The hot air around the object rises, and cold air fills up the emptied space. Whenever light from the objects come to you passing through this “arena”, it bends at different angles(refraction). This causes an illusion of objects being moved when seen. The same explanation is for twinkling of stars(atmospheric refraction).

Why objects like trees and houses appear shifting when sitting near a fire

When sitting near a fire, it is common to observe that objects on the other side of the fire appear to be shifting. This phenomenon can be attributed to various factors related to the interaction between light, heat, and the human visual system.

The Role of Heat

- The fire emits intense heat, which causes the air in its vicinity to become heated and rise. This rising hot air creates air currents that can distort the path of light. These air currents are commonly known as heat waves or convection currents.

Refraction and Shifting of Light

- When light waves pass through different mediums with varying densities, such as air at different temperatures, they can bend or refract. The heat waves generated by the fire cause the air to have different densities, resulting in the bending of light as it passes through these regions of varying density.

- As the light waves travel from the objects on the other side of the fire to the observer, they may encounter these regions of varying density, leading to the refraction of light. This refraction can cause the objects to appear shifted or distorted due to the bending of light rays.

Visual Perception

- The human visual system plays a significant role in how we perceive objects. Our brain processes the visual information received from our eyes and constructs a mental representation of the surrounding environment. However, this process is not always perfect.

- When the light rays from objects on the other side of the fire are refracted, they reach the eyes of the observer at different angles than they would in normal conditions. This change in the angle of light can confuse the visual system, leading to a perceived shift or distortion in the position of the objects.

Conclusion

In conclusion, the shifting appearance of objects like trees and houses when sitting near a fire is primarily caused by the heat waves or convection currents generated by the fire. These heat waves create regions of varying air density, leading to the refraction of light. The refracted light rays then reach the observer's eyes at different angles, confusing the visual system and resulting in a perceived shift or distortion of the objects.