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    Time is a dimension, but not like space

    (bigthink.com)
    171 points belter | 11 comments | 17 Oct 24 15:29 UTC | HN request time: 0.208s | source | bottom
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    nyc111 ◴[17 Oct 24 15:55 UTC] No.41870842[source]▶
    I would really appreciate if people writing these types of articles first give rigorous and unique definitions of space and time.
    replies(4): >>41871770 #>>41892831 #>>41892968 #>>41893041 #
    1. blackbear_ ◴[17 Oct 24 17:36 UTC] No.41871770[source]▶
    Something like (from Wikipedia):

    > In the presence of gravity spacetime is described by a curved 4-dimensional manifold for which the tangent space to any point is a 4-dimensional Minkowski space.

    Perhaps? A good way to lose 99% of the readers before the end of the first sentence.

    replies(4): >>41892048 #>>41892765 #>>41892770 #>>41892961 #
    2. mise_en_place ◴[20 Oct 24 00:58 UTC] No.41892048[source]▶
    Just represent it in a 4x4 multidimensional array that corresponds to the metric tensor.
    replies(1): >>41892096 #
    3. hn_throwaway_99 ◴[20 Oct 24 01:09 UTC] No.41892096[source]▶
    Yes, that will really pull in the laymen...
    replies(1): >>41892317 #
    4. nvader ◴[20 Oct 24 01:58 UTC] No.41892317{3}[source]▶
    Reminds me of the mathematician who was asked how he mentally visualizes a 4 dimensional space.

    "I simply imagine an n-dimensional space, and then set n to 4"

    replies(2): >>41892360 #>>41892735 #
    5. homebrewer ◴[20 Oct 24 02:07 UTC] No.41892360{4}[source]▶
    >>> After Hilbert was told that a student in his class had dropped mathematics in order to become a poet, he is reported to have said "Good--he did not have enough imagination to become a mathematician"

    https://scienceworld.wolfram.com/biography/Hilbert.html

    6. golly_ned ◴[20 Oct 24 03:55 UTC] No.41892735{4}[source]▶
    Reminds me of Geoffrey Hinton who, when asked how to imagine a 14-dimensional space, said: “imagine a 3-dimensional space, and say ‘fourteen’ very loudly”
    replies(1): >>41892928 #
    7. ◴[20 Oct 24 04:02 UTC] No.41892765[source]▶
    8. zbobet2012 ◴[20 Oct 24 04:04 UTC] No.41892770[source]▶
    I'm a huge fan of providing laymen explanations. And at some point if you _actually_ want to understand you have to stop using those and pickup and understand the math.

    http://therisingsea.org/post/mast30026/

    Has a good introduction to space, and the notion of a manifold, and what a Minkowski space is.

    replies(1): >>41898821 #
    9. esperent ◴[20 Oct 24 04:47 UTC] No.41892928{5}[source]▶
    This is great, can't believe I haven't heard it before.
    10. slashdave ◴[20 Oct 24 04:56 UTC] No.41892961[source]▶
    That's in the article on Minkowski space. It's actually a good summary, with a hyperlink to manifold.

    Here's the introduction to the "spacetime" page:

    > In physics, spacetime, also called the space-time continuum, is a mathematical model that fuses the three dimensions of space and the one dimension of time into a single four-dimensional continuum. Spacetime diagrams are useful in visualizing and understanding relativistic effects, such as how different observers perceive where and when events occur.

    11. verzali ◴[20 Oct 24 21:57 UTC] No.41898821[source]▶
    Ok, but almost nobody is going to read an article that requires you to work through 21 lectures, 9 tutorials, and 3 assignments first. It'd be great if they did, and it'd be nice to give the link for interested people, but otherwise it is just making the subject inaccessible to almost everyone.