Talk:Spacetime

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Spacetime received a peer review by Wikipedia editors, which is now archived. It may contain ideas you can use to improve this article.

Figure

I don't quite understand this. The article makes no mention of these things:

How can you have 0 dimensions of space or time? If there are 0 dimensions of space, you just have a point universe moving in time; if there are 0 dimensions of time, your universe is necessarily forever static. What's with the "unpredictable (elliptic)"?
What is "ultrahyperbolic"?
How exactly is N = 1, T = 2 too simple?
Why is N = 1, T > 3 unstable?
Do we have a source that N = 1, T = 3 would have only tachyons?

Lanthanum-138 (talk) 11:47, 23 April 2011 (UTC)[reply]

This is not an easy graph to understand. Your questions are answered in the paper written by Max Tegmark. That can be downloaded from that webpage in postscript (.ps) or Adobe (.pdf) format. – Paine Ellsworth ( CLIMAX ) 08:07, 24 April 2011 (UTC)[reply]

Questions 1, 2 and 5 got answered all right there. Still don't understand 3 and 4. Lanthanum-138 (talk) 13:54, 27 April 2011 (UTC)[reply]

Wish I could be more helpful, but frankly, much of this is way over my head and not all that interesting to me. The answers you seek may have something to do with symmetry and/or the fact that anything outside the (n,m) = (3,1) is extremely difficult if not impossible in terms of predictability. For a more in-depth read, you might try Barrow and Tipler's material that's mentioned in the References section. Best to you! – Paine Ellsworth ( CLIMAX ) 01:25, 15 May 2011 (UTC)[reply]

This graph is stupid--- 3 time and 1 space dimensions is indistinguishable from 1 time and three space dimensions. It should be symmetric about the diagonal. — Preceding unsigned comment added by 69.22.238.161 (talk) 05:58, 20 August 2011 (UTC)[reply]

Not true, time dimensions are monotonic whereas spacial dimensions are non-monotonic. — Preceding unsigned comment added by 108.198.115.76 (talk) 15:28, 8 October 2011 (UTC)[reply]

Query

can any one explain theory of relativity to a 15 yr old please???????

The best place to look would be the article Introduction to special relativity which is written in a more accessible way. --JohnBlackburne^words_deeds 12:06, 25 April 2011 (UTC)[reply]

NEW Discovery

Hi. I'm not really an editor on here nor do I know much about physics past high school. I was wondering if this page should be edited to include new information that NASA's released about their Epic Space-Time experiment. Maybe someone could make a new page about it or something? Just an idea. 124.168.140.62 (talk) —Preceding undated comment added 04:37, 13 May 2011 (UTC).[reply]

lost paragraph

Some recent vandalism was "repaired" by hand rather than reverting, and this paragraph was lost:

Philo noted that time is a result of space (universe/world) and that God created space which resulted in time also being created either simultaneously with space or immediately thereafter.<ref>The Works of Philo, Trans. C.D.Yonge, Hendrickson Publishers, 1993, ISBN 0-943575-93-1, On the Creation (26–30), On The Unchangeableness of God (23–32)</ref>

I can't tell for sure whether the omission is accidental or intentional. —Tamfang (talk) 15:57, 23 May 2011 (UTC)[reply]

Perhaps it might happen because Philo only hinted at a possible link between space and time, but had not formulated the whole mature concept of an unified spacetime. Incas did. Raoul NK (talk) 10:02, 30 September 2011 (UTC)[reply]

Minor question

"World line" or "worldline" or even "world-line"? shouldn't it be consistent? — Preceding unsigned comment added by 131.111.185.74 (talk) 15:45, 7 October 2011 (UTC)[reply]

Wrong way round?

"There exists a reference frame such that the two events are observed to occur in the same spatial location, but there is no reference frame in which the two events can occur at the same time." Surely this should be vice versa. — Preceding unsigned comment added by Andrewthomas10 (talk • contribs) 13:45, 7 December 2011 (UTC)[reply]

Please sign your talk page messages with four tildes (~~~~)? Thanks.

For time-like intervals this is correct, since one person can be present at both events and directly measure the (non-zero) proper time between the events. For space-like intervals it is the other way around. See article and literature. - DVdm (talk) 14:11, 7 December 2011 (UTC)[reply]

Thanks for the reply. But considering events with a time-like interval, if you have a reference frame in the future of both events, then that reference frame could be positioned so that light from both events reaches the frame at the same time. In which case, both events would be considered as happening simultaneously. So there does exist a reference frame in which the two events occur at the same time. Or are you suggesting the observer has to be at the actual position of the event to say when the event occurs? That is not the usual definition. Andrewthomas10 (talk) 15:12, 7 December 2011 (UTC)[reply]