4 ms·Planes did not exist before humans built them. Radium did.by anoncake 7y agoPlanes did not exist before humans built them. Radium did.boudin 7y agoRadium existed but not isolated and not usable for X-Ray for example. Plane was in nature also before humans, just not assembled yet :)anoncake 7y agoI don't think we agree on the definition of "plane" :)