The solar stocks "mini-bubble", the meteoric rise of the clean energy sector in 2007 and the backing from Silicon Valley venture capitalists have led some to compare the clean energy sector to the dot com bubble of the late 1990s, but Nasdeo is quick to point out the differences.

CNN: The smart money's on green

Proposed by Mexican theoretical physicist Miguel Alcubierre in 1994, the drive would propel a ship at superluminal speeds by creating a bubble of negative energy around it, expanding space (and time) behind the ship while compressing space in front of it.

MSN: Warp speed? Slowing down could be a real killer

Bubble memory, a way of storing 0s and 1s by manipulating energy levels, had been invented in the labs in 1966.

FORBES: Technology briefing

Sacyr was one of a trio of big Spanish construction companies that grabbed stakes in the country's biggest energy firms in the go-go days of 2006, near the height of Spain's property bubble.

ECONOMIST: A boardroom row at Repsol