Notices
Results 1 to 8 of 8
Like Tree3Likes
  • 2 Post By Strange
  • 1 Post By Strange

Thread: Am I understanding relativity correctly? and a simple question...

  1. #1 Am I understanding relativity correctly? and a simple question... 
    Suspended
    Join Date
    Dec 2013
    Posts
    78
    Ok I am not sure if I am interpreting the videos I've watched on relativity correctly, and I would like to scan by you guys/gals. Well Einstein imagined a single layer of space-time right? Then when you put an object with mas on this sheet, it bends space-time, and this bending of space-time is gravity... correct? well my question is if space-time is a single sheet then how come we stars above us? I'm also having trouble imagining four dimensions...


    Reply With Quote  
     

  2.  
     

  3. #2  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    16,965
    Quote Originally Posted by Physicsforall View Post
    Well Einstein imagined a single layer of space-time right?
    Actually, no he didn't. He visualised space-time as a four dimensional structure: the three space dimensions we are familiar with (which is why we can see stars above us) and one time dimension.

    The "rubber sheet" analogy is just a really bad attempt to try and visualise in 2 dimensions what is happening in four.



    I'm also having trouble imagining four dimensions...
    Don't worry, we all are. (Except, perhaps, the mathematicians.)


    RedPanda and dan hunter like this.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  4. #3  
    Forum Professor scoobydoo1's Avatar
    Join Date
    Apr 2010
    Location
    Singapore
    Posts
    1,240
    I think I may understand how it can be confusing. Those videos or images that you may have seen are for illustrative purposes to help us visualize with lines and grids how distances bends/warps when there is an object with substantial mass. While I can see where you are coming from, I am not well versed enough in physics to explain it any better than that. Perhaps someone else with more in-depth knowledge and expertise can weigh in when they have the chance.
    Reply With Quote  
     

  5. #4  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    16,965
    Quote Originally Posted by scoobydoo1 View Post
    Perhaps someone else with more in-depth knowledge and expertise can weigh in when they have the chance.
    Yeah ... I carefully sidestepped that bit!
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  6. #5  
    Forum Professor scoobydoo1's Avatar
    Join Date
    Apr 2010
    Location
    Singapore
    Posts
    1,240
    Quote Originally Posted by Strange View Post
    Quote Originally Posted by scoobydoo1 View Post
    Perhaps someone else with more in-depth knowledge and expertise can weigh in when they have the chance.
    Yeah ... I carefully sidestepped that bit!
    I used to face the same confusion with Physicsforall, but after a time I've realized that attempting to illustrate on a sheet of paper or even in the form of a video is a lot harder than it appears. Without those lines and grids bending/warping around an object of mass, I do not think I am able to grasp/visualize the bending effect. The only real life example I can think of may be that of a spiraling effect when water flows downwards into a drainage in a sink.
    Reply With Quote  
     

  7. #6  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    16,965
    Markus found a nice diagram that illustrates it in 3D ... not sure I can find it again...

    Edit: here it is: Curved spacetime and multiple planets in orbit : an image of this ?
    scoobydoo1 likes this.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  8. #7  
    Suspended
    Join Date
    Dec 2013
    Posts
    78
    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Physicsforall View Post
    Well Einstein imagined a single layer of space-time right?
    Actually, no he didn't. He visualised space-time as a four dimensional structure: the three space dimensions we are familiar with (which is why we can see stars above us) and one time dimension.

    The "rubber sheet" analogy is just a really bad attempt to try and visualise in 2 dimensions what is happening in four.
    Ok that makes more sense, and if you where to visualize it wouldn't space-time be bending into the object with mass? not around it?
    Nice picture by the way.
    Reply With Quote  
     

  9. #8  
    Suspended
    Join Date
    Dec 2013
    Posts
    78
    Quote Originally Posted by Strange View Post
    Markus found a nice diagram that illustrates it in 3D ... not sure I can find it again...

    Edit: here it is: Curved spacetime and multiple planets in orbit : an image of this ?
    never mind... that answered my question!
    Reply With Quote  
     

Similar Threads

  1. Replies: 3
    Last Post: December 31st, 2013, 12:52 PM
  2. Replies: 2
    Last Post: May 2nd, 2011, 10:41 AM
  3. Replies: 2
    Last Post: March 25th, 2011, 01:43 AM
  4. Understanding Relativity..
    By Mr. Monkey in forum Physics
    Replies: 5
    Last Post: July 29th, 2009, 11:00 AM
  5. Replies: 17
    Last Post: February 16th, 2008, 11:42 PM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •