“The interplay between these new theoretical ideas and new high‐quality observational data has catapulted cosmology from the purely theoretical domain and into the field of rigorous experimental science. This process began at the beginning of the twentieth century, with the work of Albert Einstein.”—Free chapter from Cosmology: A Very Short Introduction on the history of cosmology and how it extends from myth to science. This chapter is free until 25 September on Very Short Introductions Online. (via oupacademic)
“The human family - originating in one small locale in East Africa a few million years ago - wandered, separated, diversified, and became strangers to one another…”—Carl Sagan,Billions and Billions (via whats-out-there)
This fascinating work by Hudson et al. shows that as the brain recovers consciousness from a perturbation such as anesthesia, it does not follows a steady and monotonic path towards consciousness, but rather passes through several discrete activity states. They performed a principal component analysis on local field potentials recorded with electrodes inserted into rat anterior cingulate and retrosplenial cortices and the intralaminar thalamus:
It is not clear how, after a large perturbation, the brain explores the vast space of potential neuronal activity states to recover those compatible with consciousness. Here, we analyze recovery from pharmacologically induced coma to show that neuronal activity en route to consciousness is confined to a low-dimensional subspace. In this subspace, neuronal activity forms discrete metastable states persistent on the scale of minutes. The network of transitions that links these metastable states is structured such that some states form hubs that connect groups of otherwise disconnected states. Although many paths through the network are possible, to ultimately enter the activity state compatible with consciousness, the brain must first pass through these hubs in an orderly fashion. This organization of metastable states, along with dramatic dimensionality reduction, significantly simplifies the task of sampling the parameter space to recover the state consistent with wakefulness on a physiologically relevant timescale.
Like many of the good ideas that the logical empiricists had, instrumentalism did not receive the attention it deserves. In part this was because of what I’ll call the lightning rod effect. Here’s how you can witness this phenomenon in the comfort of your own home (children should not do this without adult supervision):
Put a good idea next to a bad one. Someone will then refute the bad idea. Then people will think that the good idea as well as the bad one have both been demolished.
You don’t always get the lightning rod effect when you follow these instructions, but it occurs often enough that it deservesa name.