Well not really. Cooling the patient down will give you a few hours at most under ideal conditions. Metabolism isn't turned off, just slowed down. If you freeze the patient the ice crystals damage the cells so much that revival becomes impossible.
Flash freezing (using liquid nitrogen to freeze something really quickly) is used successfully for smaller objects, such as frozen berries and frozen vegetables that you can buy at the grocery store. The Wikipedia page on flash freezing links to this [0] site with some more discussion. The Wiki page also says that flash freezing still can take a few hours, so there are still ice crystals created, but a lot less/smaller than if you just put it in the freezer.
Overall it seems it's just a matter of waiting for technology to advance to the point where we can very move a 150 pound 2-meter-tall 1-foot-deep object from 98 degrees to 30 degrees, and at that point the science fiction will become reality.
Cryonics involves vitrification, not freezing. Ice crystals do no damage if they never form in the first place.
Now the method of achieving vitrification involves pumping the body full of toxic antifreeze. But in principle it's easier to flush the antifreeze out when warming than to reverse ice crystal damage, though the techniques have not yet been worked out.
Thankfully it's not necessary for the reversal procedure to exist now for cryonics to be successfully used in preservation for the future.
There is zero chance that a human pumped full of antifreeze today will ever be successfully revised. Cryonics is a total scam by hucksters preying on desperate idiots.
And don't bother telling me that it's worth doing if there's even a tiny chance. The chance is exactly 0, and those resources are better spent on the living.
You can basically say that anyone living 500 years ago would say "there is zero chance" that what we take for granted today exists at all. Look at the technological achievements of even the past 50 years, most of it could hardly be predicted.
It didn't point out any issues... it just made the unsubstantiated claim that a cryonics patient has no chance of ever being revived.
It IS physically possible to revive cryonics patients--as in the laws of physics would permit it, even if we don't have anything near the technology required, yet. This isn't a bold claim but rather a statement of fact with respect to information preservation of the vitrification process, and long-term storage at cryogenic temperatures, both of which are well studied in the context of things like organ donor preservation.
So if you're claiming that cryonics has "a snowball's chance in hell" of working, then I presume that either you are (1) ignorant of the science, or (2) making some sort of statement about long-term storage prospects or the credibility of the organizations involved.
But neither you nor the grandparent actually made any specific claims.
A lot of "cryonically-frozen" people are only their heads, since it's been well-known for a while that there's no way to unfreeze the bodies. I suspect it may literally be easier to scan their brains than to unfreeze them, even if they were healthier to begin with. That's not a statement of my belief in the ease of scanning a brain; it's a statement of my belief in just how hard it is to "thaw" a body and get anything back. I'd say it's like getting handed a pile of slag and told to turn it back into a working engine, except that task is multiple orders of magnitude easier.
A zero chance is your opinion. I'd estimate there is a high change some of them will come back in some form. I'm more a believer in extracting information to an AI simulation than reanimating the old bodies.
There's a big difference between telling someone they aren't going to win in the casino and telling them they have "zero chance" of winning. The later is false and is probably an ineffective argument because it's obviously false.
Also, frozen oblivion is better than being brought back by those who will not honor your motivations for being frozen. If it's possible to be brought back, organ-harvesting, post-cryo-slavery, medical-experiment-subject are the likely outcomes.
If we ever do crewed interstellar travel, even if we can get the trip time down to 50 years or so, we’ll probably want something like this. But it’s useful even for Mars trips since you can fit a LOT more people in the same space.
There may be less oxidative stress as well, so it’s tough to say what wins out. Anyway, there are methods of providing radiation shielding to occupants as well.