 Carl Sagan once proclaimed that her earth was a pale blue dot, suspended in a sunbeam in a vast cosmic arena. Just how true are the words of this great scientist though? Is Earth just one of the many planets in the dark endless universe? Or is there something special about this pale blue dot? In our universe we estimate there to be about one septillion planets with an estimated 800 billion to 3.2 trillion planets in our Milky Way alone. Yet among all those planets we know only one to harbor active life forms, Earth. So what do we have that these planets presumably don't which makes us alive? Well, in order for a planet to sustain life certain conditions must be met. Yes, you have the basic triangles of needs such as food, water, and shelter. But it's way more complicated than that unfortunately. In addition to the triangle of basic needs a planet must be an appropriate distance away from the star they orbit in order to ensure appropriate temperatures and radiation exposure. Additionally the planet must have an atmosphere consisting of gases like carbon dioxide which shield the planet from radiation and help the planet to maintain a steady surface temperature. Furthermore a planet needs to be made of rock in order to have a solid surface for life. Planets like Jupiter, Uranus, and Neptune are out of the candidates for habitable planets. This also goes below the surface too as a planet in addition to the conditions listed above must also possess a molten core in order to facilitate the cycling of raw materials and generate magnetic fields to shield the planet from radiation kind of like what we have here on Earth. When we take such factors into account we get an estimated 4 to 5 trillion habitable planets in our universe with about 40 to 50 billion of them in our Milky Way alone. Now as impressive as those numbers are they're just a tiny sliver of all the planets in our universe and yes I will admit with over 1 trillion habitable planets the chances of there being life on one of those planets is certainly high but this brings up another question, what kind of life? As exciting as the prospect of being headed black eyed green aliens existing are we must also come to accept the not as exciting alternative that extraterrestrial life forms may be no more than just mere bacteria and other primitive life forms since that's what the evidence we have points to. You see in 1984 a meteorite called ALH84001 was found in Antarctica. Closer inspection revealed that the meteorite was indeed a Martian meteorite that was a couple of billion years old. Scientists still flourishing with curiosity scanned the meteorite. They found remnants of microorganisms such as organic molecules called PAHs to compounds such as iron sulfide and magnetite produced by anaerobic bacteria. Scientists came to the conclusion that Mars at one point was likely home to life though it be in the form of primitive microorganisms. So I guess we did get our wish just not in the way we expected. Fret not though we have made efforts to try and detect signs of intelligent life. One of the main ways we do this is by using a radio telescope which helps to detect and amplify weak radio wave signals for analysis. Though this method has helped us make a lot of advancements in the field of astronomy it is yielded nothing in terms of our search for intelligent life. Why have we detected nothing yet? Could it be that any existing alien civilization out there is too primitive to engage in interplanetary communication or maybe they possess our level of intellect but are too far away for the radio waves from our planet to reach them? After all, as fast as the speed of light is, it's no match for the vast distances in the cosmos or maybe they are more advanced species than us and are sending out signals through a higher form of communication which we haven't discovered yet. Whatever the answer is, one thing is for sure. As of now there is not much we can do in the search for intelligent life other than to just keep listening and look up at the night sky. If you really enjoyed this video then be sure to leave a like and subscribe. Also if you wish to learn more in depth about alien life then be sure to tell me in the comments below and I'll gladly take your request into account. Until then, be sure to stay tuned for more science videos.