Despite movies like “Passengers,” the science behind cryonics is still a long way from reviving people who have been “frozen” after they’ve died.

What if you had a life-threatening disease and someone offered an ambulance ride to a hospital that may hold the cure? You’d take it, right?

What if that “ambulance” was actually a cryonic state that kept you preserved and that hospital existed 200 years from now? Would you still go?

Cryonics, in the simplest terms, is the act of freezing someone who’s been declared legally dead. The idea is to conserve the body until science can catch up and provide treatment to whatever caused the person to die.

When that scientific breakthrough occurs, the person is then revived, given the necessary medical treatment, and goes on living.

The practice recently made headlines when a 14-year-old United Kingdom girl with cancer sought the legal right to be frozen. Her parents were divorced and her father didn’t agree with her intentions. The teenager asked the court to designate that only her mother could dispose of her remains so she could get her wish. In October a judge ruled in her favor.

“I’m only 14 years old and I don’t want to die, but I know I will. I think being cryo-preserved gives me a chance to be cured, even in a hundred years’ time … I want to live and live longer and I think that in the future they may find a cure for my cancer and wake me up,” she wrote to a judge before her recent death.

Read more: Facing death at an early age »

The theory of cryonics was first broached more than 50 years ago by Robert Ettinger.

In 1964, his book, “The Prospect of Immortality,” first introduced the idea on a mass scale. A dozen years later, he founded the Cryonics Institute.

Over the past five decades, cryonics has held on to a small but dedicated group of supporters. Today, hundreds if not thousands of people are betting on the science.

Dozens of institutions, nonprofits, and businesses around the world offer cryonic services to anyone who can afford it. Ettinger’s Cryonics Institute in Michigan and Alcor Life Extension Foundation in Arizona are two of the better known cryonics providers in the United States.

Those who are in favor of it say cryonics is ultimately about scientific exploration. Those who are opposed to the say it takes advantage of people in vulnerable positions.

In order for a body to get to a preserved, frozen state, a person must first be declared legally dead. Once that is determined, the freezing process involves a complex set of protocols. It’s designed to cool the body, so that everything slows down at a molecular level, according to Dennis Kowalski, chief executive officer of the Cryonics Institute.

Once the blood is pumped out of the body, it’s cooled even further but in a way that preserves the organs and hinders tissue damage. The body is then placed into a large thermos-type bottle of liquid nitrogen where it stays — indefinitely. Or until science can provide a viable cure.

“I guess it’s about optimism. It’s also about hope,” Kowalski told Healthline.

But hope is not cheap. At Cryonics Institute, cryonic services costs $28,000. That price, Kowalski said, is competitive.

Part of the funds go the group’s endowment, which is used to cover the long-term expenses of keeping bodies frozen for potentially hundreds of years. Kowalski does not take a salary for his work at the institute. Instead, he works full time as an emergency medical technician.

He added that if someone is interested in cryonics and is quoted a cheaper price, he’d be skeptical about that organization’s ability to keep a body preserved in a proper way with all the safeguards intact.

Read more: The changing definition of what is ‘brain dead’ »

If cryonics sounds like the stuff of science fiction, that’s because it is.

A number of well-known films such as Sleeper, Space Odyssey 2001, and the soon-to-be-released “Passengers” starring Chris Pratt and Jennifer Lawrence all employ some version of cryonics as the crux of their story line.

In these movies, the protagonists are put to sleep or frozen and “wake up” in the distant future to an entirely new world.

Usually these movies’ scenes unfold as if these people are waking up from a really good night’s sleep. Waking up is the crucial part of a cryonics equation. But Kowalski readily admits, science has yet to figure out how that will unfold for people who are in a cryonic state.

“We are not even close to being able to revive people,” he said.

Modern medicine does currently employ freezing methods to treat patients. It’s the preferred technique to store stem cells, embryos, and small tissues.

Kowalski added that all three examples are capable of being restored — free of damage — from the subzero temperatures. Even hospital emergency rooms are starting to see the benefits of a lowered body temperature, he noted. Sometimes it’s used in the treatment of gunshot wounds and heart attacks.

He says these examples show that it’s only a matter time before the human body will be able to endure similar treatment.

“The trend certainly seems to be heading that way,” he said. “Could be 20 years from now. Could be 2,000 years.”

Detractors say the science and technology needed to revive and treat people are far into the future. Encouraging people to spend thousands of dollars on a yet to-be-proven medical procedure calls into question the ethics behind the industry.

“I can understand why people are interested,” Ryan F. Holmes, assistant director of the Markkula Center for Applied Ethics at Santa Clara University in California, told Healthline.

His concern is that people get lost in the hope of cryonics and don’t really ever consider that it isn’t going to work.

“It seems overly hopefully and that for me is the hardest ethics part,” he said.

He doesn’t advocate that people should be prevented from choosing cryonics when they die, such as the case with the United Kingdom girl. But anyone who does make this choice must understand that there are a multitude of unknown factors about the science and technology.

“This wouldn’t even qualify as a phase 1 trial,” he said. “This falls into the category of experimental treatment.”

What’s more, he said potential candidates should be made aware that revival — if it can even occur — doesn’t guarantee that quality of life will be what it once was before they were sick.

“We have no evidence that they’d be who they were in a very meaningful sense,” he said.

Read more: Where we die: Less in ER and more at home »

Kowalski said the nonprofit does not guarantee to its clients that cryonics will work.

“We make every effort to educate people about their choices and what we offered. We also understand the potential for misunderstanding and misconception about what we are doing,” he said. “We try very hard to explain our position and provide as ethical a service as possible.”

Right now they have about 1,400 people as members and around 150 bodies are frozen.

Kowalski said that people usually come to the institute in two ways.

The first group is people who are interested in cryonics and sign up by their own free will. These clients are required to fill out extensive paperwork and are given an interview as well.

Others are the result of a person dying and family members scrambling to have them embalmed.

The nonprofit adheres to a list of rules when they get an urgent cryonics request. In these situations, if they accept the body it will be held for two weeks to ensure that cost and paperwork are completed. Anyone who has been declared dead for up to 48 hours is turned away. Kowalski said overall they’ve turned down about half of the post-mortem requests.

“We have returned funding many times when [a] family cannot agree on disposing remains,” he said. “There is a series of events that must be followed or we back out to protect both ourselves and the family from mistakes.”

For Kowalski, signing up for cryonics is something he got interested in as a kid. He and his family are all on board. When asked what he thinks the future will be like should the revival process work, he said he envisions a world that will be even better than today.

“I’m excited to see the future,” he said.