Spacetime: Real or Not? LIGO Lab Explores Ripples

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Discussion Overview

The discussion revolves around the nature of spacetime, particularly whether it can be considered "real" and how this relates to the detection of gravitational waves by the LIGO lab. Participants explore the conceptual underpinnings of spacetime in the context of general relativity (GR) and special relativity (SR), as well as the implications of these theories for understanding physical phenomena.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Meta-discussion

Main Points Raised

  • Some participants question the reality of spacetime, suggesting it may be a conceptual tool rather than a physical entity.
  • Others argue that if space and time are accepted as real, then spacetime must also be considered real, citing the practical applications of SR and GR, such as GPS technology.
  • There is a discussion about the "fabric" analogy often used to visualize spacetime, with some participants asserting that it is a misleading simplification.
  • One participant emphasizes that while spacetime can be measured and has real effects, the notion of a physical "fabric" is not accurate.
  • Another participant highlights the importance of operational definitions in discussing the concept of "real" in scientific terms.
  • Some contributions reflect on the philosophical implications of measuring and understanding spacetime, indicating a divergence into personal theories and interpretations.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of spacetime and its reality. There is no consensus on whether spacetime can be considered a "real" fabric or merely a conceptual framework.

Contextual Notes

The discussion includes various assumptions about the definitions of "real" and the implications of different models of spacetime. Some posts indicate that the conversation has diverged from the original question, leading to a mix of personal theories and philosophical inquiries.

mr1batman
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how does scientists discover the spacetime ripples and this things while the spacetime is not a real fabric
is this all returns to the LIGO lab and the machine that was built there ?
 
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mr1batman said:
how does scientists discover the spacetime ripples and this things while the spacetime is not a real fabric
is this all returns to the LIGO lab and the machine that was built there ?
If you can provide an operational definition of "real", we can talk. Otherwise, this is just philosophy.
 
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Space-time describes our measurement of reality. If you agree that space and time are real, then that is enough to say that space-time is real. The trade-offs between space and time in SR has passed several tests and experiments over many decades. Likewise for the distortions of space-time due to mass in GR. In fact, the GPS system must use SR and GR results to keep it accurate. Without those adjustments, GPS goes bad quickly.

The detection of gravitational ripples of space-time are very recent. The latest detection was matched exactly by the detection of light from the same event at the correct time.
 
mr1batman said:
how does scientists discover the spacetime ripples and this things while the spacetime is not a real fabric
is this all returns to the LIGO lab and the machine that was built there ?

Go back a bit. Are you saying that the fact that it took me 30 minutes to travel 25 miles into the city yesterday is "not real"?

Zz.
 
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FactChecker said:
Space-time describes our measurement of reality. If you agree that space and time are real, then that is enough to say that space-time is real. The trade-offs between space and time in SR has passed several tests and experiments over many decades. Likewise for the distortions of space-time due to mass in GR. In fact, the GPS system must use SR and GR results to keep it accurate. Without those adjustments, GPS goes bad quickly.

The detection of gravitational ripples of space-time are very recent. The latest detection was matched exactly by the detection of light from the same event at the correct time.
ZapperZ said:
Go back a bit. Are you saying that the fact that it took me 30 minutes to travel 25 miles into the city yesterday is "not real"?

Zz.
i mean the spacetime fabric it not something real right it is just to make us understand the GR
 
mr1batman said:
i mean the spacetime fabric it not something real right it is just to make us understand the GR
Again, what do you mean by "real"? We can measure properties of something that we refer to as "space time". That's about as real as anything ever gets in science.

If you are referring to some stretchy fabric (the rubber sheet analogy) that has dimples where masses press down into it then no, that's not real.
 
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It measures and explains real things. Like F = M*A. But it is true that gravity is a distortion of space-time, where the distortion travels through the universe like a wave. There is no physical "fabric". You may be using it to visualize GR, but that is not how it really works. In fact, just the opposite -- GR is the way to understand and visualize the distortions of space-time.
 
mr1batman said:
i mean the spacetime fabric it not something real right it is just to make us understand the GR

Let's get this VERY clear. What I described is an actual "spacetime", which is part of what is being described by GR. Spacetime "fabric" is a simplistic, bastardization, stupid visualization that we try to give the general public.

So how did you somehow come up with the idea that since this visualization is not accurate, that we could not discover the gravitational waves detected by LIGO? Do you think Einstein's GR came about because he STARTED with the fabric picture in mind? Or do you think that GR is fundamentally built upon such a silly picture in the first place?

Zz.
 
FactChecker said:
...the GPS system must use...
Needs a PIN number, too... I suppose ?
 
  • #10
Is a magnetic field real? I mean, we can't see it or touch it. The fact is, as stated above, it is as real as anything else. We have a very good mathematical model of it and we can measure the accuracy of the way that math describes the magnetic field to any arbitrary degree of accuracy. So for example, just because we can see the visible light reflected by the moon, and we can't see the infrared light, the visible light isn't any more real than the infrared light. Perhaps it's the word "fabric" in the phrase space time fabric that disturbs you. The word fabric is really not a scientific term. It's just a way to visualize an invisible gradient of gravitational curvature, like a fabric distorted by a weight resting on it. If the word causes confusion, then don't use it. Use the model of GR that predicts a curvature of the invisible field of space time at every infinitesimally small point in space, all adding up to a larger curvature over a larger area of space. Does that answer your question?
 
  • #11
ZapperZ said:
Let's get this VERY clear... Spacetime "fabric" is a simplistic, bastardization, stupid visualization that we try to give the general public.
That was such an authoritative disquisition... . :oldeyes:

However, that fact does not created in me a sense of obligation...
 
  • #12
There are a great many ways to objectively measure and study the passage of time, with varying degrees of accuracy and repeatability. They should be used in this discussion. There is no need to bring psychology into it at this point.
 
  • #13
The original question has been answered but unfortunately this thread started on shaky grounds and has since meandered off topic and into personal theories and philosophy (as the half-dozen deleted posts attest to).

Thread locked.
 

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