Aceleração centrífuga

Marcia Ernesto & Leila Soares Marques

Como a Terra executa um movimento de rotação ao redor de si mesma com um período de 24 horas, qualquer ponto do seu interior ou de sua superfície sofre o efeito da aceleração centrífuga [...]. Como a aceleração centrífuga é dirigida perpendicularmente ao eixo de rotação, os únicos locais onde não há aceleração centrífuga [...] são aqueles situados sobre o eixo de rotação, ou seja, nos polos. Todos os outros pontos sofrem uma aceleração centrífuga cuja intensidade é diretamente proporcional à distância do eixo de rotação, atingindo valores máximos na linha do Equador [...].

Fonte: Ernesto, M. & Marques, LS. 2000. In: Teixeira, W & mais 3, orgs. Decifrando a Terra. SP, Oficina de Textos.

Sistemas lacustres brasileiros

Francisco de Assis Esteves

[P]ode-se agrupar os lagos brasileiros (muitos deles são lagoas) em pelo menos cinco grupos bem diferenciados:

(1) Lagos amazônicos, onde devem ser distinguidos os lagos de várzea e os de terra firme;

(2) Lagos do pantanal mato-grossense, como lagos de água doce (‘baías’), que periodicamente (durante as cheias) se conectam com os rios, e lagos de água salobra (‘salinas’), que se encontram geralmente fora do alcance das cheias e permanecem, portanto, isolados;

(3) Lagos e lagunas costeiras que se estendem desde o Nordeste até o Rio Grande do Sul, com grandes ecossistemas como as lagoas de Araruama, Saquarema e Maricá, todas no estado do Rio de Janeiro; Patos, Mirim e Mangueira, no estado do Rio Grande do Sul;

(4) Lagos formados ao longo de rios de médio e grande porte, por barragem natural de tributários de maior porte ou por processos de erosão e sedimentação de meandros, que resultam no seu isolamento; e

(5) Lagos artificiais, como as represas e os açudes.

Fonte (adaptado): Esteves, F. A. 2018. Fundamentos de limnologia, 2ª ed. RJ, Interciência.

Public controversy and awareness

C. Leland Rodgers & Rex E. Kerstetter

In recent years, ecological catastrophes of varying degrees of seriousness have served as warning signals to the alert citizenry and to members of the scientific community. Efforts have been made first to collect sufficient data relevant to the particular environmental problem and then to determine the relationship between ‘cause’ and ‘effect’. In certain cases it is also a matter of establishing priorities, often between practices involving short-term convenience and long-term consequences. Because of the complexity of the environment, the relationship between cause and effect is often very difficult to establish.

In the past the public has looked to the universities and to various state and national agencies for advice and guidance concerning the use and consequences of insecticides, herbicides, wastes, etc., and are frequently dismayed by the degree of divergence in professional opinions. This is not surprising, because the nature of environmental problems is often very complex and intersects normal disciplinary lines of professional training.

Fonte: Rodgers, C. L. & Kerstetter, R. E. 1974. The ecosphere. NY, Harper.

O centro da Terra

Richard Dixon Oldham

Muitas teorias sobre a Terra têm sido propostas em diferentes épocas: já se supôs que a substância central da Terra seria ígnea, fluida, sólida e gasosa, levando os geólogos a se desesperarem com o assunto, a ponto de decidirem restringir sua atenção à crosta mais externa da Terra, deixando o centro como um parquinho para os matemáticos.

Fonte (trad. livre): Oldham, RD. 1906. The constitution of the interior of the earth, as revealed by earthquakes. Quarterly Journal of the Geological Society 62: 456-75.

Aniversário de 18 anos

F. Ponce de León

Neste sábado, 12/10, o Poesia Contra a Guerra atingiu a maioridade: 18 anos no ar (2006-2024). (Aniversário de 17 anos: aqui.)

Soldados

[Denis] Auguste [Marie] Raffet (1804-1860). Soldats de la Première République. 1840.

Fonte da foto: Wikipedia.

A grammarian’s funeral

Robert Browning

[Time – Shortly after the revival of learning in Europe.]

