How many people do you know that have left a water bottle sitting in your car on a hot summer day? While it may not seem dangerous at all, scientists have shown that the plastic bottle can act as a lense and can actually create a beam of light intense enough to start a fire.

A video created by Idaho Power shows a bottle of water burning two holes in a car seat. Light consists of numerous photons and the plastic acts as a lense to direct the photons into one beam of light. The small point of concentrated energy can cause melting and burning.

Odile Madden, a materials scientist says she was surprised that even with the light passing through the window of the car, there’s still enough light and energy going through the bottle to cause burning. She says it is a good illustration of how much energy there is coming from the sun.

Sunlight that passes through the window and then a bottle of water will hit the seat of a car with about 600 watts per square meter of energy, about the same amount of energy from a small electric space heater. This can heat up vinyl seat material and cause it to burn.

For burning to occur, the liquid in the bottle must be clear so light can pass through it. This means that soda and juice drinkers can leave their bottles in the sunlight if they want, unless the soda or juice is clear.

For a water bottle to cause a fire everything must line up perfectly. A smooth, transparent bottle full of clear liquid must be placed at just the right point so that the light source and flammable focal point line up. Scientists say that while it is possible, the chances of it happening by accident are slim.