Intuitions leading to ground breaking discovery of a theory [1905], this is an attempt to explain as intuitively as possible — a passage of development in history of physics which led to this theory that changed & advanced our civilization how we observe this universe in absolute or relativistic way & nature of its reality !
That which should be a common sense to only those who can see it !
Before Einstein - It was considered that Space & Time were Independent entities,not having any correlation with each other.
Absolute, true, and mathematical time . . . flows at a constant rate without relation to anything external. . . Absolute space. . . without relation to anything external, remains always similar and immovable.
~ Newton
This was primarily Newton argument & at that time were prime laws for motion which you can say as classical mechanics & which were never questioned before Einstein, the questions that eroded newton classical mechanics laws lead to something called — common sense as we say today, all experiments & findings were pointing to inevitable but only Einstein connected the dots.
The story starts parallelly - one thread starts from Maxwell Field’s Equation & another thread starts from very Famous failed experiment done by Michelson & Morley .
Finding Part 1 — Maxwell Field Equations:
Maxwell was trying to understand relation between electric & magnetic fields i.e…he conclusively found Mathematical proof of existence of Electromagnetic waves & using this he calculated its speed :
https://en.wikipedia.org/wiki/Maxwell%27s_equations
In a region with no charges (ρ = 0) and no currents (J = 0), such as in a vacuum, Maxwell’s equations reduces & calculates speed of EM waves
which identify
Which is speed of light. Here if you see speed of light only depends on permittivity & permeability of Medium & not on any other factors. Point to note is, it does not account for any frame of reference or co-ordinate system where EM wave is traveling !
Finding Part 2 — Michelson & Morley Failed Experiment :
Before Einstein, Understanding was light is a Wave disturbance traveling in space which is filled of mysterious Ether…as wave needs a medium it is traveling.
To Prove this Michelson & Morley did an Ingenious setup
- https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment
There idea was to calculate difference of speed of light traveling east to west & north to south..Morley set up a clever apparatus to measure any difference in the speed of light beams traveling east-west and north-south.
The motion of the earth around the sun at 110,000 km/hour (about 0.01% of the speed of light) is to our west during the day. Michelson and Morley believed in the ether hypothesis, so they expected that the speed of light would be a fixed value relative to the ether. As the earth moved through the ether, they thought they would observe an effect on the velocity of light along an east-west line.
For instance, if they released a beam of light in a westward direction during the day, they expected that it would move away from them at less than the normal speed because the earth was chasing it through the ether i.e..Speed should get subtracted ..which we usually do in relative motions of object [Absolute space & Time].
But they did not found any change…speed of light was same in both cases ! How does we account that ?
There was lot of wild speculation defending Newton Understanding of relative motions [Absolute space & Time] but as we know now Einstein did not buy those Argument after those revelations.
So we add up both stories [Part 1 + Part 2] — Maxwell field equations says Speed of light in vacuum does not depend on any inertial frame & is constant, Michelson Morley failed to establish ether theory ..further more — they raised a bigger question …Speed of light remains same irrespective of frames of references of observer !
These two were enough to Investigate further — the missing piece of puzzle & Einstein raised an interesting question —
Thought Experiment 1 :
What if he travels at speed of light , he would see Maxwell EM waves as standing still in space..not moving, that would violate highly successful theory of Maxwell EM Waves.
Thought Experiment 2 :
This anomaly can also be explained using Faraday Equation of Induction…a changing magnetic field creates an electric field, which is in addition to any electric field created by charges. (The reverse is also true : any electric field that changes over time creates a magnetic field.)
Suppose there is Positive charges kept in Linear fashion across sidewalk with a Observer A sitting…Observer A would see an electric Field Going outwards which is right.
Now Suppose another Observer B travels parallelly to sidewalks while sitting on some object…i.e.. he is stationary to himself, so he Observes three things..
1>Observer A is traveling opposite to Him
2>A electric field which was also Observed by Observer A..which is correct.
3>A Magnetic Field experienced by him, since for him Positive charges are moving opposite to him
I.e.. Observer B is Experiencing an Magnetic field in his Inertial Frame which was not Experienced by Observer A — So we are seeing Physical laws does not remain same here for different Inertial references…Which now is Violating Newton Postulates !
So this breaks Newton understanding of laws for relative motion that..The laws of physics which apply when you are at rest on the earth also apply when you are in any reference frame which is moving at a constant velocity with respect to the earth.
Matter obeys the same laws of physics in any inertial frame of reference, regardless of the frame’s orientation, position, or constant-velocity motion
~ The principle of Galilean relativity:
Before Einstein it was understood that relative nature of motion applied only to mechanics, not to electricity and magnetism — Einstein Modified this to add EM waves i.e..Light !
Einstein’s principle of relativity: Both light and matter obey the same laws of physics in any inertial frame of reference, regardless of the frame’s orientation, position, or constant-velocity motion.
So now we have ample evidence why Newtonian understanding of laws of motion & Absolute space time would not work forever i.e..for Very Large Distances of cosmos or over comparable speed of light, these Newtonian Mechanics would break down !
Einstein explained all this anomaly by rebuilding physics to add concept of Relativity of Space & time & get away from concept of Absolute Time !
Basically he intuited : space and time must be stretched and compressed as seen by observers in different frames of references. Since velocity equals distance divided by time, an appropriate distortion of time and space could cause the speed of light to come out the same in a moving frame, In Simple terms — Each Frame of reference (coordinate system) carries its own measure of time & scale/ruler, and thus space & time would need to expand or compress in order to honor this cosmological constant — speed of time ©.
He questioned on basic foundation of how we measured time & how we calculated distances in space !
Since we observe anything using Light…& light has a speed limit of c…it cannot be possible than Event E1 happening at Time T1 at one frame of reference which is distance D away from Observer O1 would not observe at same time T1, rather he will observer that Event E1 at about : T1 + D/C ie.. Information that an event has occurred at a Distance D will come to observer eyes only at time addition of (D/C) , that extra time took by Light to travel that distance — D from Event E1 to observer O1.
Example — if a Star has exploded one light year distance from us in earth, light will take 1 year to reach us & then we would be able to see bright light in sky indicating star has exploded…point to be noted here is — event happened one year before & light took 1 year to reach us & then we registered that event to occur in space.
Therefore we see by simple explanation it is now not possible to define a Event just by just Space Co-ordinates(x,y,z), we also need a reference of time to measure when this event happened in space.
This Caused concept of Time Dilation & removed concept of Absolute time !
You can go through in detail of transformations using Lorentz_transformation in given co-ordinate system.
https://en.wikipedia.org/wiki/Lorentz_transformation
Now we see from here, after such path breaking discovery…Newton Concept of Absolute time is defunct over large distance or at very high speeds & later on we see impact of this theory has caused that — time must be taken as dimension with existing three co-ordinate system (x,y,z) space to understand our universe better.
I tried to explain this in most simple way without adding too much math or physics like a story so it develops some interest & motivate to do your own research & realization in this enigmatic field, you can find more details on Maxwell field Equation, Faraday’s laws of Induction, Lorentz transformation, Galilean Co-ordinate system, my attempts was to tie all knots together & show this grand picture...hope it helped somehow !
If you can’t explain it simply, you don’t understand it well enough
~Albert Einstein