Let us begin and carry up this corpse,
    Singing together.
Leave we the common crofts, the vulgar thorpes,
    Each in its tether
Sleeping safe on the bosom of the plain,
    Cared-for till cock-crow.
Look out if yonder’s not day again
    Rimming the rock-row!
That’s the appropriate country – there, man’s thought,
    Rarer, intenser,
Self-gathered for an outbreak, as it ought,
    Chafes in the censer!
Leave we the unlettered plain its herd and crop;
    Seek we sepulture
On a tall mountain, citied to the top,
    Crowded with culture!
All the peaks soar, but one the rest excels;
    Clouds overcome it;
No, yonder sparkle is the citadel’s
    Circling its summit!
Thither our path lies – wind we up the heights –
    Wait ye the warning?
Our low life was the level’s and the night’s;
    He’s for the morning!
Step to a tune, square chests, erect each head,
    ’Ware the beholders!
This is our master, famous, calm and dead,
    Borne on our shoulders.

Sleep, crop and herd! Sleep, darkling thorpe and croft,
    Safe from the weather!
He, whom we convoy to his grave aloft,
    Singing together,
He was a man born with thy face and throat,
    Lyric Apollo!
Long he lived nameless: how should spring take note
    Winter would follow?
Till lo, the little touch, and youth was gone!
    Cramped and diminished,
Moaned he, “New measures, other feet anon!
    My dance is finished”?
No, that’s the world’s way: (keep the mountain-side,
    Make for the city.)
He knew the signal, and stepped on with pride
    Over men’s pity;
Left play for work, and grappled with the world
    Bent on escaping:
“What’s in the scroll,” quoth he, “thou keepest furled
    Show me their shaping,
Theirs, who most studied man, the bard and sage, –
    Give!” – So he gowned him,
Straight got by heart that book to its last page:
    Learned, we found him!
Yea, but we found him bald too – eyes like lead,
    Accents uncertain:
“Time to taste life,” another would have said,
    “Up with the curtain!”
This man said rather, “Actual life comes next?
    Patience a moment!
Grant I have mastered learning's crabbed text,
    Still, there's the comment.
Let me know all! Prate not of most or least,
    Painful or easy:
Even to the crumbs I’d fain eat up the feast,
    Ay, nor feel queasy!”
Oh, such a life as he resolved to live,
    When he had learned it,
When he had gathered all books had to give;
    Sooner, he spurned it!
Image the whole, then execute the parts –
    Fancy the fabric
Quite, ere you build, ere steel strike fire from quartz,
    Ere mortar dab brick!

(Here’s the town-gate reached: there’s the market-place
    Gaping before us.)
Yea, this in him was the peculiar grace
    (Hearten our chorus)
Still before living he’d learn how to live –
    No end to learning.
Earn the means first – God surely will contrive
    Use for our earning.
Others mistrust and say, – “But time escapes, –
    Live now or never!”
He said, “What’s Time? leave Now for dogs and apes!
    Man has For ever.”
Back to his book then: deeper drooped his head;
    Calculus racked him:
Leaden before, his eyes grew dross of lead;
    Tussis attacked him.
“Now, Master, take a little rest!” – not he!
    (Caution redoubled!
Step two a-breast, the way winds narrowly.)
    Not a whit troubled,
Back to his studies, fresher than at first,
    Fierce as a dragon
He, (soul-hydroptic with a sacred thirst)
    Sucked at the flagon.
Oh, if we draw a circle premature,
    Heedless of far gain,
Greedy for quick returns of profit, sure,
    Bad is our bargain!
Was it not great? did not he throw on God,
    (He loves the burthen) –
God’s task to make the heavenly period
    Perfect the earthen?
Did not he magnify the mind, show clear
    Just what it all meant?
He would not discount life, as fools do here,
    Paid by instalment!
He ventured neck or nothing – heaven's success
    Found, or earth’s failure:
“Wilt thou trust death or not?” he answered “Yes.
    Hence with life’s pale lure!”
That low man seeks a little thing to do,
    Sees it and does it:
This high man, with a great thing to pursue,
    Dies ere he knows it.
That low man goes on adding one to one,
    His hundred’s soon hit:
This high man, aiming at a million,
    Misses an unit.
That, has the world here – should he need the next,
    Let the world mind him!
This, throws himself on God, and unperplext
    Seeking shall find Him.
So, with the throttling hands of Death at strife,
    Ground he at grammar;
Still, thro’ the rattle, parts of speech were rife.
    While he could stammer
He settled Hoti’s business – let it be! –
    Properly based Oun –
Gave us the doctrine of the enclitic De,
    Dead from the waist down.
Well, here’s the platform, here’s the proper place.
    Hail to your purlieus,
All ye highfliers of the feathered race,
    Swallows and curlews!
Here’s the top-peak! the multitude below
    Live, for they can there.
This man decided not to Live but Know –
    Bury this man there?
Here – here’s his place, where meteors shoot, clouds form,
    Lightnings are loosened,
Stars come and go! let joy break with the storm –
    Peace let the dew send!
Lofty designs must close in like effects:
    Loftily lying,
Leave him – still loftier than the world suspects,
    Living and dying.

