As a pilot for over ten years, I get asked the above question by many people. What is the point in dimming the cabin lights for takeoff and landing?
It is human nature to ask this type of question, especially when there is doubt or fear of flying mixed into the situation.
We like to say that about 50% of the world has a fear of flying, and that 20% of the remaining half develop a fear of flying on their first trip, usually because they do not know what is going on around them.

Over the next few articles, in an effort to make you more well informed as passengers, I'm going to cover the more common questions about air travel and also try (maybe not the best descriptor given the circumstances) to explode some of the common myths associated with aircraft and the people who operate them.

Flying is one of the safest forms of travel and they say that you have a better chance of being struck by lightning while climbing out of a car that has just been hit by a falling piano, then you have of being in a plane crash. 

Getting down to statistics for a moment, we have learned that take-off and landing are the most dangerous times within any flight. The seriousness of the issue can be seen in how airlines go through a lot of preparation to make sure that passengers are fully briefed on evacuation procedures and that the cabin is secure. 
One of the things that we do, is to dim the cabin lights for takeoff and landing. There are a few reasons for this.

First of all, if you can remember the last time you were on a flight, the cabin crew as part of their safety brief, told you that in the event of an evacuation that you could follow the floor-path lighting to your nearest exit. These marker lights (or sometimes a luminous green guide-line) are much easier to see when the cabin is dark.

Secondly, the primary element of dimming the cabin lights, is borne out of your body's reaction times to a change in lighting. Your eye uses two sensory elements to see. Rods and cones.
In bright conditions, your eye uses cones and when it gets dark, your eyes switch to the more efficient rods in order to see in the dark. 

But, take a moment to remember the last time you were in a bright room and someone turned off the lights. Could you see in the dark immediately, or did it take some time for things to become visible? 
This time delay in being able to pick up shapes and see in the dark, that biological switch from cones to rods, is the main reason why we dim the cabin lights. 

If the cabin was bright, and we needed to evacuate the aircraft on a dark night, you would not be able to see well enough or fast enough to exit the aircraft safely. Most cabin crews aim to get you out of a fully loaded airplane in under 60 seconds. Trying to do that when you are trying to fumble and grope your way through the cabin increases this time significantly, therefore jeopardizing your safety and that of your fellow passengers.

Dimming the cabin, gives your eyes time to adjust to low light conditions and also reduces your chance of exiting the aircraft and then walking into a hole in the ground or falling over a low wall. Trying to drag yourself away from a burning plane while suffering a broken leg is not the most comfortable of places to be.

Just to alleviate your concerns, however, the chances of you ever being involved in a cabin evacuation is even less than being a part of the piano scenario that I spoke about earlier. 

In the meantime...sit back, relax and enjoy your flight.