Well, I could pretend that we all know about ancient Greek pronunciation, but the real truth is that it's all hypothetical.
We don't actually know how ancient Greek was pronounced, because we weren't there to listen in, and no one had invented any recordings.
We can assume the pronunciation was a certain way based on the letters, the names of the letters, the way the words were represented in other known writing systems, using modern Greek, Latinised versions of words, all sorts of things. But the REAL truth is we just don't know.
But I think that ancient Greek was a very logical language - in my considered opinion, it's unlikely that they would have used any silent letters.*
*Unless they were looking into the future and did it specially to confuse you, Salmotrutta!