"Can someone give me a hand with the facts."
Facts are fun:
Earth travels around the Sun at an average orbital speed of:
29.79 km/sec.
[To turn 29.79 km/sec into miles per hour, you times the kilometers by .621 and times by 3600 (that's how many seconds there are in an hour):
This comes out to be 65,598 mph. Which is about 1000 times faster then cars traveling on a freeway or about 100 times faster than bullet.]
More facts on Earth:
Here
In the above link it mentions Earth's escape velocity: 11.18 km/sec
This means that if some object is accelerated to 11 km/sec it will leave earth gravity effects. It also means if you were to "somehow to drop any object so that it falls and hits earth" it would hit the Earth at 11 km/sec {in order to "drop an object on Earth" the object would first need to be travelling at the same orbital speed as Earth, but this isn't the way that objects would actually hit earth- I bring it up merely to indicate that roughly the slowest an object *could* hit earth would be around 11 km/sec}. Rocks (NEOs) which are near Earth will generally hit Earth somewhere around 20 km/sec. Objects which intersect Earth orbit and have their orbit extending out to Jupiter and beyond are going to have a much higher impact speed.
Any object which is say made of any solid material (rock, frozen water, or whatever) which is larger than say 10 miles in diameter and impact Earth at speeds of 11 km/sec or higher will have a serious affect upon everyone on the planet. Object travelling higher velocity will have more energy and create a much larger explosion. Comet are objects which have part of their orbit going beyond Juptier. They are in a highly eccentric orbit with the Sun (they come closer and then further away from the Sun).
Comets
Halley's Comet Diameter is : 16 x 8 x 8 km
Halley's Comet
If Halley's comet hit earth at would have global affect- even a near miss would wreck your day. There are millions of objects the size of Halley's comet in our solar system, a few of them are in highly eccentric orbits such as Halley's comet (a few relative to millions; so, somewhere in the order of thousands).
Since objects can have different orbital inclinations- it's quite possible for an cometary object to come closer to the Sun than Earth orbit yet at the same time not come anywhere near Earth's orbital path (less alone our planet- we live a 3 dimensional existance). And even if an object crosses our orbital path, the can just as easily be on the opposite side of the sun as be near the object. In other words Space is a big place. Worrying about one object impacting Earth is NOT THE PROBLEM, it's the thousands of objects which intersect Earth orbit which are the problem. Given enough time the chance of one of these thousands hitting is a near certainty. Car size rock hit earth monthly, house size rocks hit less often. Planet size rocks won't hit Earth (or even get closer than Mars or Venus:)