Astronomers and other scientists have been hard at work lately going through all the various doomsday scenarios that could possibly destroy us tomorrow, and ruling each of them out to show us that there's nothing to worry about. However, is there anything for us to actually worry about?
The planets of our solar system are scattered all around the Sun now, so there's no so-called planetary alignment. The galactic alignment among the Earth, the Sun, and Sag A* (the super-massive black hole at the centre of our galaxy) actually happened in 1998, and we're still here. An alignment between the Earth, the Sun, and the galactic equator makes no sense because we have been 'above' the galactic equator for years and continue to move away from it. Planet X and Nibiru don't exist, as we would have seen them by now or at least the effect of their gravity on the solar system. The Sun is quiet, and given that it takes around 48 hours for even the fastest coronal mass ejections to reach us, we would already be alerted to one if it was going to fry us tomorrow. There's no comet bearing down on us (although, fingers-crossed, Comet ISON will make a spectacular pass by us late next year).
So, what does that leave? What is there that actually could destroy us tomorrow?
Well, according to Prof. S. Jocelyn Bell Burnell — the British astrophysicist who discovered radio pulsars — while we don't see any normal comets on a collision course with the Earth, it is possible a 'dark comet' could be flying towards us.
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A dark comet — or black comet — is similar to a typical comet, in that it is a dirty ball of ice with a highly eccentric orbit around the Sun, however the ball is much more dirt than ice. This would make it much harder to see.
"Comets normally are big, dusty snowballs. A dark comet has not much snow and a lot of dust. They are much harder to get a handle on," she said, according to the Daily Mail.
If a dark comet the size of Halley's comet (11 km across and over 200 billion tonnes) struck the Earth, it would be the equivalent of a magnitude 10.4 earthquake — stronger than any earthquake ever measured in the history of the human race — which would destroy everything within 1,500 km of the point of impact. The atmospheric blast wave would incinerate everything up to around 2,000 km away, destroy everything out to about twice that distance, cause major damage out to around 5,000 km, and minor damage out to 10,000 km away. The rest of the planet would be relatively unscathed by the direct impact, however the strike would kick up so much debris into the atmosphere that it would cause a global collapse of the Earth's ecosystem as the Sun's rays are blocked from reaching the surface, and the rest of humanity would likely die a slow, lingering death over the next few decades.
Vulcanologist Dr. Dave Rothery, who is a lecturer at the Open University, believes that it won't necessarily be a solar eruption that takes us all out. An eruption right here on the Earth would serve just as well as the prophesied doom-bringer — the eruption of a supervolcano.
Likely the best candidate for this supervolcano eruption lies under Yellowstone National Park, in the northwest corner of Wyoming. There have been three super-eruptions from the hot-spot that currently lies under the Yellowstone Caldera — one 2.1 million years ago, one 1.3 million years ago, and one 640,000 years ago. The last time it happened, it blasted nearly a million cubic metres of earth, dust and ash into the atmosphere. If it happened again tomorrow, the effects would be quite similar to the supposed comet impact mentioned above — catastrophic, to say the least.
What are the chances of these events happening? Overall, pretty slim.
Even a dark comet could be detected before it struck the planet. Solar radiation tends to cause comets to start out-gassing, creating an 'atmosphere' of icy gas around them, shortly after they pass the orbit of Jupiter. Although the dark comet would be covered with dust, solar radiation would still have an effect on the ice inside the comet, and the closer it got to the Sun, the greater that effect would be. If it was about to have a close encounter with the Earth tomorrow, we'd still have a pretty good chance of seeing some evidence of it by now.
As for a supervolcano eruption, although there have these kinds of eruptions in the past, that is no indication that they will happen again in the future, as these do not happen with any regularity. Thus, we are not 'due for one.' There have been some powerful earthquakes in recent years, with several of them around the Pacific plate's Ring of Fire, and according to some geologists these powerful quakes have caused some swarms of smaller earthquakes in the Yellowstone area — due to the hydrothermal system under ground. However, generally earthquakes do not cause volcanic eruptions (unless the earthquake and volcano lie along the same seismic fault). There are reports in the news today of a volcano erupting in Russia right now, called Plosky Tolbachik, after lying quiet for nearly 40 years. However the eruption actually started three weeks ago, and it was a rather quiet one, so it was certainly nothing unusual.
So, should we be worried? Not a chance.