Last year, I posted about a mystery from the 8th century involving a sudden increase in Carbon-14 particles found in trees during the years of 774-775. Something hit the Earth with a powerful burst of energy that last all year.
One scientist believes that the source of that energy was possibly from a collision of two black holes, or neutron stars or something similar. This collision would cause a huge burst of gamma rays that would hit the Earth, bathing it in radiation, and causing the increase in Carbon-14.
But what are gamma rays?
All energy like visible light, radio, microwaves and ultraviolet are actually the same energy called electro-magnetic energy. The difference between X-rays and radio-waves isn’t the type of energy, but the wavelength. All E.M. energy moves like a wave, but shorter waves are more powerful, while longer waves are weaker. Even the colors red, green and blue have different wavelengths:
Red has a longer wave, while blue has the shortest.
And, in the same way, radio waves are very, very long waves, while ultraviolet and X-rays are much shorter:
X-rays are very short, powerful waves, so they can go through skin and make images used by doctors and hospitals. But, even stronger than X-rays are gamma-rays.
Gamma rays are quite powerful. Shorter wavelength gamma rays can go through up to 9cm of lead without trouble. Strong gamma rays like this can easy go through concrete, radiation protection, etc. Obviously, they’re extremely dangerous.
Thankfully gamma rays are rare. On Earth, they’re usually caused by nuclear reactors or in rare cases by lightning, but gamma-rays also come from space. For example, if a star explodes (mentioned here), that creates a burst of gamma rays, and these beams of energy travel trillions of kilometers before hitting Earth. Since we have the ozone-layer to protect us, usually there isn’t much effect.
However, an even stronger source of gamma-rays is when two high-energy bodies (two black-holes, two neutron stars, etc) hit each other. This creates an extremely powerful burst of gamma rays. Here’s a good NASA video that explains what happens:
Even if it doesn’t make sense, the video is fun to watch 🙂
These gamma-ray bursts are so powerful, that one burst can kill all life on Earth instantly if it is too close. Fortunately, the bursts happen very far away, so they usually don’t affect the Earth.
However, if that scientist is right, Earth was a little bit too close to a gamma-ray burst in 774-775. The effect was minimal, but it could have been much worse.
As the Japanese say, ギリギリ (close call).