Is Space-Time Dilation Just a Funny Concept or Does It Have Real Properties?

[Bandersnatch]

You know this is why nobody talks to you people.

Hey, I resent this statement! I talked to the mailman back in 1996. He seemed to enjoy it, though I haven't seen him since.

 

[Adrian2000]

Hey, I resent this statement! I talked to the mailman back in 1996. He seemed to enjoy it, though I haven't seen him since.

Hehe, at least some of us still have a sense of humour ;)

 

[Dale]

It's logical and deductive, as you say, a result of a self-supporting framework of the definition of a 2-dimensional triangle.

Only in Euclidean geometry.

Consider a triangle on the surface of the Earth (idealized as a 2D curved manifold called a 2-sphere). You can draw a triangle with three right angles (270 degrees). Just start at the equator, go due north to the north pole, turn 90 deg, go due south to the equator, turn 90 deg, and go back to where you started where you will need to turn 90 deg again to face the direction you were originally facing.

In a positively curved manifold, like a 2-sphere, a triangle's interior angles will add up to greater than 180 deg. The 180 deg result only holds for Euclidean geometry, and does not hold for other geometries. The Euclidean geometry is called "flat" and deviations from the 180 deg are an indication of intrinsic curvature.

 

[Adrian2000]

Only in Euclidean geometry.

Consider a triangle on the surface of the Earth (idealized as a 2D curved manifold called a 2-sphere). You can draw a triangle with three right angles (270 degrees). Just start at the equator, go due north to the north pole, turn 90 deg, go due south to the equator, turn 90 deg, and go back to where you started where you will need to turn 90 deg again to face the direction you were originally facing.

In a positively curved manifold, like a 2-sphere, a triangle's interior angles will add up to greater than 180 deg. The 180 deg result only holds for Euclidean geometry, and does not hold for other geometries. The Euclidean geometry is called "flat" and deviations from the 180 deg are an indication of intrinsic curvature.

I agree wholeheartedly.

 

[PAllen]

I get it, you know more physics than me and are apparentely more up for a confrontation than I am at this hour; that doesn't mean you can put words in my mouth that I never said. So try to understand what I was actually trying to say.

It seems to me that you are not not listening, and I am trying my best to understand where you are coming from.

I still don't see, from your posts, that you understand that Euclids axioms that you learned in plane geometry include arbitrary choices. That consistent, logical systems follow by making different choices. If you change just one assumption (the parallel postulate), then the angles of triangles no longer add up to 180 degrees. I have not seen an indication that you at least understand this mathematical fact.

[Edit: well now maybe I do, for the first time: #54, made after I posted this.]

 

[harrylin]

Hi Harrylin!

Yes, and this is what I meant - IF said measuring rod appears shorter to an outside observer, does it have to do with the actual object (rod) being physically shortened, or does it have to do with space contracting around a gravitational field? And if it is the latter, then clearly this space, nothing IS actually something, and has internal properties, does it not? (according to GR, whether explicitly or implicitly?)

Imagine a "stationary" observer in "deep space" with an equally stationary rod in a reasonably stationary universe; and he sends the rod in vertical orientation slowly down to Earth with an Earth lander. Most people would then agree with the point of view that the stationary observer has not significantly changed, which logically implies that actually (or "really") it's the rod's length that has changed, and thus the rod has become shorter. And as you may have seen, a clock will similarly tick slower.

Moreover, the speed of light is also governed by space, even far away from matter. Therefore we must conclude that "empty space" is of course empty of matter, but it has properties. GR can say nothing more than that; Einstein was smart but he was not a prophet or a medium! And probably no serious book will tell you about "space contraction".

Ok, and this is where the rubber hits the road - how can it have properties, 'information' and still be space? Surely that means that it's not space at all, but some sort of 'zone' (if you like)? And then, if it does have said properties, in what 'space' does it exist in? [..]

"Space" means a volume that is free to move in, and "empty space" only means that there is no matter inside. ;)
And near a heavy mass such as the Earth there certainly is a "zone" of which the properties are affected by the mass: the common term is "gravitational field". :)

 

[Adrian2000]

Imagine a "stationary" observer in "deep space" with an equally stationary rod in a reasonably stationary universe; and he sends the rod in vertical orientation slowly down to Earth with an Earth lander. Most people would then agree with the point of view that the stationary observer has not significantly changed, which logically implies that actually (or "really") it's the rod's length that has changed, and thus the rod has become shorter. And as you may have seen, a clock will similarly tick slower.

Moreover, the speed of light is also governed by space, even far away from matter. Therefore we must conclude that "empty space" is of course empty of matter, but it has properties. GR can say nothing more than that; Einstein was smart but he was not a prophet or a medium! And probably no serious book will tell you about "space contraction".

"Space" means a volume that is free to move in, and "empty space" only means that there is no matter inside. ;)
And near a heavy mass such as the Earth there certainly is a "zone" of which the properties are affected by the mass: the common term is "gravitational field". :)

Harrylin, I love your avatar, and you are hands-down the most helpful member on this forum :) That is *exactly* what I was wondering about, and you hit the nail square on its head. I was confused by the prescriptions of space-time as described by GR, but am calmed by the fact that its prescriptions appear to be more tame than I thought. I don't dispute the effects of space-time dilation, but was confused with regards to what it actually meant for the nature of our universe (specifically, the nature of spacetime). As I've already mentioned (before Paul here managed to drag me back into the discussion) I think the wisest thing to do here is to say thank you for all of your help, and to go back to the literature so I could make some informed conclusions of my own. :)

Thank you all,
Farewell, Godspeed, LL&P, Gesundheit & Adieu
Adrian

 

[Dale]

With that I think we will close the thread