The Alleged non-physicality of Quantum Gravity

[sethoflagos]

Has physics stagnated for seventy years on this dilemma?

 

[joigus]

Nah. It's not physics that's stagnated. It's string theory. Physics is not just superstring theory. Physics is not just unification or superunification or cosmology either. Physics is not just theoretical physics.

Has the pace of theoretical physics slowed down considerably in comparison to other branches of physics? Arguably, yes.

I think humanity periodically loses vivid memory of the 'intelectual turmoil' of past times. It's normal. Before the next revolution there's a time when this intelectual territory is up for grabs, and people start staking their claims.

Superstring theory has not lived up to the expectations. So what? The most dangerous man in the world? Witten is a mathematical physicist that's turned out to be more useful to mathematicians than to physicists so far. He didn't win a Nobel Prize, but he did win a Fields Medal.

Michio Kaku is out of control? Is he publishing dangerously? 🤣 Gimme a break!

The way I see it, this is like the centuries between Galileo-Newton and Faraday-Maxwell, when nothing new in physics seemed to appear, but robust and powerful progress in the formalism was accruing.

People, be patient. It's not gonna be you, it's not gonna be in your lifetime, it's not gonna be your pet theory that gets chosen. What's going on is not making the headlines, it's not on the podcasts, it's not on TV, that's all.

Edited March 22, 2023 by joigus
minor correction

[Genady]

2 hours ago, joigus said:

Nah. It's not physics that's stagnated. It's string theory. Physics is not just superstring theory. Physics is not just unification or superunification or cosmology either. Physics is not just theoretical physics.

Has the pace of theoretical physics slowed down considerably in comparison to other branches of physics? Arguably, yes.

I think humanity periodically loses vivid memory of the 'intelectual turmoil' of past times. It's normal. Before the next revolution there's a time when this intelectual territory is up for grabs, and people start staking their claims.

Superstring theory has not lived up to the expectations. So what? The most dangerous man in the world? Witten is a mathematical physicist that's turned out to be more useful to mathematicians than to physicists so far. He didn't win a Nobel Prize, but he did win a Fields Medal.

Michio Kaku is out of control? Is he publishing dangerously? 🤣 Gimme a break!

The way I see it, this is like the centuries between Galileo-Newton and Faraday-Maxwell, when nothing new in physics seemed to appear, but robust and powerful progress in the formalism was accruing.

People, be patient. It's not gonna be you, it's not gonna be in your lifetime, it's not gonna be your pet theory that gets chosen. What's going on is not making the headlines, it's not on the podcasts, it's not on TV, that's all.

Thank you for the review. Well said. +1

Has solved my dilemma: to click or not to click.

[swansont]

I notice he never answered the question about how many people are working on this problem. It’s probably a relatively small number.

 

[Sensei]

34 minutes ago, swansont said:

I notice he never answered the question about how many people are working on this problem. It’s probably a relatively small number.

The same as "time travel", "parallel universes" etc..

Ordinary people do everything for money.. No money, no work..

ps. This would be an interesting topic for a "how much Thomas Swanson" spent in physics doing something he wasn't paid for (and seeing the results obviously!)..

 

Edited March 22, 2023 by Sensei

[swansont]

55 minutes ago, Sensei said:

The same as "time travel", "parallel universes" etc..

More than that, I think.

55 minutes ago, Sensei said:

Ordinary people do everything for money.. No money, no work..

People are paid to do physics. I know a number of theoreticians. 

The research costs are probably not high for a university position - a computer, summer salary, travel (and overhead). More if you have a grad student, but they’re pretty cheap, too.

 

55 minutes ago, Sensei said:

ps. This would be an interesting topic for a "how much Thomas Swanson" spent in physics doing something he wasn't paid for (and seeing the results obviously!)..

 

I do this for free.

I was paid to do research. I was paid a lot less to do research when I was a postdoc (and worked more hours), and even less when I was a grad student. One could take the view that I did a lot of work I wasn’t paid for before I got my research gig building atomic clocks and facilities to house them.

[Sensei]

I wish we had more physicists than politicians, soldiers, humanists, etc. etc. combined, you could understand me better..

 

31 minutes ago, swansont said:

People are paid to do physics. I know a number of theoreticians. 

I have feeling that you took my words up-side-down..

 

You should say (way too late) "I know a lot of theoretical physicists who do it for free without getting paid and still do it.".. THEN put this in your message to me for it to have any meaning in the discussion..

 

If someone does theoretical physics and has no results and takes money for it, it looks even worse..

 

Edited March 22, 2023 by Sensei

[swansont]

2 hours ago, Sensei said:

I

You should say (way too late) "I know a lot of theoretical physicists who do it for free without getting paid and still do it.".. THEN put this in your message to me for it to have any meaning in the discussion..

I don’t know why I would say that.

2 hours ago, Sensei said:

 

If someone does theoretical physics and has no results and takes money for it, it looks even worse..

 

Who said they have no results? Ones that I know publish papers. Books, too.

[sethoflagos]

10 hours ago, joigus said:

Has the pace of theoretical physics slowed down considerably in comparison to other branches of physics? Arguably, yes.

@Genady opened my eyes somewhat a couple of weeks ago by suggesting I look into the extension of GR into a fifth dimension by Kaluza-Klein which seems to have been a catalyst for QED. A similar extension into a sixth dimension (if I understand correctly) led to Yang-Mills and thence to QCD.

What seems odd to me is that having started with GR, why should extensions into yet further dimensions be expected to 'give birth' to a theory of gravity when GR already seems to have that one covered? Is there some reason why Ouroboros must swallow its tail like this? All particles we have ever observed are accounted for by these theories so what more do we need (other than some tidying up of the mathematics perhaps)?

 

[joigus]

1 hour ago, sethoflagos said:

@Genady opened my eyes somewhat a couple of weeks ago by suggesting I look into the extension of GR into a fifth dimension by Kaluza-Klein which seems to have been a catalyst for QED. A similar extension into a sixth dimension (if I understand correctly) led to Yang-Mills and thence to QCD.

What seems odd to me is that having started with GR, why should extensions into yet further dimensions be expected to 'give birth' to a theory of gravity when GR already seems to have that one covered? Is there some reason why Ouroboros must swallow its tail like this? All particles we have ever observed are accounted for by these theories so what more do we need (other than some tidying up of the mathematics perhaps)?

 

I don't know. In QED there is no curvature, and no gravity. Kaluza-Klein did propose a generalisation of GR meant to package EM and gravity together. Einstein liked it at first but for some reason found problems with it. Every now and then people revive the idea for model-building purposes...

Yang-Mills is a generalisation of electromagnetism, rather than gravity. It's what gives rise to weak and strong interactions.

In all these YM theories we have a group of symmetry that defines the particles, their properties, how many there are... Everything.

In the case of EM it does remind one of Kaluza-Klein's idea in the form of an internal dimension, because the group is U(1), which is the group of symmetries of a circle.

But the group for electroweak is U(1)xSU(2)_L (L for "left") is bizarre in terms of a Kaluza-Klein kind of thinking. 

Today, these extra parameters are sometimes referred to as "internal", but I don't think anybody thinks about it in terms of dimensions. They're rather quantum numbers. Further physical variables and conserved quantities.