on a cool night with no wind people facing a campfire feel a breeze on their backs. why?

The campfire is hot

The air above the fire is hot
so its density decreases
so it rises
air rushes in from all sides to replace it
as it rises.

Sail much?

a coion and a piece of glass are both heated to 60 degress celsius . Which will feel warmer when you touch it?

sorry, I do not know what a coion is.

whichever one has a higher heat transfer coefficient will transfer heat to your hand faster.

a coin and a piece of glass are both heated to 60 degress celsius . Which will feel warmer when you touch it?

The perception of a breeze on their backs while facing a campfire on a cool night with no wind could be due to a phenomenon called convection. Convection occurs when there is a temperature difference in the air, causing it to move.

Here's how it works:

1. The campfire generates heat, which warms the air around it. The air in contact with the fire becomes hotter and rises due to decreased density. This process is called thermal convection.

2. As the hot air rises, it creates a convection current. The rising hot air creates a region of low pressure above the fire.

3. To balance this pressure difference, cooler air from the surroundings starts to flow towards the low-pressure area above the campfire. This cooler air is often felt as a breeze.

4. Since people are facing the campfire, they may perceive the airflow as a breeze coming from behind them.

It's important to note that even though there might not be any actual wind present, the convection currents created by the temperature difference can produce a sensation of moving air.