**Ask a monkey a physics question thread**

[OngBonga]

Dinner was good. That video was a bit heavier than PBS. Questions I have none, other than ones you can't answer... such as, where's gravity?

I thought this would be about string theory tbh, To someone uneducated, that seems like the most promising theory when it comes to combining QM and GR. The SM is great except for the elephant in the room.

[MadMojoMonkey]

Dinner was good. That video was a bit heavier than PBS. Questions I have none, other than ones you can't answer... such as, where's gravity?

Dude. I got this. It's not in the Standard Model of Particle Physics.

It's in the Lambda-CDM model.
Lambda for dark energy, CDM for Cold, Dark Matter.

The Lambda-CDM model assumes Einstein's GR is correct and adds on some hypotheses about dark energy and dark matter.

The current state of physics is we use the both the Standard Model and Lambda-CDM Model as proves most useful.
The SM describes 3 of the 4 known forces and Lambda-CDM describes the other 1.
It certainly doesn't feel complete, or like we have full understanding, yet. We have come a long way in the past 200 years, though. A long way.

I thought this would be about string theory tbh, To someone uneducated, that seems like the most promising theory when it comes to combining QM and GR. The SM is great except for the elephant in the room.

While there is a lot of work yet to be done, it's not as though there is no bridge at all between QM and relativity.

The Dirac Equation (the relativistic big brother of the Schroedinger Equation) takes relativistic effects into account for quantum wave functions. Applying this equation to gold atoms shows that the innermost electrons absorb light in the blue-purple band, explaining why gold is yellow-ish in color.

We have a piece of how QM describes mass in the Higgs field (7%) and a piece that describes mass in the spacetime field (93%). So we do use both theories together in many useful cases.

Not to downplay the work that needs to be done, of course. But I think there's a popular misconception that there is no link at all between QM and GR - that the 2 models are totally incompatible - which is not the case.

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I can't help but point out that string hypotheses (they're not theories by scientific standards) have been "the most promising" lead for almost 50 years, now. I'm less and less enamored of string hypotheses every year that goes by.