In summary, speed is a numerical value only and velocity has a numerical value and a direction. Velocity = change in direction/change in time; whereas speed is the absolute value of distance/time. Absolute value means that if an object is moving forwards or backwards, it will not have a negative number in front of it. So if you travelled 30 kilometers per hour backwards from your current position, you would not describe your speed as -30 kilometes per hour; it would simply be 30 kilometers per hour.

Interestingly, one of the physicists who worked on Tsar Bomba’s development, Andrei Sakharov became strongly opposed to nuclear weapons. In the late 1960′s he ramped up his opposition to nuclear proliferation and helped to broker the Partial Test Ban Treaty in 1963. When ABM’s (anti ballistic missiles) came onto the scene), he was strongly opposed to them, saying that they would increase the likelihood of a nuclear war. He was awarded the Nobel Peace in 1975 for his work in promoting peace and for his role in establishing the Moscow Human Rights Committee. Sadly, he wasn’t allowed to leave Russia to claim the prize, so his wife accpeted it on his behalf. He was also strongly opposed the Soviet Invasion of Afganistan.

Of particular note, is that the gravitational force exerted on the body can vary as much as 0.5% depending upon your location on the earth. In the image on the right, the different colors represent changes in the force of gravity. Wikipedia has an excellent chart that details the force of gravity in different cities around the world. In order for scientists to determine mass with better accuracy, a balance measure is used. A traditional balance is a beam with arms of equal length each holding a scale. The product of unknown mass is placed on the scale and measured against objects with known masses. This technique overcomes the variation in Earth’s gravitational field because both the known and the unknown masses are being equally acted upon.

To summarize mass versus weight, mass is constant and is a measure of how much matter an object contains, whereas weight changes according to the gravitational force exerted upon it.

In summary, heat is energy introduced into a system and is a measure of all the energy in an object. Temperature is proportional to the amount of kinetic energy an object has.

Leptons are more complicated to explain and I will do my best. Leptons are the other component particle to make up an atom. Leptons come in 6 flavors: electrons, muons, and the tau. The other three are these particles combined with their associated neutrino: electron neutrino, them muon neutrino and the tau neutrino. Neutrinos have very little mass and almost no charge and result from nuclear fusion and beta decay. Beta decay produces electron neutrinos and happens when neutrons change to protons or vice versa. The human body is penetrated by quadrillions of neutrinos every second and most come from our Sun.