Speed

1. Speed is a dual concept: Distinguishing between physical speed and systemic rates of change

Understanding these fundamentals is requisite for appreciating the modern preoccupation with speed in general and with acceleration in particular.

Defining the variables. Speed in its strictest physical sense is a scalar quantity representing distance divided by time ($L/T$), whereas velocity is a vector that includes both magnitude and direction. In contrast, the broader definition of speed ($N/T$) measures the rate of change of non-spatial quantities per unit of time. This distinction is crucial because modern society often conflates physical movement with systemic acceleration.

Systemic rates of change. This broader category of speed encompasses a vast array of modern metrics that dictate our economic and social realities. These include:

• The speed of chemical reactions and material processing
• The rate of monetary transactions and GDP growth ($/T$)
• The acceleration of global warming and energy decarbonization
• The rapid processing and storage of digital information

The power proxy. Power, defined as energy expended per unit of time (Joules per second or Watts), serves as an indirect measure of speed. Historically, James Watt defined "horsepower" based on the physical speed of a working horse, establishing a benchmark that proved how deploying more power allows us to complete tasks exponentially faster. Today, our massive energy consumption is simply a proxy for our obsession with saving time.

2. Geological and evolutionary speeds are non-intuitive, operating on vast timescales

Geologically speaking, human evolution has unfolded at a very rapid speed.

Vast temporal scales. Human brains are evolutionarily optimized to comprehend short, immediate timeframes, making the billions of years of planetary history difficult to grasp. To make these non-intuitive spans comprehensible, we can compress the Earth's 4.5-billion-year history into a single 24-hour day. This exercise reveals that the vast majority of our planet's existence was characterized by exceedingly slow, near-imperceptible changes.

The compressed timeline. When viewed on a 24-hour scale, the slow and punctuated nature of evolution becomes starkly apparent:

• Simple single-celled life does not appear until 4:00 AM.
• The Great Oxidation Event occurs around noon.
• The Cambrian explosion of diverse life happens late at night, at 9:10 PM.
• Hominins do not arrive until a mere minute and a half before midnight.
• Recorded human history occupies only the final hundredths of a second.

Punctuated acceleration. While the overall history of life is characterized by immense periods of stagnation, it is punctuated by episodes of rapid evolutionary acceleration. The transition of hominins to Homo sapiens, marked by a tripling of brain volume in just three million years, represents an unprecedented evolutionary sprint. This rapid encephalization laid the groundwork for our species to eventually alter the biosphere at geological speeds.

3. Tectonic and geomorphic processes operate in an ultra-slow lane punctuated by sudden disasters

The creation of this new Earth’s crust proceeds at speeds of no more than about 20 cm/year—seven orders of magnitude slower than slow walking...

The slow drift. The physical stage for life is set by plate tectonics, which move massive continental and oceanic plates across the Earth's mantle. These movements proceed at speeds comparable to the growth of human fingernails, typically ranging from 1 to 20 centimeters per year. Despite their slowness, these relentless movements have rearranged oceans, created continents, and driven the long-term climate cycles of our planet.

Uplift and denudation. Mountains are formed when colliding plates force the crust upward, a process countered by the relentless, slow forces of erosion and denudation.

• Tectonic uplift in the Himalayas averages about 1 to 4 millimeters per year.
• Mechanical denudation by rivers wears down landscapes by fractions of a millimeter annually.
• Isostatic rebound causes land once depressed by heavy ice sheets to rise slowly over millennia.

High-speed geological events. While the background rate of geological change is incredibly slow, it is punctuated by sudden, high-speed releases of energy. Earthquakes propagate ruptures through rock at supersonic speeds of several kilometers per second, while volcanic pyroclastic flows and tsunamis can travel at speeds exceeding 700 kilometers per hour. These catastrophic events can reshape local landscapes in minutes, contrasting sharply with the background tectonic crawl.

4. Organisms balance reproduction, growth, and longevity through distinct speed strategies

A fast life means limited longevity (most rats do not make it past a year), and only parasitic r-selected species, provided with a reliable supply of nutrients, are long-lived...

