Every time you ask ChatGPT a question, read a Google summary or make an online bank payment, a data centre is working behind the scenes.

Now Scotland is part of a global race to build many more of them – on a massive scale.

The explosion in artificial intelligence (AI) over the past few years has seen tech firms scrambling to build new "hyperscale" data centres, including some which would rank among the biggest in the world.

Plans are in place to build at least 23 giant AI-powered data centres.

Supporters say they are vital for the future and could bring billions of pounds in investment, as well as thousands of jobs.

Opponents fear the impact of their size on local communities, the vast amounts of energy they use and even the noise they will make.

So what exactly are data centres, and why have they become one of Scotland's most controversial planning battles?

From the outside, data centres look like a factory or a warehouse.

On the inside, thousands of flashing lights blink and fans whirr as rows of computer servers power AI.

While some are built by tech giants like Amazon, other developers claim commercial sensitivities when asked what they are actually powering.

Scotland's centres are currently quite small, but some of proposals for the hyperscale versions are immense.

One of the biggest is at Auchtertool in Fife.

The site would span 60 hectares (150 acres) – about the size of 84 football pitches.

AI is seen by some as the most transformative technology ever made but others have warned there is chance that if the frightening pace of development continues it "could kill all humans" within the next decade.

But Scotland's data centre debate is not really about the technology inside the building – it's about the scale and impact of the centres themselves.

At the moment, the biggest data centre in Scotland is thought to be DataVita's site in Airdrie, which has a capacity for 12MW.

The new data centres being proposed are a whole new level.

If one planned for Chapelcross in Dumfries and Galloway goes ahead, it will have a capacity of 1,000MW – making it one of the largest data centres in the world.

At Auchtertool, the planned 600MW data centre would be the same size as the neighbouring village.

Other concerns focus on:

The Scottish Greens and campaign groups have called for a moratorium on large data centres, arguing they could undermine climate targets and place additional pressure on renewable energy supplies.

The Scottish government has so far refused to impose a moratorium.

One of Scotland's biggest selling points for data centre developers is its strong renewable energy sector.

Scotland generates huge amounts of electricity from wind, and some of that power is currently wasted because the grid does not have enough capacity to move it from where it is produced to where it is needed.

However, experts caution that this does not mean data centres would run entirely on renewable energy.

During periods of low wind or when clouds are blocking the sun, it may mean having to fire up fossil fuel power stations to provide the energy required to keep the servers blinking.

As well as using huge amounts of electricity, the giant data centres can require large quantities of water to prevent them from overheating.

While the tech industry says it is developing more efficient cooling systems, industry sources told the BBC last year the UK government's plan to make the UK a "world leader" in AI could put already stretched supplies of drinking water under strain.

An expert recently claimed that Scotland's current data centres use less water each day than its libraries, but there are significant concerns over what the water consumption could be if any of the hyperscale centres were given the go-ahead.

And what about the hum?

Data centres have many fans cooling down the servers inside and people in the US who live near them have reported hearing a constant noise, with concerns it has also driven away wildlife.

As well as having a stake in a key future technology, those behind AI data centres say they will create jobs.

Lanarkshire has been designated an AI growth zone by the UK government, with data centres at its heart.

When it was announced in January, external, £8bn of investment and 3,400 jobs were promised.

The type of jobs a data centre creates has also been debated.

About 800 are expected to be in AI, with 50 apprenticeships. The rest are in construction.

Apatura – the developer behind 10 of the hyperscale data centre proposals in Scotland – highlights its green credentials with its access to renewable energy and battery storage.

With China and the US hoping to win the AI race, the UK government does not want to be left behind.

The Scottish government also supports the investment in the AI growth zone.

In August, it announced that ministers would have to be notified of proposed centres over 50MW in capacity.

A month later, it rejected the Scottish Greens' call for applications to be paused until new national guidelines are in force.

However, it said environmental impact assessments would have to be submitted.

The government also said it was "highly unlikely" any large data centres would be given the green light before Christmas, and promised that new guidance would be published by the festive season.