<img src="https://d5nxst8fruw4z.cloudfront.net/atrk.gif?account=iA1Pi1a8Dy00ym" style="display:none" height="1" width="1" alt="" />
Skip Navigation


Scientists use a variety of methods to locate and describe exoplanets.

Atoms Practice
Practice Exoplanets
Practice Now
Are We Alone in the Universe

Are We Alone in the Universe

Credit: NASA
Source: http://en.wikipedia.org/wiki/File:Andromeda_galaxy_2.jpg
License: CC BY-NC 3.0

If you’re like millions of people, you look up at the night sky and you ask, “Are we alone in the universe?” Not surprisingly, scientists are looking for the answer. But how are they looking? And what are they looking for?

Why It Matters

For nearly all of Earth history, life was simple, single-celled. You wouldn’t know it was there unless you had a microscope. It would certainly be hard to detect from a far-off planet!  Yet scientists are looking for signs of life on other planets and moons in our solar system. Some scientists are even looking for life in other solar systems. Looking for intelligent life may be easier than finding microbes. So far, with all this looking, no one has found any aliens. But there are lots more places and ways to look.

Credit: NASA
Source: http://en.wikipedia.org/wiki/File:ALH84001_structures.jpg
License: CC BY-NC 3.0

Meteorite Allan Hills (ALH84001) shows structures that some scientists believe to be bacteria-like life forms that have been fossilized (found in Antarctica, 1984) [Figure2]

Explore More

With the link below, learn more about the search for extraterrestrial life. Then answer the following questions.

  1. What do astrobiologists study?
  2. What are the two major topics that astrobiologists study?
  3. What are two reasons that scientists think that planets or moons with water are the most likely to have life?
  4. How do astronomers tell if a planet in another solar system has water?
  5. How do SETI-project scientists look for life? What type of life are they looking for?
  6. As yet scientists have not found life elsewhere in the universe? Do you think they will in your lifetime?

Image Attributions

  1. [1]^ Credit: NASA; Source: http://en.wikipedia.org/wiki/File:Andromeda_galaxy_2.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: NASA; Source: http://en.wikipedia.org/wiki/File:ALH84001_structures.jpg; License: CC BY-NC 3.0


Please wait...
Please wait...

Original text