6 When flying, owls make almost no sound even when recorded in a room with microphones. 

The wings of owls are quite different from that of other birds. For one, the feathers are larger than average. The edges of the feathers are serrated reducing aerodynamic disturbances and making the flapping motion nearly silent. Another feature is that the feathers are covered with a velvety structure that absorbs the sound of wing movement. What little sound its flight does generate is out of the hearing range of most prey but can be heard by the owl. The silent flight gives the owl an added advantage while hunting at night.

Unfortunately, there is also a downside to this feather adaptation. In order to retain the softness and silent flight, owls cannot use preen oil or powder dust to keep the feathers waterproof. They cannot hunt when the weather is wet. They also often drown in water when they land to drink or bathe but cannot climb out. (source)

7 The black mesh that lines a microwave oven’s door physically blocks the microwaves. It works as a Faraday cage, and the waves are so large they cannot pass through the holes. 

Microwaves are a type of electromagnetic radiation between infrared and radio waves with wavelengths ranging from one millimeter to one meter and frequencies 300 GHz to 300 MHz. One of the most common frequencies used for microwave ovens is 2.45 GHz and has a wavelength of 12.2 centimeters. The holes in the black mesh are too small to let the microwaves pass through them.

The oven’s cooking chamber along with the mesh acts as a Faraday cage – an enclosure made of conductive material that acts as a shield that blocks electromagnetic fields. Faraday cages are used to protect sensitive equipment from external radio frequency interference as well as to prevent the radio waves from transmitters from interfering with outside equipment. (1, 2)

8 The human fetus is kept asleep 95% of the time in the womb. The womb has an oxygen content equivalent of the top of Mt. Everest and is designed to keep the baby asleep while it grows. 

The necessary neuronal network for the brain to experience consciousness finishes forming by the third trimester. Even if the baby is born prematurely at this stage, it is equipped to survive with the right medical care. After observing premature babies and various animal fetuses, scientists have found that at least 95% of the time they are in two states of sleep – the active sleep and the quiet sleep. These are similar to rapid-eye-movement (REM) sleep and slow-wave sleep seen in mammals.

During this time, the fetus is actively sedated to keep it sleeping. This is achieved by low oxygen pressure and the warm, cushioned environment of the uterus as well as various neuroinhibitory and sleep-inducing fluids. (source)

9 Liquid oxygen is paramagnetic. It can be moved around and even be suspended between magnetic poles.

Liquid oxygen, also known as LOX, exists between −218.79°C ( −361.82°F) and −182.962°C ( −297.332°F) and is slightly denser than water. The light blue liquid is strongly paramagnetic, and when it is poured into a strong magnetic field, it is suspended. Interestingly, it does not obey Curie’s law which states that the amount of magnetization of a paramagnetic material is directly proportional to the strength of the magnetic field. In 1924, Gilbert N. Lewis predicted it was because of the formation of tetraoxygen molecule (O₄), though modern computer simulations show that it is because of the oxygen molecules (O₂) with antiparallel spins forming pairs. (source)

10 You see flashes of light when you rub your eyes because the pressure activates visual receptors in you retina. Since the brain can’t tell the difference, it interprets the pressure as if you were seeing lights in front of you. 

The phenomenon of seeing flashes or blobs of light is called “phosphene.” Apart from the mechanical stimulation of rubbing, electrical and magnetic stimulation can also cause it. People who meditate for long periods of time, those who are kept in dark cells devoid of visual stimulation, truck drivers, and pilots also report experiencing phosphenes.

A team of scientists from the University of Washington in Seattle and Carnegie Mellon University in Pennsylvania believe this phenomenon can be used to develop mind-to-mind communication technology. In an interesting experiment, they had two subjects (senders) wearing electroencephalography (EEG) electrodes, and one subject (receiver) wearing a transcranial magnetic stimulation (TMS) helmet. Together, the subjects were to play Tetris. The senders must decide the move and communicate it without speaking to the receiver who will make the move.

When the new brick falls, the sender focuses on the icon denoting left or right rotation. The EEG electrode picks up the signal and sends it to the TMS helmet which stimulates a relevant phosphene reaction. The receiver would then make the move accordingly. The test succeeded 81% of the time. (source)