Ask A Scientist

How does thunder work?

Asked by: Riley Skube
School: Glenwood Elementary School
Grade: 1
Teacher: Amanda Herzog
Hobbies/Interests: Hobbies:  Pretending Career Interests: Teaching
Career Interest: Teacher

Answer from Lucas Sabalka

Riley Assistant Professor

Research area: Geometric group therapy
Family: 1 spouse and 2 cats
Interests/hobbies: The environment, cards, movies, and Do-It-Yourself projects

Thunder and its companion, lightning, are simply awesome.  They are caused by mind-boggling amounts of raw power.  I mean, literally, power: the stuff that makes up lightning is the same stuff that your cell phone uses to operate.  But in lightning, that power is on a much larger scale.  Just a single lightning bolt, if harnessed, could power an entire house for almost a month! So how do thunder and lightning happen?  In a cloud, water droplets are moving up and down, past each other.  The droplets that move down tend to steal subatomic particles called electrons from the droplets moving upward.  Electrons are what make electricity:  electricity is nothing more than the flow of electrons.  Eventually a TREMENDOUS number of extra electrons pile up on the bottom of the cloud.  But electrons don't like to be piled up together, so they all start looking for a place to go and then spread out.  When the electrons find that place (for instance, in another cloud, in a tree, or in a building), they move all together faster than the blink of an eye down the same path to get there, and then spread out.  That great movement of electrons releases lots and lots of energy, in the form of light and heat.  The light gives us lightning:  we see the paths that the electrons traveled down.  The heat can be up to 60,000 degrees F -- more than five times hotter than the surface of the sun!  The air nearby the lightning becomes extremely hot extremely quickly, which makes it move away from the lightning extremely quickly.  When all that air rushes outward, it creates a sound wave.  That sound is called thunder. The light in lightning travels at 186,000 miles per second (that's over 7 times around the earth in just one second).  The sound of thunder travels at a much slower rate of .2 miles per second.  That means you will always see lightning before you hear its thunder, because lightning is much faster.  Because of this, you can figure out how far away the lightning is:  once you see the lightning, count how many seconds it takes to hear the thunder.  The lightning is 1 mile further away for every 5 seconds it takes the thunder to reach you! So I guess the short answer to your question is that thunder is the sound of air running away from the lightning bolt.  And I don't blame it!


Last Updated: 9/18/13