Getting to grips with Relativity

fret_wimp2

Ive been trying to get to grips with Relativity for some time now.
Initially i read a brief history of time which although is great, is just pigeon science, dummed down to give normal people a gist of how things work.

I then tried various websites to try and get a handle on relativity and the mathematics that help prove it but nothing clicked.

Im now reading an eBook that is supposed to be an intro to relativity but its just so badly laid out, with missing diagrams etc that its not a whole lot of use. the mathematics also dont have any real explanation, it just shows a formula and expects you to be at a level to comprehend it.

I know my maths are the weak point here. Can anyone advise a good starter course/book/site to help in proper understanding of relativity, and in particular explains the maths at a level that a secondary school student might understand.

Edit - mods, if you think this would be better in the Physics forum, apols for posting here.

etoughguy

Perhaps try A most Incomprehensible thing? You can find plenty of reviews on amazon. School level mathematics wont cover tensors and the like so you will potentially need some self study to cover some parts

ps200306

You could also try Relativity, Gravitation and Cosmology by Robert Lambourne which is a good undergraduate level text, but if you are a novice at the maths end of things you'll need something like "Incomprehensible" anyway.

If you need additional help with the maths, "Paul's Online Maths Notes" are great, and Wolfram Alpha is a great help in experimenting, testing results, and generally playing around.

gkell11

fret_wimp2 wrote: »

I know my maths are the weak point here. Can anyone advise a good starter course/book/site to help in proper understanding of relativity, and in particular explains the maths at a level that a secondary school student might understand.

Edit - mods, if you think this would be better in the Physics forum, apols for posting here.

There hasn't been a huge uptake on this topic so perhaps it is time to give an alternative approach and tease out all the meaning you require . Try the original book and we will go on a journey through the ins and outs of these things . As I am a new user I can't post URLs but Bartleby have ' Relativity: The Special and General Theory' if you care to look it up.

Here is a good place to start -

"AS is well known, the fundamental law of the mechanics of Galilei-Newton, which is known as the law of inertia, can be stated thus: A body removed sufficiently far from other bodies continues in a state of rest or of uniform motion in a straight line. This law not only says something about the motion of the bodies, but it also indicates the reference-bodies or systems of co-ordinates, permissible in mechanics, which can be used in mechanical description. The visible fixed stars are bodies for which the law of inertia certainly holds to a high degree of approximation. Now if we use a system of co-ordinates which is rigidly attached to the earth, then, relative to this system, every fixed star describes a circle of immense radius in the course of an astronomical day, a result which is opposed to the statement of the law of inertia. So that if we adhere to this law we must refer these motions only to systems of co-ordinates relative to which the fixed stars do not move in a circle. A system of co-ordinates of which the state of motion is such that the law of inertia holds relative to it is called a “Galileian system of co-ordinates.” The laws of the mechanics of Galilei-Newton can be regarded as valid only for a Galileian system of co-ordinates." Einstein

gkell11

As nobody else is using this thread in a meaningful way, I may as well add a few comments. The tendency is to focus on the conceptions of the early 20th century however those people too had their own version of incomprehension going back a few centuries to Newton.

"The demonstrations throughout the book [Principia] are geometrical, but to readers of ordinary ability are rendered unnecessarily difficult by the absence of illustrations and explanations, and by the fact that no clue is given to the method by which Newton arrived at his results." Rouse Ball 1908

In the other thread where Kepler outlines his reasoning where the motion of the Earth through space and its distance from the Sun is compared to Saturn's 30 year period and its distance which is 9 times of the Earth's diameter was turned into the 'inverse square law' in the late 17th century.

"The proportion existing between the periodic times of any two planets is exactly the sesquiplicate proportion of the mean distances of the orbits, or as generally given,the squares of the periodic times are proportional to the cubes of the mean distances." Kepler

This was distorted by Newton into a completely different format -

"That the fixed stars being at rest, the periodic times of the five primary planets, and (whether of the sun about the earth, or) of the earth about the sun, are in the sesquiplicate proportion of their mean distances from the sun...This proportion, first observed by Kepler, is now received by all astronomers; for the periodic times are the same, and the dimensions of the orbits are the same, whether the sun revolves about the earth,or the earth about the sun." Newton

What he did was create a relative space and motion (observations of the planets seen from Earth) and asserted an absolute space and motion (observations of the planets viewed from the Sun ) hence this -

"It is indeed a matter of great difficulty to discover, and effectually to distinguish, the true motion of particular bodies from the apparent; because the parts of that absolute space, in which those motions are performed, do by no means come under the observation of our senses. Yet the thing is not altogether desperate; for we have some arguments to guide us, partly from the apparent motions, which are the differences of the true motions;" Newton

It is not such a good thing to throw good information after bad and I would be eager to distance the approach of Kepler and his contemporaries from the later mutations as the whole point would be to make researches productive by untangling astronomical language from poor and distorted formats. When Rouse Ball wrote that they had no clue as to the method Newton used he was merely stating a fact but after relativity appeared that fact was conveniently buried.