I have said this to a friend, but I am not sure if it is true. If we imagine a photon traveling in interstellar space, there is nothing to interact with so it will continue to move in its direction forever, or until it finds something to interact with (such as matter). Infrared light is made up of photons too, of less energy than visible light (E=hf). Microwaves are quantised similarly, and the quantum of microwave radiation has even less energy. In short, any electromagnetic wave is quantized. The brain emits electromagnetic waves. Typical frequencies, around 10 Hz. No need to detail brain states here, the point is that brain e/m wave frequencies are very low. More on the significance of this below. Software such as shown below can be used to solve Maxwell's equations in the time-domain. So we can obtain the attenuation of even brain frequency e/m waves as they travel through the air, as they spread in all directions and get absorbed partly by air. https://www.physicsforums.com/showthread.php?t=219480 Attenuation is asymptotic (energy tends to zero as distance tends to infinity), which translates into the probability of a quantum reaching an observer at a distance tending to zero as distance tends to infinity. Some of the quanta of brainwaves survive through the atmosphere long enough to reach space, because of the very large total number of quanta (the number being very large because each quantum at 10 Hz has a very low energy according to E=hf so a large number of them are emitted to make up the energy measured around the brain). So some brainwave quanta escape the earth. And therefore, they go through space, they continue forever if they find nothing to interact with, or they get absorbed if they find something. They bend a little due to gravity, but with no other interaction, they continue. It follows our brainwaves live forever, or at least they live for an extremely long time. Is there any error in the above reasoning?