Imagine a future where nobody dies— instead, our minds are uploaded  to a digital world. They might live on in a realistic, simulated environment with avatar bodies, and could still call in and contribute  to the biological world. Mind uploading has powerful appeal— but what would it actually take to scan a  person’s brain and upload their mind? The main challenges are scanning a brain  in enough detail to capture the mind and perfectly recreating  that detail artificially. But first, we have to know what to scan. The human brain contains  about 86 billion neurons, connected by at least a  hundred trillion synapses. The pattern of connectivity  among the brain’s neurons, that is, all of the neurons and  all their connections to each other, is called the connectome. We haven’t yet mapped  the connectome, and there’s also a lot more  to neural signaling. There are hundreds, possibly thousands  of different kinds of connections, or synapses. Each functions in a slightly  different way. Some work faster, some slower. Some grow or shrink rapidly in  the process of learning; some are more stable over time. And beyond the trillions of precise,  1-to-1 connections between neurons, some neurons also spray out  neurotransmitters that affect many other neurons at once. All of these different kinds of  interactions would need to be mapped in order to  copy a person’s mind. There are also a lot of influences on  neural signaling that are poorly understood  or undiscovered. To name just one example, patterns of activity between neurons are likely influenced by a type  of cell called glia. Glia surround neurons and,  according to some scientists, may even outnumber them  by as many as ten to one. Glia were once thought to be purely  for structural support, and their functions are still  poorly understood, but at least some of them can generate  their own signals that influence information processing. Our understanding of the brain isn’t good  enough to determine what we’d need to scan in order  to replicate the mind, but assuming our knowledge does  advance to that point, how would we scan it? Currently, we can accurately scan a living human brain with resolutions of about half a  millimeter using our best non-invasive  scanning method, MRI. To detect a synapse, we’ll need to scan  at a resolution of about a micron— a thousandth of a millimeter. To distinguish the kind of synapse and  precisely how strong each synapse is, we’ll need even better resolution. MRI depends on powerful magnetic fields. Scanning at the resolution required to determine the details of  individual synapses would requires a field strength high  enough to cook a person’s tissues. So this kind of leap in resolution would require fundamentally  new scanning technology. It would be more feasible to scan a dead brain using an electron microscope, but even that technology is nowhere  near good enough– and requires killing the subject first. Assuming we eventually understand the  brain well enough to know what to scan and develop the technology to safely  scan at that resolution, the next challenge would be to recreate  that information digitally. The main obstacles to doing so are  computing power and storage space, both of which are improving every year. We’re actually much closer to attaining  this technological capacity than we are to understanding or scanning  our own minds. Artificial neural networks already run  our internet search engines, digital assistants, self-driving cars,  Wall Street trading algorithms, and smart phones. Nobody has yet built an artificial network with 86 billion neurons, but as computing technology improves, it may be possible to keep track  of such massive data sets. At every step in the scanning and  uploading process, we’d have to be certain we were capturing  all the necessary information accurately— or there’s no telling what ruined  version of a mind might emerge. While mind uploading is  theoretically possible, we’re likely hundreds of years away from the technology and scientific understanding that would make it a reality. And that reality would come with ethical  and philosophical considerations: who would have access to mind uploading? What rights would be accorded to  uploaded minds? How could this technology be abused? Even if we can eventually upload  our minds, whether we should remains  an open question.