Fusion vs. Fission

The nuclear energy can be generated in two ways – fusion and fission. Both fusion and fission energy are generated by altering atoms. What is the difference between fusion and fission? And which way will generate more energy?

As the word “fission” means separate a thing into different parts, nuclear fission means releases energy by splitting atoms. Nuclear fission happens when an unstable isotope is contacted by some high-speed particles. At this time, the unstable isotope is accelerated and then break into small particles.

Unlike “fission”, nuclear fusion means “fusing” several particles into “one”. Nuclear fusion happens when several low-mass particles compress together and release the neutron they do not need anymore. By uniting different particles and releasing neutron, a huge amount of energy is released.

Although nuclear fission can generate higher energy than nuclear fusion, we can hardly found any nuclear fission in our sun. The reason is that nuclear fission requires a particle with enough mass so that it can be “split” into several particles. However, the major element inside Sun are Hydrogen and Helium, which are both low-mass particles. Therefore, the major nuclear energy inside the sun is generated by nuclear fusion.

Nuclear Fusion, pic source 

Moon and Tides – The Magic of Gravity

Tides, picture source

Our sea has a periodic rising and falling phenomena. At a time, the sea will go up and reach to the peak, and at another time, the sea will go down and leaves us an island or a beach. This phenomena is called tides.

The tides are mainly caused by gravitational force from Moon. When we are at the near side of Moon, we are closer to Moon and therefore we will experience a larger gravitational force from Moon. Thus, as the seawater near us will also experience a larger gravitational force, it will be pulled a little bit closer towards Moon and then a rising tide occurs. Besides, when we are at the far side of Moon, we will experience the least gravitational force, which means we will experience the most centrifugal force. Therefore, we the gravitational force from Moon cannot hold the water at the far side of Earth from it, and the seawater at that part will also experience a rising tide. On the contrary, when we are at middle way between the far side of Moon and near side of Moon, the gravitational force from Moon will be neither too large nor too small. Therefore, neither will the seawater be pulled towards Moon nor will it loosed by the Earth. The seawater will come closer towards the earth surface and then a falling tide occurs.

Besides the liquid tide such as tide of seawater, there are some other kinds of tides. An interesting one needs to be mentioned is solid tide. Solid tide occurs on Moon due to the gravitational force from Earth. Unlike Earth, Moon always faces Earth from one direction, that is – one part of Moon will always be the near side of Earth and another part will always be the far side of Earth. As Moon is orbiting Earth and experiencing the gravitational force from Earth, its near side and far side of Earth gradually stretched out, which slowly makes it transit from sphere towards a ellipsoid. Scientists call this phenomenon “Tidal Locking”