Fonte (v. 139): Carpeaux, OM. 2011. História da literatura ocidental, vol. 3, 4ª ed. Brasília, Senado Federal. Poema publicado em livro em 1855. O autor foi casado com a poetisa Elizabeth Barrett Browning.

Phylogeny, models and inference

Elizabeth Alison Thompson

The aim of this book is to provide a method of solution to a specific problem, and yet one which has attracted a wide interest in recent years. This is the problem of the statistical assessment of the phylogenetic relationships between various ethnic groups within the human species, on the basis of genetic data currently available in present-day populations. The basic difference between the approach to be considered here and that of some previous approaches is that inferences are to be based on a probabilistic model for the genetic evolution of the populations under consideration. The criteria of likelihood inference are to be used to assess alternative hypotheses of evolutionary history. No model can cover all aspects of the complex process of evolution, and inferences are necessarily made within the framework of the model. However statistical inferences cannot be made in the absence of a model, and, even if this model is necessarily a simplification of the true situation, an explicit statement of the assumptions under which inferences are made enables the effect of such assumptions and the possibilities of extending the model to be considered.

We shall consider only the problem of making inferences concerning several, often large, populations within the human species, these populations having a common source but having evolved largely independently, there being little interchance between them. Population differences reflect the length of time since the existence of a common ancestral population, and an evolutionary tree model is required. Some specific problems of population admixture may also be analysed on the basis of a model of independently evolving populations, and one such is considered in Chapter 6, but we shall not consider more generally the analysis of relationships between smaller populations where the pattern of differentiation depends mainly on the interchange between them and where migration has been sufficient for them to evolve substantially as a single unit.

Fonte: Thompson, E. A. 1975. Human evolutionary trees. Cambridge, CUP.

Hora da festa

P. J. O’Rourke

Qual é o objetivo de seus anfitriões ao oferecerem uma festa? Com certeza, não é para que você se divirta; se esse fosse o seu único propósito, eles simplesmente mandariam o champanhe e as mulheres de táxi para sua casa.

Fonte: Conniff, R. 2004. História natural dos ricos. RJ, Zahar. P. J. O’Rourke é a assinatura literária do jornalista e escritor estadunidense Patrick Jake O’Rourke (1947-2022).

San Vicente

Fernando Brant

Coração americano
Acordei de um sonho estranho
Um gosto, vidro e corte
Um sabor de chocolate
No corpo e na cidade
Um sabor de vida e morte

Coração americano
Um sabor de vidro e corte

A espera na fila imensa
E o corpo negro se esqueceu
Estava em San Vicente
A cidade e suas luzes
Estava em San Vicente
As mulheres e os homens

Coração americano
Um sabor de vidro e corte

As horas não se contavam
E o que era negro anoiteceu
Enquanto se esperava
Eu estava em San Vicente
Enquanto acontecia
Eu estava em San Vicente

Coração americano
Um sabor de vidro e corte

Fonte: álbum Clube da Esquina (1972), de Milton Nascimento & Lô Borges.