If a 1km wide asteroid hit the Earth?

Yes, you would see it coming and then the rings on Uranus would start quivering.

Ask yourself a few questions. How fast is an asteroid traveling? How far away can you see a 1km rock? Day or night?

Keep in mind we can see the ISS clearly and its just a few hundred feet long. It is also a couple hundred miles up. If something the size of the ISS were hurtling towards us at 10miles/sec, it would be easily visible well before it hit the atmosphere and doubtless afterwards.

It would be too quick to notice and you would be dead from the intense radiation of it entering the atmosphere before it hits. You wouldn't last even a fraction of the 3 seconds.

We would see it coming. The sound itself would give it away. But the sound that will reach us will be the sound that has already happened since the Asteroid is moving at such a fast speed.

unlikely because the earths atmosphere will vaporizer the astroid . you might be able to see the vapourised trail

yes

its only impossible to see an object if its travelling with speed of light and that's merely impossible

Maybe u can see it miles away cuz it's freaking km wide .....

Look on the bright side:-D

It kind of depends on velocity.