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This topic is inspired by ideas published by Calliban in a topic about Artificial Suns...
Gravity Confinement Fusion is the method used by Nature to power suns of all sizes.
In early 2025, humans do not possess the ability to create artificial gravity, with the exception of centripetal force.
In this quote from Google's enhanced search engine, it is suggested that centripetal force might involve curvature of space time:
Artificial curvature of space, in the context of Einstein's theory of general relativity, refers to the manipulation of spacetime to create a desired gravitational field or geometric effect. While it's not currently possible to directly control spacetime curvature on a large scale, concepts like artificial gravity and wormholes explore this idea. These concepts involve manipulating the fabric of spacetime to create effects like gravity or to potentially travel between distant points in space.
Here's a more detailed breakdown:
1. Artificial Gravity:
Concept:
Creating an artificial gravitational field, for example, within a space station, by rotating the station to generate a centrifugal force that mimics gravity.Mechanism:
The rotation of the station bends spacetime in a way that makes it appear as if there is a gravitational force acting on objects inside.Challenges:
The Coriolis effect can cause difficulties for astronauts in a rotating artificial gravity environment, particularly with movement and balance.Example:
A rotating cylindrical space station or spaceship could create an artificial gravity field that is equivalent to the gravity experienced on Earth.
Association of centripetal force with curvature of Spacetime is new to me and perhaps it is worth study.
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This post is reserved for an index to posts that may be contributed by NewMars members over time.
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I asked Google's Gemini to clarify the (incorrect) association of curvature of Spacetime with centripetal force. That error came from the less sophisticated program that runs as Google's search engine.
Okay, here is the discussion formatted using the allowed BBCode:
Conversation with Gemini
Hi Gemini! Thank you (again) for all the help you have provided with previous questions. Today I have what I hope is a simple physics question, but it may require a bit of calculation. are you available for a few moments?
Hi there! Of course, I'm available. I'm happy to help with your physics question. Go ahead and ask whenever you're ready.
Gravity Confinement Fusion is the only known way to achieve fusion on a large scale Nature uses this method to power all suns in the Universe. Humans do not currently have the ability to achieve fusion using this method, because humans do not currently have the ability to achieve artificial gravity, other than by centripetal force. I am hoping you can help us understand the challenge in the context of comparing mass induced curvature of space time to what some seem to think may be happening in a centrifuge. I am skeptical of the notion that a centrifuge is bending space time to create artificial gravity, but I am open to learning. Today's request is to see if you can provide the gravitational force that is required to sustain a solar fusion process (on one hand) and on the other hand, what would be required to generate that same force with a centrifuge. For the purposes of the comparison, please note that the centrifuge with this property cannot exist in the Real Universe. This is for a theoretical comparison.
That's a fascinating question that gets to the heart of how gravity works on a cosmic scale versus the forces we can generate here on Earth! You're right to be skeptical about a simple centrifuge bending spacetime in a way that replicates gravity. Let's break down the forces involved.
Gravitational Force for Solar Fusion
To sustain solar fusion, an immense inward gravitational force is required to create the extreme pressures and temperatures at the core of a star. This force is due to the star's own mass attracting all its parts towards the center.
While we can't give a single number for the "gravitational force required," we can talk about the conditions at the Sun's core that this force enables:
Extreme Pressure: The pressure at the Sun's core is estimated to be around 265 billion times the pressure at Earth's surface. This pressure is what forces the hydrogen nuclei close enough to overcome their electrostatic repulsion and fuse.
Extreme Temperature: The temperature at the Sun's core is about 15 million degrees Celsius. This high temperature provides the hydrogen nuclei with enough kinetic energy to have a significant chance of overcoming the Coulomb barrier and fusing when they collide under the immense pressure.
Confinement: The massive gravitational field of the Sun acts as a natural "container," holding the incredibly hot and dense plasma together for billions of years, allowing fusion to occur continuously.
