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Magnetic fields, subatomic particles, etc., traveling in different directions fill the universe. Do they deflect or otherwise affect one another? If so, isn’t the information we get from them distorted?

John R. Miller, Chipley, Florida
Cassiopeia-A
Supernova remnant, Cassiopeia A.NASA/the Hubble Heritage Team (STScI/AURA)
Yes, there are many ways in which the components you list can influence each other. Lower-energy cosmic-ray ions, for instance, change direction readily in galactic magnetic fields, making it impossible to easily identify their source locations. This is one form of distortion.

Cosmic rays also collide with ambient matter in the galaxy (mostly protons). This can convert particles from one variety into another, making what we detect on Earth different from what started out. By carefully studying this conversion process, we can learn about the propagation history of those particles.

These collisions produce high-energy gamma rays. Such particles are excellent astrophysical messengers because they do not change direction in magnetic fields, so when we detect them in space, we get a direct glimpse into the processes occurring in those places. Unfortunately, even gamma rays are sometimes susceptible to meddling. At high energies, they can interact with the background radiation fields that fill the universe (such as microwave and infrared). These interactions destroy the gamma rays and decrease the signal from distant objects.

Neutrino astronomy, which is still in its infancy, is attractive because neutrinos interact so weakly with matter that few of these distorting effects occur. Unfortunately, the very property that makes them immune to this interference also makes them difficult to capture in detectors. — Scott Wakely, University of Chicago, Illinois
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