far as we know was the first writing

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and then only a little over a hundred years ago

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was the discovery of radio-activity, so radio-activity

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and then the ability to use radio activity

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so radio activity is interesting

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its the idea that elements can change

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from one variation to another variation over a long

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periods of time through radio activity

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they become kind of this natural clock

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no one had to go there and set up a time piece for it

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that luckily there are these things that decay at a very

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predictable rate

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so we discover radio activity a little over a hundred

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years ago and then over the course of the twentieth century

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we got better and better, more sophisticated

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at understanding radio activity to be able

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to use it to measure the times of things

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and if you fast forward to second half of the twentieth

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century, so now we're at 1950, this is where

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the second chronomentric revolution really took hold

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where we started to understand carbon-14 dating

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we started to understand other techniques that we

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talk as we can start to date older and older things

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and I want to be clear, radio activity, the understanding of

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radio activity was just the beginning of the second

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chronometric revolution, the second chronometric revolution

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which frankly we're still a part of isn't just radio activity

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its also understanding the expansion of the universe

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the constancy, the speed limit of light, that allows us

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to figure out that, wow, that background radiation that

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we're getting that must have be traveling for

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13.7 billion years ago, so now we can look at evidence

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from our environment and our environment isnt just

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earth it's self its radion bombarding us from space

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that allows us to make -- that gives us clues as to not just

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the age of us, the age of species, the age of the planet

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but the age of the universe it's self, so it isn't just about

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radio activity, radio activity is a big part of the chronometric

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revolution, this is what allowed us for the first time

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if we have layers on the earth

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people have known for a long time that if we assume

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these layers haven't been jostled

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that something at a lower layer down here is probably

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going to be older than an upper layer

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because year after year you have deposits

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if it hasn't been messed up in some way

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but no one knew, they said ok

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well this is relative dating this is older, this is younger

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but we had no way of knowing is this a hundred years old

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is this a billion years old

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but now with radio activity we can start to say hey

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we can date some of the rocks here that are a 150 million

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years old and some of the rocks here are 100 million

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years old

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so maybe this fossil of a fish we're finding

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or this primitive fish like creature over here would be

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between 100 - 150 million years old

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and the only way we're able to do this is with being able

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to date things using radio activity

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but radio acitivity is just the start as I mentioned

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we're getting better and better understanding of cosmology

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we're getting better measurements of the universe it's self

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we're understanding physics and a deeper level

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now we can start to look at the genome

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and think about how the genome diverges