Neutrinos and photons are both elementary particles, but they have distinct properties, including their mass and interactions with other particles.
Photons are massless particles and travel at the speed of light. They are the quantum particles associated with the electromagnetic force and are carriers of electromagnetic radiation, such as light. Photons are considered to be point-like particles with no spatial extent.
Neutrinos, on the other hand, were originally believed to be massless, but it has been experimentally determined that they have a small, nonzero mass. However, the exact mass of neutrinos is still not precisely known, as it is challenging to measure. The masses of neutrinos are extremely tiny compared to other particles, but they are not considered to be point-like particles like photons.
Neutrinos are weakly interacting particles, meaning they interact very weakly with other particles, including electromagnetic radiation. This property makes them difficult to detect. Neutrinos come in three different types or flavors: electron neutrinos, muon neutrinos, and tau neutrinos, and they can change from one flavor to another through a phenomenon called neutrino oscillation.
In terms of size, it is more appropriate to say that neutrinos have a small mass rather than a size in the traditional sense. While photons are considered to be point-like particles, neutrinos have a nonzero mass and are not strictly confined to a single point in space. However, the actual spatial extent or "size" of a neutrino is not well-defined or easily characterized in the same way as macroscopic objects.
In summary, while both neutrinos and photons are elementary particles, photons are massless and considered point-like, while neutrinos have a small mass and are not strictly point-like but still have extremely small sizes in terms of traditional measurements.