Gravity seems to work in all parts of the solar system space probes sent from Earth have visited so far, just as it does here on Earth*.

(I'll return to tests of the uniformity of gravity throughout the rest of the observable universe later).

From a great deal of very good observational and experimental results, obtained here on Earth^, it seems that the Sun has been pretty constant for several billion years. Can we use the Sun to test the uniformity of the weak and strong forces, at least out to ~150 million kms or so? Yes we can: we can build models of the Sun, using gravity, electromagnetism (EM), the weak, and the strong force exactly as we describe them from experiments (etc) here on Earth, and the Sun behaves just like we expect it to, in terms of its output of photons and the solar wind.

Of course, these are rather indirect tests - the place where the rubber of the solar models meets the road of reality is deep within the Sun, in a small region around its centre. Is there a way we can probe the Sun's core, to see the weak and strong force at work, powering the Sun?

Turns out there is ... if the solar models are right, then we are, here on Earth, bathed in stream of neutrinos, of various energies, from various nuclear reactions, in the Sun's core.

Although it took some 40 years, from the time solar neutrinos were first observed, for the results to be fully reconciled, today we know that the weak force seems to operate in the Sun's core just as it does here on Earth. And, by implication and the general success of the solar models, so does the strong force.

So, even though we have not yet visited the Sun's photosphere, much less its core, the strong conclusion we can draw from a wealth of good experimental and observational results, both here on Earth and from the Moon (and various 'photon counts' from space probes in all kinds of places in the solar system) is that the Sun's behaviour is consistent with the uniformity of EM, gravity, and the weak and strong forces ... over a distance of at least an au or so.

Next: from the Sun to stars in general.

*With the exception of the Pioneer anomaly, which is extremely small ...
^And on the Moon - the imprint of the solar wind in lunar soils, for example.