Life-history strategies. Organisms have evolved diverse strategies to manage the speed of their life cycles, categorized broadly into r-selection and K-selection. The r-selected species focus on rapid, high-volume reproduction with minimal parental investment, while K-selected species prioritize slow growth, high investment, and longevity. This ecological trade-off determines how quickly a species can recover from environmental disruptions or colonize new niches.

Gestation and maturation. The speed of physical development varies dramatically across the animal kingdom, dictated by body mass and metabolic constraints:

• Gestation ranges from a mere 12 days in opossums to 645 days in elephants.
• Small rodents reach sexual maturity in weeks, whereas large mammals require years.
• Postnatal growth curves typically follow an S-shaped sigmoid pattern of early acceleration and eventual plateau.

The metabolic clock. Longevity is closely tied to an organism's metabolic rate and heart rate. Across most mammalian species, there is an inverse relationship between heart rate and life expectancy, suggesting that each species is allotted a relatively fixed number of heartbeats—roughly one billion—in a lifetime. Humans and some birds are notable outliers, living significantly longer than their metabolic rates would predict.

5. Animal locomotion is optimized for environmental physics, not maximum body size

The fastest animals (cheetahs, marlins, falcons) are of intermediate size.

The physics of medium. Animal locomotion is strictly governed by the density and viscosity of the medium through which they move. Swimming is energetically the most efficient because of neutral buoyancy, flying is intermediate, and running on land is the most expensive. These physical constraints dictate the anatomical adaptations and maximum speeds achievable by species in each environment.

The size-speed paradox. While one might expect larger animals to be faster due to greater muscle power, maximum speed actually follows a hump-shaped relationship with body mass. The fastest speeds are achieved by intermediate-sized animals:

• Cheetahs reach sprinting speeds of nearly 100 km/h on land.
• Peregrine falcons exceed 130 km/h in diving flight.
• Sailfish and marlins achieve burst swimming speeds of 30 to 40 km/h.

Acceleration limits. The largest animals, such as elephants and blue whales, cannot achieve extreme speeds because they run out of rapidly mobilizable anaerobic energy before their massive bodies can fully accelerate. Consequently, their locomotion is optimized for steady, continuous movement rather than short, high-speed bursts. This physical limit prevents the evolution of giant, ultra-fast land predators.

6. Humans are evolutionary outliers optimized for endurance and bipedal mobility

We are outstanding walkers and admirable runners as we combine endurance with speed.

The bipedal advantage. The evolution of upright, bipedal walking was a foundational milestone that freed human hands for tool use and optimized our energy expenditure. While humans are mediocre swimmers and cannot fly, our walking and running mechanics are exceptionally efficient. This unique posture allowed our ancestors to cover vast distances while consuming minimal energy compared to quadrupeds.

Endurance and thermoregulation. Humans possess a unique combination of physical traits that make us the ultimate long-distance endurance runners:

• An abundance of eccrine sweat glands allows highly efficient heat dissipation.
• The ability to uncouple breathing frequency from stride frequency prevents hyperventilation.
• These traits enabled "persistence hunting," allowing ancestors to run prey to exhaustion in hot climates.

Sprinting limits. While human endurance is unmatched, our maximum sprinting speed is strictly limited by the physics of ground-force application. Elite sprinters like Usain Bolt can briefly exceed 12 m/s (44 km/h), but further speed gains are constrained by the briefness of foot-ground contact times. Our evolutionary path traded raw sprinting speed for unmatched thermal regulation and long-distance endurance.

7. Premodern societies were bound by the slow speeds of muscles, crops, and wind

Traditional human societies were energized by human and animal muscles... wood... and wind and flowing water converted by mills and sails.

Biological speed limits. For the vast majority of human history, the pace of society was dictated by the natural maturation rates of crops and the physical limits of muscle power. Agriculture required months of waiting for harvests, and field preparation was a slow, grueling process. This biological bottleneck kept human populations low and restricted the growth of non-agricultural urban centers.

