Se o Big Bang não foi o começo, foi o que?

terça-feira, setembro 22, 2020


Sep 17, 2020,02:00am EDT

If The Big Bang Wasn’t The Beginning, What Was It?

Ethan Siegel Senior Contributor

Starts With A Bang Contributor Group


The Universe is out there, waiting for you to discover it

Our entire cosmic history is theoretically well-understood, but only because we understand the theory of gravitation that underlies it, and because we know the Universe's present expansion rate and energy composition. Light will always continue to propagate through this expanding Universe, and we will continue to receive that light arbitrarily far into the future, but it will be limited in time as far as what reaches us. We still have unanswered questions about our cosmic origins, but the age of the Universe is known. NICOLE RAGER FULLER / NATIONAL SCIENCE FOUNDATION

For more than 50 years, we’ve had definitive scientific evidence that our Universe, as we know it, began with the hot Big Bang. The Universe is expanding, cooling, and full of clumps (like planets, stars, and galaxies) today because it was smaller, hotter, denser, and more uniform in the past. If you extrapolate all the way back to the earliest moments possible, you can imagine that everything we see today was once concentrated into a single point: a singularity, which marks the birth of space and time itself.

At least, we thought that was the story: the Universe was born a finite amount of time ago, and started off with the Big Bang. Today, however, we know a whole lot more than we did back then, and the picture isn’t quite so clear. The Big Bang can no longer be described as the very beginning of the Universe that we know, and the hot Big Bang almost certainly doesn’t equate to the birth of space and time. So, if the Big Bang wasn’t truly the beginning, what was it? Here’s what the science tells us.

Our Universe, as we observe it today, almost certainly emerged from a hot, dense, almost-perfectly uniform state early on. In particular, there are four pieces of evidence that all point to this scenario:

- the Hubble expansion of the Universe, which shows that the amount that light from a distant object is redshifted is proportional to the distance to that object,

- the existence of a leftover glow — the Cosmic Microwave Background (CMB) — in all directions, with the same temperature everywhere just a few degrees above absolute zero,

- light elements — hydrogen, deuterium, helium-3, helium-4, and lithium-7 — that exist in a particular ratio of abundances back before any stars were formed,

- and a cosmic web of structure that gets denser and clumpier, with more space between larger and larger clumps, as time goes on.


Megalodon, um antigo tubarão extinto de grande dimensão corporal.

segunda-feira, setembro 07, 2020

Body dimensions of the extinct giant shark Otodus megalodon: a 2D reconstruction

Jack A. Cooper, Catalina Pimiento, Humberto G. Ferrón & Michael J. Benton 

Scientific Reports volume 10, Article number: 14596 (2020) 


Inferring the size of extinct animals is fraught with danger, especially when they were much larger than their modern relatives. Such extrapolations are particularly risky when allometry is present. The extinct giant shark †Otodus megalodon is known almost exclusively from fossilised teeth. Estimates of †O. megalodon body size have been made from its teeth, using the great white shark (Carcharodon carcharias) as the only modern analogue. This can be problematic as the two species likely belong to different families, and the position of the †Otodus lineage within Lamniformes is unclear. Here, we infer †O. megalodon body dimensions based on anatomical measurements of five ecologically and physiologically similar extant lamniforms: Carcharodon carcharias, Isurus oxyrinchus, Isurus paucus, Lamna ditropis and Lamna nasus. We first assessed for allometry in all analogues using linear regressions and geometric morphometric analyses. Finding no evidence of allometry, we made morphological extrapolations to infer body dimensions of †O. megalodon at different sizes. Our results suggest that a 16 m †O. megalodon likely had a head ~ 4.65 m long, a dorsal fin ~ 1.62 m tall and a tail ~ 3.85 m high. Morphometric analyses further suggest that its dorsal and caudal fins were adapted for swift predatory locomotion and long-swimming periods.

FREE PDF GRATIS: Scientific Reports

A estátua de Darwin vai ser demolida por causa do seu livro racista The Descent of Man???

