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CBSE Class 9 Answered

Is fourth dimension time?   
Asked by ameyareddy9 | 27 Jan, 2021, 07:04: PM
answered-by-expert Expert Answer
Conventional mechanics followed in our day-to-day problems , where speed of objects is much less than speed of light,
is called Newtonian mechanics. In Newtonian mechanics , space and time are independent and absolute.
 
A single concept that recognizes the union of space and time,  called space-time  is used in Einstein's relativistic mechanics,
where speed of objects are comparable to speed of light.
 
From common intution , we know there is no connection between space and time.  Physical space was held to be a flat,
three-dimensional  continuum—i.e., an arrangement of all possible point locations.  
Time was viewed independent of space—as a separate, one-dimensional continuum, completely homogeneous along its 
 infinite extent. Any “now” in time could be regarded as an origin from which to take duration past or future to any other time instant.
 
In mechanics , to describe objects position and movement, we follow a coordinate system like Cartesian coordinate system.
If we are at a location , then this location is considered as reference point or origin.  Left-to-Right is one direction of coordinte system.
Front-to-back is the other direction and top-to-bottom  is the third direction. Hence any location from our position is described
in terms of distances along these three direction. Such a coordinate system assumed by every one is called frame of reference.
If an observer-A is standing on a platform watching another observer-B moving on a train, then observer-A is having his own
frame of reference and observer-B is also having his own frame of reference moving with train.
 
If a frame of reference is moving with constant speed without any acceleration, then this frame of refernce is called inertial frame reference .
It is accepted and observed that laws of physics are same in all inertial frame of reference.

In relativistic mechanics, the time coordinate of one coordinate system depends on both the time and space coordinates of another
relatively moving system according to a transformation rule. According to Einstein’s theory there is no such thing as “simultaneity” at two
different points of space, hence no absolute time as in the Newtonian universe.
 
Relativistic mechanics follows a distinct class of inertial reference frames, where time also considered as one of the coordinate
in addition to space coordintes. A point in such an inertial frame is not space but it is called space-time.
Spatial dimensions, mass, time and velocities are all relative to the inertial frame of the observer.
Only the speed of light is the same in all inertial frames.  Again, in every inertial reference frame, all physical laws remain unchanged.
 
Answered by Thiyagarajan K | 28 Jan, 2021, 03:28: PM

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