4.56 billion years ago
The Hadean eon begins with the origin of the Earth 4.56 Gya.
Take a look at the Moon tonight. It’s a waning crescent, a few days from the new moon; you can cover it with your thumb. 4.56 billion years ago the new moon was ruddy with volcanic activity even on its far side. The Moon seen from Earth was 16 times wider, covering 250 times more sky, and 250 times brighter when full. That is what you would have seen just after Earth acquired a surface you could stand on, although you would have needed an oxygen mask. And watch out for massive meteorites, still falling frequently, and volcanism.
Chance events late in the history of planet formation played a huge role in shaping the solar system, including the collision with the planet Theia (named after the Greek goddess of the Moon) that gave Earth her outsized satellite. We’ve known about Theia for a while; the latest theory is that the collision resulted in the formation of a synestia, a donut of vaporized rock, which condensed to form Moon and Earth. Life might have developed very differently – there might be no intelligent life — without the Moon’s influence on tides and on Earth’s axis.
Here’s a movie from NASA showing the whole moon, including her far side, as seen by the Lunar Reconnaisance Orbiter. And here’s the famous picture of Earthrise, taken December 24, 1968, by William Anders abroad Apollo 8.
In 1969, the Brazilian singer Caetano Veloso was imprisoned by Brazil’s military dictatorship. He was expelled from the country and lived in exile until 1972. In prison he saw a picture of the Earth from space and wrote this song, “Terra” (Earth).
|TerraQuando eu me encontrava preso, na cela de uma cadeia
Foi que eu vi pela primeira vez, as tais fotografias
Em que apareces inteira, porém lá não estava nua
E sim coberta de nuvens
Terra, terra, Por mais distante o errante navegante Quem jamais te esqueceria?
Ninguém supõe a morena, dentro da estrela azulada
. Na vertigem do cinema, mando um abraço pra ti
Pequenina como se eu fosse o saudoso poeta
E fosses a Paraíba
Eu estou apaixonado, por uma menina terra,
Signo de elemento terra. Do mar se diz terra à vista
Terra para o pé firmeza, terra para a mão carícia
Outros astros lhe são guia
Eu sou um leão de fogo, sem ti me consumiria
A mim mesmo eternamente, e de nada valeria
Acontecer de eu ser gente. e gente é outra alegria
Diferente das estrelas
De onde nem tempo e nem espaço, que a força te de coragem
Pra gente te dar carinho, durante toda a viagem
Que realizas do nada, através do qual carregas
O nome da tua carne
Na sacadas do sobrado, Da eterna São Salvador
Há lembranças de donzelas, do tempo do Imperador
Tudo, tudo na Bahia faz a gente querer bem
|EarthWhen I found myself arrested
In a prison cell
, That’s when I first saw
Those famous pictures
In which you appear entire,
However you were not naked
But covered by clouds.
Earth! Earth! However distant The wandering navigator Who could ever forget you?
Nobody thinks of the brunette
Inside the bluish star.
In the vertigo of the movie
I send you an embrace,
Little one – as if I were
the homesick poet
And you were the Paraíba
I’m just in love
With an earth girl,
Sign of the element “Earth.”
From the sea is said “Land in sight.”
Earth to the foot: solidity.
Earth to the hand: a caress.
Other stars are guides for you
I am a lion of fire
I would burn myself up eternally
And it would be worth nothing,
The fact of my being human.
And human is another joy
Different than the stars’
From where there’s neither time nor space
May the force send courage
For us to treat you tenderly
During all the journey
That you carry out through nothing
Through which you bear
The name of your flesh
In the townhouses’ terraces
Of eternal Salvador
There are reminders of maidens
From the time of the Emperor
Everything, everything in Bahia
Makes us fond
Bahia has such a way.