From the TED-Ed YouTube channel:
We only know 4% of what the universe is made up of. Can we also know what lies beyond our galaxy … and if there are undiscovered forms of matter? Luckily, we have space messengers — cosmic rays — that bring us physical data from parts of the cosmos beyond our reach. Veronica Bindi explains what cosmic rays are, and how they transmit information about our universe from the great beyond.
Lesson by Veronica Bindi, animation by TED-Ed.