All life has the light flash at the moment the egg gets fertilized. Book of John speak of this.
“And the light shineth in darkness; and the darkness comprehended it not.” John 1:5 KJV
“Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life.” John 8:12 KJV
“Ye are the light of the world. A city that is set on an hill cannot be hid.” Matthew 5:14 KJV
“That was the true Light, which lighteth every man that cometh into the world.” John 1:9 KJV

When sperm and egg meet, ‘fireworks’ go off at microscopic level | CBC News
When you meet someone who ignites your passion, it can feel like fireworks are going off. New research by Northwestern University researchers, published in the journal Scientific Reports, shows that when human sperm meets an egg, it can also set off sparks.
www.cbc.ca

Scientists witness ‘flash of light’ during conception, say discovery could aid IVF
For the first time, researchers have witnessed the exact moment conception occurs— and have recorded the ensuing explosion of sparks that form when sperm meets an egg.
www.foxnews.com