Yes,
evolution did a great job!
No wonder it took its time; 4.7 billion
years, plus minus some;
Yes, 4.700.000.000 years.
How
long is 4.7 billion years?
Is there any chance for us to feel that
elapse of time?
None whatsoever!
Nevertheless,
I would like to take the challenge. I fold that very long line of millions, billions
of years into something that could mimic the human time-line.
How? I
will count years of Earth's history as seconds of human life. Thus,
each year of Earth, or the time needed that Earth circles once the
Sun, I will count as one Earth-second. This different manner
of counting shall put in perspective both the passing of time that
we, humans, feel and the passing of time that describes the
development of a planet.
When
expending upon that way of counting from seconds to years, sixty
Earth-seconds add up to one Earth-minute, three-thousand
six-hundred Earth-seconds add up to one Earth-hour,
eighty-six-thousand four-hundred Earth-seconds add up to one
Earth-day, and
thirty-one-million-five-hundred-thirty-six-thousand Earth-seconds add
up to one Earth- year (1), and so on.
How
does it all feel?
A second feels like an elapse of time that we know.
A year feels like an elapse of time that we know, too.
Now you:
How
does the difference between the two feel?
A year counts for many
seconds, namely thirty-one-million-five-hundred-thirty-six-thousand;
what sounds like a lot, indeed. That thirty-one-million… number does
not feel like anything, although a year feels specific and a second
feels specific, too. So, try hard to feel a second, or a year. Feeling the
difference between both elapses of time should give you quite a
particular sensation. That sensation is the thirty-one-million…
something by which I like to fold the Earth’s timeline onto a human
timeline.
A fairy tale?
 |
| Babylonian records of Venus (from Wikipedia) |
Now
imagine counting a year as a second of Earth's life-time. Next, a
minute of Earth's life would make up for most of a human life-time;
time for sixty circles of planet Earth around the Sun. An hour of
Earth's life-time, or three-thousand six-hundred Earth-seconds, would
cover most of the period of which we, humans, have some written
records.
It would go back to the 16th century B.C., when
the Babylonian people kept astronomical records of the motion of
planet Venus.
Half an hour earlier, counted in Earth-seconds, the Egyptians would
have built the big Pyramids of Giza.
A day of Earth's life would go
back to times when our human species had evolved in Africa, just more
or less ready to conquer the globe and to replace other hominid
species.
And a year of Earth's life would go back before modern fauna
evolved, before continents had drifted to their present positions,
before rapidly cooling Antarctica had become more isolated, and
before the Antarctic Circumpolar Current had started flowing. Within
a year of Earth's time-line several biological, climatic and
geological changes of the Earth system occur. Just like a year in
human life may be marked by substantial change.
Earth has an age of 65 million times the span of a human life. This is an enormous number. However, counting Earth-years the count is only hundred-forty-nine. Happily, when counting a year as a second of Earth's life, then Earth’s history folds on a timespan that can be captured by human perception.
The span of a human lifetime would be
equivalent to 60 to 90 Earth-seconds. When counting the 4.7 billion
years of Earth's existence, i.e. 4,700,000,000 Earth-seconds, then,
the result adds up to hundred-forty-nine Earth-years or one and a
half Earth-century. That kind of elapse of time our perception can
capture.
It means thinking back to times when your great-grandparents
were young. We know them from pictures that were made when they were
old.
Thus,
when counting years as Earth-seconds, the time line of Earth's
history is folded in such a manner, that Earth's history becomes
imaginable for a human mind. It simply means mapping Earth's history
on the combined lifespan of our great-grandparents, grandparents,
parents, us and our children. Thus, four or five generations are
needed to illustrate the painstakingly long period of time that has
passed since Earth was formed out of stellar dust, since the very
first forms of life have emerged, since more complex organisms have
formed and, finally, since human beings have conquered the globe.
Fold one: how long is a billion or two?
Our
planet, Earth evolves since about 4.7 billion years, since it had
formed as ball melting old stellar dust and ice into something new.
Ticking years as Earth-seconds Earth started to form nearly 150
Earth-years ago.
A
billion Earth-seconds counts for little less than 32 Earth-years.
Thus,
ticking years as Earth-seconds, Earth emerged from stellar dust as
great-grandparents were born. During their childhood, Earth grew.
More and more interstellar dust and ice aggregated by gravitation.
Messengers from those very early times are iron-nickel meteorites
that hit the Earth still today. When great-grandparents were
youngsters, the surface layer of the Earth cooled so much that rocks
formed. First heavy basalts emerged that got recycled and, then,
lighter granites and gneiss consolidated that float on the basalts.
 |
| Acasta Gneiss (from Wikipedia) |
Some
of the oldest rocks, Acasta Gneiss (4.3 billion years) can be found
in the Canadian Northwest Territories. Since the time of their
formation, the chemical evolution of Earth was been spinning-up;
different kinds of minerals and rocks have formed.
