I've just heard on the news that some comet named ISON is passing by the Sun. And they said that it will split and then it may hit us. They are citing Nostradamus prophecies and stuff. It appears that he predicted an event like this. Also they said Russia has put their armed forces on alert.
So, is there any chance it will head towards Earth? :)
Well, there are many objects out there that "may or may not" impact Earth. ISON (a "sungrazer," incoming from the Oort Cloud) is headed for a close roundabout of our Sun and may wholly or partially disintegrate or may come back round intact. Earth MAY pass through the remnants of very tiny particles of ISON's pass-through; most, burning up in the atmosphere and possibly illuminating high-up clouds, potentially causing a "glowing cloud effect." This does not mean humans on the ground will also glow or suddenly develop mutant abilities. Particles hit Earth 24/7. A similar panic existed when Halley's Comet swung through about a century ago. Read this:
"As Halley's Comet approached the sun in 1910, astronomers announced that Earth would actually pass through the tail of this comet during May of that year. They assured everyone that our planet was safe and suggested the possibility of some spectacular sunsets. Meanwhile, the doomsayers latched onto a potential link: if comets contain a poisonous gas and if Earth is going to pass through the comet's tail, then the people of Earth were in serious danger. Numerous newspapers actually published this story. Astronomers countered by saying the material in the tail was so spread out that there could be no ill affects, but few newspapers published this accurate information. Interestingly, a minor panic arose in some cities and entrepreneurs took advantage of it. They sold "comet pills" which were said to counter the effects of the poisonous gas. The pills sold like crazy. On May 20, after Earth had passed through the tail, everyone who had taken the pills was still alive...but, then, so was everyone else."
As for a direct hit (in ISON's current state), it does not seem likely.
Firstly, you must determine the reliability of the "they said" source you refer to. Although, NASA and certain nationally funded US Astronomical resources are offline or somewhat stagnant and delayed in data posting, there are other world-wide observatories still contributing daily data on ISON. My advice is to compare a variety of resources and images and certainly, not solely rely on conspiracy and non-scientific online sources. Although, there may be a human desire for conspiracy and potential doom, cross-referencing multiple Science-based resources will help you determine for yourself any potential hazard ISON may or may not represent. I say this so you might have an opportunity to include/compare scientific data with any other facts and or metaphysical/spiritual/theoretical data or inclinations you may have already aligned yourself with.
FYI: I am not a scientist but I often try to include scientific understanding and knowledge on events that contain potential to change the world as we know it. I am not waving off your concerns in the way some pure Scientists might do to a deeply Spiritual person (or vice-versa). I am a deeply Universal and Spiritual person and I think I understand "where" you are asking you question from.
WARNING: There is a lot of nonsense out there, especially, on YouTube. Be cautious of tight editing, doom music, frozen images with graphic additions added and Biblical/other religious cross-referencing. Anything you find out there like that, is likely, complete and utter nonsense; usually geared to increase the self-importance of whomever posted the article.
I have always been open to greater purpose for ISON but to date, ISON has not demonstrated anything exceptionally peculiar that would indicate it is anything but a comet coming in for a Sun dive. There are a few independent suggestions (metaphysical & conspiracy) suggesting ISON was ejecting "controlled jet outbursts," as if, to imply an intelligent control for spacial guidance. However,it has not been wholly determined whether those suggestions are devised, for promoting a particular agenda, or factual.
Now, to answer your question "will it head towards Earth?"
Well, if it breaks apart, the possibility MAY exist any broken parts COULD, potentially, fall to Earth but we do not have that exact data yet, as the comet has not knowingly broken apart. Again, currently, the full object (ISON) trajectory is calculated to make a Sun swoop, at about 730,000-ish miles from the Sun but this does not include any additional calculations should the comet slow, reposition or break apart prior to Sun approach or what ISON (or what is left of) do upon re-emergence from the Sun orbit.
It is a Java app that can be used to model the orbits, and is used and vetted by hundreds or thousands of astronomers every night. If you animate the orbit, you will see the you will see the nearest point is about Dec 26, 2013, and the earth distance is 0.428 AU.
You can also confirm from the app that the uncertainty in the orbits is very low.
In other words, it's very clear that the comet is going to miss us.
But the larger the chunk of the comet, the less likely it is to be diverted very far away from the main body, so a large chunk won't be diverted enough to hit the Earth.
Scientists (and amateur astronomers) are hoping that a fair amount of dust-sized pieces of ISON might make it to Earth's atmosphere in mid-January (after our orbit has carried us the tens of millions of kilometres the comet will miss us by). That might make a nice meteor shower, which would be lovely.