relativity & drugs

[iceworks]

Hi everyone, have been busy reading " A brief history in time" (four times in fact) and researching articles on relativity on the net. I have deduced that this book is best read and understood whilst sitting on the toilet- this being a quiet place to read without being disturbed. I haven't resorted to taking drugs(other than legal ones) to understand relativity, but it certainly takes some mind elasticity. An article I found useful was "Albert Einstein's Theory of Relativity- In Words of Four Letters of Less" at the following website www.muppetlabs.com/~breadbox/txt/al.html (http://www.muppetlabs.com/~breadbox/txt/al.html) .
Now for some thought benders,
Einstein said that gravity is a fake pull, and that the earth doesn't veer constantly to circle the sun but that instead the earth travels in a straight line in space and that space-time is bent by the sun's mass. This means that in our three dimensional existence the earth appears to curve around the sun, but in fourth dimensional space-time it is in fact travelling in a straight line. Next he says that no true body is at rest, if I hold a ball in my hand and let it go, who can say that the ball moves towards the earth? It holds just as true that the ball stays put and that the earth moves up to the ball. I understand the theory but it doesn't pass the commensense test. Any thoughts from any intelligent beings out there?

[janoskiss]

In Einstein's words: "Common sense is the collection of prejudices acquired by age eighteen."

If one becomes a little bit familiar with the theory, it makes a lot more common sense than a Newtionian action-at-a-distance gravitational force. The curved spacetime concept is very natural one - it even feels right. The pull of gravity on my body pressed against a support on the surface of our planet feels just like going around a corner, a curve in the road, in a vehicle travelling at considerable speed. And zero gravity or freefall feels like free unimpeded motion, like the uniform straight line motion of the old Newtonian inertial frame.

[iceworks]

Thanks for the reply, I appreciate it. I assume that when light is bent near a large mass(like the sun) that the same applies, space-time is bent and the light is actually travelling in a straight line in space-time, hence no need to try and explain in a Newtonian way how light(with no mass) is bent by gravity.

[DobDobDob]

Personally I would try to distance myself from concepts like bent and straight....you can make a case for both and in fact they are the same thing. They only apparently change to us due to scale.

If the human observer is taken away, then the scale is removed thus light or energy travels as it does, bent, straight, sideways and spiral all at the same time, it doesn't really matter :whistle:

I would rather try to understand these concepts using anything but terms I am familiar with as a human. To humanise or to use our vocabulary of non-human activity is really tricky...thus....as you sit on your favourite seat, perhaps one way to try and make a little more sense of it is to think like a computer, in terms of black and white, yes and no.

Of course I am human so I fall into the same old trap, trying to use words to describe phenomena, but every time, the words chosen don't seem to do justice to the reality of what's going on.

For an exercise try writing the action of a wave and use words that a five year old child would understand, it's harder than you think :P

That exercise is more or less the same problem amplified that Hawking had in his book, trying in words to explain things that are not part of the human experience. Of course you can switch to mathematics which is easier, however if you are not much good at maths then you are no better off.

Anyway, just drifting off topic a bit, so sorry, but my point is, don't be too dismayed if you had to read the book 4 times and still can't get some concepts, not many people can, not because of the concept per se, but more so in the telling (the words chosen to describe it).

Well, I'll shrink away now, cheers :whistle:

[xelasnave]

Can anyone tell me what they think of the example of mass bending space using a ball on a rubber sheet:shrug: ?

I maintain this is a poor example and is confusing as I say that the proper relationship of the ball the blanket, er rubber sheet, would be that the ball should be under the blanket:shrug: however the dimple where the ball would lay on the blanket be in place:) .
Does space bend to mass or away from it:) ?

Having answered that do you see why the rubber sheet is not appropriate:) ?

Also space time does not say if gravity pushes or pulls we have only the bending of space time due to mass;) ... this is my plea to explain it to me please:D .
alex:) :) :)

[DobDobDob]

Oh my Gosh Alex, we seem to agree that the way we express certain phenomena is more a convenience to 'us' rather than an accurate description of 'force', or 'electromagnetisms etc.

In fact I doubt that we can ever really describe what is really going on. Perhaps trying to explain the result of what is happening is a better approach.

For example, rather than saying a space is bent, it might be better to say that after a force has been exerted on space, the result might be....

I know this is somewhat pedantic but I think everyone at school today is walking around thinking that space bends in the style you suggested when in fact, I would guess there is nothing remotely like that happening.

I put it to you that all these statements of what happens on astronomical levels, should always be preceded with a statement saying that if observed 'by a human' (usually impossible), the effect of certain phenomena, might be...

Sorry to harp on about this, but bending space, warping space, stretching space and so forth just annoys me a bit because you get an impression in your mind, hard to shake once it's in there and then when you dig deeper, you find that you can't really fully appreciate these forces and never will.

You will never truly understand the force of gravity on an astronomical level because you are not an astronomical object, and because an apple falls to the earth off your head, IMHO does nothing to explain why a super massive black hole can consume light, or why a large galaxy can strip away mass from a smaller galaxy that comes within range.

Okay, I know I am setting myself up to be abused here, because I can offer no better description....BUT....that is my point, I doubt that we can ever truly describe so that we fully understand what is going on, at a fundamental level. I would lobby for a new approach to education in this respect, with people saying that as a result of certain actions, the following conditions may occur.

It just seems to me that every statement I read (on a daily basis) is said so matter of fact that too many people are accepting these 'ideas' as dogma and it goes into urban myth or folklore, and hardly ever seems questioned.

Okay, it surely must be time for breakfast :whistle:

[xelasnave]

Sorry Ron when I use the word “space” it is in the context of “space time” and all that one thinks of when that term is mentioned:) .

My point being in an effort to describe a geometric principle “space time” it seems counter productive to use examples that demonstrate the opposite to the effect sought to clarify by the example.

I know it is frustrating that we don’t know more but you must know I am doing my best to answer all the questions before I leave the planet;) :whistle: .

But if you think about GR being the reason why the different pressures exist, pressures sought to be described as gravitational effect, you will notice that GR bends the space time grid with current and excepted thinking:thumbsup: .

The ball on the sheet in its current form is very misleading to the GR cause and without an understanding of space time you can not move on to GR:lol: :lol: :lol: .

So I say the geometry “space time” is not represented fairly by the ball and the rubber sheet... needless to say I agree that “space time” says nothing at all about force, reasons or does it offer explanation….. :eyepop:

And it does not have to offer explanation or reason for it is merely geometry, not a commentary on how anything really works just peculiarities we expect to find in attempting to apply human measurement.

"Merely geometry" seeks to state its classification not underestimate the complexity of applying such geometry.


Alex

[DobDobDob]

I still agree with you (watch your wallet).... :whistle: