In this Gizmodo series, we ask questions about everything and get answers from a variety of experts.

Corpse-freezing hasn’t exactly gone mainstream, but most people are now familiar with the concept: you lay out a ton of cash, sign some papers, and spend a couple post-death decades in a cutting-edge meat locker, calmly awaiting the conditions for your eventual revival. Over 300 cold, dead Americans—or dead, cold American brains, depending on which procedure they opted for (whole-body vs. brain-only)—can currently be found in storage facilities across the country. All of them took a gamble—one that was pretty cheap, metaphysically speaking: the worse case scenario here is just continued death.




For the time being, that is also the only scenario. Only time will tell whether these extremely dead optimists will once more, someday, get stuck in traffic, and/or roam an uncanny Singularity-scape with their AI-abetted computer brains. But we can at least start to guess whether—or if—that day will ever come. For this week’s Giz Asks, we reached out to a number of neuroscientists, bioethicists, cryo advocates and skeptics to get some sense of what will happen to those frozen former consciousness-havers. Honestly it’s not looking good for them just yet—but the future’s main business is to show up the past’s myopia/blinkeredness, so, who knows!

Dr. Joao Pedro de Magalhaes

Biologist at the University of Liverpool and coordinator of the UK Cryonics and Cryopreservation Research Network

I’d say that with today’s technology, cryonics severely damages the body’s cells. Even under optimal conditions (i.e., the procedure starts right after death), there are several problems in cryonics. In particular, cryoprotectant agents have toxic effects on human tissues with prolonged exposure. Vitrifying large organs like the brain can also result in fractures due to different cooling rates in different parts. Under non-optimal conditions (i.e., if a significant time elapses between death and being cryopreserved) much more damage can occur because cells start to die, and brain cells in particular start to die within minutes after cardiac arrest, due to lack of nutrients and oxygen (called ischemia). Therefore, it will take huge scientific advances in areas like tissue engineering and regenerative medicine to make cryopreserved individuals alive and healthy again. In addition, repair at the molecular level using nanotechnology will be necessary, yet this remains in the realm science fiction. That said, it is impossible to predict how technology will progress in the coming decades or centuries. As such, I would say that the chances of cryopreserved individuals ever be revived is low but not impossible. And then the argument is that the worse possible outcome of being cryopreserved is to remain dead, so cryonics gives you a chance of future revival that will not happen if you are buried or cremated.


Moreover, reversible and safe human cryopreservation would be a revolutionary technology in the field of critical-care. Patients with terminal diseases, including children, could opt to be placed on cryostasis until a cure were discovered. In a sense, we would have an alternative to death, which has profound philosophical, ethical and medical implications.

“The chances of cryopreserved individuals ever be revived is low but not impossible.”

Mark Kline

Co-Founder and CTO, X-Therma Inc., a company improving cold storage of stem cells, tissues, and whole organs

There are two different ways of cryogenically freezing people. One involves freezing just the brain or the head—the thinking here is that there’s a smaller amount of tissue and you should preserve the essence of the person. It’s also cheaper and easier. But storing the brain’s underlying structure, and the connections between cells, is likely much, much harder. The other method involves freezing the whole body, in the hopes that you could be revived one day when the right technology is available to fix your disease state and repair damage from the process. There are a ton of barriers here, in both cases. The hardest thing to solve is: how do you freeze things without damaging them? You mix in all these cryoprotectants—like antifreeze for your car, but geared towards biology—in an effort to prevent ice formation within the cells and tissues. But you need to drastically lower the temperature—down to about -196 degrees C, liquid nitrogen temperature. Preventing ice formation at that temperature, throughout a very large tissue, is very, very difficult. When the ice forms, it’s going to shear and cut the cells like a knife—it’s basically going to run a knife through the organs you’re trying to preserve. And then there’s desiccation: once you put those chemicals into an organ or a cell, it causes the water to leave the cells and dries them out, which damages cell to cell connections. Once those are damaged, repair becomes near impossible, since cells don’t seem to rebuild those connections properly after being frozen. At least researchers see very little repair of the matrix.


