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20.Telescope (a little bit of history)

  In 1608 Hans Lippershey, an eyeglass maker, submitted the first patent of telescope. But who made the first telescope, it is not clear. Later on, Galileo improved the design and started applying in Astronomy. This telescope had convex objective lens and concave eyepiece lens. In 1611 Kepler developed the design using convex lens in both objective and eyepiece and this design was more useful than the previous one developed by Galileo. Diagram of Galilean and Keplerian Telescope In 1655 Huygen was making powerful and enhanced Keplarian telescopes using compound eyepiece but those telescopes were proved inaccurate. In 1688 Isaac Newton built the first reflector telescope which consisted of a tiny flat diagonal mirror to reflect the incoming light on an eyepiece. Using achromatic lens, in 1733, Chester Moore Hall built a telescope. First Reflector Telescope built by Newton Diagram of Achromatic Lens When light of white color passes through a medium it splits into several colors. For exam
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Multi-dimension

Two dimensional projection of a ten dimensional cube

Dimensions:

The word dimension can be referred to as degrees of measurement. Such as, velocity is two dimensional because to measure velocity of something we need distance and time. Same way, acceleration is three dimensional because to measure acceleration we need velocity and time and velocity itself is two dimensional. Again, a company can be a multidimensional company by having several businesses under it.

In physics, the concept of multidimensional space is interesting but it gets confusing as the number of dimensions increases. For instance, a dot on a paper is zero dimensional; if two dots are connected then we get a line which is one dimensional. Furthermore, when two parallel lines are connected then we get a square shape and it is two dimensional  and also when two parallel squares are connected then we get a cube which is a three dimensional object. If we connect two parallel cubes we get a three dimensional projection of a four dimensional cube and so on.

A four dimensional cube

A three dimensional cube

In classical physics we have three spatial dimensions where we can move up and down, right and left, forward and backward. Moving at any direction in space can be measured in terms of these three dimensions. In this case, the fourth dimension is time. Using time as fourth dimension we can measure an event or trajectory of a moving object. Nevertheless that is for recorded data. What if we could go back and forth simultaneously in time? If it was possible then the reality would seem like a three dimensional history book where we could choose all the three spatial coordinates and specific time to observe an event. With respect to time the classical mechanical equations are symmetric and quantum mechanical equations can be symmetric if both time and other quantities could be reversed. The sensation of time flowing in one direction is an artifact of the laws of thermodynamics such as we experience the flow of time in the direction in which entropy increases. 

We experience the flow of time in one direction

There are more dimensions beyond these four dimensions but they are hypothetical. String theory gives rise to extra seven dimensions besides the four dimensions, in attempting to unify the four fundamental forces in the nature. But these extra dimensions are not experimentally proved yet.

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