Imagine that the source of energy in the interior of the Sun changed abruptly. a. How long would it take before a neutrino telescope detected the event? b. When would a visible-light telescope see evidence of the change?

Neutrino detection is crucial for understanding processes happening inside the Sun. Neutrinos are subatomic particles generated during nuclear reactions, such as those that power stars. What makes neutrinos unique is their weak interaction with matter. This means they can pass through the Sun and reach Earth without being absorbed or deflected significantly.
Detecting neutrinos requires specialized telescopes called neutrino detectors. These detectors are often placed underground to shield them from other cosmic rays that might interfere with the readings. Since neutrinos travel almost at the speed of light, any change in the Sun’s energy source would be detectable within 8 minutes, the time it takes for neutrinos to travel from the Sun to Earth.
Given their weak interaction with matter, neutrino detectors need to be highly sensitive to capture these elusive particles. Neutrino detection helps us timely understand changes in solar activities and other cosmic phenomena.

Solar neutrinos are a specific type of neutrino that come from nuclear reactions in the Sun's core. In these reactions, hydrogen nuclei fuse to form helium, releasing energy that powers the Sun.
This energy also releases neutrinos, which then travel outward from the Sun’s core. Unlike photons, which interact often with matter and hence take a long time to surface, neutrinos travel straightforwardly without much hindrance.
Because of this straightforward travel, observing solar neutrinos gives scientists a direct way to study the conditions within the Sun's core. This allows us to understand more about the nuclear processes happening inside and how they change over time. Solar neutrinos offer vital clues for solar physics and stellar evolution studies.

Photon travel time in the context of the Sun is significantly different from that of neutrinos. Photons are particles of light and are produced in the Sun's core alongside neutrinos.
However, unlike neutrinos, photons interact frequently with matter in the Sun. This frequent interaction causes them to take a

Radiative diffusion is the process by which photons, produced in the Sun’s core, make their way to the surface. Due to the Sun's dense interior, these photons continually interact with matter, being absorbed and re-emitted countless times along their journey.
This zigzag path significantly delays their travel time, turning what could be a short trip into one lasting thousands to millions of years. This extremely slow movement contrasts sharply with neutrinos, which travel nearly at the speed of light and are not significantly hindered by interactions with solar matter.
Understanding radiative diffusion is essential for comprehending how energy produced in the Sun’s core eventually reaches the surface as visible light. It also explains why any abrupt changes in the Sun’s core take so long to become observable by visible-light telescopes on Earth.