Scientifically, Reiki can be explained to some degree using Quantum Physics. In the scientific communities, Ki is referred to as the human electromagnetic field. Most people are aware of various medical devices such as the electrocardiogram (EKG) or electroencephalogram (EEG) which read the energy fields around the heart and the brain. What about an embryo that doesn't have a heart or brain to produce these types of fields? Biologists from Tufts University made a discovery in 2011, that shows bioelectrical signals within an embryo map out where the various facial features will appear in an embryonic tadpole. This means that embryos develop via an electrical manner. If a Reiki practitioner is able to draw measurable energy to themselves, acting as a conduit and sending it to a separate entity, you can only imagine the possibilities in which Reiki energy can be explained when speaking in quantum terms. Read the official study and watch the video showing the bioelectrical pulses at Tufts Now.
Because light travels at a fixed rate, you could teleport (and had an insanely powerful telescope) farther and farther away from our planet and you could look back to see any point in history depending on your distance away from Earth. Just as time-lapse works with photography, the light that has been traveling through space carries a snapshot of what was happening right in that moment. If we think about this, it means that history is technically happening simultaneously and instantaneously with the present as we know it. With this in mind it's a lot easier to make sense of distance Reiki. Using the HSZSN symbol to send the healing energy through time and space, meaning that you can send Reiki to someone in the present who is located elsewhere, or, you can send Reiki out into the universe to help heal an event that happened in the past where the all knowing energy will find the light particles that are carrying that image stamp of the past. Of course, sending Reiki into the past doesn't change what happened but it can make dealing with those past traumas easier in the present moment. Another phenomenon that can help to explain how Reiki can actually be sent through time and space without losing any power is Quantum Entanglement. This phenomenon states that if one particle is affected or changed another is instantaneously changed as well, even if they are over 50,000 light years apart. This helps to explain why Reiki energy doesn't diminish or lose power when being sent over long distances. Entanglement happens when two particles interact, either by being too close together or by interacting with particles that are already entangled with others. Once the phenomenon on entanglement happens, it's there indefinitely even if the particles become separated.
Jeremy O'Carroll, the founder of Om Reiki Centre in Melbourne, Australia, uses a high-tech Aura machine which reads the human electromagnetic field, as well as other physical responses in the body to produce these results. In this video, Jeremy treats a client with Reiki. Within just a few minutes you can see drastic changes in the clients responses on the machine. You can find more information at Om Reiki Centre