Understanding Time

Introduction to Time

• Everyone is familiar with linear time: 60 seconds = 1 minute, 60 minutes = 1 hour, 24 hours = 1 day.
• Common representations of time: clocks, calendars (surface level understanding).
• Time as an enigma: difficult to explain, even for experts.

Philosophical Perspective

• Aristotle: "Time is the most unknown of all unknown things."
• Definition of time: often described as a dimension.

Flaws in Definitions

• Time also serves as a measurement.
• Example: "I was born in the 1990s" vs. "I was born 18 billion kilometers in the past" (the second statement lacks sense).

Time vs. Spatial Dimensions

• Spatial dimensions allow easy movement back and forth.
• Time, unlike space, cannot be retrieved once it has passed.

The Arrow of Time

• Time moves in one direction: forward.
• Concept of the "arrow of time" is fundamental.

Origin of Time

• Time originates from the Big Bang; history is fixed in the past.
• Present is a prison of time; future remains unknown.
• Memory of past events vs. inability to predict future events.

Entropy and Time

• Second law of thermodynamics: entropy is a measure of disorder.
• Big Bang: low entropy situation (orderly).
• Post-Big Bang: increasing entropy leads to galaxies, stars, planets, and life.
• Entropy differentiates past from future.

Macro vs. Micro Perspective

• Arrow of time evident on macro scales; easier to distinguish years and events.
• Micro scale: time appears to flow in all directions; no physical laws differentiate past from future.
• Example: reversing footage of an egg vs. a pendulum.

Importance of Arrow of Time

• Governed by entropy and the universe's beginning.
• Questions about why the universe initially had low entropy.

Scientific Limitations

• Current physics can trace back to seconds after the Big Bang, but not before.
• No law states there wasn’t time before the Big Bang.

Future of the Universe

• Expansion of the universe leads to a future where everything is far apart (high entropy).
• Possible quantum fluctuations could create conditions similar to the Big Bang.

The Theory of Everything

• Need to unite quantum mechanics with Einstein’s general relativity.
• Potential to explain the universe's existence and the concept of a multiverse.

Learning Resources

• Recommendation for Brilliant.org for courses on relativity and quantum mechanics.
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