[Davidzheng]

How is it clear at all that extraterrestrial life is more likely carbon based than not. Is there any evidence other than it's the only one we know?

[ziddoap]

PBS Space Time has a very good & informative episode covering this. I'll try to dig it up.

Most elements are missing some key properties that carbon has.

Silicon is the next most-likely element, but it's still missing out on a few properties that carbon has.

Here:

https://www.pbs.org/video/what-if-alien-life-were-silcon-bas...

Or on YouTube:

https://www.youtube.com/watch?v=469chceiiUQ