Time and space

  • Thread starter superbk
  • Start date

Answers and Replies

  • #2
Simon Bridge
Science Advisor
Homework Helper
17,874
1,657
How about summarizing the video and relating how you understand what it is saying.
The term "the fourth dimension" has a variety of meaning depending on who you are talking to.

In relativity, time can be treated as a special case of a dimension of space.
There are models which include many more dimensions. Michio Kaku is relating the kinds of ideas that lead to these in this video. Time would certainly be included in any multi-dimensional model ... though, off Kaku's description, time would have to be the 12th dimension since he describes 3D universe-bubbles on the surface of an 11D multiverse which are expanding in time (implying that the 11D mess is evolving in time).

I'm not sure that's the impression he intends - we have to be careful not to read too much into these kinds of lay-descriptions: they are all hopelessly lacking.
In this case Kaku is trying to answer a question - and the questoner appears to have left time off the number of dimensions that our universe has.
 
Last edited:
  • #3
Drakkith
Staff Emeritus
Science Advisor
2022 Award
22,248
6,324
Let's put it this way. It takes 3 separate numbers to describe the spatial position of an object relative to a point in space or another object. Since it takes 3 numbers, we refer to each of these as being a "dimension" of space. If we want to describe the position of something in space AND time it takes 4 numbers, with time being the 4th. (It's a little more complicated, but I trust you get the general idea)
 
  • #4
Simon Bridge
Science Advisor
Homework Helper
17,874
1,657
Yeah - number of dimensions could just be seen as the number of degrees of freedom.
eg. A bicycle can be described by numbers:

x,y,z location (3)
orientation (lean, yaw and pitch) at the location (3)
the relative rotation-angle of each wheel (2)
the relative turn-angle of the handle-bars (1)
the angle of the pedals (1)
time it got there (1)
height and rotation of the seat (2)
... that's 13 dimensions, and I have not gone into it's gears yet.
 

Suggested for: Time and space

Replies
25
Views
900
  • Last Post
2
Replies
48
Views
2K
  • Last Post
2
Replies
61
Views
2K
Replies
70
Views
2K
Replies
12
Views
122
Replies
16
Views
556
  • Last Post
Replies
11
Views
688
  • Last Post
Replies
14
Views
1K
  • Last Post
Replies
3
Views
815
Replies
11
Views
517
Top