Gravity and the bending of spacetime

[Strange]

Can physicists authoritatively say that, for example, spacetime is quite literally bending as modelled in relativity or would they accept there is a very small chance that relativity is nothing more than modern epicycles?

 

I think many philosophers of science would say that we never have anything but "better epicycles". Science doesn't (and cannot) determine anything about reality. All it can do is make useful models. This is a fairly 20th century view, but it has much older origins.

 

Very few philosophers of science now think that science is about discovering "truth". More scientists might do, but that is probably because they don't know anything about the philosophy of science!

 

So, is space-time literally bending? Well, it certainly appears that way. It is a conceptually simple and very powerful model. We haven't, yet, found anything that contradicts it. It is the best description we have.

[swansont]

 

Can physicists authoritatively say that, for example, spacetime is quite literally bending as modelled in relativity or would they accept there is a very small chance that relativity is nothing more than modern epicycles?

 

Since spacetime is not a physical entity but a convenient way of describing nature, from one view it's hard to defend that it is literally bending. It's a way of saying that the geometry best used to describe things is not Cartesian in nature. But that geometry is literally bent.

 

Using the phrasing "nothing more than epicycles" is a tad pejorative. It's models all way down. Science doesn't lay claim to the true nature of nature.

[Thorham]

No, not really. The theoretical framework has to match with observations. You don't get to disregard evidence.

Right. I think I misinterpreted what ajb wrote. I thought it meant that what you see is based on the theoretical framework you're using. Don't know how I thought that.

Edited February 17, 2016 by Thorham

[ajb]

Now people may have their opinions on this but my own is that relativity is a modern version of epicycles, basically a mathematical model that works but does not reflect the underlying reality.[/size]

But this is not really an issue with relativity, but all model used in physics.

 

Can physicists authoritatively say that, for example, spacetime is quite literally bending as modelled in relativity or would they accept there is a very small chance that relativity is nothing more than modern epicycles?[/size]

Really the best we can say is that we model gravitational phenomena using the notion of space-time as a manifold and its local geometry.

 

 

I thought it meant that what you see is based on the theoretical framework you're using.

How you start to look for something, how you interpret it and so on are deeply rooted in the theoretical framework one is using.

[Thorham]

How you start to look for something, how you interpret it and so on are deeply rooted in the theoretical framework one is using.

Clear, I misread it.

[SimonFunnell]

 

I think many philosophers of science would say that we never have anything but "better epicycles". Science doesn't (and cannot) determine anything about reality. All it can do is make useful models. This is a fairly 20th century view, but it has much older origins.

 

Very few philosophers of science now think that science is about discovering "truth". More scientists might do, but that is probably because they don't know anything about the philosophy of science!

 

So, is space-time literally bending? Well, it certainly appears that way. It is a conceptually simple and very powerful model. We haven't, yet, found anything that contradicts it. It is the best description we have.

 

 

 

Since spacetime is not a physical entity but a convenient way of describing nature, from one view it's hard to defend that it is literally bending. It's a way of saying that the geometry best used to describe things is not Cartesian in nature. But that geometry is literally bent.

 

Using the phrasing "nothing more than epicycles" is a tad pejorative. It's models all way down. Science doesn't lay claim to the true nature of nature.

 

I am not trying to denigrate Einstiens contribution or science, I am all for science and Einstien moved us forward and brought us today, his work was essentially pagadigm changing.

 

I am currently writing another post which will be in 'other science', because it doesn't fit in the others, that elaborates why I am a skeptic of certain aspects of science and explains my intentions with the posts (as part of a video).

 

I guess I am just trying to get the hard facts, you know, if you were pinned down and brutally honest, is there a chance, it doesn't matter how small, just a tiny, tiny chance that relativity is mathematical model that works (modern epicycles) as opposed to being the literal truth.

[studiot]

 

 

 

I am not trying to denigrate Einstiens contribution or science, I am all for science and Einstien moved us forward and brought us today, his work was essentially pagadigm changing.

