The Earth has a violent history: About 4.5 billion years ago, a maelstrom of gas and dust circled in a massive disc around the sun, gathering in rocky clumps to form asteroids. These asteroids, gaining momentum, whirled around a fledgling solar system, repeatedly smashing into each other to create larger bodies of rubble — the largest of which eventually cooled to form the planets.

Countless hypotheses, simulations and geologic observations support such a scenario, but there remains one lingering mystery: If the Earth arose from the collision of asteroids, its composition should resemble that of meteoroids, the small particles that break off from asteroids.

On July 16th, 2013, at 12:09 a.m. EDT, the sun erupted with an Earth-directed coronal mass ejection, sending billions of tons of particles into space. These particles cannot travel through the atmosphere to harm humans on Earth, but they can affect electronic systems in satellites and on the ground.   The particles will reach Earth over the next few days.  

Experimental NASA research models, based on observations from NASA's Solar Terrestrial Relations Observatory, show that the CME left the sun at speeds of around 560 miles per second, a fairly typical speed.

90% of East Asian adolescents in British Columbia are not sexually active, so East Asian parents are doing something right, but the ones who do have sex engage in some risky behavior

The paper in the Canadian Journal of Human Sexuality
also says it is the first population-based survey in Canada that asked East Asian adolescents their reasons for abstaining from sex: the top two reasons for waiting were not feeling ready and wanting to meet the right person. 

In 2011 the Very Large Telescope (VLT) discovered a gas cloud with several times the mass of the Earth accelerating towards the black hole at the center of the Milky Way.   The cloud is now so stretched that its front part has passed the closest point and is traveling away from the black hole at more than 10 million km/h, whilst the tail is still falling towards it.

The black hole at the center of the Milky Way, known as Sgr A* (pronounced Sagittarius A star), is estimated to have a mass of about four million times that of the Sun and is the closest supermassive black hole known - so it is the best place to study black holes in detail.

Despite much research on the many processes that erode rocky coastal cliffs, accurately predicting the nature, location and timing of coastline retreat remains challenging. This is also confounded by the apparently episodic nature of cliff failure. 

Coastline retreat via progressive failure of rocky coastal cliffs

The dominant drivers of coastal erosion, marine and sub-aerial processes, are anticipated in future to increase, so understanding their present and combined efficacy is fundamental to improving predictions of coastline retreat.

When is a tuna more like a seahorse than a marlin?

Science!

The first comprehensive phylogeny of the "spiny-rayed fish," a group that includes about a third of all living vertebrate species, has been published in the Proceedings of the National Academy of Sciences.