The labor bottleneck. Before mechanization, producing food required an immense expenditure of human and animal labor:

• Hand-hoeing a single hectare of land required up to 500 hours of manual labor.
• Plowing with oxen increased the speed but was still limited to a slow walking pace.
• Milling grain by hand produced only a few kilograms of flour per hour.

Inanimate energy pioneers. The introduction of waterwheels and windmills represented the first major step away from muscle power. These wooden machines multiplied the speed of repetitive tasks, allowing a single water mill to grind as much grain in an hour as dozens of manual laborers. However, these early energy converters were geographically restricted and highly dependent on seasonal water flows and wind patterns.

8. The modern era accelerated by transitioning from reciprocating to rotary motion

The technical advance that characterizes specifically the modern age is that from reciprocating motions to rotary motions.

The rotary revolution. Premodern work was dominated by reciprocating (back-and-forth) motions, which are inherently inefficient and limited in speed. The defining technical achievement of the Industrial Revolution was the conversion of linear piston movements into continuous, high-speed rotation. This mechanical shift allowed engines to run continuously without the energy losses associated with stopping and reversing direction.

Engines of acceleration. The development of rotating prime movers unlocked unprecedented speeds and power capacities across all sectors of human activity:

• Steam turbines replaced reciprocating steam engines, spinning at thousands of revolutions per minute.
• Internal combustion engines converted liquid fuels into rapid wheel and propeller rotations.
• Electric motors provided highly efficient, easily controllable rotary power for factories and homes.

Precision machining. The acceleration of industrial output was further enabled by high-speed metal cutting and turning. Modern machine tools, utilizing ultra-hard materials like cubic boron nitride, can cut steel at speeds exceeding 2,000 meters per minute, allowing the rapid mass-production of standardized parts. This self-reinforcing cycle of rotary power enabled the exponential growth of the modern technosphere.

9. The ultimate speed-up occurred in the realm of computation and communication

This has been the greatest speeding-up in history: I am not aware of any other increase in performance that could compare with this spectacular (and still-continuing) rise.

The death of distance. For millennia, communication was tied to the physical speed of transportation. The invention of the telegraph, telephone, and radio decoupled information from physical travel, allowing messages to propagate at or near the speed of light. This transition represented a million-fold increase in communication speed, effectively shrinking the globe into a single, interconnected network.

Exponential computation. While physical transportation speeds have largely stagnated since the mid-20th century, computing power has experienced a mind-boggling, trillion-fold acceleration:

• Early electronic computers processed a few hundred operations per second.
• Modern supercomputers operate in the exaflop range, performing quintillions of calculations per second.
• Microprocessor clock speeds have risen from kilohertz to gigahertz.

The mobile web. The rapid global adoption of mobile networks has created an environment of instant, ubiquitous connectivity. Latency times have shrunk to milliseconds, enabling real-time global data sharing but also fostering widespread psychological addiction to constant digital stimulation. This hyper-connected state has accelerated the pace of financial markets, social interactions, and cultural change.

10. Unchecked speed carries severe physical, economic, and environmental penalties

The speed of any process must eventually reach its limits, be it because of social, safety, and environmental concerns... or fundamental physical constraints.

The cost of haste. The modern obsession with acceleration has generated severe negative externalities that threaten human well-being and planetary stability. High-speed road travel results in over a million annual fatalities, as kinetic energy increases with the square of velocity, making high-speed collisions inherently catastrophic. The pursuit of physical speed has outpaced our biological reaction times and structural safety margins.

Systemic friction. In many sectors, pushing for higher speeds yields diminishing returns or outright failures:

• High-speed assembly lines in meatpacking plants dramatically increase worker injury rates.
• "Slow steaming" in maritime shipping has been reintroduced to curb exponential fuel consumption and emissions.
• Urban traffic congestion has actually reduced average travel speeds in major cities to walking paces.

The call for deceleration. Recognizing the limits of physical and psychological acceleration, movements advocating for "slowness" have emerged. From Slow Food to decelerated urban design, these initiatives argue that true quality of life is often found in deliberate deceleration rather than the relentless pursuit of hyperdrive. Balancing our need for speed with physical and ecological limits is the defining challenge of the Anthropocene.

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