Is there any experimental or observational confirmation of curvature of spacetime?

What you call it is neither here nor there, and changes nothing: The facts and theories are what is and what is accepted, despite your nonsense. Parrotised but correct!

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No, its also gravitational lensing as I have shown you with two links.
You are getting too confused with your Alien abduction scenarios and Bigfoot encounters.

http://www.universetoday.com/118751/what-is-gravitational-lensing/

http://w.astro.berkeley.edu/~jcohn/lens.html

 

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Pad it has nothing to do with gravity ; spacetime or any of the sort .

It's just simply matter and energy emanating from our star , atmosphere ; from the Sun ; refracting the light from another star .

End of story .

river

 

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Please stop posting your pseudoscience in the science section. reported.

 

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I guess I thought all I needed to do was clarify what you didn't understand about Pad's comment. It seemed you didn't understand the circumstances of time dilation.


I'm not actually sure why there is any debate about this at all.

There is no question that time dilation occurs both at high velocities and in gravitational wells. It has been epxerimentaly confirmed and is put into proactice in consumer products.
There is a model for how this time dilation occurs - relativity, both Special and General - and currently no competing models.

Colour me obtuse, could someone clarify exactly what is being refuted?

 

I'm not sure you're serious with such a reply, but in case you are, it is demonstrably false in a host of ways.

 

Here is Eddington's explanation of why the refraction by the sun's atmosphere (corona) can be ruled out of causing the observed deflection.
My bold.
Eddington's own book...
Page 110 and onwards. Download the book (free) at Gutenberg. This will take you straight to the download page...
https://www.gutenberg.org/ebooks/29782

 

Would it be appropriate to ask why the geometry of spacetime should not be curved?

If the geometry of space is fractal (CDT) curvature is an entirely natural result, IMO.

p.s. Time just comes along for the ride.

 

Certainly the geometry of the universe should be "up for grabs". The majority of our experience is with Euclidean geometry, so I can understand the bias towards that geometry.

A fractal geometry would be non-Euclidean by definition. But there is essentially no evidence for fractal geometry in our universe.

 

I appreciate my understanding is rudimentary but is it possible, so far as possible in layman's language to explain why a particular geometry (eg euclidean) is unable to describe the universe?

Is it simply because euclidean geometry does not take account of distance and time being two sides of the same coin and also that it is not possible to take a "snapshot" of the universe (or a part of it) without resorting to approximations which grow increasingly inaccurate as the distance /time intervals increase?

Is it at least theoretically possible for another geometry to exist that could describe the universe provided that it took into account the interwoven nature of space and time ? (not that I know of one

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)

 

Of course. The trick is finding a geometry that solves more problems than it creates.
The only reason GR is the standard solution is because of that - it solves more problems than it creates.

For example: naively, we here on Earth live on what seems to be a stationary flat surface. We cannot explain why hurricanes form the way they do, moving north/south and rotating as they do so.
We have to invent a new force, called the Coriolis Force to cause hurricanes to twist into spirals. But now we have to explain what causes the Coriolis Force.

A new model comes along, of an Earth that is spherical and rotating. Suddenly, there is no need for a mysterious force - it is already expalined by the geometry of a rotaing sphere. The model of a spherical Earth solves more problems than it creates. Therefore, it is a better model.

I'm not comparing curved Earth to curved spacetime - not at all! - I'm simply demonstrating how a different geometry nad model can eloquently and succinctly explain many phenom of a system that are otherwise hard to explain.

 

Because nothing in the universe comports with Euclidean geometry when gravity gets involved.

Euclidean geometry is a model of geometry where parallel lines can be extended forever and always be the same distance apart. That's not the case in gravity where some trajectories in space-time converge and some diverge. Newton would call that a force, but it's a very curious force because it's proportional to the affected object's inertial mass and no other property. But then evidence came in about the motion under gravity of high speed objects and the gravity of collapsed stars and precision tests of motion. So now we have a number of confounding factors, but still the effect of gravity is not affected by the composition of the test mass.

But by using space-time geometry, the action of gravity on various masses (and light) could be described as the natural shape of the straightest possible space-time line (a trajectory) with a given origin event and initial velocity. This would naturally lead to a model not affected by the composition of masses, just their mass, momentum and motion. And Einstein, after much reasoning about the nature of curved smooth objects (manifolds) made the simplest assumption of the relation between mass, momentum and motion and the effect of gravity, he assumed a simple proportionality between a description of the curvature and the description of mass, momentum and energy that automatically enforces conservation laws. Less simple assumptions either don't comport with the behavior of reality or have additional free parameters that have to be tuned until the predictions of the less simple model are physically indistinguishable from the predictions of Einstein's GR.

The model of geometry from GR describes with precision that bullets and teddy bears fall at the same rate, that Mercury's orbit varies slightly from the predictions of Newton's Universal Gravitation, that light bends twice as much about the sun as Newtonian estimates would have it, that binary neutron stars and black holes radiate away energy and momentum until they collide, and we don't have evidence of anything that doesn't comport with a model of curved space-time.

So the behavior of nothing in the universe comports with Euclidean geometry when gravity gets involved, which means Euclidean geometry (of space — you need to use the equivalent, Minkowski, if you want to talk geometry of space-time) is best used only as an approximation when gravity is weak just like in civil engineering, Euclidean geometry is best used for projects of a few tens of meters or less while the curvature of the Earth becomes apparent in precision jobs involving tens of kilometers or more.

 

He may have slipped-up and forgot his sock puppet cover here. Remember he once spoke of ninjas in the dark, I took that as his use of sock puppets on this site. Do I give a damn if I'm wrong...no.

 

I am not sure if you are familiar with Causal Dynamical Triangulation (CDT) developed by Renate Loll and others. Below is quote from wiki.

highlights mine.

 

A hypothesis is not evidence. [Newton, Principia]

 

That is what I call bereft of meaning.

Any accepted theory must not create any observational (or theoretical ?) problem..

 

You'd be wrong.

All theories leave unanswered questions.

 

Obviously Dave means the fabricated problems that religious zealots and other anti science types automatically have re anything that on face value is counter-intuitive. Obviously these Ptolemy induced flat Earthers cannot remove themselves from that 2000 year old era.
Anything remotely unanswered in any theory, is then grabbed and run with by our same god bothering posters.

 

There is a difference between creating problems and leaving unanswered questions !! You see what you have written..

And BTW have you appointed Paddoboy as your advocate ?

 

Being rebuffed and shown to be demonstrably wrong, is the job of all science supporters everywhere.
I'm just doing my small part in showing you for what you are.

 

Show what I am saying is wrong !
You don't have to bother what and who I am..