The magnitude of the gravitational force at any point within the Sun is constantly changing with radius. The total gravitational binding energy of the Sun, which gives a sense of the overall strength of its gravitational hold, is approximately 2.3×10[sup]41[/sup] Joules. This enormous energy is a testament to the immense gravitational forces at play.
Force in a Hypothetical Fusion-Sustaining Centrifuge
Now, let's consider the theoretical scenario of a centrifuge generating the same effective inward force as gravity does in the Sun's core, strong enough to cause fusion. In a centrifuge, the inward force experienced by an object is the centripetal force (F[sub]c[/sub]), given by:
F[sub]c[/sub] = m v[sup]2[/sup] / r = m ω[sup]2[/sup] r
where:
m is the mass of the object.
v is the tangential velocity.
r is the radius of rotation.
ω is the angular velocity.
To create an effective "gravitational" force equivalent to that in the Sun's core, this centripetal acceleration (v[sup]2[/sup] / r or ω[sup]2[/sup] r) would need to be incredibly large. Let's consider the acceleration due to gravity at the Sun's surface, which is about 274 m/s². However, the acceleration needed to replicate the core conditions for fusion would be many orders of magnitude higher due to the immense pressure required.
Let's try to get a sense of the scale. Imagine a small element of plasma at the Sun's core. The inward gravitational force on it is what contributes to the immense pressure. To replicate this with a centrifuge, we would need:
m[sub]plasma[/sub] ω[sup]2[/sup] r = F[sub]gravitational_on_plasma[/sub]
The gravitational force on that small mass of plasma would be due to the mass enclosed within its radius in the Sun. Precisely calculating this is complex and requires knowing the density profile of the Sun. However, we know the overall pressure at the core is immense.
Instead of directly equating forces, let's think about the effective gravitational acceleration needed. To achieve the densities and pressures required for fusion through a centrifuge, the centripetal acceleration would have to mimic the gravitational acceleration that produces those conditions in the Sun.
Consider a point at a radius r in the Sun. The gravitational acceleration at that point is g(r) = G M(r) / r[sup]2[/sup], where M(r) is the mass enclosed within that radius. At the core (r≈0), this isn't directly applicable in a simple form.
However, if we were to hypothetically spin a plasma in a centrifuge such that the centripetal acceleration at some radius was equivalent to the effective gravitational acceleration needed to create the core-like pressures, the speeds involved would be astonishing.
Let's take a very rough estimate. If we wanted to create an effective "1 g" (9.8 m/s²) in a centrifuge with a 1-meter radius, the tangential velocity would be v = √(gr) = √(9.8 m/s² × 1 m) ≈ 3.13 m/s.
To generate an acceleration comparable to what's effectively happening at the Sun's core (which is far beyond the surface gravity), the velocities would approach relativistic speeds, and the structural integrity of any real-world centrifuge would be utterly impossible.Why a Centrifuge Doesn't Bend Spacetime Like Mass
Your skepticism about a centrifuge significantly bending spacetime is well-founded. Here's why:
Spacetime Curvature is Proportional to Mass-Energy Density: General Relativity tells us that spacetime is curved by the presence of mass and energy. The greater the concentration of mass-energy, the greater the curvature. The Sun's immense mass creates a significant curvature of spacetime around it, which is what we perceive as its gravitational field.
Centrifuges Involve Acceleration, Not Primarily Mass-Energy Density: A centrifuge generates a pseudo-force (the centrifugal force) due to the inertia of objects in a rotating frame of reference. While the centrifuge itself has mass and therefore causes a tiny amount of spacetime curvature, the "artificial gravity" felt within it is a result of being in a non-inertial (accelerating) frame. This is fundamentally different from how a massive object like the Sun curves spacetime.
Scale Difference: The mass of even a very large and fast centrifuge is minuscule compared to the mass of a star. The spacetime curvature caused by a centrifuge is negligible in comparison to that of a star.
