When we talk of extraterrestrial visitor(Alien) or thought of exploration or space Travel comes to mind, let us be mindful of certain aspects of such cosmic travel.
To take a measure of distances in cosmos, a ray of light can cross our solar system in a couple of minutes or so. There are billions of such star systems-such as our own, in our galaxy that is the Milky Way. Our galaxy is a spiral one; at the speed of light, will take about 100,000 years (about 10 trillion Kms) to get across it. That means, to travel & explore thorough our own galaxy it will take almost infinite years at present speed of rockets .Let us remind that if we take average human life to be 70 years, at today’s speeds, we cant reach anywhere and come back!
According to one model, the cosmos is ever expanding, right from the instant of ‘Big Bang’. That means, galaxies are moving far away from each other continuously at enormous speeds. Even at the speed of light, we are going to take longer than what it seems today. Intergalactic distances of the cosmos are enormous from the point of view of light travel, even if not physical travel. So human travel, as it is, ruled out. If traveling at speed of light is going to be of any help, let us acquaint ourselves with the fact that science indicates that ‘the speed of light’ is such a threshold that it cannot be achieved! If at all it becomes possible to cross this threshold; time will slow-down or clock may turn back. s I should better try to explain this with an example like following.
John, at the age of 40, sets on a exploration journey, at the speed more than that of light, saying good-bye to his son Michael who is 10 years old. According to the watch on the wrist of John, he comes back from his travel after a year or so, to find his son celebrating his 50th birthday! John is younger to his own son by 9 years! The time is relative to the speed of travel.
This is as far as smaller distances go (on a cosmic scale of course). We can thus say, if ever we set forth on such exploration journey, it is going to be a one - way journey.
