Panspermia is a concept suggesting that life on Earth may have originated from microorganisms brought here from space. However, Bill Bryson in "A Short History of Nearly Everything" points out two main issues with this theory. The first problem lies in the lack of evidence for extraterrestrial life, making it difficult to validate the idea that life could have been transported from elsewhere in the universe.

The second problem concerns the practicalities of surviving cosmic travel. Microorganisms would need to endure extreme conditions like radiation and temperature fluctuations in space. Bryson underscores these challenges, arguing that while panspermia is an intriguing possibility, significant scientific hurdles remain that need to be addressed for it to gain acceptance.