Why is the spin of the graviton 2?

Question

Electromagnetic and gravitational interactions are similar - they are mediated by massless particles, they have infinite range and they diminish with $1/r^2$. The main difference is that gravity is always attractive while electromagnetic force is not.

A photon intermediating electromagnetic force has spin 1 while graviton should have spin 2. What is a reason for different spin values of photon and graviton?

Possible duplicates: https://physics.stackexchange.com/q/108230, https://physics.stackexchange.com/q/39476 — Nihar Karve, Feb 23 '21 at 08:21
If what you casually state here is true, then why is physics struggling to define quantum gravity? 'The main difference is that gravity is always attractive while electromagnetic force is not.' — my2cts, Feb 23 '21 at 09:30
Gravitons are conjectured to be excitations of the metric field at the quantum level, thus it has the same spin as its field by definition. — Jeanbaptiste Roux, Feb 23 '21 at 09:40
Your question essentially boils down to "why is General Relativity (which predicts spin-2 gravitons) the correct description of gravity". The ultimate answer to this and similar questions is, of course, "because it works so well". — Prof. Legolasov, Feb 23 '21 at 13:04
Does this answer your question? How can I read off the fact that gravity is associated with spin-2 particles from the Einstein-Hilbert action? — Cosmas Zachos, Feb 23 '21 at 14:17

score 1 · Accepted Answer · answered Feb 23 '21 at 16:28

As I understand it, this is because spin-2 yields forces which are only attractive, as opposed to spin-1 which can mediate forces which are attractive or repulsive. I invite the experts to weigh in on this as I would like to understand this better myself. I'll delete my answer if a more complete one is furnished.

Why is the spin of the graviton 2?

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