natural phenomenon

But we still can't be sure it isn't some sort of natural phenomenon.

No known conditions in space would support it as a natural phenomenon.

"No one has ever seen a problem like this, and it may very well turn out to be a natural phenomenon."

I don't know who did it, or why, but this is not a natural phenomenon.

Fire is one of the most useful natural phenomena in the world.

Death is a natural phenomenon and the dead must be buried.

How is it they make use of a natural phenomenon for their dirty work?

Far more likely, you had accidentally come across a natural phenomenon.

A force of nature is a natural phenomenon that humans cannot control.

A natural phenomenon, you might say - but you'd be wrong.