If there were a large object, say a meteorite falling straight down where you are standing, what kind of warning would you notice? Would there be an accompanying sound that could warn you? Or would you not know until it's too late? Plus we ask, can you catch cancer?....
Assuming the meteorite was travelling at supersonic speeds, there would be no sound until after the impact. So, you would have to rely on either tracking the meteorite before it impacts Earth with our NEO warning system, or watching the flash of light as the meteorite enters our atmosphere.
You can always tell if you're on a collision course with anything by a simple rule known as "constant bearing, decreasing range."
I think you might feel a shock wave a few milliseconds before you are squashed and you might notice a bright light from re-entry.
air compression? CZARCAR, Wed, 7th Mar 2012
Ah. But the air between you and the asteroid hitting the top of the atmosphere will be compressed to a fraction of its size in about 1/100 of a second. This will raise the temperature on top of his head to about 8000K. So, theoretically you will know the meteor will hit you before it does as all your hair will be burnt off just before impact. Of course, you'll be to busy being incinerated and turned into a plasma to bother noticing. steve, Mon, 5th Nov 2012