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“At breakfast time I was sitting by the house at Vanavara Trading Post, facing north…. I suddenly saw that directly to the north, over Onkoul’s Tunguska Road, the sky split in two and fire appeared high and wide over the forest. The split in the sky grew larger, and the entire northern side was covered with fire. At that moment I became so hot that I couldn’t bear it, as if my shirt was on fire; from the northern side, where the fire was, came strong heat. I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few metres. I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn a part of the iron lock snapped.”
The quote above was taken in 1930 from an eyewitness named S. Semenov, who had been located about 40 miles south of the June 30, 1908 Tunguska event. A small asteroid or comet likely exploded above the Tunguska river in Siberia. The air burst flattened nearly 800 square miles of forest and shattered windows and knocked people off their feet hundreds of kilometers away.
Estimates of the energy of the impact vary, but it’s likely it resulted in somewhere between 3 and 30 megatons of TNT. A smaller but similar event shattered windows in another area of Russia, Chelyabinsk, last year.
Because the Chelyabinsk meteor happened in more modern times with many more witnesses, more data is available. You can use our asteroid impact calculator to make theoretical predictions of what might happen if an asteroid hits the Earth (or explodes in the air as it approaches). The actual mechanics can be quite complicated, so the observed effects may differ a bit from theoretical predictions.
The Tunguska Event of June 30, 1908, is likely the reason that June 30 is known as Meteor Day. Megaton-sized explosions of the size of the Tunguska event are rare, happening perhaps once every 300 years or so. Often these events happen over remote and sparsely populated regions or oceans, leaving no eyewitnesses. Even smaller events usually go unnoticed for the same reasons.
These days the media are really good at turning unlikely or obscure events into things that you should be worried about. Movies such as Armageddon and Deep Impact are a couple good examples of this. The chances of large impacts like those movies depict are highly unlikely, but they make for great drama.
In reality, large meteor impacts on Earth are rare. Far more common are meteor showers. Meteor showers have a peak on the same day every year. Each streak of light is the result of a grain of sand or perhaps a pebble-sized meteor moving tens of thousands of miles per hour and violently slowing down in the Earth’s atmosphere, usually burning up in the process. These meteors usually originate from the tails of comets, which leave the dusty “exhaust” in their wake. When the Earth passes through one of these exhaust trails each year, the meteors become like bugs hitting the windshield of your car. The best time to observe meteor showers is in the hours after midnight because this is usually when you are “looking into the windshield” of the Earth as it sweeps through its orbit.
Typically, a given meteor shower produces dozens of meteors per hour. The next meteor shower after June 30, the Pisces Austrinids, is not a great performer, usually only generating about 5 meteors per hour, all of which appear to originate in the southern constellation of Piscis Austrinus. A few other meteor showers may appear sooner, but they are such poor performers that they are not included here.
As we head into summer here in the northern hemisphere, you might want to familiarize yourself with our collection of meteor showers. It’s a nice family-friendly activity that just requires a dark sky and a blanket to lie on. When a meteor shower is happening, just lie down and look up. The meteors can appear in almost any part of the sky, seeming to fly away from a radiant point in a specific constellation for which that shower is named. My favorite shower is the Perseids, which peaks on or about August 12. The weather is usually warm and the meteors are often bright. Do you have a favorite?