Femtosecond

What Is Femtosecond?

A femtosecond is a unit used to measure a very small amount of time. One femtosecond is one quadrillionth of a second. Written as a number, that is 0.000000000000001 second.

Scientists use femtoseconds to study events that happen incredibly fast, such as light traveling, atoms moving, and chemical bonds breaking and forming.

Definition

A femtosecond is a unit of time in the International System of Units prefix family.

• 1 femtosecond = 10^-15 second
• “Femto” is the prefix that means 10^-15, or one quadrillionth part of something
• Symbol of a femtosecond: fs

So, if you split one second into 1,000,000,000,000,000 equal parts, one of those parts is one femtosecond.

History / Origin

The word femtosecond comes from two parts:

• Femto comes from the Danish word “femten” which means fifteen, because it stands for 10 to the power of minus 15
• Second is the basic unit of time in the International System of Units

The femto prefix was officially added to the metric prefix list in the late 20th century when scientists needed clear names for very small and very large values. As lasers and ultrafast cameras improved, researchers started to measure processes that happen in femtoseconds. This helped create the field of femtochemistry, where scientists watch chemical reactions almost as they happen.

Symbol & Abbreviation

The standard symbol and abbreviation for femtosecond is:

• fs

Writing examples:

• 5 femtoseconds = 5 fs
• 250 femtoseconds = 250 fs

The letter “f” comes from the prefix femto, and the letter “s” stands for second.

Current Use Around the World

Femtoseconds are not used in everyday life, because they are far too small for normal activities. You will not see femtoseconds on clocks or stopwatches. They are mainly used in science and advanced technology all over the world.

Common uses include:

• Laser physics: ultrafast laser pulses are often a few femtoseconds long
• Chemistry: to watch how molecules change shape or how bonds break and form in femtochemistry
• Electronics and photonics: to study how electrons move in materials and in very fast circuits
• Astronomy and space science: to time very quick light events in experiments and instruments
• Biology and medicine: in special imaging tools that take extremely fast pictures of cells and proteins

Scientists, engineers, and researchers in many countries use femtoseconds in their work, usually along with other very small time units like picoseconds and attoseconds.

Example Conversions

Here are some helpful comparisons and conversions to understand how small a femtosecond is.

Femtoseconds to seconds

• 1 fs = 0.000000000000001 second
• 1,000 fs = 1 picosecond (ps) ≈ 0.000000000001 second
• 1,000,000 fs = 1 nanosecond (ns)
• 1,000,000,000 fs = 1 microsecond (µs)

Seconds to femtoseconds

• 1 second = 1,000,000,000,000,000 fs (10¹⁵ fs)
• 1 millisecond (0.001 s) = 10¹² fs
• 1 microsecond (0.000001 s) = 10⁹ fs
• 1 nanosecond (0.000000001 s) = 10⁶ fs

Real world style examples

• Light travels about 300,000 kilometers in one second, but in 1 femtosecond light travels only about 0.3 micrometers, which is less than 1 hundredth the width of a human hair.
• A typical blink of a human eye takes around 0.3 second. That is about 300,000,000,000,000 femtoseconds.

Related Units

Femtosecond is part of a family of time units that use metric prefixes. Here are some related units, from larger to smaller than a second:

• Millisecond (ms) = 10^-3 second = 0.001 second
• Microsecond (µs) = 10^-6 second
• Nanosecond (ns) = 10^-9 second
• Picosecond (ps) = 10^-12 second
• Femtosecond (fs) = 10^-15 second
• Attosecond (as) = 10^-18 second

In everyday life we usually use:

• Second (s)
• Minute (min) = 60 seconds
• Hour (h) = 60 minutes

Femtoseconds sit far below these everyday units and are used mainly in advanced scientific work.

FAQs

Is a femtosecond smaller than a nanosecond?

Yes. One nanosecond is 10^-9 second, and one femtosecond is 10^-15 second. So 1 nanosecond = 1,000,000 femtoseconds.

What is smaller than a femtosecond?

An attosecond is smaller. One attosecond (as) is 10^-18 second, which is 1,000 times smaller than a femtosecond.

Why do scientists need femtoseconds?

Some things in nature happen so fast that normal time units like seconds or milliseconds are too large. Femtoseconds let scientists measure how fast light moves, how electrons shift, and how chemical reactions start.

Can a normal stopwatch measure femtoseconds?

No. Regular stopwatches and clocks are far too slow for femtoseconds. Special laboratory tools, such as ultrafast lasers and high speed detectors, are needed to work with femtoseconds.

How long is a femtosecond compared to one second?

If one second were stretched to the age of the universe, then a femtosecond would be like less than one second in a human life. It is extremely tiny compared to one full second.

Where might I hear about femtoseconds in the news?

You might hear about femtoseconds in stories about Nobel Prizes in chemistry or physics, ultrafast lasers, or new cameras that can record very quick events such as light moving or molecules changing.