Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

In rallies across coal country, Donald Trump made a big, crowd-pleasing promise: He’d bring back the mining jobs.

“We’re gonna open the mines,” he said to big cheers in Charleston, West Virginia, as if the shuttered coal mines across eastern America’s coal country could hit a switch and reinstate the jobs once he won the White House.

“He can’t bring back coal jobs in any meaningful way unless he’s capable of inventing a time machine.”

But experts say despite Trump’s election, those jobs aren’t coming back.

While regulation sped the shuttering of older coal mines in the last decade, experts say it was natural gas that turned the screws on the industry. Cleaner and cheaper, the natural gas market share is growing rapidly and putting as much — if not more — pressure on the coal industry as regulations.

“He can’t bring back coal jobs in any meaningful way unless he’s capable of inventing a time machine,” explained Eric de Place, energy policy director of Sightline Institute, a progressive environmental nonprofit. “Waving your hands and saying you’re going to bring the coal industry back is misleading at best, malicious at worst.”

It’s no surprise that Trump, who has positioned himself as a champion of blue-collar workers and a vocal critic of President Barack Obama’s environmental regulations on coal, has rallied behind the coal industry, which lost 50,000 jobs during Obama’s first term, according to one study. Robert Murray, owner of the largest private mine in America, is also quick to note that coal mines create jobs around them, as mining towns need doctors, lawyers, restaurants, and more, and their shuttering created the kind of economic anxiety that fueled Trump’s presidential bid from the start.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

But as the industry has changed, the geography of coal itself has, too. “The dominant coal fields are no longer in the East,” De Place said. “The vast majority of coal is mined in the West and is done in highly-mechanized ways. That’s not really reversible."

Related: Trump Appears to Push Contradictory Gas and Coal Boosting Plans

Rick Smead, a managing director at RBN Energy who specializes in the natural gas industry, agreed with De Place’s predictions for the coal market under Trump.

“It’s very unlikely that coal can regain its market from natural gas where they would be hiring a lot of miners back,” he said.

There is some hope to stem the losses. Murray, who has met with Trump several times to advise him on coal issues, said the president can stop future jobs from disappearing, but he can’t add them back rapidly.

“You can’t bring it back, but he can stop the destruction right where it is,” the mine owner, who cautioned Trump to soften his election promises during the election, told NBC News.

Murray said he believes he can compete with natural gas if coal isn’t mired in regulations, but acknowledged that the slew of jobs Trump promised are unlikely to emerge from his industry quickly. Job growth, he said, would be completely dependent on the domestic economy.

“It’ll be a function of how well America creates jobs,” Murray said, noting that a surge in manufacturing — something else Trump has promised — would help.

Related: Could Trump Really Bring Back Manufacturing Jobs?

Smead said the biggest coal boon from 2016 would have come not from Trump or Democratic rival Hillary Clinton, but rather Democratic runner-up Bernie Sanders, who promised a national ban on fracking that would have gutted the natural gas industry.

"It’s very unlikely that coal can regain its market from natural gas where they would be hiring a lot of miners back."

“That would have been a bright day for the coal industry,” he said. “I thought it was ironic that the president campaigned in Pennsylvania and on the same day promised coal miners their jobs back and promised shale miners that he’d get everything out of their way — when in fact he was talking to the guy who just killed off the coal industry.”

Trump’s policies seem likely to make it easier for fracking and the natural gas industry.

In his first week in office, Trump signed two executive orders to advance the Keystone XL and Dakota Access pipeline, a boon to the natural gas industry, which he claimed would create “thousands and thousands” of jobs. He boasted that the Keystone XL pipeline would create “28,000 jobs, great construction jobs” — seven times more than the government actually estimates would be created. The government estimates note that construction jobs could create more jobs through contracts, but none of their estimates rise to Trump’s number.

Once construction is ended, however, the pipeline would create just 35 full time jobs. It’s a number that puts a spotlight on the difference between the future of the energy indstury and the way the coal industry used to be.

“Almost anything else you do with a dollar of investment — including digging a hole in the ground — would produce more jobs than in modern energy production,” De Place said.