霍金《时间简史》A Brief History of Time 学习笔记（第二章）

news2024/11/19 1:38:57

CHAPTER 2 : SPACE & TIME

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Footnote: Second chapter. Mainly talks about spacetime.

Footnote: “Thought Experiment”, which is quite common in the field of physics.
False: Galileo dropping weights from the Tower of Pisa
(Assertedly) True: Galileo rolling balls down slopes.

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Footnote:
Zero dimension (0 - D): A dot
One dimension (1 - D): A line
Two dimension (2 - D): A plane
Three dimension (3 - D): A cube
n-dimension (n > 3): hypercubes.
Illustration:

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In summary, n-D, n-dimensional --> takes n coordinates to represent.
E.G.
a 1-D space is just a line. It can be represented by only 1 coordinate (x)
Similarly, it takes 2 coordinates (x, y) to represent a 2-D space (a plane), and so on.
Although n coordinates (x1, x2, … xn) can be used to represent an n-dimensional space, it is very difficult to imagine, or to plot such high-dimensional spaces.

CONCLUSION (END OF CHAPTER)

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Footnote: Revolutionary shift in theory from “static & steady universe” to “dynamic & expanding universe”. Einstein’s general & special theories of relativity played huge parts in this revolution.