I'm just frustrated because I just watched (a few hours ago) a fifty-minute lecture of something I didn't get any of, and then with five minutes left I'm informed that this is how we know there is no life after death. It just seemed to me that there was nothing there in support of that claim.
I'll answer any questions as best I can, but please bear in mind that I took one semester of this stuff, and that was 28 years ago. So while I'm familiar with the terminology, I only have a layman's understanding of any research in the last 30+ years. (Since the course I took wasn't completely up to date even at the time.)
I'm not saying there is nothing in quantum field theory that supports ruling out astrology, reincarnation and black magic, I just didn't really get how the impossibility of introducing new particles, fields or laws means that the supernatural cannot exist. Exactly why can't it exist within the limits of the Standard Model? That's not a rhetorical question, BTW.
Okay, let's take astrology as an example. Supposedly the position of the planets at the time of our birth influences the course of our lives in ways that can be predicted using pretty simple mathematics.
Is this possible, using what we know of physics?
Well, the only two forces that work over that sort of distance are the electromagnetic force and gravity. We know immediately that it's not the electromagnetic force, because that's
light, and if you live in a big city you don't see that planets much.
That leaves gravity. The force of gravity goes by the inverse-square law, which means that when you double your distance from an object, the gravity goes down by a factor of four.
The planet Mars has a mass of about 1,000,000,000,000,000,000,000 tons and at its closest approach to Earth is about 50 million kilometres away. If we do the calculations we work out that the influence of Mars on you is about the same as any passing car when you're standing at the crosswalk waiting for the lights to change.
So that means that any effect Mars might potentially have would be totally randomised by the world around you.
What the result Dr Carroll discusses means is that this is the end of the discussion. There are no undiscovered laws of physics that can change this. Astrology is simply wrong.
The same thing goes for homeopathy, for reincarnation, magic, psychic powers, and so on. Once we show that they contradict the laws of physics, that is
it. If any of these things were real, even if we hadn't worked it all out yet, we would have found a subatomic particle that we hadn't expected.
There may be subatomic particles we haven't found yet, but they're in the other part of the diagram - the part that corresponds to galaxies, exploding stars, and atomic nuclei. The part where we spend our lives has been fully mapped out.
As an analogy - there are almost certainly creatures in the depths of the ocean that we didn't expect and have yet to discover. But there aren't any living in your bathtub.