TedEd: When is a pandemic over?

A TedEd by Alex Rosenthal

Several months ago, the COVID-19 disease transferred to humans through animals. It quickly spread when public health measures couldn't contain it, and the WHO declared a pandemic. As the death tolls rise, many are wondering the same thing: When will it be over? The WHO will declare it over when the virus is contained and infection rates drop. There are three main ways this could happen. Race Through It, Delay and Vaccinate, or Coordinate and Crush. The first is when governments do nothing to stop the virus and allow people to be infected. Doctors and researchers have little time to learn about the virus, and hospitals quickly overflow. Many millions die, and people either die or become immune. At this point, we gain herd immunity and the virus cannot infect anymore people. The pandemic is over as soon as it began. The second method also involves herd immunity. Delay and vaccinate works when governments enforce strict public health protocols the minute the pandemic breaks out. Widespread testing, quarantine of those infected, and physical distancing slow the spread of the virus. This gives researchers time to study the virus and find a vaccine over the next few years. Once a majority of a population has received it, herd immunity eradicates the virus. The death toll here is just a few hundred thousand, much lower than in race through it tactics. Coordinate and crush occurs when governments work together to stop the virus from spreading instead of only looking at their own countries. In a typical pandemic, one country peaks as another sees its first cases, and when things like quarantine and travel restrictions are coordinated properly, the virus is contained. However, the virus could return unless it is eradicated, which is highly unlikely. So which method is best? Vaccination is often considered to be the best, as it has low death tolls and is more likely to work than the other two. Plus, it could be reused in the future.

TedEd: Are ghost ships real?

A TedEd by Peter B. Campbell

In 1884 the British steam ship "Rumney" collided with the French ship "Frigorifique". The French crew saw their boat filling with water and boarded the Rumney. But as it sailed away, the Frigorifique sailed out of the fog and sank the Rumney. What happened? The French sailors had left the engine of their ship on, and it had sailed in a circle before hitting and sinking the Rumney. It became a tale of a ghost ship, ships that seemingly sail themselves without a crew. One of the most famous is the Mary Celeste. It was seen in the Atlantic in 1872 with no crew and water in its hold. The reasons it didn't sink can be contributed to buoyancy and fluid dynamics. Buoyancy works by creating a force up on an object when it displaces a fluid. The strength of the buoyancy is equal to the weight of the fluid that was displaced. This is called Archimedes's Principle. This is why things less dense than water float, while things more dense, like steel boats, need big hulls to float. But if it fills with water, it gets heavier, causing it to sink. However, the flooding of the Mary Celeste stopped when the water reached the equilibrium point, the same level as the hull. This is fluid dynamics at work. Another strange tale is of A. Ernest Miller, a boat transporting salt. It sank in a collision, yet was seen on the surface a few days later. What happened was that the heavy salt in the hold dissipated over time, and it was just enough to reduce the weight of the ship and bring it back up. The final part of the ghost ship legends - multiple sightings of one boat in locations far apart. This can be attributed to ocean currents. Caused by differences in temperature, salinity, and wind, they are like little rivers in the ocean, and they carried ships around the world. This is how scientists identified some of the largest currents, such as the Gulf Stream. So ghost ships aren't supernatural phenomena, but ships kept afloat by the mysterious powers of physics.

Of Mice and Men

Of Mice and Men

By John Steinbeck

Read in 9th grade

George and Lennie have traveled to a ranch in the countryside. George is a small, intelligent man, while Lennie is massive, but has the brains of a child. Lennie got them in trouble by trying to touch a girl. Just liked the dress, he says. When she panicked, he wouldn't let go because he didn't know what to do, and he hid with George in a ditch until they could get away. They have decided to work on the ranch and make enough money to buy their own place, with rabbits for Lennie. When they get there, they meet the owner, who is nice enough, but his son is the problem. His son is a fighter with a flighty wife, always afraid the men on the ranch are after her. He is especially wary of Lennie because of his size.

TedEd: How bones make blood

A TedEd by Melody Smith

Your body has trillions of blood cells circulating inside you. All of these originate in your bones. Bones may seem hard, but they're actually porous inside, allowing blood vessels to enter. Most of the bone is filled with soft bone marrow. The most important part of this is blood stem cells. These multiply many times, turning into red and white blood cells, and platelets. They go out into the blood stream through capillaries. This is why many blood cancers occur in bone marrow. If the stem cells have a mutation, they could produce malignant blood cells, which are bad for the body. For patients with diseases like leukemia and lymphoma, their best bet at survival is a bone marrow transplant. To do this, stem cells are taken from a donor in one of two days. The first is by extracting blood and then separating stem cells, the second by direct extraction from bone. Chemotherapy or radiation are used to kill existing bone marrow, then the donor's is transplanted in the patient. This can also cause graft-vs-tumor activity. This is when the transplanted immune cells from the donor wipe out cancer cells that the patient's immune system couldn't. However, there could also be adverse effects. Graft-vs-host disease occurs when the donor's immune cells begin attacking the patient's organs, causing life-threatening conditions. This occurs in about 30-50% of people whose donor isn't an identical twin. To prevent this, patients can take immunosuppressants, or immune cells can be removed from the donor's cells. But if they overcome this obstacle, they face the possibility of their own immune system denying entry for the new stem cells. In order to find the best donor, genetic samples are taken and key strands that control the immune system are matched. For this reason, siblings and close relatives are often the best donors, as these genes are passed down. If you want to donate, go to join.bethematch.org to enter yourself in the registry. The donating process is just giving some blood.