N0vember asteroid approuching the world INSIDE between the moon and us that close! is this a worry

How accurate can the scientists be? 400 metre ball, if hits us will be same as 6000 atomic bombs simultaneously. Whats your thoughts?

Despite the surveillance of near space, asteroids do occasionally sneak up on Earth. But those are new ones that hadn't bee discovered before. Astronomers (or some of them) know about the orbits of the already-discovered asteroids, and they can predict when one of those will hit us. You'd hear about it, certainly. But there's always a chance we'll get hit by something we have never seen before.

A typical impact speed for an asteroid would be 30 kilometers per second. Given an average density of 2800 kilograms per cubic meter, a 400-meter diameter asteroid would convert 4e19 Joules of kinetic energy into heat upon impact. That's about 10000 megatons TNT equivalent. A typical nuclear bomb has about 20 megatons, so your estimate is pretty good.

Assuming you refer to 2005 YU55, no, it isn't a worry. JPL calculates that this rock is no threat for at least another hundred years. Orbital mechanics is a well-established set of principles, so you can rest easy.

As for "6,000 atomic bombs," I'm not even sure where you got that number. A 400-meter asteroid, if it were to collide on land, would probably do severe local damage, maybe moderate damage out to a regional level, but not much else.

no, this is not a worry. the path of know asteroids not expected to impact the earth have high degree of confidence. I believe scientists can be accurate--several manned moon missions and missions to outer solar system--high precision in judging orbits and trajectories.

We had something smaller approach Earth only 0.1 lunar distance from Earth mid-March this year. You were entirely unaware of that, weren't you? Don't sweat it. Yes, scientists are and can be that accurate. They know not to drop too many decimal places