Answer:
Well, movies and TV shows would have you believe they might look a bit like us—albeit, with big (bald) heads, green skin, and humongous eyes. But we weren't satisfied with that old cliché. So, we decided to ask the foremost alien experts—sci-fi authors, science experts, E.T. buffs—what they think aliens really would look like.
The problem is that figuring out what aliens will be like isn’t so easy. We have only one example of life – life on Earth – to learn from. To see why this is challenging, imagine we wanted to learn about butterflies.
Normally, we would look at as many butterflies as possible, and figure out from all those examples what things are true of all butterflies. We might learn that butterflies can come in a range of different colours and sizes, but that all butterflies have, for example, two antennae and six legs. If we only looked at one butterfly, say a Monarch, we might wrongly predict that all butterflies were orange and black.
Similarly, with only one example of life (life on Earth), it’s hard to know which features of life are universal and which are special to Earth. Here, all life is carbon-based and needs water. Is that true for all aliens, or a special feature of life on Earth?