 

I am currently writing another post which will be in 'other science', because it doesn't fit in the others, that elaborates why I am a skeptic of certain aspects of science and explains my intentions with the posts (as part of a video).

 

I guess I am just trying to get the hard facts, you know, if you were pinned down and brutally honest, is there a chance, it doesn't matter how small, just a tiny, tiny chance that relativity is mathematical model that works (modern epicycles) as opposed to being the literal truth.

 

First gravity v epicycles.

 

Gravity is big, fundamental and long range.

 

Epicycles were a small correction to a big fundamental theory to explain small perturbations. the main geocentric theory of the celestial sphere otherwise worked quite well.

 

So they are quite different.

 

Perhaps the caloric theory would be a better example?

 

 

 

Strange

I think many philosophers of science would say that we never have anything but "better epicycles". Science doesn't (and cannot) determine anything about reality. All it can do is make useful models. This is a fairly 20th century view, but it has much older origins.

 

Perhaps, though that is debatable.

 

However can Science not determine that which is definitely untrue / unreal?

 

Did not new and better data allow us to move on from the geocentric theory to more modern and better theories, heliocentrism being the subsequent step, but not the last or latest.

 

I think we are all saying (Simon included) that Science moves on in the light of better data.

 

 

SimonF

Can physicists authoritatively say that, for example, spacetime is quite literally bending as modelled in relativity or would they accept there is a very small chance that relativity is nothing more than modern epicycles?

 

 

Please remember that, as swansont has hinted, what you understand 'bending' to mean and what GR means are also quite different.

 

I attribute that to the popular analogy of the 2D surface of a 3D sphere. The analogy is poor to put it mildly

[Strange]

I guess I am just trying to get the hard facts, you know, if you were pinned down and brutally honest, is there a chance, it doesn't matter how small, just a tiny, tiny chance that relativity is mathematical model that works (modern epicycles) as opposed to being the literal truth.

 

I think that is exactly what we are saying. But that is true of every other theory in physics and always will be.

[ajb]

I guess I am just trying to get the hard facts, you know, if you were pinned down and brutally honest, is there a chance, it doesn't matter how small, just a tiny, tiny chance that relativity is mathematical model that works (modern epicycles) as opposed to being the literal truth.

What could one mean by the 'literal truth'?

 

The best we have is models that we try our best to match to nature. Any physical theory is 'true' if it matches nature well. I cannot really see any deeper meaning of 'true' in this context.

[swansont]

 

 

 

I am not trying to denigrate Einstiens contribution or science, I am all for science and Einstien moved us forward and brought us today, his work was essentially pagadigm changing.

 

I am currently writing another post which will be in 'other science', because it doesn't fit in the others, that elaborates why I am a skeptic of certain aspects of science and explains my intentions with the posts (as part of a video).

 

I guess I am just trying to get the hard facts, you know, if you were pinned down and brutally honest, is there a chance, it doesn't matter how small, just a tiny, tiny chance that relativity is mathematical model that works (modern epicycles) as opposed to being the literal truth.

 

I'm sorry, I thought I was clear. No need to pin me down. There is no claim that scientific models are the literal truth. The models work in describing what happens. Beyond that, you can't claim they are "truth"

[Robittybob1]

I have seen this visualisation expressing the suns gravitational effect on our planet quite a bit:

 

 

However, what I don't see, and what this question asks, is how does this work with the gravity and objects on the earth, me for example?

 

I was hoping somebody could provide a link or explain this. Thanks.

As I understand it in the picture imagine the globe in the center is the Earth, with you standing on the Earth this would be represented by you standing on the lowest point on the rubber sheet or maybe just above the rubber sheet but directly above the lowest point. So you are not going to orbit but just fall straight to the center of the Earth (represented as the lowest point on the sheet).

Edited February 18, 2016 by Robittybob1