To deviate an asteroid you need…

In the Solar System, collisions between minor bodies occur frequently; in fact, hundreds of thousands of tonnes of dust and small-sized stones rain down on Earth, wandering residues of these vigorous interplanetary collisions.
Due to the influence of the bigger planets, some minor bodies can, in fact, deviate from their original orbit and undergo changes that cause them to come into collision with other objects. In particular, asteroids are continuously subjected to the gravitational pull of Jupiter which, in the majority of cases, provokes their ejection from the Solar System or, worse still, their destruction on the Sun’s surface. A part of these asteroids however may become a NEA (Near-Earth Asteroid), i.e. asteroids that orbit close to the Earth. Asteroids that might have catastrophic consequences on our planet are those with a diameter greater than 1 km; despite the low probability that they might collide with the Earth (from 0.75 to 6 impacts every million years) it has been proven that in past eras asteroid impacts have caused mass extinctions on Earth.
How can we avoid collisions with a dangerous asteroid? One of the traditional, more popular methods is the bombardment at a safe distance. Its aim is to reduce the dangerous object into fragments and to change its course. However, there are less violent means of deflecting an asteroid: covering it with sugar, for example! This solution is based on the physical phenomenon known as Yarkovski effect: during its period of rotation, the surface of an asteroid does not absorb the light coming from the Sun uniformly; subsequently it re-emits it in the form of thermal radiation. The variations in the emission create a thrust in the opposite direction as a result of the action-reaction principle. Despite its modest entity, the thrust is applied continuously for a long time and it produces significant effects. From this we can infer that it would be possible to deflect an asteroid’s path by modifying its capacity to absorb light: it would be sufficient to cover a thousandth of its surface with white dust. This demonstrates that with politeness you can get whatever you want.

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