Thursday, June 23, 2005

Why does the Moon appear larger when it's on the horizon?

We just had a spectacular June moon conincident with the summer solstice - see this article on the BBC for example.

Why does the moon (or the sun) look bigger when it's on the horizon? First of all, the image of the moon isn't actually smaller when it's high in the sky. Compare it to a coin held at arm's length when it's high and when it's low and you'll see it's the same. (Though the moon can be bigger on particular days, such as we had recently).

The explanation is that we judge the moon to be futher away when it is on the horizon, because we have objects on the horizon for comparison. See this page at IBM for more details.

Brain Scans of Female Orgasms

The BBC and numerous other sites reported Dutch research of brain scanning couples having orgasms. The couples took turns manually stimulating each other while one partner had their head in a brain scan machine. First, there was little to report about male orgasms, they were too brief to register on current scanning devices. Also cold feet were a problem - literally. Only 50% of the couples were able to achieve orgasm with bare feet, while 80% could come wearing socks. Definitely something to keep in mind.
As it turns out, no particular part of the brain was activated during female orgasm - but there were definitely large parts of the brain deactivated. Specifically the parts of the brain associated with higher mental functions shut down, but also parts of the brain which are associated with the emotion of fear.
The women were also asked to fake an orgasm. The researchers reported they were quite convincing to the observer, but the difference was obvious on the brain scans.

Genuine orgasm: less brain actvity

Tell tale brain activity in a fake orgasm

a 'Jennifer Aniston' cell?

In Nature this week, there's a report and a News and Views article supporting the previously dismissed idea of a "grandmother cell".
How do neurons in the brain represent movie stars, famous buildings and other familiar objects? Rare recordings from single neurons in the human brain provide a fresh perspective on the question.

'Grandmother cell' is a term coined by J. Y. Lettvin to parody the simplistic notion that the brain has a separate neuron to detect and represent every object (including one's grandmother). The phrase has become a shorthand for invoking all of the overwhelming practical arguments against a one-to-one object coding scheme. No one wants to be accused of believing in grandmother cells. But on page 1102 of this issue, Quiroga et al.3 describe a neuron in the human brain that looks for all the world like a 'Jennifer Aniston' cell. Ms Aniston could well become a grandmother herself someday. Are vision scientists now forced to drop their dismissive tone when discussing the neural representation of matriarchs?

A specific neuron responded to pictures of Ms. Aniston

But not however, when she was depicted with Brad Pitt
(watch that hand, Jennifer!)

Astronomical pacing of late Palaeocene to early Eocene global warming events

Letter in Nature.

The Palaeocene−Eocene thermal maximum was a strong global warming event about 55 million years ago. The authors discovered another, somewhat smaller warming episode which occurred about 2 million years later. They related these events to periodic changes in Earth's orbital parameters. See also my previous blog entry on the Paleo/Eocene event.