15 March 2014 | NewScientist | 17

FEELING dopey? Wake up your “circadian eye” with orange light.

Light is a powerful wake-up call, enhancing alertness and activity. Its effect is controlled by a group of cells in the eyeball that make the light-sensing pigment melanopsin. These cells, which work separately to the rods and cones needed for vision, are thought to reset our body clocks – or circadian rhythms.

To find out how melanopsin wakes up the brain, Gilles Vandewalle at the University of Liege, Belgium, and his team gave 16 people a 10-minute blast of blue or orange light while they performed a memory test in an fMRI scanner. They were then blindfolded for 70 minutes, before being retested under a green light.

People initially exposed to orange light had greater brain

activity in several regions related to alertness and cognition when they were retested, compared to those pre-exposed to blue light. Orange light, which has the longer wavelength, is known to make melanopsin more light-sensitive. Blue light has the opposite effect, with green lying in the middle.

Vandewalle thinks melanopsin is acting as a kind of switch, sending different signals to the brain depending on its state (PNAS, DOI: 10.1073/pnas.1320005111).

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Surf’s down dude! Gnarly Aussie waves hit by climate

BODACIOUS tubes on Australia’s east coast are being

quashed by global warming. At current rates, by the end

of the century, climate change will reduce the number of

big waves by a third, according to the latest research.

Andrew Dowdy and his colleagues from the Australian

Bureau of Meteorology in Melbourne ran 18 climate

models forwards and backwards to see how the changing

climate influences big waves. They found that these

waves were caused by storms in the west Pacific known

as ”east coast lows”, driven by differences in air pressure.

The models showed that climate change is pushing down

the number of big waves and that trend will increase

exponentially. Where there might have been waves taller

than 6 metres on 36 days a year in the 1950s, now it

happens on about 34 days a year. If we continue along a

high-emissions path, that number will reduce by almost

30 per cent by the end of the century. They saw a similar

trend for waves of between 4 and 6 metres high (Nature Climate Change, doi.org/rth). Surfers might take comfort

in the thought that the biggest waves may get even

bigger, Dowdy says, something his study didn’t examine.

These changes could also affect beaches, says Mark

Hemer from CSIRO, Australia’s national research

organisation in Hobart. The amount of sand on a beach is

determined by the balance between what gets washed in

and out, “and waves are the primary driver of that”.

Orange light wakes our circadian eye

Is dark matter a dinosaur killer?

DARK matter might live up to its ominous name. A recent theory about the behaviour of the elusive stuff leads to a scenario in which dark matter could be to blame for killing off dinosaurs.

Last year, Lisa Randall at Harvard University and her colleagues suggested that dark matter can clump up into a thin, flat disc in a galaxy’s plane. As the solar system orbits the centre of our galaxy, it bobs up and down on a regular cycle, so if the galaxy contains a dark matter disc, we would pass through it every 35 million years.

In a study released last week, the team say that comet impacts on Earth appear to spike every 35 million years, perhaps because of dark matter perturbing comets within the solar system (arxiv.org/abs/1403.0576). While the timing is not a perfect match, the cycle could encompass the giant impact linked to dinosaur extinctions.

Comets herded by invisible planet

A CLOUD of carbon monoxide may have just revealed a strange, comet-shepherding exoplanet.

Radio observations show a huge clump of carbon monoxide gas close to the star Beta Pictoris. Starlight rapidly breaks down carbon monoxide, so such a large clump would have to be regularly replenished, says Mark Wyatt at the University of Cambridge.

One possibility is that an unseen Saturn-sized planet is attracting comets, which are then smashing together and releasing trapped gas (Science, doi.org/rsz). Or two icy planets laden with gas may have previously collided, and pieces are still hitting each other today. Studies that can make out the cloud’s shape and orbit may help distinguish between these.