# Incoming!

The meteor that flew over Chelyabinsk Russia recently certainly gained media attention, and it now has its own wiki page. This was one instance of an impact event, which have been occurring throughout the earth’s history.

## Energy on the move

All objects entering the earths atmosphere from outer space, have one thing in common - a lot energy.

Energy from being on the move is called Kinetic Energy.. The amount of kinetic energy an object has, is related to:

• its weight
• and its speed.

We can describe this relationship with a formula.

## Captured as a formula

A formula is just an equation that tells us how to calculate something. They consist of numbers and variables - which we plug our values into to get the answer.

The formula for energy from being on the move (a.k.a. kinetic energy) is:

$KE = 0.5 \times \, mass \, in\, kilograms \times (speed \, in \, meters \, per \, second)^2$

For our purposes, mass can be considered as the weight of the object, and speed we all know.

The units being used here for mass and speed are known as SI units, which are commonly used in science. If you don’t think units matter, then this might make you have second thoughts.

## Baseball energy

As not that many people regularly handle a meteorite, lets take a more common object – a  baseball, and calculate its kinetic energy when thrown as a 100 mph heater:

$KE = 0.5 \times \, 0.145 \, \times (44.704)^2 \, = \, 144.887$

Energy is measured in a unit called Joules (J), so 144.887 J

The nice thing when you have a formula figured out, is that (especially if you have a spreadsheet) you can plug-in all kinds of values, and see how the formula performs.

I took our baseball, and ran the formula multiple times, all the way up the reported speed of the Chelyabinsk meteor – 40,000 mph.

You can see, that the energy increases more quickly, the faster it travels. This is due to the $(speed)^2$ term in the formula:

## Incoming weigh in

When it comes to impact events, the weigh in is a lot more serious that our baseball. These objects are made of rock and iron, so they are very dense. Also and size can be on the large side, for something moving above our heads at 1000s of mph.

For instance Meteor Crater in Arizona, shows that a meteorite reported as 54 yards across, is good for a crater 4,000 ft wide by 570 ft deep.

However don’t worry too much. The “incoming” of the large variety doesn’t happen that often.