The title is borrowed from a 1951 movie in which an alien lands and tells the people of earth they must live peacefully or be destroyed as a danger to other planets. To show he means business, he halts all mechanical things and instantly nothing that is powered by oil or electricity can move.

Fast forward a century, and substitute the alien arrival with the moment when the last drop of earth's oil is consumed.

BP, ExxonMobil, Texaco and the like with their ostentation and awesome financial power will never find a cosy place in the public heart, but oil giants can take the edge off the world's cynical view of them by assuming a lead in the search for non-oil energy alternatives.

No one will ever misinterpret such activity as corporate altruism, and most will recognise that oil companies must sooner rather than later start looking for ways to profitably survive when the oil runs out.

BP, for instance, has started beating its public relations drum with an expensive Beyond Petroleum publicity campaign in which it unveils its search for such oil replacements as natural gas, solar energy and hydrogen.

Gas can be a bridge to clean, renewable energy by shifting the balance of the fuel mix from coal to hydrogen. Carbon dioxide emission in new power generation can be reduced by 50 percent, says BP.

To prove the point, it has created a partnership to develop a power station in Scotland that will run on natural gas. "This will produce electricity with 90 percent lower carbon emission for 250 000 homes," says an advertisement.

It also points out that it has taken solar energy to 160 countries world-wide, including the Philippines where it has installed the world's largest solar off-grid generating system.

Other oil companies have joined the parade to demonstrate their earnestness in putting the planet on a low-carbon diet. Chevron points out that "it took us 125 years to use the first trillion barrels of oil. We'll use the next trillion in 30." It concedes that the era of easy oil is over.

"We can wait for a crisis to force us to do something," says Chevron in a corporate announcement. "Or we can commit to working together, and start by asking the tough questions: How do we meet the energy needs of the developing world and those of industrialised nations."

Not as vociferous or visible are the state owned oil companies. Monolithic national oil companies (NOCs) such as Saudi Aramco, Iraq National Oil and Kuwaiti Petroleum dwarf even the biggest privately-owned producers. Ranked by oil reserves, nine out of the top ten are NOCs, while eight out of ten control the biggest gas deposits.

In most cases, fossil fuels are by far their biggest source of national income and although their vanishing reserves must be of growing concern, they say little about the development of alternative energy generation, despite the threat of the approaching apocalypse.

It'll take massive effort and investment, however, before the hold oil has on energy generation can be loosened. For all the trumpeting about alternatives, they account for just a few percent of the world's current total.

Solar energy holds out the most immediate promise, although wind, tides and hydrogen show potential, but largely under-explored possibilities, while nuclear still wears the Chernobyl mantle and governments and corporations must tread warily along this road.

Japanese electronics colossus, Sanyo, is tapping into a solar market said to be worth around $7-billion annually and growing rapidly.

"In fact," it says, "the pace at which the sector is taking off, particularly in Europe and Japan, has been compared to the revolution in the telecommunications market over the past decade, suggesting that the current surge in activity is just a foretaste of things to come."

Earth receives more energy from the sun in an hour than its total human population uses in a year. What's more, says Sanyo, it's free, produces no noise or pollution and solar power systems are easily installed and require minimum maintenance.

With the right government will and public and private investment, photovoltaic systems alone could, by 2020, be generating the electricity needs of ten percent of the expanded European Union, the equivalent of the output of 76 coal-fired power stations, predicts Greenpeace.

A further 20 years down the road, the sun could be providing up to 20 percent of the entire planet's electricity.

This article was first published in Energy in Africa Magazine, November 2005 - January 2006.