Discovering Gravity & the Last Step of General Relativity

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Discussion Overview

The discussion centers around the conceptual and historical aspects of general relativity, particularly focusing on the nature of gravity as the deformation of spacetime and the process of its discovery. Participants explore the steps leading to the formulation of general relativity, including the role of mathematical equations and experimental confirmations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the last step of general relativity was indeed discovering gravity as the deformation of spacetime, seeking clarification on this point.
  • Another participant argues that the last step was the publication of the paper, emphasizing that science is an ongoing process and that the true nature of gravity remains uncertain.
  • A different viewpoint suggests that the understanding of gravity as spacetime curvature was a gradual process, involving the development of the correct field equations over several years.
  • One participant challenges the notion that discovering gravity as spacetime deformation was a singular event, highlighting the importance of experimental confirmation in the ongoing discovery process.
  • Another participant notes that while the equivalence principle allows for the deduction of light bending in a gravitational field, the complexity lies in deriving the mathematics that describe this curvature.
  • A further contribution outlines two fundamental aspects of general relativity: how spacetime influences matter and how matter influences spacetime, indicating that Einstein's understanding evolved over time.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the last step in the development of general relativity, with no consensus reached on whether it was the discovery of gravity as spacetime deformation or the publication of related theories. The discussion reflects multiple competing perspectives on the topic.

Contextual Notes

Participants highlight the complexity of defining "what gravity actually is," indicating that assumptions about the nature of gravity and spacetime curvature may vary. The discussion also points to the ongoing nature of scientific inquiry and the role of experimental evidence in confirming theoretical predictions.

KarminValso1724
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Sorry if this seems like a stupid question but I cannot find an answer. I am asking this because to me, it seems like the hard part of coming up with general relativity would be discovering what gravity actually was ( the deformation of spacetime ), and the field equations and mathematics would simply follow, not the other way around. Can someone correct me if I'm wrong? The last step of general relativity was discovering that gravity was the deformation of spacetime, true or false?
 
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The last step was publishing the paper ... though, really, there is no last step because science is never finished.
"Discovering what gravity actually was" has not happened yet ... we don't even know what "actually" would mean in this context.

Starting with special relativity and Newton ... I understand the first step was to realize that there is no way to distinguish gravitation from accelerating reference frames. The development of a geometrical description for gravity was, loosley, the middle step ... and the covariant mathematics finished it off.
https://en.wikipedia.org/wiki/History_of_general_relativity

You should realize that the "fabric of space time" is not what "actually" is there - that's a poetic metaphor for describing a mathematical model.
 
KarminValso1724 said:
The last step of general relativity was discovering that gravity was the deformation of spacetime, true or false?

Mu.

Discovering that gravity is spacetime curvature is not a single event. It took a number of years; the whole process of Einstein developing the correct field equation for gravity was the process of discovering that gravity is spacetime curvature. (More precisely, of discovering that all of the effects of gravity could be accounted for by modeling spacetime as curved instead of flat, as it is in special relativity.) And if you think experimental confirmation should be part of the process of discovery (which is certainly a defensible point of view), then the process didn't end with Einstein's publication of the correct field equation; it arguably is still going on, since we are still making new experimental discoveries that confirm predictions of GR that had not been confirmed before (the recent LIGO observation of gravitational waves, for example).
 
KarminValso1724 said:
...The last step of general relativity was discovering that gravity was the deformation of spacetime, true or false?

I would say false. By using the equivalence principle, one can deduce that light will bend in a gravitational field. This implies a curvature of spacetime. The hard part was in the details - deriving the mathematics to describe such curvature and the specific way it is caused by mass/energy.
 
Roughly speaking, there are two parts to General Relativity, as it was put in Misner, Thorne and Wheeler's "Gravitation":
  1. Spacetime tells matter how to move.
  2. Matter tells spacetime how to curve.
So once you have thought of the equivalence principle, and you've hit on the idea that freefall is just motion along geodesics of spacetime, then you've basically got the first part down. Einstein had this part figured out by about 1907, just a couple of years after he developed Special Relativity. It's the second part that took him another 8 years of work. He knew that he wanted an equation of the form "Something involving spacetime curvature = Something involving matter and energy", but exactly what the something on left was was a puzzle.
 

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