[horo1988]

I did this experiment and have no clue what they r trying to teach me.

-Light your candle, and allow it to burn for 1 minute.
-Quickly lower a white 3" x 5" index card (held horizontally) down into the candle flame.
-Hold the card in this position until the upper side of the card begins to scorch, but not until it catches on fire. Hold it steady.
-If it does catch on fire, place the burning index card in a beaker, and try again with a new card.
Note the scorch pattern on top of the card.

Source: nasaexplores.com
All I saw was a yellowish brown circle on the card.

Can somebody please give me some hints? What r they trying to show us?

[agrobert]

I would assume they want you to understand how the flame has different concentrations of heat that dissipate along a radius as you leave the center of the flame.