Quora .

This question originally appeared on Quora. Answer by Gary Larson.

Ultraviolet light is the minimum frequency in the spectrum of electromagnetic radiation that can produce ionizations. That is, this is the least energetic form of radiation that has enough energy to actually knock an electron out of an atom. When an ionization occurs in the right type of molecule (a DNA molecule), this may create a break which will alter the way the DNA codes for replication. When the right sort of mutation occurs, the cell may begin to divide indefinitely - and you have cancer.

In reality, most DNA breaks are repaired by enzymes designed to maintain the integrity of life’s blueprint. It probably takes more than one break in a strand of DNA to cause a cell to become cancerous. Most cells that become cancerous are recognized by our immune system and are eliminated. (We probably have thousands of cells that become cancerous every day, but our immune system takes care of them. When random events cause mutations which give rise to a clone of cells that our immune system can’t recognize, then they proliferate - giving rise to the hundreds of forms of known cancers.)

Minimizing ultraviolet light exposure is one of the most efficient ways to prevent cancer. Sun-screen, hats and other clothing that minimize our skin’s exposure to ultraviolet rays will decrease the probability that we will develop skin cancer.

Most skin cancers are curable with surgical removal or radiation therapy (basal cell carcinomas and most squamous cell carcinomas), but malignant melanoma is an exception. It requires aggressive local treatment and is almost always fatal once it metastasizes.

More from Quora: