Now... I'm not going to lie to you and say that I understand all of this stuff... but even the little bit I did understand... was really interesting!
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Sal, a question... if a large planet-sized object is sitting still, it will bend space-time in a certain way... (gravity well) now... if that object is moving at 1% of C, will it produce some sort of a "bow wave?"
Hello, Allan.
Short answer: yes, something like a bow-wave exists in General Relativity... but it is not a shock wave, and it behaves very differently from fluid or sound bow waves.
Let me unpack that cleanly.
Motion, Memory, and Meaning!
Why Experience... and Suffering... Require an Asymmetric Universe:
At first glance, the question seems purely technical: "If a massive object bends spacetime when it is at rest, does that bending change when the object is moving?"
But buried inside that question is a much deeper one... one that reaches beyond gravity and geometry into experience, ethics, and meaning itself.
Motion and the Shape of Spacetime!
In classical General Relativity, a stationary mass produces a static curvature of spacetime. Objects move along geodesics within that curvature, following paths determined by geometry rather than force!
When the mass remains at rest, nothing propagates outward except changes in the field itself. The spacetime geometry is steady!
When a mass moves, however, that symmetry is broken.
Spacetime curvature becomes direction-dependent! (Because gravitational influences propagate at the speed of light, changes in the field do not update instantaneously. The result is a subtle skewing of curvature in the direction of motion!)
In addition, moving mass generates velocity-dependent gravitational effects... what is known as gravitomagnetism or frame dragging... phenomena that have been experimentally confirmed!
What does not occur is a classical bow wave.
There is no shock front, no piling up of spacetime, and no gravitational equivalent of a "Mach Cone" at ordinary velocities!
Because the mass moves slower than the speed at which its gravitational influence propagates... spacetime always “keeps up!”
The correct analogy is not a bow wave but a wake: "A directional asymmetry rather than a discontinuity!"
Only in extreme, ultra-relativistic limits... far beyond anything planets or stars can achieve... does spacetime curvature become strongly forward-compressed, approaching something shock-wave-like!
In everyday cosmic conditions, motion produces distortion, not rupture!
Why Geometry Matters!
The deeper issue is not whether spacetime forms a shockwave, but how it encodes motion at all!
In standard General Relativity, spacetime is modelled using Riemannian (more precisely, pseudo-Riemannian) geometry.
In this framework, the metric depends only on position, not on direction or velocity!
Motion is handled indirectly... through stress... energy tensors, frame dragging, and coordinate transformations!
Directional effects exist, but they are not built into the geometry itself!
This choice was deliberate and profoundly successful. By insisting that local physics not depend on absolute velocity, General Relativity achieved extraordinary empirical confirmation... from gravitational lensing to black holes to gravitational waves!
Any future theory must reduce to it in the regimes where it works!
But that success comes with a conceptual cost: "Spacetime, at the geometric level, is memoryless!"
It does not intrinsically care how something arrived where it is!
Enter Finsler Geometry!
Finsler geometry generalizes Riemannian geometry by allowing the metric to depend not only on position... but also on direction or velocity.
In symbolic terms, the difference is stark:
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Riemannian geometry: g = g(x)
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Finsler geometry: g = g(x, v)
That single change has enormous implications.
In a Finsler-type spacetime, paths matter more than points!
The same location can have different geometric meanings depending on how it is reached. (Motion leaves a structural trace. Directional asymmetries are not emergent afterthoughts... they are fundamental features of the geometry!)
This reframes the original question entirely!
Instead of asking whether a moving mass creates a bow wave, the more precise question becomes: "Does spacetime itself become anisotropic around moving matter?" (Anisotropic refers to the directionality of properties in materials, indicating that the same property can have different values depending on the direction in which it is measured. In contrast, isotropic materials exhibit properties that are independent of direction!)
In a Finsler framework, the answer is yes... by construction!
No shock wave is required!
No violation of causality occurs!
Geometry simply becomes sensitive to motion directly!
This is why Finsler-based approaches keep resurfacing in discussions of velocity-dependent gravity, modified inertia, and subtle anisotropies at large scales.
Not because General Relativity is wrong, but because it may be incomplete!
If such an extension ever succeeds, it will not replace Einstein any more than Einstein replaced Newton outright.
As with every major advance in physics, the older theory would remain as a limiting case.
General Relativity would become the isotropic, low-velocity approximation of a deeper, direction-aware structure!
From Geometry to Experience!
At this point, a surprising question emerges: "If spacetime can be path-dependent, could it also be compatible with experience?"
To be precise... this does not mean spacetime is conscious! It does not feel, think, or possess qualia!
But experience, as it exists in biological systems, has strict structural requirements:
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History matters: Past states influence present ones!
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Direction matters: Inputs are not interchangeable!
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Context matters: The same stimulus has a different meaning depending on the state!
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Trajectories matter: Experience unfolds along irreversible paths!
A purely position-based spacetime is indifferent to all of these.
It can host brains, but it does not structurally participate in what makes experience meaningful!
All memory, context, and consequence belong entirely to biology!
A path-sensitive geometry changes that. It does not create experience... but it removes a geometric prohibition against it!
It allows the universe to be compatible with systems whose states depend on how they got there!
Spacetime does not experience... [Omnia/Qualia does that] but it no longer has to pretend that history is irrelevant.!
Ethics, Value, and Asymmetry!
Ethics depends on harm, growth, loss, learning, and responsibility!
All of these are trajectory-based phenomena.
They exist only if how you arrived at the present time matters!
In a perfectly symmetric universe... where all paths are equivalent... and all states are recoverable... events can occur, but consequences cannot!
Regret becomes impossible!
Responsibility becomes cosmetic!
Value becomes a bookkeeping convention rather than something real!
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Biological systems, by contrast, are fragile. They can be wounded, scarred, and permanently altered!
They carry consequences forward! (This is why ethics emerges from biology... and nowhere else!)
Spacetime does not judge, command, or care... but it must allow consequences to persist if ethics is to exist at all!
A geometry that remembers motion does not create value!
BUT: It allows value to stick!
Why Suffering Is the Price of Meaning!
This leads to an uncomfortable but unavoidable conclusion...
Suffering is not what gives meaning to things... but it is the signal that meaning is real. (Pain, loss, grief, and fear are biological indicators that a boundary has been crossed that cannot simply be reset!)
They mark the existence of "consequences!"
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A world of pure pleasure fails structurally!
Pleasure can be repeated without cost. It does not force learning, restrict futures, or impose consequences!
Without the possibility of suffering... pleasure just becomes noise!
One cannot have all four of the following simultaneously:
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Meaning
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Freedom
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Irreversibility
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No suffering
One must give! A universe with meaning... but no suffering... is not a moral ideal... it is a logical contradiction!
The universe does not impose meaning!
Living systems pay for it!
The Final Line!
If one sentence survives all of this analysis, it is this:
Suffering is the price paid by finite beings for inhabiting a world where their choices can matter!
That is not a justification.
It is a diagnosis!
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Ever forward!
