Assume now that you introduce a curvilinear coordinate system $u^1,u^2,u^3$ (the superscripts are simply indices numbering the coordinates, NOT exponents this time). document.getElementById("af-header-1264678350").className = "af-header af-quirksMode"; rev 2020.12.10.38158, The best answers are voted up and rise to the top, Physics Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us.  To ensure that this defines a well-defined coordinate system, we demand that these functions are sufficiently differentiable, that they are invertible (eg. @pbsspacetime Facebook: facebook.com/pbsspacetime Email us! The rest of the matter must be in another dimension. })(); We have measured that our visible universe only has about 4% of the mass in the universe. What is outside of the “fabric of spacetime” or visible universe? Thanks for your insight. This popular myth comes from Einstein when he postulated that gravity in space was not a force but a distortion of space. Time, on the other hand, is when things happen. The Earth sends the space craft two signals at an interval t. The space craft receives them at an interval kt on the space craft’s clock. Probably the reason why this whole "fabric" thing was brought into existence was to attempt to make it possible for laypeople to visualize the fact that "spacetime geometry" is not something set in stone but something that is dynamical. Let’s put the theory of ‘curved fabric’ of SpaceTime to rest. document.getElementById("af-body-1264678350").className = "af-body inline af-quirksMode"; } Superstring theory says there must be 9 or 11 dimensions that make up the Universe. The mass of Earth dimples this fabric, much like a heavy person sitting in the middle of a trampoline. The famous physicist Albert Einstein helped develop the idea of space-time as part of his theory of relativity. The only distortion gravity makes is a force of attraction. Related: Newton's Laws of Motion But experimen… // Special handling for facebook iOS since it cannot open new windows