Unraveling Cosmic Rays: Universe's Hidden Messages

The Universe has a unique method of revealing its existence to us. Apart from electromagnetic radiation, numerous celestial bodies discharge high volumes of charged particles that travel almost at light speed. These particles, dubbed cosmic rays, provide an alternative way to perceive reality, aiding our comprehension of the immense complexity of the Universe. Cosmic rays comprise primarily of hydrogen nuclei or protons (90%), which form the basis of atomic nuclei. They also contain helium nuclei or alpha particles (9%), and a combination of heavier particles such as iron nuclei, or lighter elusive ones like neutrinos, electrons, and positrons.

The Cosmic Rays Sky

Suppose our eyes had the capacity to perceive cosmic rays. In that case, the sky would appear 10 to 100 times brighter than the night sky, akin to a starless and uniformly illuminated sky under the light-polluted sky of a bustling city like Milan or Rome. Cosmic rays, composed of charged particles, are incredibly sensitive to magnetic fields. The Milky Way has a complex magnetic field that scatters and deflects these rays, causing them to lose their original trajectory. This makes it challenging to trace them back to their emitting celestial bodies, thus sparking debates about their mysterious and violent origins. Supernovae explosions and rapidly spinning neutron stars are possibly involved. Some cosmic rays originate from the Sun and intensify during solar storms, emitting numerous charged particles, albeit at lower energies than cosmic rays from open space. Some cosmic rays are so potent that they traverse other galaxies at nearly the speed of light, possessing energies millions of times higher than what can be achieved by the most advanced particle accelerators on Earth, like the LHC.

The Perils of Cosmic Rays

Cosmic rays pose a significant risk to life due to their powerful radioactivity. Protons moving at near-light speeds can penetrate our skin, destroy cells and DNA, leading to severe and potentially fatal illnesses, much like the radioactivity produced by substances like uranium. Thankfully, our atmosphere acts as a natural shield, providing us substantial protection. In space, the energetic cosmic ray flux reaches 10,000 particles per second, per square meter of surface area, and per unit solid angle. On Earth, with our planet below and the atmosphere above, this particle flux is drastically reduced to a few hundred particles, at most a thousand. Moreover, harmful protons are transformed into secondary particles such as muons, neutrinos, and electrons, which are less potent and harmful to our health. Muons and neutrinos can even pass through our bodies without causing harm due to their reluctance to interact with other particles.

Earth's magnetic field serves as a vital shield against cosmic rays, particularly those emanating from the Sun. As altitude increases, so does our exposure to radioactive particles. A mere 10-hour flight at airliner altitude exposes us to radiation equivalent to 3-5 dental X-rays. 

In the International Space Station, where only Earth's magnetic field provides protection, radiation levels soar to about 800 times higher than at sea level. This increased exposure limits astronauts' stay in space, typically a year maximum. Beyond our planet's magnetic field, the cosmic ray flux intensifies further by one and a half times. 

Solar storms generate cosmic rays that, while relatively low in energy, can prove fatal to astronauts in interplanetary space if hit directly. The absence of Earth's magnetic field protection and the unpredictability of solar threats are significant hazards for long-term manned missions to Mars. Any future Mars mission must address cosmic ray shielding, a daunting task considering thick lead walls would be required, dramatically increasing spacecraft weight.

However, cosmic rays aren't just a threat. Those penetrating Earth's magnetic field, particularly galactic ones with energies above 1 GeV, are believed to be vital for our survival. They are thought to play a crucial role in cloud seeding, a process necessary for significant precipitation on Earth. 

The creation of clouds requires two ingredients: a temperature lower than the condensation point of water vapor and condensation nuclei. Atmospheric atoms ionized by cosmic rays provide ideal condensation nuclei. In the right amounts, cosmic rays can limit their damage and potentially prove beneficial to our planet.

Cosmic rays are also observable in photographs. For example, images from the Soho probe often show small bright lines that vanish between successive images due to a cosmic ray crossing the sensor. These rays carry significant energy, producing not just a bright spot but a trail of light in images. Amateur astronomers with long exposures and CCD or CMOS cameras often detect these cosmic ray effects. There's even a specific field of astronomy, particle astrophysics, dedicated to understanding the number, energy, origin, and chemical composition of these charged particles.

Unraveling the Antimatter Mysteries with Cosmic Rays

Cosmic rays carry an intriguing secret - antimatter. This mysterious substance makes up a tiny portion of cosmic rays, yet its study is paramount. Antimatter particles mirror their matter counterparts but bear opposite charges. For instance, an electron's antimatter equivalent is a positron, identical in all but its positive charge, while a proton's antiparticle, an antiproton, bears a negative charge.

The early universe was believed to have created matter and antimatter in equal measures. So, why does our universe seem to teem with matter, with antimatter scarcely seen? Could there be realms where antimatter reigns supreme? These questions are at the crux of our cosmic exploration.

Via the lens of cosmic rays, we're attempting to answer one of the greatest enigmas: why do we, beings of matter, exist? When matter and antimatter meet, they dissolve into energy, producing high-energy electromagnetic waves or gamma rays. If the early universe generated equal amounts of matter and antimatter, we wouldn't exist, because everything would have turned into energy, leaving a universe filled only with photons.

We owe our existence to an unexplained asymmetry in the physical laws that slightly tipped the scales in favor of matter creation, leaving an excess of one part in a billion. This surplus matter is all that survived, and it's the stuff we're made of.

Incredibly, our existence is due to one particle in a billion that endured the chaotic infancy of the universe, an event rarer than any lottery win. We are here, and the reason for our existence, if there is one, remains a mystery yet to be revealed.