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I always Saw in movies ,cartoons every where that asteroids hit the earth at an angle 
(not 90 degree).

But Why ?

We are living in 3-dimensional world(probably more....) .So is there an every chance that 
an asteroid on one day would slam into earth at 90 degrees or is it happening at times

Or Is there any physics phenomenon that would prevent this from happening ?

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    $\begingroup$ I would guess that there is nothing preventing asteroids to hit Earth at an 90° angle, but all other angles might have similar probabilities. So the probability of an asteroid Earth at roughly 90°±1° would be small compared to the probability of all other angles. $\endgroup$ – fibonatic Jan 10 '15 at 3:42
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There is nothing that prevents the asteroid coming in at 90 degrees, but it is very improbable. To the extent that the asteroid velocity is large enough that the Earth's gravity doesn't change it, there is little solid angle around 90 degrees altitude. It is like a Rayleigh distribution where there is little area near the origin. To the extent that Earth's gravity changes the asteroid velocity, angular momentum is conserved and you need it to be (close to) zero to come in at 90 degrees.

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I will assume that the relative speed of the asteroid irt the Earth (centre) is between 0 and 2*30 km/s (I will not check the values ). The fall to Earth centre future position started a while ago from a distant position. The in fall will take a considerable time (how much? between __ and ___, put the numbers if you wish) . Admit that the Earth is only 1km radius: The angle between the surface and the asteroid is 90º, sure ?. But the Earth radius is much larger and the contact time is a little bit earlier than in the previous situation, and I will assume that the angle is near 90º unless the numbers __ to __ are 'on the contrary' . I admit that the above can be wrong (I used only my imagination), an the distribution of speeds and angles of impact deserve a detailed analysis. But the next sentence is valid, imo, and deviates the angle of observation very much from 90º.
The observer on the Earth surface, due to its rotation, is in motion between 0 km/s at the poles to 30 km/s (+-) at the equator, and in motion irt the asteroid trajectory. Due to this fact only at high latitudes the asteroid can be 'seen' as falling from 90º. Even if the asteroid had to be seen by an observer as falling from 90º then it will be perceived as an immobile star for a brief moment at zenit, and the brilliant trajectory that we observe in the meteorite fall could not be seen by that observer.
See also the Atmospheric_entry problem.

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Asteroids and the Earth are both traveling in orbits around the Sun.

The Asteroids that cross the Earth's path are in highly eliptical orbits, while the Earth is in a near circular orbit.

If you draw the two orbits on a piece of paper, they intersect at two points, but notice that the two orbits are not perpendicular to one another, and the two points of intersections are also not perpendicular to one another.

Also the speeds of the Earth and the Asteroids are not the same, so the colission if and or when it occurs will be very energetic. Energy = 1/2 Mass x Velocity Squared.

The probability that the Earth, and the Asteroid will be exactly on the same plane of the ecliptic is very very small, and the probability that it will collide exactly at 90 degrees, while being exactly on the same plane of the ecliptic is vanishingly small.

MikeClark Golden, Colorado, Usa

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I may be totally wrong, but I doubt that a 90 degree angle is ever possible simply due to the fact that the earth is always in motion. No matter what comes at it, it will have to hit it at some sort of an angle due to earths rotation. The only exception to this, I would presume, is if the object were headed straight towards either pole, where the rotation is static. If the object is headed perpendicularly towards the pole, it would maintain the same trajectory as the earth's spin will not alter the placement of the impact. Maybe???

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  • $\begingroup$ You are totally wrong, yes. The earth's rotation does not effect the impact angle. $\endgroup$ – Chris May 6 '18 at 23:56
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Let's try agreeing to a percentage. If 10,000, or even 100,000 "rocks" impact the earth, what would the estimated percentage of them striking at perfect orthogonal angles. Further, what would be the odds of 2 out of 2, 3 out of 3, 10 out of 10, or even 20 out of 20 rocks striking orthogonally? Given a larger asteroid, an impact that dead-on-center would probably be felt all over the planet (if it struck a land formation). Striking at an angle would increase the collision time, and significantly lower the force of impact. Lets say a 1 kilometer-wide asteroid has an orthogonal impact right over the Mariana trench in the Philippine Sea; is that part of the ocean "deep enough" to slow down the collision event? -- The ensuing tidal wave would obviously be felt by the entire planet (eventually--because all Pacific coastal manufacturing and shipping facilities would be gone), but given an impact of that magnitude, would the flood waters completely blow past the Panama Canal and spread to the Atlantic?

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