The biggest tab the public picks up for fossil fuels has to do with what economists call 'external costs,' like the health effects of air and water pollution.

In the world of energy politics, the sudden vanishing of the word 'coal' is a remarkable and unprecedented event.

Bloomberg is famously impatient with beltway politics and believes that to get anything done you need to work from the ground up.

Nowhere has the political power of coal been more obvious than in presidential campaigns.

When it comes to energy, cost isn't everything - but it's a lot. Everybody wants cheap power.

In reality, Republicans have long been at war with clean energy. They have ridiculed investments in solar and wind power, bashed energy-efficiency standards, attacked state moves to promote renewable energy and championed laws that would enshrine taxpayer subsidies for fossil fuels while stripping them from wind and solar.

Mark Ruffalo, aka the Incredible Hulk, is the natural gas industry's worst nightmare: a serious, committed activist who is determined to use his star power as a superhero in the hottest movie of the moment to draw attention the environmental and public health risks of fracking.

The coal industry is an even larger part of the Australian economy than it is of the American, and it has an enormous amount of political power.

Bloomberg's $50 million is not going to revolutionize the electric power industry. But his willingness to fight is already inspiring others to see Big Coal differently.

One thing you can say about nuclear power: the people who believe it is the silver bullet for America's energy problems never give up.