... a needle would hit the earth at the speed of light?

We are used to consider dangerous objects from space as very big like for example asteroids or black holes. But could also very small objects become dangerous for us, like an ordinary sewing needle if it is fast enough?

First of all, nothing that has any weight can be accelerated to the speed of light. This is because the faster an object travels, the more its mass increases. At the maximum of speed, the speed of light, the mass of a needle would be infinite big, which is just not possible. That’s why for this article, we consider the needle to be 99,99% as fast as light.

Objects from space are crashing into earths atmosphere every day and we don’t even notice them most of the time. We don’t notice them because they are moving very slow compared to universal scales. But an object accelerated to nearly the speed of light could cause some serious damage, even though it’s small. But it’s all about speed. We experience this in our daily life too. For example, if a car hits a human with about 50 km/h, the human is very likely to survive. But if the car is just a little bit faster (63 km/h), chances are very high, that the human dies.

So, if a needle with this enormous speed would enter earth’s atmosphere, it would not burn or explode in the air, because it’s simply too fast. The danger of the needle is its kinetic energy. The kinetic energy of a needle at the speed of light hitting the earth equals an object weighing 100 tons that is falling from a 15-story building. Once the needle hits the ground all this energy will be released in a massive explosion with the power of two nuclear bombs or 43 tons of TNT!

If the needle would hit for example New York, most parts of the city would be destroyed and in a radius of nearly two kilometers around the detonation all people would die. Furthermore, all windows would burst in a radius of 4 km and the explosion would cause a massive crater.

This would cause almost unimaginable destruction and the consequences would be terrible. But fortunately there are no needles or any other objects flying around in the universe at the speed of light, so you don’t have to worry!