It's called knowing basic quantum mechanics and perhaps it's how you define 'spark'. What do you think happens when molecules get hot anyway? They're not billiard balls. Orbitals get high and photons do fly.
Were you there when I learned physics and chemistry through experiments?
Be sure in the legal finger-pointing sense 'spark' is usually something that comes from outside. Kind of like how around 1980 in court, 8086 code was not 8088 code though the same PCDOS ran on both.