The 4 guage boson- electromagnetic, strong and weak and gravity?

Question

i have been told that if gravity has a quantum particle that carries the force of gravity it has to have spin2.

the spin is the inherent angular momentum of a particle.

electromagnetism=spin1/2 example electron

strong and weak=spin1 ex. photon, W+/-, Zparticle

?gravity=spin2 ex.?graviton

My question, if the mediator(boson) is determined by the spin(inherent angular momentum) then why are they convinced the earths spin(rotation) has nothing to do with gravity? how can the spins be so unrelated? and also if gravity has to do only with mass, how can a supposed black hole have so much gravity that light can't escape if light has no mass?

i don't have much education so please answer simply.

Answer 1

Light does have mass.

Answer 2

I would like to start an answer to your question by clarifying some points. If you will permit me?

There are four fundamental forces in nature and these are: the strong nuclear force, the weak nuclear force, the electromagnetic force, and gravity. Each of these forces is transmitted by a mediator particle known as a boson. The forces and theories that describe them may be summarised by the following table: -

Interaction.............. Current Theory ......... ......... Mediators

Strong Nuclear. .....  Quantum chromodynamics . gluons

Electromagnetic... .  Quantum electrodynamics .. photons

Weak....................   Electroweak Theory... ..... .. W and Z bosons  

Gravitation ...... ..... General Relativity............... gravitons (not yet discovered)

All of the force mediating or transmitting particles have integer spin because they are bosons. The photon has a spin of one as do the gluons and weak force's transmitters the W  +/- and the Z0! Wikipedia, the free encyclopaedia, comments, 'the graviton is a hypothetical elementary particle that mediates the force of gravity in the framework of quantum field theory. If it exists, the graviton must be massless (because the gravitational force has unlimited range) and must have a spin of 2 (because gravity is a second-rank tensor field).

Gravitons are postulated because of the great success of the quantum field theory (in particular, the Standard Model) at modelling the behaviour of all other forces of nature with similar particles: electromagnetism with the photon, the strong interaction with the gluons, and the weak interaction with the W and Z bosons. In this framework, the gravitational interaction is mediated by gravitons, instead of being described in terms of curved space-time as in general relativity.'

However, the particles that 'feel' the forces are quarks (strong nuclear force) with a half integer spin, leptons (electrons and neutrinos- weak nuclear force and electromagnetic force) with half integer spin. Gravity is ‘felt’ by mass and space-time and is not, as of yet, understood in terms of a particulate transmission! Any particle with a half integer quantum spin is referred to as a fermion.

Now, here is the important point,  Wikipedia, further comments, '...quantum mechanical [sic] ...spin refers to a non-classical kind of angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its centre of mass about an external point. A particle's spin is essentially the direction a particle turns along a given axis, which in turn can be used to determine the particle's magneticism. Although this special property is only explained in the relativistic quantum mechanics of Paul Dirac, it plays a most-important role already in non-relativistic quantum mechanics, e.g., it essentially determines the structure of atoms.

In classical mechanics, any spin angular momentum of a body is associated with self rotation, e.g., the rotation of the body around its own centre of mass. For example, the spin of the Earth is associated with its daily rotation about the polar axis. On the other hand, the orbital angular momentum of the Earth is associated with its annual motion around the Sun.

In fact, in classical theories there is no analogue to the quantum mechanical property meant by the name spin. The concept of this non-classical property of elementary particles was first proposed in 1925 by Ralph Kronig, George Uhlenbeck, and Samuel Goudsmit; but the name related to the phenomenon of spin in physics is Wolfgang Pauli.'

Thus, to finally answer your question - the spin of a 'macro' body such as the earth is described by classical mechanics and not by quantum mechanics. Hence, the angular momentum, of the earth’s rotation, does play a part in the transmission of the force of gravity. However, the rotation of the earth does give rise to the centrifugal force, which acts in a radially opposite direction to gravity. It is the centrifugal force, that results in the oblate spheroid shape of the earth and a very slight reduction in the acceleration due to gravity at the equator!

I hope this answer is of some help!