When sperm meets egg, a bright flash of light occurs, signifying a successful calcium/zinc reaction

From the story in the UK Telegraph here:

The bright flash occurs because when sperm enters an egg it leads to a surge of calcium which triggers the release of zinc from the egg. As the zinc shoots out, it binds to small molecules which emit a fluorescence which can be picked up by camera microscopes.

It's an old saying that "you began as a twinkle in your father's eye".

So began the universe.

And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness. -- Genesis 1:3f.