What Actually Are Space And Time?

History of the Universe

27 Jul 202275:18

EducationalLearning

32 Likes 10 Comments

TLDRThis philosophical video explores the mysterious nature of space and time, from Newton's ideas of absolute space and time, to Einstein's relativity upending this with curved spacetime, to speculation that space and time may not fundamentally exist. It recounts humanity's quest to understand if space and time are real or merely emerge from deeper physics. Along the journey it touches on black holes, the expansion of the universe, the arrow of time, entropy, and the potential for time travel. In the end, it wonders if some mysteries like the essence of space and time may always remain beyond our grasp.

Takeaways

😲 Space and time are mysterious and not fully understood despite seeming obvious
😮‍💨 Newton thought space and time were absolute, but Einstein showed they were relative and intertwined
🤯 Einstein's theories of relativity revolutionized our understanding of space and time
😵‍💫 Gravity is not a force, but a consequence of the curvature of spacetime according to general relativity
🫣 Black holes severely warp space and time due to their immense gravity
🧐 Quantum mechanics and general relativity have not yet been unified
🤔 Space and time may be emergent phenomena and not fundamental
🤯 The arrow of time seems to emerge from low initial entropy in the early universe
😮 Time travel appears possible mathematically in general relativity
😵 The true nature of space and time remains elusive and may be unknowable

Q & A

What does the civilization in the twilight of the cosmos use to power their existence?
-The civilization uses the swirling black hole to harvest energy to power their existence.
What scientific principle allows the civilization to experience time more slowly?
-The principle of relativity, particularly the effect of gravity on time around a black hole, allows the civilization to experience time more slowly.
Why does the civilization build a shell around a black hole?
-They build a shell around a black hole to create a new home, using it as a source of energy and a way to slow down time, extending their existence.
What led to the universe's inevitable decline, as observed by the civilization?
-The universe's inevitable decline is due to the dying of the stars and the overall increase in entropy, leading to a cold, dark, and desolate universe.
How does Einstein's theory of relativity relate to the story?
-Einstein's theory of relativity, which changed our understanding of time and space, underpins the civilization's ability to slow down time near a black hole and the overall narrative of the universe's decline.
What is the significance of antimatter in the context of Dirac's equation?
-Dirac's equation predicted the existence of antimatter, specifically the positron (anti-electron), as a natural consequence of combining quantum mechanics with special relativity.
What challenge does combining quantum mechanics with general relativity pose?
-Combining quantum mechanics with general relativity poses the challenge of dealing with the dynamic and evolving nature of spacetime, which introduces uncontrollable infinities in the equations.
What is the AdS/CFT correspondence, and how does it relate to the nature of spacetime?
-The AdS/CFT correspondence is a relationship found in the mathematics of string theory and gravity, suggesting that space and time may be emergent phenomena from more fundamental, quantum-level structures.
How does loop quantum gravity view spacetime?
-Loop quantum gravity views spacetime as a quantum phenomenon, where spacetime is made up of tiny, discrete chunks or grains, giving it a granular nature at the Planck scale.
What ultimate fate does the civilization face in the story?
-The civilization ultimately faces the complete decay and evaporation of their black hole home, leading to their final demise as the universe succumbs to entropy and darkness.

Outlines

00:00

🪐 Beginning of a lonely civilization in a dying universe

Describes a civilization hiding in darkness at the end of time in a dying universe where stars are going out. They had built a great empire in the past but now only their last feats of engineering remain around a black hole which gives them time.

05:04

⚖️ Debate on the nature of space between Newton and Leibniz

Discusses the historical debate on the nature of space between Isaac Newton, who saw it as absolute, and Gottfried Leibniz, who said it only had meaning relative to objects. Leibniz said space and time don't exist without matter.

10:08

🔬 Discovering the speed of light and the relativity of motion

Covers experiments to determine if the speed of light is infinite, leading to Ole Rømer showing it's finite. Also discusses Galileo's realization that uniform motion is relative, an idea later expanded into the theory of relativity.

