Gamma rays are a type of electromagnetic radiation, just like X-rays, radio waves and visible light. Like light, gamma rays are composed of photons, which behave in some ways like a particle and in other ways like a wave. Of all types of electromagnetic radiation, gamma waves have the shortest wavelength, highest frequency and most energy. Scientists have harnessed gamma waves for such purposes as killing cancer cells and understanding the universe, but they can be very dangerous tools.
Gamma rays are extremely powerful. The incredibly high-energy photons can ionise atoms they come in contact with. That means they knock electrons off the atom, leaving them as electron-deficient ions. If the atoms in question happen to be part of a cell in a living organism, this can kill the cell. Doctors aim focused beams of radiation, including gamma rays, at tumours. The high-energy radiation either directly damages the DNA of the cancer cells or creates highly reactive free radicals that in turn damage the DNA of the cancer cells, killing them.
Scientists measure gamma radiation in their attempts to understand how the universe works. The first gamma-ray telescope was carried into orbit on the Explorer XI satellite in 1961. In the late 1960s and early 1970s, gamma-ray detectors on the Vela satellite series recorded bursts of gamma rays from deep space. Scientists are still trying to determine the source of these bursts of gamma rays and hope their continued observation will reveal clues as to the origins of the universe and its rate of expansion.
These gamma ray bursts release an enormous amount of energy. Fortunately, they typically originate thousands of light years away. But scientists speculate that a gamma burst from as far away as 6,500 light years could still wreck havoc. And there is significant evidence that they already have. About 440 million years ago, about 70 per cent of all marine species disappeared in a massive extinction, and scientists think a gamma burst may have been responsible. It could happen again, eventually, but nobody should panic. The likelihood that one of these bursts could happen again during the next 1,000 years is very close to zero.
Dangers of Radiation Exposure
While the ability of gamma rays to kill cells by breaking down DNA has been exploited as a cancer therapy, gamma radiation can kill regular cells, too. That's why cancer patients undergoing radiation therapy get sick. Long-term exposure to low levels of radiation is associated with increased risks for cancer. Gamma radiation is teratogenic, and pregnant women exposed to gamma radiation have an increased risk for birth defects when they deliver. Acute exposure to gamma radiation, that is exposure to a high level of radiation in a short period of time, can cause immediate negative effects, including nausea, hair loss, skin burns and diminished organ function resulting from damage to cells and tissues. Exposure to a lethal dose of gamma radiation will usually kill the victim within two months.