Until a few years ago many of us may have been blissfully unaware of what a data centre was.

These giant, warehouse-like buildings power virtually all our internet activity, from our web searches and emails to movie downloads and online banking.

They are at the heart of the AI boom, housing the advanced computer chips and servers needed to run services like ChatGPT and Claude.

But the speed at which they're growing, the enormous amount of electricity they consume and concerns about their environmental impact are fuelling a public backlash around the world.

In the US, they've become a huge issue ahead of the midterm elections on 3 November, with both Republicans and opposition Democrats coming out against their development.

It's putting opponents of data centre expansion on a collision course with US President Donald Trump, who has dismissed the pushback as a "sick conspiracy", even as public anger grows.

Here's what you need to know about the data centre boom, and why opposition is growing.