But for gravity

Question

"Copiously produced in high-energy collisions, travelling essentially at the speed of light, and unaffected by magnetic fields, neutrinos meet the basic requirements for astronomy. Their unique advantage arises from a fundamental property: they are affected only by the weakest of nature's forces (but for gravity) and are therefore essentially unabsorbed as they travel cosmological distances between their origin and us." (South Pole Neutrino Observatory.)

What does the bracketed phrase "but for gravity" exactly mean in the above context?

GPY · Accepted Answer

It is not very well expressed in my opinion. I think it means "ignoring gravity" (possibly because gravity is not relevant to the point being made, or possibly because it is not known how they interact with gravity).

Tkacka15 · Answer

GPYIt is not very well expressed in my opinion. I think it means "ignoring gravity" (possibly because gravity is not relevant to the point being made, or possibly because it is not known how they interact with gravity).

Thanks for the reply.

I've thought along this line, but wasn't 100% sure. Indeed, the gravity, as the weakest force out of the other weak ones, in the space, doesn't interact with neutrinos. The "ignoring gravity" matches my understanding of the (but for gravity) as "excluding gravity".

GPY · Answer

tkacka15Indeed, the gravity, as the weakest force out of the other weak ones, in the space, doesn't interact with neutrinos. The "ignoring gravity" matches my understanding of the (but for gravity) as "excluding gravity".

If it is known that neutrinos definitely don't interact with gravity then my explanation makes less sense (or no sense). The explicit exclusion of gravity implies that the statement would be (or might be) different if gravity were included. Otherwise why mention it?

Tkacka15 · Answer

GPYIf it is known that neutrinos definitely don't interact with gravity then my explanation makes less sense (or no sense). The explicit exclusion of gravity implies that the statement would be (or might be) different if gravity were included. Otherwise why mention it?

I think that it is put there as the additional information for the science-articles readers who are not familiar enough with particle physics.

GPY · Answer

tkacka15I think that it is put there as the additional information for the science-articles readers who are not familiar enough with particle physics.

I don't think it matters whether the reader is familiar with particle physics or not. The sentence is still equally confusing, and, in the interpretation discussed above, seems to imply that gravity does (or at minimum might) affect neutrinos, which you say is not true.

Tkacka15 · Answer

GPY tkacka15I think that it is put there as the additional information for the science-articles readers who are not familiar enough with particle physics.I don't think it matters whether the reader is familiar with particle physics or not. The sentence is still equally confusing, and, in the interpretation discussed above, seems to imply that gravity does (or at minimum might) affect neutrinos, which you say is not true.

Thanks for that interesting discussion. I take into consideration your argument and have to say that I'm back in the square one regarding the semantics. It may equally be that "ignoring gravity" doesn't necessarily mean "excluding gravity" here.

My supposition that neutrino doesn't interact with gravity is based on the knowledge that neutrino, formed in the solar interior, is an uncharged, massless (or at least extremely light) particle which passes the whole Sun matter unobstructed before reaching the Earth when, for example, the photon is affected by billions collisions inside the Sun structure before reaching our planet.

GPY · Answer

tkacka15My supposition that neutrino doesn't interact with gravity is based on the knowledge that neutrino, formed in the solar interior, is an uncharged, massless (or at least extremely light) particle which passes the whole Sun matter unobstructed before reaching the Earth when, for example, the photon is affected by billions collisions inside the Sun structure before reaching our planet.

I'm not sure that this supposition is correct. The English Wikipedia article says:

"Neutrinos are affected only by the weak subatomic force, which is of much shorter range than electromagnetism, and gravity, ..."

Tkacka15 · Answer

GPYI'm not sure that this supposition is correct. The English Wikipedia article says:"Neutrinos are affected only by the weak subatomic force, which is of much shorter range than electromagnetism, and gravity, ..."

I'd argue that your cite from that article supports my supposition.

GPY · Answer

tkacka15I'd argue that your cite from that article supports my supposition.

I don't see how. Your supposition was that "that neutrino doesn't interact with gravity". The Wikipedia article says "Neutrinos are affected [...] by [...] gravity". These two statements are contradictory.

Tkacka15 · Answer

GPY tkacka15I'd argue that your cite from that article supports my supposition.I don't see how. Your supposition was that "that neutrino doesn't interact with gravity". The Wikipedia article says "Neutrinos are affected [...] by [...] gravity". These two statements are contradictory.

Read carefully: "Neutrinos are affected only by the weak subatomic force..."

Gravity is a week interactive force, indeed, in fact the weakest of the fourth of them, i.e gravitational, electromagnetic, strong nuclear, and weak nuclear forces, but it is not a subatomic force.

But for gravity

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