Speed Journey
Scroll to accelerate — feel the speed in km/h, Mach and the speed of light, and watch time dilate.
Walking pace
A relaxed human walk is about 1.4 m/s, or roughly 5 km/h. This is where the journey begins.
1.4 m/s·Mach 0
Usain Bolt
At his 2009 world-record peak Usain Bolt hit about 12.4 m/s — nearly 44.7 km/h, the fastest a human has ever run.
12 m/s·Mach 0.04
Car on the highway
A car cruising at 100 km/h moves about 28 m/s. Already eight times faster than the fastest sprinter.
28 m/s·Mach 0.08
Cheetah
The cheetah is the fastest land animal, sprinting at about 33 m/s (≈120 km/h) for short bursts.
33 m/s·Mach 0.1
Bullet train
High-speed and maglev trains cruise near 300 km/h — about 83 m/s, gliding faster than any animal can run.
83 m/s·Mach 0.24
Passenger jet
An airliner cruises at roughly 900 km/h, about 250 m/s — close to, but still below, the speed of sound.
250 m/s·Mach 0.73
The speed of sound
In dry air at 20 °C sound travels at 343 m/s — Mach 1. Break it and you leave your own sound behind in a sonic boom.
343 m/s·Mach 1
SR-71 Blackbird
The SR-71 flew above Mach 3 — around 980 m/s. It is still the fastest crewed air-breathing aircraft ever built.
980 m/s·Mach 2.86
Rifle bullet
A typical rifle bullet leaves the muzzle at about 1,000 m/s — roughly three times the speed of sound.
1,000 m/s·Mach 2.92
ISS orbital speed
The International Space Station circles Earth at 7.66 km/s — 7,660 m/s — fast enough to orbit the planet every 90 minutes.
7,660 m/s·Mach 22.3
Earth escape velocity
To break free of Earth's gravity you need 11.2 km/s — 11,200 m/s. Anything slower falls back down.
11,200 m/s·Mach 32.7
Voyager 1
Voyager 1, the most distant human-made object, races away from the Sun at about 17 km/s — 17,000 m/s.
17,000 m/s·Mach 49.6
Parker Solar Probe
Diving toward the Sun, the Parker Solar Probe reached about 191 km/s — near 690,000 km/h, the fastest human-made object ever.
191,000 m/s·Mach 556.9
1% of light speed
At 2,997,925 m/s you are travelling at 1% of light speed. Time dilation is still tiny — γ is just 1.00005.
2,997,925 m/s·Mach 8,740
10% of light speed
At 29,979,246 m/s — 10% of light speed — relativity becomes visible: γ ≈ 1.005, so clocks already run measurably slow.
29,979,246 m/s·Mach 87,403·γ 1.01
The speed of light
Light travels at exactly 299,792,458 m/s — the cosmic speed limit. Here γ goes to infinity: no object with mass can ever reach it.
299,792,458 m/s·Mach 874,030·γ ∞
You reached the speed of light — the cosmic speed limit.
Every scroll speeds you up. Speed spans eight orders of magnitude here, from a 5 km/h walk to 299,792 km/s. Near the speed of light, special relativity takes over: the Lorentz factor γ grows without limit, so one second for the traveller stretches into many seconds back on Earth. Light speed itself is the cosmic speed limit — γ goes to infinity and no object with mass can reach it.
Sources: BIPM definition of the metre (speed of light), NIST / U.S. Standard Atmosphere (speed of sound), NASA/JPL spacecraft data, and special relativity (Lorentz factor).
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