15:12

⏳ Understanding time through thermodynamics and entropy

Explores attempts to determine the efficiency of steam engines which led to the laws of thermodynamics and the concept of entropy. Entropy and the tendency towards disorder seem to dictate an arrow of time.

20:19

🕰️ Questioning the meaning of past, present and future

Considers inherent issues with defining past, present and future in physics due to relativity and the block universe theory which states all moments in time coexist. Speculates on the origin of time's arrow.

25:30

⏱️ Discovering time travel mathematically

Details mathematician Willem Jacob van Stockum's discovery of closed timelike curves in a hypothetical rotating universe, allowing time travel. This was later rediscovered by Kurt Gödel to disturb Einstein.

30:32

⚛️ Attempts at unifying relativity and quantum mechanics

Traces Paul Dirac's early success deriving relativistic quantum mechanics to describe the electron. But incorporating gravity and curved spacetime has proven immensely difficult, spurring ideas on the nature of space and time.

35:32

🤯 Speculation on whether space and time really exist

Considers whether space and time are emergent phenomena arising from unknown fundamental entities and relationships. Explores ideas like loop quantum gravity and the holographic principle that space and time might not exist at all.

40:36

🌌 Contemplating mysteries before the end of all things

Returns to the dying civilization waiting as their black hole evaporates. Though they manipulated space and time, the decay of the universe could not be defeated. Ends noting some mysteries about space and time may never be grasped.

Mindmap

Keywords

💡spacetime

Spacetime refers to the union of space and time proposed by Einstein's theory of relativity. According to relativity, space and time are interwoven into a four-dimensional continuum known as spacetime. The video discusses how spacetime can curve, bend, and warp due to the presence of mass and energy. This flexible nature of spacetime is a core concept explored throughout the video in relation to black holes, time travel, and the expansion of the universe.

💡entropy

Entropy is a measure of disorder and randomness. The second law of thermodynamics states that entropy increases over time as concentrated energy dissipates into waste heat. The video explores how entropy and the thermodynamic arrow of time relate to the expansion and eventual heat death of the universe. It suggests that the low entropy state of the early universe may have imprinted an arrow of time.

💡arrow of time

The arrow of time refers to the asymmetry between the past and the future, and the overall direction in which time flows. Unlike space, time has a directionality. The video discusses whether there is a fundamental arrow of time at the microscopic level, or whether the arrow emerges from entropy changes on cosmic scales.

💡black hole

A black hole is a region of spacetime with such immense gravity that nothing can escape from it, including light. The video explores how black holes were derived from Einstein's equations, and how they can severely warp spacetime and slow down time due to their gravitational pull.

💡cosmic expansion

The video discusses how observations by Edwin Hubble revealed that space itself is expanding, with galaxies moving away from each other. This cosmic expansion adds complexity in understanding curved spacetime, as space was smaller in the past.

💡general relativity

Einstein's general theory of relativity, published in 1915, states that gravity arises from the curvature of spacetime. Mass and energy warp and distort spacetime, influencing the motion of objects. The flexible nature of spacetime in general relativity enabled solutions like black holes and cosmic expansion.

💡quantum gravity

Quantum gravity refers to the hypothesized theory that would reconcile general relativity's picture of curved spacetime with quantum mechanics. The video discusses the challenges in merging these two fundamental pillars of physics into a single framework.

💡special relativity

Einstein's special theory of relativity, published in 1905, revealed that space and time are intertwined and relative based on one's motion. It showed that the speed of light is the same for all observers, leading to consequences like time dilation.

💡time travel

Several solutions of Einstein's equations suggest the possibility of time travel through warped spacetime, like traversing a wormhole. The video discusses mathematicians like Kurt Gödel who found solutions allowing closed timelike curves that loop back on themselves.

💡theory of everything

A theory of everything aims to fully explain all physical aspects of the universe through a unified framework. The video discusses how this hypothetical theory may finally elucidate the fundamental nature of space and time at the deepest level.

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Transcripts

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