How do vaccines work?
Vaccines essentially teach your immune system to fight off particular diseases. Think of it as a practice test for the real final exam. Vaccines are usually composed of an agent that is similar to a virus or bacteria that causes a disease. Typically, they’re made from dead or weakened forms of the original disease-causing germ. When the vaccine enters our bodies, our immune system responds to it by destroying it and learning how to create a defense against that agent, so that when you encounter that virus or bacteria is its live form, your immune system already knows how to fight it off. The immune system develops antibodies that can recognize the foreign disease-causing agent and mark it for inactivation. Because of vaccines, we’ve been able to effectively eradicate or restrict once-dangerous diseases, like smallpox, polio and measles.
What causes northern lights? Is there a such thing as a southern light?
Northern lights, or Aurora borealis, have been long famed for their prismatic, dancing nighttime light displays. These dancing lights are actually an atmospheric phenomenon. They are caused by collisions between gas molecules in Earth’s atmosphere and electrically charged particles radiated across space from the sun. The charged particles are often flung towards Earth by solar flares at the sun’s surface. The different colors of the northern lights result from that fact that different types of gas molecules collide with the charged particles. For example, oxygen often causes the typical green colored northern lights, while nitrogen causes blue and purple northern lights.
There are absolutely southern lights, also known as Aurora australis. They work in the same way as northern lights, only at the south magnetic pole instead of the north.