I have a doubt regarding the speed of light. What makes it impossible to achieve it. Why cant we have a relative velocity greater than that of C. Some say you should not apply common physical world logic in these fields. But, Consider we have 2 laser sources separated by 2c distances. Say we switch it on at the same time. Why is the relative velocity between these 2 light (not the sources) be not more than c. Common logic says for laser emitted from source A light from source B is coming at it at 2c speed. I myself had an answer for it in my younger days, but now seems to forget it. I want to know why. Many may be fed up with this question coming up again and again. But sure if you help me now some other day I would help others who post the same question later. Sorry just now realized there are similar threads in the forum already. But none had a discussion regarding what prevents us from reaching light speed. Thanks for reading. Waiting for your reply.