We may be able to find more and more exoplanets,  but it would be harder to find any ETs. Why?<br>For hundreds of years, earth scholars have found countless evidences of alien activities here on Earth. Many ancient cultures have the same old story that thousands of years ago, some Alien "Gods" came to Earth from the stars to create amazing things here, such as the pyramids... They taught earth people knowledges. But they all ended up leaving, sometimes with the promise of  "I shall return".<br>It made sense for the aliens to venture to our planet to live among us during the time when earth people did not have any weapons or technology that could have been a threat to them, but<br>as soon as our weapons turned from cold to hot,   maybe right before we  invented the nuclear weapons,  they decided to leave and hide.<br>With more and more deadly weapon we created, any interstellar visitors wouldn't want to be seen or to be attacked. For a few who needed to stay as observers, they would rely on disguise and stealth. Human eyes can't see much anyway.  Conflicts between human and aliens would mean great disasters.<br>So depends on your purpose of looking for exoplanets, we may not need to look any further, for there are most likely Aliens hidden among us.<br>With development of new technologies, we may not only  be able to see things we couldn't see before, but also  see entities that are hidden under stealthy and disguise.<br> Our Army soldiers already use some kind of stealthy clothes to hide themselves. <br>Clearly, scientists should put in more efforts and resources to find the aliens who are already here,  rather than looking for far away exoplanets. Simply because we might be able to convince some of the interstellar travellers to teach us where are the best habitable planets, and how to get there...