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How Does Time Really Work?

History of the Universe・42 minutes read

The perception of time is influenced by various factors, including speed, activity, and the processing speed of our senses, with different creatures experiencing time differently. Concepts of time, including relativity, entropy, and brain processing, all contribute to shaping our subjective experience of the present moment.

Insights

  • Human perception of time varies based on evolution, activity, and speed, potentially leading to individuals witnessing events in different orders.
  • The brain constructs a sense of time through visual illusions and sensory inputs, with the insular cortex playing a crucial role in our perception of time linked to emotions.

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Recent questions

  • How do pigeons perceive time?

    Pigeons perceive time at over 100 frames per second, allowing them to react faster to dangers due to their rapid perception of the world.

  • What is the delay in sensory perception for touch signals?

    Touch signals travel at around 75 m/s to the brain, creating a delay in sensory perception as the brain processes the received signal.

  • How do smells register in the brain?

    Smells travel at varying speeds, taking hundreds of milliseconds to register in the brain depending on factors like temperature and air currents.

  • What is the concept of time in the universe?

    The concept of now in the universe is questioned, with differing time perceptions based on speed and the influence of factors like light speed.

  • How does the brain construct a sense of time?

    The brain constructs a sense of time through visual illusions and sensory inputs, with the insular cortex playing a crucial role in our perception of time linked to emotions.

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Summary

00:00

Time Perception Across Species and Space

  • The legend of the star whale, a creature capable of swallowing solar systems whole, is passed down through generations in advanced civilizations.
  • The star whale's skin is said to be covered in star stuff barnacles and interplanetary plankton, with time passing differently for it due to its speed.
  • Pigeons experience time differently, perceiving the world at over 100 frames per second, allowing them to react faster to dangers.
  • Human perception of time varies based on evolution, activity, and speed, with two individuals potentially witnessing events in different orders.
  • The taste of food involves a complex process where signals travel through the nervous system, with the brain registering taste milliseconds after consumption.
  • Touch signals travel at around 75 m/s to the brain, with the brain needing time to process the received signal, creating a delay in sensory perception.
  • Smells travel at varying speeds depending on factors like temperature and air currents, taking hundreds of milliseconds to register in the brain.
  • Sight and sound are time machines, with lightning and thunder showcasing the delay in perceiving events that have already occurred.
  • When observing the moon, the light reaching Earth reflects different moments in time, with sunlight taking over 8 minutes to reach Earth.
  • Traveling further into space increases the delay in communication, with signals taking minutes, hours, or even years to reach their destinations due to vast distances.

17:29

"Time, Light, and Relativity in Universe"

  • Television originated from the first light to stream in the universe around 13.8 billion years ago.
  • Our senses do not deliver information instantly; there is always a delay affecting our subjective sense of now.
  • The concept of now in the universe at large is questioned.
  • Einstein's special theory of relativity explains how traveling close to light speed condenses a planet's history into a fraction of a second.
  • Galileo's theory of relativity dates back to the 17th century, illustrating differing viewpoints based on reference frames.
  • Maxwell's equations described light's fixed speed, leading to the concept of luminiferous ether.
  • Michelson and Morley's 1887 experiment disproved the existence of the ether, showcasing the absolute speed of light.
  • Hendrik Lorentz's work influenced Albert Einstein's special theory of relativity, highlighting differing time perceptions based on speed.
  • The Lorentz factor quantifies the time difference experienced at varying speeds relative to the speed of light.
  • The photon, a particle of light, experiences timelessness, challenging the concept of time passing.

34:57

Time's Arrow: Entropy, Thermodynamics, and Perception

  • Time is typically experienced as a forward progression, akin to a horse galloping from left to right.
  • Some films, like one showing a broken egg reforming, instantly reveal if played in reverse, highlighting time's irreversible nature.
  • Sir Arthur Edington coined the term "time's arrow," indicating the direction of time based on randomness in events.
  • Leonard Sardi Caro's work on thermodynamics, including the Carno cycle, remains influential despite its impracticality.
  • Rudolph Clausius furthered thermodynamics with the second law and the concept of entropy, measuring energy unavailability.
  • Entropy, akin to disorder, increases over time, illustrated by the randomness of coin flips and gas molecules.
  • The universe's entropy increase from order to disorder drives time's forward progression, evident in the cosmos and biological systems.
  • Julian Barber theorizes a universe split into two parts with time flowing in opposite directions, suggesting a midpoint of time symmetry.
  • The brain constructs a sense of time through visual illusions like the stopped clock illusion and flash lag illusion, altering perception.
  • The brain's temporal integration window lasts 2-3 seconds, allowing coherent construction of the present moment based on sensory inputs.

52:24

Insular cortex linked to sense of time

  • Psychologist Mark Witman conducted an experiment using an fMRI machine where participants had to match the duration of sounds; those who could accurately time the sounds showed activation in the insular cortex, suggesting this region is responsible for our sense of time, which is closely linked to our emotions and controlled by the same brain region.
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