Natural History Museum to review potentially 'offensive' Charles Darwin collection

An internal review in the wake of the Black Lives Matter protests has led to an audit into some rooms and items

By Craig Simpson

5 September 2020 • 7:00pm

Museum bosses are now desperately seeking to address what some staff believe are “legacies of colonies, slavery and empire” by potentially renaming, relabelling, or removing these traces in the institution.

The executive board told staff in documents seen by The Sunday Telegraph that “in light of Black Lives Matter and the recent anti-racist demonstrations around the world” the museum would undertake a review of existing room names and “whether any statues (or collections) or could potentially cause offence”.One of the institution’s directors said in internal documents that new action taken to address these issues would alter “the use and display of our collections and public spaces”.

Craig Simpson, “Natural History Museum to review potentially ‘offensive’ Charles Darwin collection” at Telegraph


Nota deste blogger: Eu considero deplorável a derrubada/demolição de estátuas pelo seu valor histórico. Que Darwin era racista, e racista sutil, sempre expus aqui neste blog, apesar de seus outros escritos e defensores contemporâneos dizerem o contrário. A fúria da cultura do cancelamento vai demolir a estátua de Darwin no Museu de História Natural em Londres? É melhor proteger sua estátua ali.

Ajuste fino de máquinas e sistemas moleculares: mero acaso, fortuita necessidade ou design inteligente?

sexta-feira, setembro 04, 2020

Journal of Theoretical Biology

Volume 501, 21 September 2020, 110352

Using statistical methods to model the fine-tuning of molecular machines and systems 

Steinar Thorvaldsen a Ola Hössjer b

Under a Creative Commons license Open Access


• Statistical methods are appropriate for modelling fine-tuning.

• Fine-tuning is detected in functional proteins, cellular networks etc.

• Constants and initial conditions of nature are deliberately tuned.

• Statistical analysis of fine-tuning model some of the categories of design.

• Fine-tuning and design deserve attention in the scientific community.


Fine-tuning has received much attention in physics, and it states that the fundamental constants of physics are finely tuned to precise values for a rich chemistry and life permittance. It has not yet been applied in a broad manner to molecular biology. However, in this paper we argue that biological systems present fine-tuning at different levels, e.g. functional proteins, complex biochemical machines in living cells, and cellular networks. This paper describes molecular fine-tuning, how it can be used in biology, and how it challenges conventional Darwinian thinking. We also discuss the statistical methods underpinning fine-tuning and present a framework for such analysis.

Se não há ancestral comum e nem seleção natural, por que ainda chamamos de evolução?

quinta-feira, setembro 03, 2020

Annals of the New York Academy of Sciences

Patterns and impacts of nonvertical evolution in eukaryotes: a paradigm shift

Toni Gabaldón

First published: 28 August 2020


Evolution of eukaryotic species and their genomes has been traditionally understood as a vertical process in which genetic material is transmitted from parents to offspring along a lineage, and in which genetic exchange is restricted within species boundaries. However, mounting evidence from comparative genomics indicates that this paradigm is often violated. Horizontal gene transfer and mating between diverged lineages blur species boundaries and challenge the reconstruction of evolutionary histories of species and their genomes. Nonvertical evolution might be more restricted in eukaryotes than in prokaryotes, yet it is not negligible and can be common in certain groups. Recognition of such processes brings about the need to incorporate this complexity into our models, as well as to conceptually reframe eukaryotic diversity and evolution. Here, I review the recent work from genomics studies that supports the effects of nonvertical modes of evolution including introgression, hybridization, and horizontal gene transfer in different eukaryotic groups. I then discuss emerging patterns and effects, illustrated by specific examples, that support the conclusion that nonvertical processes are often at the root of important evolutionary transitions and adaptations. I will argue that a paradigm shift is needed to naturally accommodate nonvertical processes in eukaryotic evolution.

Site sobre bioluminescência

quarta-feira, setembro 02, 2020

 Pyrosomes, colonial salps, continue to be one of the most mysterious of bioluminescent organisms. Their glow can last 15 seconds or more, and it can be triggered by light, even cascading from one end of the colony to the other. The chemical origin remains unknown. It was thought to be bacterial, in part because of similar kinetics, but now appears to be intrinsic chemistry that lets this animal emit its impressive glow.