16. If you apply an electric current to a pickle it will excite the sodium ions in the salt, causing the pickle to glow.
This experiment uses a pretty interesting demonstration of the law of conservation of energy. Pickles have very high concentration of salt and salt is an ionic molecule with Na+ and Cl– ions. When electricity is passed, the electrons in Na+ ions are excited and jump to a higher level energy state. Then they jump back down emitting the energy they received in the form of light just like in sodium lamps. However, if you are planning on doing this experiment, caution is advised as it requires 120 V of electricity.(source)
17. In a vacuum, if you were to drop two objects from the same height, they’d hit the ground at exactly the same time, regardless of their respective masses.
In 1589 Galileo two objects of different masses from the Tower of Pisa to prove that the time they take to reach the ground is the same. At first it might seem counter-intuitive and would be hard to believe objects of different masses would reach ground at the same time. But, on Earth, since we have an atmosphere of air, the objects are subjected to air resistance when falling which affects their speed. In 1971 an astronaut demonstrated the proof of Galileo’s theory by dropping a feather and a hammer on the moon. In the absence of air resistance, both of them reached the ground at the same time.(source)
18. NASA has 2 satellites chasing each other around the Earth tracking the distance between themselves to measure gravitational anomalies. Their nicknames are Tom & Jerry!
Formally called GRACE or Gravity Recovery And Climate Experiment, the function of these two satellites is to make detailed measurements of Earth’s gravitational field. By knowing gravitational anomalies, the mass distribution of Earth can be calculated which is important for studying oceans, geology and climate. The two satellites constantly maintain a microwave-ranging link between them and distance measurements are made by comparing frequency shifts of the link.(source)
19. In zero gravity, a candle’s flame is round and blue.
On Earth, when the candle burns the heated gases rise upward pushing combustion products along with them while drawing fresh air with oxygen towards the flame. This process is called convection, hot air becomes light and goes up, while the cool air stays heavier and comes down. But it doesn’t occur in space. Instead, the combustion products accumulate around the flame causing it to be cut off from oxygen and eventually going out. Though the candle does get oxygen through diffusion, the process is a 100 times slower than it is on Earth.(source)
20. Vantablack, a substance made of carbon nanotubes that is the blackest substance known on Earth. It absorbs 99.965% of radiation in the visible spectrum.
Named after Vertically Aligned NanoTube Arrays (Vanta), the light striking its surface gets trapped within the forest of nanotubes and comes out as infrared light (heat). The remaining visible light, 0.04 percent, is so small that the human eye cannot perceive the depths and elevations on its surface making even a 3D object look flat and 2D.(source)