Once again, we – on Earth – will be passed by a Near-Earth Asteroid. This time on April 12^{th}. Don’t worry! Its nearest approach will be about 38 thousand kilometers (23,800 miles). For reference, the diameter of the Earth is about 8000 miles. The size of this is a rock that you could hide a Ford Expedition behind.

Near Earth Asteroid…Date……….Miss Distance…..Velocity (km/s)…..Diameter (meters)……

Figure 1: Parameters of Near-Earth encounter with 2021GW4

Figure 2: Orbits of Earth, the Moon and 2021GW4. These are calculated without the Earth’s gravity effect on the asteroid’s orbit. The red line suggests what might happen in reality.

The question on everyone’s lips is always what will happen IF this asteroid were to collide with the Earth. It will not do that, OK?

People just love to imagine catastrophe and asteroids are their greatest opportunity. So, I have developed a macro to calculate such a disaster given the mass of the asteroid and the relative velocity of that asteroid with the Earth. Now, there are many variables (also referred to as “parameters”) that effect such calculations and I have made many assumptions – based on “average” values of density – and so forth. So, if you calculate a different number, please let me know – and show your work!

With all those disclaimers, I will say that the asteroid’s impact – if its course were to coincide with the position of the Earth (which WILL NOT HAPPEN, by the way!) – would generate an explosion equivalent to 1.3 kilotons of TNT. This is calculated by the Kinetic Energy using the estimated mass of the NEA and the velocity from the table in figure 1.

For reference, the bombing of Hiroshima yielded an explosion estimated at 12 to 18 kilotons. For an extreme example the “Tsar Bomba” detonated by the Soviet Union in 1961 yielded about 50 Megatons (50,000 Kilotons). So, we have already done far more damage on our own than this particular object could heap upon us.