- 23 Dec '17 17:34When I read Lee Smolin's "Three roads to Quantum Gravity" I was surprised at Smolin's confidence that space-time is discrete. Not everybody agrees with that and I used to be a skeptic myself, but I honestly don't know the answer. There are arguments for both sides so feel free to make your case for either side. I hope to learn something from it.

https://phys.org/news/2016-04-universe-space-time-discrete.html - 23 Dec '17 18:46

One thing the piece mentioned was they may be able to test it and there is an image of a device to be held close to 0 degrees Kelvin and hit one with a laser and I presume they would look for a quantum harmonic coupling to the other unit in the image.*Originally posted by @metal-brain***When I read Lee Smolin's "Three roads to Quantum Gravity" I was surprised at Smolin's confidence that space-time is discrete. Not everybody agrees with that and I used to be a skeptic myself, but I honestly don't know the answer. There are arguments for both sides so feel free to make your case for either side. I hope to learn something from it.**

https://phys.org/news/2016-04-universe-space-time-discrete.html

Sounds tricky, one thing I see is how would you isolate the incoming laser light from the one you hit to the one you want to measure, and other considerations.

I have not found out if they performed the experiment or not. This was a year and a half ago so it could have been done but don't see results.

Here is a piece suggesting space time may be continuous and discrete at the same time

http://iopscience.iop.org/article/10.1088/1367-2630/12/11/115001/meta

More quantum weirdness. - 25 Dec '17 02:36

use the Higgs Singlet to get all your answers*Originally posted by @metal-brain***When I read Lee Smolin's "Three roads to Quantum Gravity" I was surprised at Smolin's confidence that space-time is discrete. Not everybody agrees with that and I used to be a skeptic myself, but I honestly don't know the answer. There are arguments for both sides so feel free to make your case for either side. I hope to learn something from it.**

https://phys.org/news/2016-04-universe-space-time-discrete.html - 27 Dec '17 00:39

But math reaches us into places we never would have connected had it not been for the study of deep connections between math and reality. Math has its own reality, for instance string theory, a beautiful work but no way to predict results so far anyway.*Originally posted by @apathist***I see people trying to make reality conform with math. It should be the other way around.** - 27 Dec '17 22:59

I don't see how that gives me any answers.*Originally posted by @ogb***use the Higgs Singlet to get all your answers**

Richard Feynman said positrons go backwards in time. I don't know how he would know that. Doesn't seem like there is a way to prove that. Is that what you think the Higgs Singlet does? - 28 Dec '17 02:41

I'm not at all sure what it even means for "time" to be discrete and continuous at the same "time."*Originally posted by @sonhouse***One thing the piece mentioned was they may be able to test it and there is an image of a device to be held close to 0 degrees Kelvin and hit one with a laser and I presume they would look for a quantum harmonic coupling to the other unit in the image.**

Sounds tricky, one thing I see is how would you isolate the incoming laser light from the one you hit ...[text shortened]... http://iopscience.iop.org/article/10.1088/1367-2630/12/11/115001/meta

More quantum weirdness. - 28 Dec '17 04:31

A line is continuous although individual points are discrete.*Originally posted by @soothfast***I'm not at all sure what it even means for "time" to be discrete and continuous at the same "time."** - 28 Dec '17 10:55

yes, thanks for telling us all what we already know.*Originally posted by @eladar***A line is continuous although individual points are discrete.** - 28 Dec '17 17:06

I know. A siren calls.*Originally posted by @sonhouse*

But math reaches us into places we never would have connected had it not been for the study of deep connections between math and reality. Math has its own reality, for instance string theory, a beautiful work but no way to predict results so far anyway.

Re string theory - the crystal spheres of heaven are beautiful too. - 28 Dec '17 20:15 / 1 edit

Lee Smolin is good at raising thought-provoking questions, but often falls short of furnishing convincing answers. And it is during those times when he is the least convincing that he frequently sounds the most sure of himself. Maybe it's just his writing style, but some of his chapters have the feel of going to church or listening to a sermon on the mount.*Originally posted by @metal-brain*

https://phys.org/news/2016-04-universe-space-time-discrete.html

However, I've only read two of his books, and read some reviews about others. It so happens I just finished reading the second book,*Time Reborn*, less than a week ago. I think I started it over two years ago, but kept putting it aside for months at a time on account of it being difficult to read -- and all for the wrong reasons. His attempts to describe many of the latest cosmological theories are often clumsy and vague to the point of being meaningless. A couple times I found it easier to understand what was going on by skimming through the original research papers he referenced. There's not a single equation in the entire book, and it is not a trivial matter to describe what are essentially mathematical constructs without using any mathematics. Most laymen's books on modern cosmology or quantum theory fail in this regard.

The first Smolin book I read was*The Trouble with Physics*, which was much more engaging and convincing. That so-called "string theory" is verging on becoming a religion amongst the high priests of cosmology is a hard sell, and while he doesn't come out and say that as such, he strongly implies it and makes a good case for it.

So I think Smolin is a proponent of something called quantum loop gravity, which is an alternative to string theory. - 30 Dec '17 01:18

And may the best theory win. I also read 'trouble with physics' and thought he made cogent points like the fact there are no predictions in string theory for experimentalist's to grab on to.*Originally posted by @soothfast***Lee Smolin is good at raising thought-provoking questions, but often falls short of furnishing convincing answers. And it is during those times when he is the least convincing that he frequently sounds the most sure of himself. Maybe it's just his writing style, but some of his chapters have the feel of going to church or listening to a sermon on the mo ...[text shortened]... a proponent of something called quantum loop gravity, which is an alternative to string theory.** - 30 Dec '17 18:57

So we already know that a line is both continuous and descrete depending on how we choose to look at it.*Originally posted by @humy***yes, thanks for telling us all what we already know.** - 30 Dec '17 20:25

No.*Originally posted by @eladar***So we already know that a line is both continuous and descrete depending on how we choose to look at it.**

A line is continuous.

No matter how you look at it.

A line can be used to represent discrete data (for example population growth)

but that is not the same as saying it is discrete, that doesn't make sense.