Just about when
great-grandparents were grown ups and grandparents were toddlers, a
billion years of chemical evolution had led to quite advanced living
cells (cyanobacteria). They were releasing oxygen into the world and
evolution of Earth was made to spin faster. New kinds of minerals
appeared and never seen before rocks could form. Living slim started
to cover the rocky shores of the ocean. Since that time,
stromatolites (3) have been on Earth.
Once a sufficient amount of
oxygen had been produced and released into the atmosphere, iron got
oxidised and large iron ore deposits formed on Earth. Grandparents
were already old when the oxygen concentration in the atmosphere was
approaching levels that we know today, and the deep ocean got
oxidised.
Thus, it took the life span of two generations - about half
the history of the Earth or more than 2 billion years – to evolve
from molten stellar dust to a planet with reddish land, blue oceans
and slimy live along the shore.
Fold two: how long are some millions?
 |
| Fossil Stromatolith (Huy, Germany) (from Wikipedia) |
Modern
terrestrial animals, mammals as we know them, exist since about 50
million years. The geological epoch when they emerged (Eocene)
started after 99% of Earth’s history had passed already. It started
warm, and wide oceans created a moist global environment. Apart from
the driest deserts, forests were spreading from pole to pole. These
forests would look reasonably familiar to our eyes. Dinosaurs had
started off, lasted for more than 180 million years and had
disappeared well before. Trilobites in the sea had started off half a
billion years ago, lasted for 300 million years and disappeared
before the Dinosaurs.
50
million Earth-seconds are close to one and a half Earth-year. 180
million Earth-seconds are little less than 6 Earth-years and 300
million Earth-seconds are little less than 10 Earth-years.
Thus,
ticking years as Earth-seconds and thinking in generations, the
Eocene is part of my very recent past; me being now 32 years old.
Dinosaurs I saw a few Earth-years ago, as well as Trilobites when I
was an adolescent. Grandparents, as they were young, have seen first
stromatolites and other microbiological mats along the shore line of
the sea. Forefathers mostly knew rocks only, and witnessed
bio-molecules emerging from more simple chemistry, but my parents, me
and my children saw and see life conquering Earth.
Fold three: how long is a million or two?
Early
human beings (Homo erectus) evolved about one million years from
earlier hominid species. These species evolved three to four million
years ago, leaving apes well behind them.
Again,
ticking years as Earth-seconds one million seconds are a little more
than 11.5 Earth-days, and four million Earth-seconds are about one
and a half Earth-months.
Thus, folding time scales and counting years
as Earth-seconds, human beings emerged on Earth a little earlier this
month, agriculture started just three hours ago, steam engine’s
puffing was heard three minutes ago, and the first atom bomb blow up
a minute ago.
A fair story!
So,
when counted in Earth-seconds, our human history is a story of a few
minutes or hours. Counting Earth-seconds, living plants and animals
populate the planet since some years, at best since two decades;
first they lived in the sea and much later they lived on land as
well. Using the same folded time scale, the beginning of
microbiological life on our planet dates back hundred to
hundred-twenty years from today or up to four billion Earth-seconds
ago. That is a century of Earth-years before more developed forms of
life could emerge on planet Earth.
Thus
indeed, evolution took its time and seized its chances. We are
witnessing the very recent bursts of life. However, the endless aeons
of ancestor's times stay hidden. It took an enormous elapse of time
for simple forms of life to emerge and develop before we could burst
into being, as we know it. It is to us to preserve it!
p.s.
If you like to read more about Earth's history over billions of
years, then I recommend "The Story of Earth: The first 4.5
Billion Years, from Stardust to Living Planet" by Robert M.
Hazen.
(1)
Approximating the year to 365 days. The sidereal years has 365 days,
6 hours, 9 minutes and 9.54 seconds, or 31,558,149.54 seconds. (2)
The contorted white bands in the Acasta gneiss consist of quartz and
feldspar, two minerals common in granite. Their occurrence tells us
the gneiss was metamorphosed from granitic rock contained in Earth's
earliest continental crust. Most granite forms by melting of an older
basaltic crust in the presence of water, rather than by direct
melting of Earth's mantle. Thus, the Acasta gneiss provides indirect
evidence of the presence of water on the early Earth, and for a
basaltic crust that formed approximately 4.03 billion years ago. (3)
Stromatolites are formed in tidal zones by colonies of cyanobacteria
accumulating sand grains into layered structures.
Note: This text was published some years ago on this blog; it got re-edited for better reading. Thank you LL !
Pictures not credited to third parties are mine.
No comments:
Post a Comment