What are some things in science and technology that we will likely never achieve?

What are some things depicted in speculative science and science fiction that you feel will never come to pass no matter how hard we try to brute force it or find loopholes for? I came to one today that I believe truly is absolute. Freezing time. Einstein’s theory of general relativity says that a persons point of reference frame cannot be vastly different so close to another reference frame. Meaning you can’t stop time just for yourself and have everyone be frozen around you. A big one would seemingly be FTL and teleportation YET I think FTL will be allowed someday with clever loop holes and teleporting is merely an engineering challenge (but will also never be done on people as you are essentially destroying the person and rebuilding an exact replica at the destination site) What are some of yours? Freezing time seems to be the only one I can think of. Forward time travel is confirmed to be possible (just go very fast) and Einstein’s equations allow for the existence of... Read more