So there’s the chemistry problem (preventing ice), the biology problem (tissue damage, connection damage), the physics problem (how do you evenly cool something as large as an organ? And how do you warm it up evenly afterwards, without damaging it?). I think there are much more imminent applications for cryopreservation, like organ preservation. Preserving organs has a high-value impact for the medical system, and also is much more feasible than preserving a whole body. You can save many, many lives with organ preservation.

“The hardest thing to solve is: how do you freeze things without damaging them?”

Nick Bostrom

Professor at the University of Oxford and Director at the Future of Humanity Institute and the Governance of AI program



Technically it seems like it should probably work. The freezing (rather: vitrification or plastination) and storing we can do now. The bringing back part may however require the assistance of machine superintelligence in order to repair the extensive cellular damage that occurs during the suspension process.


Dennis Kowalski

President, Cryonics Institute

The scientifically correct answer is that we do not know, since no one knows the future and what will be possible. However, that is why some people have signed up to preserve their bodies at liquid nitrogen temperatures in hopes that future technology and medicine will be able to answer that very question. Just as it was impossible to raise the dead 100 years ago, they believe that new technologies like CPR and Cardiac defibrillation will change the definition of what it means to be dead. New technologies moving forward might mean advanced, AI-guided stem cell therapies that regenerate tissues that have been damaged by aging, freezing, or death itself. Ray Kurzweils’ law of accelerating returns suggests that technologically we are advancing at an exponential pace, and this means that things considered impossible even a few decades ago will become reality. For instance: the cell phone in your pocket that lets you communicate worldwide in real time while being able to access all of human knowledge at your fingertips. In the past such a device was called a crystal ball and was considered a myth. It seems likely—but only time will tell.

“We do not know, since no one knows the future and what will be possible.”

Cathal O’Connell

Researcher in 3D bioprinting and biofabrication at BioFab3D, St Vincent’s Hospital, Melbourne


All signs point to no. The freezing-down process is critical. Doing this in a way that preserves cell function—especially regarding connectivity in the human brain—is way beyond our current capabilities. Unfortunately, everyone who has ever been frozen so far is essentially turned to mush. These people will never be revived. Cryonics in its current form is more of a religion than a science. Rather than a divine entity, its followers place their faith in technological progress—believing that future advances will compensate for the terrible damage caused during current freezing techniques. There is no evidence or indication that this is possible. Though I don’t doubt its prophets are well intentioned, contemporary cryonics is essentially a belief system providing comfort against the fear of death. The ability of some organisms to survive freezing is a sign from nature that what cryonics promises might one day be possible. But getting there will require a massive investment—billions of dollars, thousands of scientists, decades of research. Without a clear economic incentive, that investment is not forthcoming. As my old professor says, a vision without funding is hallucination. Think that today it typically takes a couple of decades and a few hundred million dollars to develop one new medical treatment. The problems faced by cryonics are at least an order of magnitude more complex. By the time humanity solves them we might all be immortal anyway.

“...massively challenging and far beyond what is currently possible...”


Ralph Merkle

Director of Alcor Life Extension Foundation, the world’s leading cryonics organization



The short version is: many of the patients at Alcor will likely be revived sometime this century. Had you asked a random person in 1940 if flight to the moon was possible, you’d likely have been told “no.” If asked why, a typical answer was “because there’s no air to push against in space.” This scientific-sounding but totally false objection was infamous among knowledgeable scientists, and was the basis for the New York Times’ 1920 editorial denouncing Robert Goddard. It was retracted on July 17th, 1969, one day after the launch of the Apollo 11 spaceflight. Yet those knowledgeable about space flight had been forecasting flight to the moon for decades before the event. Similarly, those knowledgeable about nanomedicine have also been forecasting the revival of cryopreserved patients for decades, and those forecasts are likewise based on a sound assessment of physical law. While we still hear skeptical sounding statements about cryonics, the obvious lack of any sound technical argument against the feasibility of cryonics is becoming increasingly obvious. Until the structures in the brain that encode our memories and personality have been so obliterated that they cannot in principle be inferred and restored to a functional state, you are not dead. This information theoretic criterion of death is obviously much more difficult to meet than current legal or medical definitions, hence the belief that cryopreserved patients are not actually dead.


