Q:

What comes first: thunder or lightning?

A:

Quick Answer

Though it is theoretically possible to hear thunder and then see lightning, lightning actually causes thunder, so it has to come first. Thunder is the noise that's caused by the sound of the rapid expansion of air that gets suddenly heated by a bolt of lightning.

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What comes first: thunder or lightning?
Credit: Richard Hurd CC-BY 2.0

Full Answer

Lightning is extremely hot, and it can reach temperatures as high as 54,000 degrees Fahrenheit. When lightning hits the air, there's a huge temperature difference, and the air around the lightning bolt heats up very quickly as a result. The heat causes the air to essentially explode because it expands so quickly, which causes the loud cracking noise that starts a roll of thunder. The rumbling noise that follows the crack is a result of vibrations in the air column.

The speed of light travels much faster than the speed of sound, so people should see lightning before they see thunder. If someone hears a clap of thunder before they see a flash of lightning, the thunder they are hearing is the result of a different bolt that the person didn't notice. Because lightning occurs before thunder, lightning that is followed directly by the sound of thunder is a good indicator that a storm is quite close.

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Related Questions

  • Q:

    What is the difference between thunder and lightning?

    A:

    The difference between thunder and lightning is that lightning is electromagnetic energy and thunder is sonic energy. Lightning actually causes thunder by rapidly heating and expanding the air around the path of the strike, explains a Library of Congress website.

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  • Q:

    Why do you hear thunder one or more seconds after you see the lightning?

    A:

    Both lightening and thunder occur at the same time, but the sound of thunder is heard after lightening is seen because light travels faster than sound. While lightening may be seen for miles, thunder is seldom heard beyond a 10-mile radius.

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  • Q:

    Are lightning and thunder the same thing?

    A:

    Thunder and lightning are not the same phenomenon, though both are caused by the same event. As a cloud equalizes its electric charge with the ground, the current must pass through a column of air. Air is not a perfect conductor of electricity, so some of the energy is lost to heat as the charge travels downward. An observer experiences this visually as lightning and audibly as thunder.

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  • Q:

    How is thunder formed?

    A:

    Thunder is formed as air heats up and expands when lightning occurs. The rate of expansion is so fast that the air vibrates, causing sound waves. Since light travels faster than sound, lightning is seen before thunder is heard.

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