Scientist are using a variety of methods to search for life beyond Earth. Discuss the problems involved in using these methods.
There are scientists who search for signs of any type of living organisms beyond the earth, and others who are looking for signs of intelligent life. Both are difficult. We don't have the means to travel out of the solar system to look, so in looking outside of the solar system we have to use indirect methods. Scientists use space telescopes such as the Hubble to look for indicators of elements and compounds that are typically found in association with living things on earth. So far, we have only been able to send probes to a few planets in our own solar system. Recent news of water on Mars is exciting news that might indicate life is either there now or existed in the past. We don't know if the fact that having the same chemicals means the chance of finding life there is higher.
Searching for intelligent life involves sending out signs that we exist, and looking for signs that would indicate intelligent beings. Sending out the "golden record" on Voyager is an attempt to send information about us to other species. Indicators of intelligence we could detect might be an artificial satellite, use of radio or other waves in a way that seems to communicate information, or some sort of artifact that can't be accounted for by any other means. Carl Sagan organized SETI (Search for Extraterrestrial Intelligence); one method used is that there is constant monitoring of any potential incoming signals that show a pattern indicating intelligence. A problem here would be that we have no idea if we are in range of any signals.
A problem common to both searches is the sheer size and age of the universe. Even if intelligent species exist, there has been an extremely long time frame for those civilizations to have formed and died out. We humans have only had enough self-awareness for 10,000 years or so to even think to look for other intelligent species. Although we are finding more and more planets that look like they could support life, the chance of an intelligent species'"lifespan" overlapping our own is slight, let alone being anywhere near us in the universe.