“This information theoretic criterion of death is obviously much more difficult to meet than current legal or medical definitions, hence the belief that cryopreserved patients are not actually dead.”

Michael Hendricks

Canada Research Chair in Neurobiology & Behaviour and Assistant Professor of Biology at McGill University and wrote “The False Science of Cryogenics” for the MIT Technology Review

If you mean people who have already had their brains, heads, or bodies cryogenically stored after death (or are doing so with current technology): no, they will never be revived. They are dead, and will remain dead forever. Will it ever be possible to store a dead person (or a dead person’s brain) in such a way that they can be revived? Almost certainly not. Will it ever be possible to cryogenically “suspend” a living person for some period of time? Almost certainly. For how long? Impossible to say. Will it ever be possible to “upload”—transfer—someone’s consciousness into a digital form? No. Consciousness is not a thing, it’s a bunch of different things that brains do. In theory, you could create a digital simulation that is a different thing from the person, and the person can still be either alive or dead. Either way, the new thing isn’t them. A person is a particular physical causal system, not a computational abstraction. Will it ever be possible to create a simulation or digital version of a dead person based on examination of their brain? This is not theoretically impossible, but it is so far outside our technology (both biological and computational) that anyone who says they know they answer of whether it will ever happen is probably selling something. The belief that a theoretically possible technologically will ever be practically possible and will come true if we want it bad enough is just quasi-religious wish fulfillment. Look at the world. The only good thing we still reliably do for future generations is get out of their way. Let’s not take that away from them too…they will have their hands full with all the horrific problems we’ve left them because of our selfishness and greed. We shouldn’t making them responsible for keeping our bodies cold, too.


Matthew I. Gibson

Professor, Chemistry, Warwick Medical School, whose team researches new cryoprotectants to help store biologics

The cryopreservation of cells underpins a huge range of fundamental and medical science; just like with food, we cannot leave cells lying around at room temperature and expect them to be fine to use, so low temperatures are essential to let us store (or bank) the cells. Successful storage of cells requires careful addition and removal of cryoprotectants, as well as the precise control of freezing and thawing rates. In small volumes (for cells) this can be simple, but it becomes much harder as the volume increases and is one of (very) many problems of freezing a person. We must remember a human is a community of cells linked together, and those links need to be maintained for a tissue to be viable, especially for complex organs like the brain. It is appealing to think that just because cells, or some tissues, are routinely cryopreserved that the same could be applied to an entire person, but this is really an over-simplification. No one can predict future technologies, but I don’t see how this is possible, and claims that nanotechnology will ‘put back together’ the damaged parts of the brain/body do not agree with scientific reality at the moment.

Simon Woods

Reader in Bioethics, Newcastle University


First, I believe that any cryo-preserved corpse or brain that is already frozen (or will be in the near future) has zero chance because the individuals concerned are already dead and their death caused by fatal diseases currently incurable. Waking these corpses would involve so many major breakthroughs way beyond what is possible now, thawing complex tissue and organ systems into a viable state, applying regenerative technologies to make good the tissue damage, curing the fatal disease which killed them and finally reviving the dead person. Each of these is individually massively challenging and far beyond what is currently possible (and remember in most definitions death is an irreversible condition). What is open as a possibility is if the cryo-person was not dead or terminally ill to begin with—so this might involve combining cryo-preservation with euthanasia (thus compounding the moral problems, especially if the person was not terminally ill which is a requirement in most jurisdictions that allow euthanasia). I suppose this technique might be used to enable deep space exploration where the person was placed into a suspended animation – though in this case cryo-preservation might not be the best thing because, using current technologies, the techniques are very damaging to cells though work is going on to improve the technique. To touch on some of the wider social problems—if a person were cryo-preserved for several hundred years what would be their status in the future community—awoken alone with no friends or living relatives, like a ship-wreck survivor thrown up on some foreign shore.

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