Limits of our abilities, some stuffs which might remain mystery forever!
Human beings are the most unique of living organisms. We are special, because of so many gifts from nature; our intellect, our hunger for knowledge and never ending curiosity, our ability to think, our self-consciousness. Indeed, using this gift from nature, today we are the species which is apparently ruling on the planet!
However, even with so much scientific advances and the vast amount of knowledge gained, there might always be some mysteries of nature which will always stay in the dark!
Now, some of these might stay in the dark because of our limited time as a surviving species in the universe, for example, human beings might never see the time when sun will collapse after billion years because by then life along with humanity might be long gone, but there might be some stuffs which will remain a secret even if we had so much of time and life spans!
Some of these might include
What's there outside of the observable universe!
The universe might be very well infinite, according to Einstein's calculations, there is so much stuffs out there to explore, however, this is limited for us to actually observe or to know because since we know that the universe is expanding, and expanding faster than the fastest speed possible, which is speed of light or C, whatever lies outside of our observable universe will forever be out of our reach since light from those regions will never ever reach our planet and our eyes! So what is out there? We don't know, we can predict, we can speculate but we will never know!
What happens after death!
Okay, we will all die and then know, but not before that. We might believe in our respective religions, be the firmest on our beliefs, but it is "belief" and not "knowing". So, although our beliefs and faith say what will be our destination, but to see it practically before dying? I guess, not possible!
Creating a living cell artificially out of non-living stuffs!
We know what a living cell is made up of, we have created genetically modified items, created new organisms by cross-breeding, cloned, but these are all creation of life from an already pre-existing cell. We are so far away from creating life or a living cell totally artificially out of purely non-living stuffs and it might very well be something which will never achieve!
To travel at a speed faster than light!
Okay, nothing in the universe can travel faster than light, since it is the universe's maximum allowed speed according to laws of physics, but it is human beings who love to break the laws of nature for its own satisfaction, but this dream will forever remain un-fulfilled! Even in the rarest hypothetical scenario in which we might travel at this speed, our mass will completely turn into energy so we will not remain a human being any more so I guess that's the same thing!
To travel back and forth time is probably a wish and dream of human beings since ancient time, since when man started to understand and measure time, be it the ancient system of using stellar and climatic changes or today's atomic clocks. As thinkers, we love to contemplate the idea of going back in time and make changes to regrets we have, change the course of history for good, change the way nature works by making modifications in its very core, to go to future and see what the last generation of human beings look like and how much advancements and progress they might have made, but sadly, the laws of physics don't allow us to travel back and forth in time, time is a dimension probably and we move only in one direction apparently, which is forward and to travel through it and taking it under our control might always be possible in sci-fi movies only, but not in reality!
There are so many things which will forever remain mystery and I will add more once it comes to my mind! For now, that's it I guess!