"Change is in the air. Nights are becoming cooler," Col said, adding that the days can be sparkling this time of year.

Col, of Kurri Kurri, said vapour trails dissect the sky when the "icy cold stratosphere descends into the flight path of the jets".

"I have a theory that vapour trails are the largest structures mankind creates but they are also the most ephemeral," he said

The vapour trails brought out the poet in him.

A tiny silver dart, a high flying 737, pulls a stark white vapour streamer across a million miles of clear blue sky.

It hangs motionless for a moment then begins to curve and undulate, a victim of the capricious jet stream winds.

Conspiracy theories abound about so-called "contrails", which are the same thing as vapour trails.

There's a nutty online myth that contrails are actually "chemtrails" - chemical or biological agents sprayed at high altitude by secretive government agencies for strange and sinister purposes.

In his book, Cockpit Confidential, US pilot Patrick Smith said the truth wasn't so fanciful.

"Contrails are formed when humid jet exhaust condenses into ice crystals in the cold, dry, upper-level air - it's not unlike the fog that results when you exhale on a cold day," he wrote.

"Contrails are clouds, you could say. Water vapour, strange as it might sound, is a byproduct of the combustion within jet engines, which is where the humidity comes from."

Nevertheless, the conspiracy theory gained so much traction that in the year 2000, federal authorities in the US - including NASA and the US Environmental Protection Agency - published a report to bust the myths. They re-released the report in 2015.

"Aircraft engines emit water vapour, carbon dioxide, small amounts of nitrogen oxides, hydrocarbons, carbon monoxide, sulphur gases and soot and metal particles formed by the high-temperature combustion of jet fuel during flight. Of these emittants, only water vapour is necessary for contrail formation," it said.

"Persistent contrails pose no direct threat to public health," it said, while adding "contrail cloudiness might contribute to human-induced climate change".

The US EPA added that it was "not aware of any deliberate actions to release chemical or biological agents into the atmosphere".

Topics read with interest the story in the Newcastle Herald on Wednesday about an apparent lack of soap in Newcastle High School's toilets.

A Topics spy sent us this little interaction.

The scene: A seven-year-old has just visited the bathroom.

Concerned uncle: "Have you washed your hands?"

Kid: "No [totally dumbfounded at the concept]".

Uncle: "Do you ever wash your hands if an adult hasn't told you?"

Kid: [blank look, still dumbfounded].

Uncle: "Don't they teach you at school? Do they get you to wash your hands? Any recent reminders?"

Kid: "No".

Uncle: [dumbfounded, watches nephew walk away].