Isaac Newton's Second Laws

Isaac Newton’s first law states that the real effect of a force is always to change the speed of a body, rather than just set it moving, as was previously thought. It also meant that whenever a body was not acted on by any force, it will keep on moving in a straight line at the same speed. What happens to a body when a force does act on it is given by Newton’s second law which states that the body will accelerate, or change its speed, at a rate that is proportional to the force.

In addition to his laws of motion, Newton discovered a law to describe the force of gravity, which states that every body attracts every other body with a force that is proportional to the mass of each body. Thus the force between two bodies would be twice as strong

Time was completely separate and independent of space. At least, this is what most people would take to be the commonsense view. However, we have had to change our views of time and space. That original view was fine until one started dealing with things moving at or near to the speed of light. Bear in mind at all times that nothing travels faster than the speed of light – and for the mathematically minded – also bear in mind Einstein’s famous equation E = mc sq (E is energy, m is mass and c is the speed of light.) Because of the equivalence of energy and mass, the energy which an object has due to its motion will add to its mass. In other words, it will make it harder to increase its speed. This effect is only really significant for objects moving at speeds close to the speed of light. For example, at 10 per cent of the speed of light an object’s mass is only 0,5 percent more than normal, while at 90 percent of the speed of light it would be more than twice its normal mass. As an object approaches the speed of light, its mass rises ever more quickly, so it takes more and more energy to speed it up further. It can in fact never reach the speed of light, because by then its mass will have become infinite, and by the equivalence of mass and energy, it would have taken an infinite amount of energy to get it there,

In Newton’s theory, if a pulse of light is sent from one place to another, different observers would agree on the time that the journey took, since time is absolute, but will not agree on how far the light travelled, since space is not absolute. Since the speed of light is just the distance it has travelled divided by the time it has taken, different observers would measure different speeds for the light. As the observers could not agree on the distance the light travelled, they had to disagree, as well, over the time it has taken. (The time taken is the distance the light has travelled – which the observers could not agree on – divided by the light’s speed – which they did agree on.) In other words, the theory of relativity puts an end to the idea that time is absolute! Because everything is relative!

By now it will have become apparent to the reader that the normal rules of “common sense” to somebody who has been born and raised on Earth and had little exposure to travelling at great speeds, will not apply to an environment that involves such things as floating around in space or travelling at speeds close to the speed of light. Fortunately for us, people such as Newton and Einstein were able to see beyond the “common sense”