logo

English
                 

Our Unbounded Finite Universe

posted by Jason Kottke   Jan 08, 2019

I’ve always had a hard time wrapping my head around the idea that the universe could be both finite and infinite at the same time (or something like that *takes bong rip*), but this passage from Coming of Age in the Milky Way by Timothy Ferris succinctly explains what’s going on:

General relativity resolved the matter by establishing that the universe could be both finite — i.e., could contain a finite number of stars in a finite volume of space — and unbounded. The key to this realization lay in Einstein’s demonstration that, since matter warps space, the sum total of the mass in all the galaxies might be sufficient to wrap space around themselves. The result would be a closed, four-dimensionally spherical cosmos, in which any observer, anywhere in the universe, would see galaxies stretching deep into space in every direction, and would conclude, correctly, that there is no end to space. Yet the amount of space in a closed universe would nonetheless be finite: An adventurer with time to spare could eventually visit every galaxy, yet would never reach an edge of space. Just as the surface of the earth is finite but unbounded in two dimensions (we can wander wherever we like, and will not fall off the edge of the earth) so a closed four-dimensional universe is finite but unbounded to us who observe it in three dimensions.

In the terms of Edwin Abbott Abbott’s Flatland: A Romance of Many Dimensions, we are Flatlanders living in a Lineland world who, with the aid of mathematics, have been able to peer into Spaceland.

No. Subject Date Author Last Update Views
Notice How to write your comments onto a webpage [2] 2016.07.06 운영자 2016.11.20 18098
Notice How to Upload Pictures in webpages 2016.07.06 운영자 2018.10.19 32223
Notice How to use Rich Text Editor [3] 2016.06.28 운영자 2018.10.19 5811
Notice How to Write a Webpage 2016.06.28 운영자 2020.12.23 43744
8837 육군 방첩대. 미군 CIC, 그리고 김창룡 update 2024.04.17 온기철*71 2024.04.19 12
8836 김구의 일생과 암살의 원인 2024.04.14 온기철*71 2024.04.14 15
8835 OPERA MIGNON: Connais tu le pays [1] 2024.04.12 정관호*63 2024.04.12 21
8834 “쏘니,너와 함께 뛴건 행운!”, 400경기 감동 축하영상 [4] 2024.04.06 황규정*65 2024.04.08 27
8833 길에서 만난 한식 [1] 2024.04.03 정관호*63 2024.04.09 27
8832 돌아오는 기러기 [1] file 2024.03.27 정관호*63 2024.04.18 39
8831 이강인-손흥민 ‘골 합작’ 한국, 태국 3-0 완승…월드컵 최종 예선 진출 성큼 [2] 2024.03.26 황규정*65 2024.03.27 37
8830 1945년 8월 15일 오후 강릉 홍제정 안마을에서 [2] 2024.03.19 정관호*63 2024.03.24 70
8829 이승만은 왜 김구를 제거 했을까? [1] 2024.03.17 온기철*71 2024.03.18 46
8828 My Grandson [1] 2024.03.15 노영일*68 2024.03.18 100
8827 蜀相(촉상): 촉한 승상 제갈량 [1] 2024.03.15 정관호*63 2024.04.12 53
8826 1945년 8월15일에는 서울에 아무일도 없었다. [1] 2024.03.13 온기철*71 2024.03.14 50
8825 왕소군 고향에서 [1] 2024.03.08 정관호*63 2024.03.20 53
8824 정약용; 늙어가면 친구가 점점 없어진다. [5] 2024.03.06 온기철*71 2024.03.08 84
8823 Trump is OK to be a candidate. 2024.03.04 온기철*71 2024.03.17 55
8822 AMAZING GRACE [1] 2024.03.01 정관호*63 2024.03.08 64
8821 한국에의 복수국적 - 이중국적이 더 불리한 경우를 알려 드립니다 [1] 2024.02.24 운영자 2024.02.24 80
8820 신진서, 농심배 16연승... 중국 기사 올킬로 한국 4연속 우승 [1] 2024.02.23 황규정*65 2024.02.23 46
8819 古朝鮮:고조선 [1] 2024.02.23 정관호*63 2024.02.26 52
8818 한국진공작전; Eagle Project and Napko Project [2] 2024.02.22 온기철*71 2024.02.28 90