Is space infinitely divisible?

  • Thread starter Thread starter ktoz
  • Start date Start date
  • Tags Tags
    Space
ktoz
Messages
170
Reaction score
12
I've been pondering the measurement of distance and how it is affected by relativity and was wondering if there is some general consensus on whether spacetime is infinitely divisible?

I spent a few hours Googling but didn't come across any definitive statements either way.

I came up with the following experiment which could conceivably answer the question but find my limited knowledge isn't getting me any closer.

If you have a photon source and a photon detector and systematically fire individual photons at the detector from all points on a geodesic sphere with extremely fine tesselation (on the order of an atom between points) could there conceivably be some radius where light took longer to travel along a given vector than other vectors?

If there is a limit to how finely space can be divided then at some point, there should be a time difference because light would have to hop from node to node of the underlying structure of space and some vectors would have more nodes to hop.

If space is infinitely divisible then no matter how far the photon source is from the detector, the time would always be the same for a given radius.

Anyone care to hazard a guess?
 
Last edited:
Physics news on Phys.org
This is a very wriggly can of worms. Extrapolating from quantum physics, it is believed there is a smallest length, time and energy. But at these scales space-time is not as we know it. Experiments are out of the question with our current technology because of the factor of about 10^30 btween the Planck scale and the nuclear scale.

Do a Google on 'Planck length', 'Planck time' and 'space-time foam'.

M
 
Last edited:
Mentz114 said:
Experiments are out of the question with our current technology because of the factor of about 10^30 btween the Planck scale and the nuclear scale.

Just to get some perspective on the 10^30 scale difference, I did a calculation and unless I messed up, that's like comparing a volume 1/50 the radius of this period ->.<- with the Earth. Yikes! That is small.

Thanks for the search terms Mentz114

Ken
 
I started reading a National Geographic article related to the Big Bang. It starts these statements: Gazing up at the stars at night, it’s easy to imagine that space goes on forever. But cosmologists know that the universe actually has limits. First, their best models indicate that space and time had a beginning, a subatomic point called a singularity. This point of intense heat and density rapidly ballooned outward. My first reaction was that this is a layman's approximation to...
Thread 'Dirac's integral for the energy-momentum of the gravitational field'
See Dirac's brief treatment of the energy-momentum pseudo-tensor in the attached picture. Dirac is presumably integrating eq. (31.2) over the 4D "hypercylinder" defined by ##T_1 \le x^0 \le T_2## and ##\mathbf{|x|} \le R##, where ##R## is sufficiently large to include all the matter-energy fields in the system. Then \begin{align} 0 &= \int_V \left[ ({t_\mu}^\nu + T_\mu^\nu)\sqrt{-g}\, \right]_{,\nu} d^4 x = \int_{\partial V} ({t_\mu}^\nu + T_\mu^\nu)\sqrt{-g} \, dS_\nu \nonumber\\ &= \left(...
In Philippe G. Ciarlet's book 'An introduction to differential geometry', He gives the integrability conditions of the differential equations like this: $$ \partial_{i} F_{lj}=L^p_{ij} F_{lp},\,\,\,F_{ij}(x_0)=F^0_{ij}. $$ The integrability conditions for the existence of a global solution ##F_{lj}## is: $$ R^i_{jkl}\equiv\partial_k L^i_{jl}-\partial_l L^i_{jk}+L^h_{jl} L^i_{hk}-L^h_{jk} L^i_{hl}=0 $$ Then from the equation: $$\nabla_b e_a= \Gamma^c_{ab} e_c$$ Using cartesian basis ## e_I...

Similar threads

Replies
13
Views
3K
Replies
30
Views
2K
Replies
7
Views
1K
Replies
47
Views
579
Replies
12
Views
2K
Replies
15
Views
2K
Back
Top