What is a Millisecond (ms)?
Formal Definition
The millisecond (symbol: ms) is a unit of time equal to one thousandth (10⁻³) of a second. In the SI system, it is formed by combining the prefix "milli-" (one thousandth) with the base unit "second." One millisecond equals 0.001 seconds, and one second contains exactly 1,000 milliseconds.
The millisecond is the most commonly used sub-second time unit in everyday technology. Computer response times, network latency, display refresh rates, and audio processing all operate on the millisecond scale. Human perception also operates at this timescale: we can perceive audio delays of 10-20 ms and visual changes at about 13-50 ms.
Practical Scale
To understand the millisecond's scale: a human blink takes 100-400 ms. A housefly's wing beats once every 5 ms. A bullet fired from a rifle travels about 1 meter in 1 ms. Sound travels about 34 cm in 1 ms. These comparisons show that the millisecond, while very short by human standards, corresponds to significant physical events.
Etymology
Latin Prefix
The word "millisecond" combines "milli-" (from Latin "mille," meaning thousand, used in SI to denote one thousandth) with "second." The prefix was part of the original metric system created in the 1790s.
History
From Stopwatches to Electronics
Mechanical chronographs capable of measuring milliseconds were developed in the late 19th century for scientific and sporting applications. Electronic timing systems in the 1930s-1950s made millisecond precision routine in athletics and industrial processes. The computer revolution of the 1960s-1970s made the millisecond a standard engineering unit, as early computer operations took milliseconds to complete.
The Internet Era
The rise of the internet made millisecond latency a household concept. Web page load times, online gaming responsiveness, and video call quality are all measured in milliseconds. High-frequency financial trading has pushed the importance of milliseconds even further.
Current Use
Computing and Networks
Network ping times are measured in milliseconds: local network 1-5 ms, same city 5-20 ms, same continent 30-100 ms, intercontinental 100-300 ms. SSD access times are 0.1-0.5 ms versus 5-15 ms for hard drives. RAM access is about 0.00001 ms (10 ns).
Audio Engineering
In audio, milliseconds are critical. Human ears detect delays above 10-20 ms as echoes. Digital audio latency in music production is typically 5-15 ms. Bluetooth audio has 40-200 ms latency. Concert venue acoustics are designed around sound travel times of 1-100 ms.
Medical Applications
ECG (electrocardiogram) intervals are measured in milliseconds: the PR interval (120-200 ms), QRS complex (80-120 ms), and QT interval (350-440 ms) are critical diagnostic parameters. Nerve conduction velocity tests measure signal travel times in milliseconds.
Everyday Use
Screen Refresh and Gaming
Monitor response time (1-5 ms for gaming monitors) affects visual smoothness. Input lag (the delay between pressing a button and seeing a response) is typically 20-100 ms. Competitive gamers notice differences of just 10-20 ms.
Photography
Camera shutter speeds are expressed as fractions of a second but correspond to milliseconds: 1/1000 s = 1 ms, 1/250 s = 4 ms, 1/60 s ≈ 17 ms. Flash duration is typically 1-5 ms. Fast-moving subjects require shutter speeds of a few milliseconds to freeze motion.
Reaction Time
Human reaction time to visual stimuli averages 200-300 ms. Audio reaction time is slightly faster at 150-200 ms. Sprint starts in athletics have a 100 ms threshold — any reaction faster is considered a false start.
In Science & Industry
Neuroscience
Neurons fire in bursts lasting 1-5 ms, with refractory periods of 1-2 ms. Synaptic transmission takes 0.5-5 ms. EEG recordings sample brain activity at rates corresponding to millisecond resolution, revealing oscillations in the 1-100 Hz range that correspond to different cognitive states.
High-Speed Photography
High-speed cameras capture events at thousands to millions of frames per second, with each frame corresponding to a fraction of a millisecond. This technology reveals phenomena invisible to the naked eye: bullet impacts, droplet splashes, and explosive shockwaves.
Interesting Facts
The fastest human reaction time ever reliably recorded is about 100 ms. Below this threshold, a sprint start is considered a false start, as it's assumed the runner anticipated the gun rather than reacting to it.
Light travels approximately 300 km in one millisecond — roughly the distance from London to Paris.
A hummingbird's wings beat once every 12-80 ms (12-80 beats per second). The bee hummingbird, the smallest bird, beats its wings about once every 12 ms.
The human eye cannot distinguish individual images displayed faster than about every 13 ms (roughly 75 Hz), which is why movies at 24 fps (42 ms per frame) appear smooth with motion blur.
In high-frequency trading, a millisecond advantage can be worth millions of dollars. Companies have built straight-line microwave relay networks across continents to shave a few milliseconds off trading latency.
A professional drummer can play consistent beats with timing accuracy of about ±10 ms — remarkably precise considering each beat involves complex motor coordination.