Gravitational Anomaly: (asked by a student for very simple explanation)
Basically it means the new laws of physics known as Quantum Mechanics invalidates the sanctity of nature’s principles or laws (that is QM brings exceptions to the validity of the physical laws of nature itself)
Let us discuss this in simpler ideas from the basics only.
Remember the most basic physics, that of principle of conservation of energy and the principle of conservation of (linear) momentum.
In the more rigorous formalism of physics these two principles emanate (that is derivable) from two ideas of symmetry. In-fact every conservation principle of physics are manifestations of a corresponding principle of symmetry and vice-a-versa (also every symmetry must correspond to a conservation law). This general idea of connection between conservation laws and symmetry is collectively known as Noether’s theorem and is a central underpinning in all of today’s conceptual physics.
All of Physics is this “Inherent ability = difficulty * accomplishment”. Thats just intuitive but can easily be seen to correspond mathematically with the Principle of least action.
First the edifice: whats the problem? The problem is given you move in straight line when every direction is same around you, which direction will you chose? While you are waiting for a good answer from astrologers intelligent people already give a good hint. Think you have some inherent ability which is fixed.
fixed: which changes only if estimated wrong.
That inherent ability is actually action. Accomplishments are adjusted for difficulties, you waded through a swamp 5 meters you would have accomplished in sand 8 meters with that given inherent ability called action. Because action is abstract we have been sticking to time and path-length, but they are not as fundamental, they are merely specifics.
But all of them are not stable. We have made great strides in understanding them collectively called as standard model of particle physics which involves electroweak and strong interactions. Its a weird mess of beautiful list of particles and their behavior toward each other. Sometimes there is symmetry breaking sometimes there is symmetry and sometimes there is confinement.
What such an astounding theory backed by the most swashbuckling experimental measurements have meant is there are only countable number of stable particles.
Let’s begin counting out of 100s electron, proton, photon and neutrinos … That’s it. End counting.
It explains almost everything we see around us. The matter. If we are to see dark matter we would be explaining that as well. But hold your breath we haven’t seen that so far.
Since almost everything we have seen are so unstable we wouldn’t be created.
But the very few stable particles made atoms possible and the atoms made life possible.
Here is how the atom is possible.
The neutron guy is not very happy as its not stable. It met proton on a blind date and they got
Particle Physics is collectively an effort to study the exciting world of subatomic particles and the nature of their interaction. By subatomic we mean anything that happens within the atom or below and not above. The implications could cover as much above, as it would be entailed by the precincts of natural laws.
eg If a process corresponds to as big a size as is a micro-gram, its evidently not subatomic size in length dimension. The subatomic size by its definition of length scale would correspond to a femto-meters. But the given process is subatomic, while the result of having a size of micro-gram would not be.
Hence while the size of the subatomic entity can roughly be put by a femto meter, nonetheless a particle of the size of pico-meter might find relevance in the study of subatomic processes due to such eerie connections. For another matter a micro-gram is the unit of mass and not that of magnitude of distance.
This fact is inherently, nothing but the concept of Quantum Entanglement. Unlike classical particles which are completely independent of each other the quantum sized objects are not. For physical intuition they are at a very small and subtle level intertwined with each other as if threads are kind of tied onto each other. We can-not toss an electron because the whole concept of one electron completely independent of all other makes sense only when all other electrons are not interacting because they are arbitrarily far away.