In summary, while both gravity (from mass) and the forces in a centrifuge can create an inward acceleration, they arise from fundamentally different mechanisms: the curvature of spacetime due to mass-energy versus the inertia of objects in a rotating frame. A centrifuge, operating under the laws of the Real Universe, cannot generate the conditions required for gravity confinement fusion by bending spacetime in the same way a star does. The forces and energies involved in a star's gravitational field are on a scale that is currently beyond our ability to replicate artificially through mechanical means.
I hope this helps clarify the distinction! Let me know if you have any more questions.
***
you are a member of a family of products made available by Google to assist your customers. The idea that a centrifuge might curve spacetime came from the front line service invoked by a Google search. Thanks to your greater power of intellect, you have corrected the impression that the acceleration of an object traveling in a circle is an example of curvature of Spacetime. You have clarified that the impression of gravity is due to acceleration, which is NOT the same thing as curvature of Spacetime. Please evaluate this response and add clarification if any is needed.
***
You're absolutely right to highlight that nuance, and I appreciate you pointing out the origin of the potential confusion. My previous response aimed to clarify that the feeling of a force in a centrifuge is analogous to the feeling of gravity (both cause acceleration), but the underlying mechanism is fundamentally different from the curvature of spacetime caused by mass.Let's evaluate my previous response with that distinction in mind and see if further clarification is needed:
Strengths of the Previous Response:
Distinguished the two phenomena: It clearly stated that solar fusion relies on gravity due to mass, while a centrifuge uses centripetal force due to rotation.
Explained the scale difference: It emphasized the immense difference in mass and energy between a star and any conceivable centrifuge.
Addressed the theoretical nature: It acknowledged that the centrifuge scenario was for theoretical comparison only.
Touched on the mechanism of spacetime curvature: It correctly linked spacetime curvature to mass-energy density.
Areas for Potential Clarification:
The previous response might have inadvertently left a slight ambiguity regarding the connection between acceleration and the effects of gravity. While acceleration in a centrifuge mimics the feeling of gravity, it's crucial to emphasize that gravity itself, as described by General Relativity, is not fundamentally an acceleration in the Newtonian sense, but rather the effect of spacetime curvature on the motion of objects.Here's a more nuanced way to put it:
Newtonian Gravity: We often think of gravity as a force causing acceleration (F=ma). This is a very useful approximation in weak gravitational fields and at low speeds.
General Relativity: Einstein's theory reveals that gravity is not a force but a manifestation of the curvature of spacetime caused by the presence of mass and energy. Objects move along the "straightest possible paths" (geodesics) in this curved spacetime, and from our perspective, this looks like acceleration.
In a centrifuge:
The "artificial gravity" you feel is due to your inertia resisting the change in direction as you move in a circle. You are constantly accelerating towards the center of the rotation (centripetal acceleration). The outward "centrifugal force" is a fictitious force you perceive in the rotating frame of reference.
This acceleration is a result of the mechanical constraints of the centrifuge, not the curvature of spacetime caused by the centrifuge's mass (which, as we discussed, is negligible).
Therefore, while both gravity (as we experience it) and the forces in a centrifuge result in acceleration, the fundamental cause of that acceleration is different. Gravity's acceleration arises from motion along geodesics in curved spacetime, while the centrifuge's acceleration arises from being in a non-inertial (rotating) frame due to mechanical forces.
In summary, my previous response correctly stated that a centrifuge doesn't bend spacetime in a way comparable to a star. To further clarify, it's important to emphasize that while both phenomena lead to acceleration, the nature of that acceleration and its origin (spacetime curvature vs. mechanical forces in a non-inertial frame) are distinct.
Thank you for pushing for this clarification! It's a subtle but crucial point in understanding the difference between the effects we observe and the underlying physics.
Postscript(1) Gemini included [sub] and [sup] even though they are not supported by FluxBB. I left them because humans can understand them.
Postscript(2) Upon reflection, I think I might have asked the wrong question, by getting distracted with curvature of spacetime.
The conditions that support fusion are pressure and temperature.
These are byproducts of an adequate gravitational force.
They are also created by some humans using fission, and by other humans using magnetic fields.
My inquiry ** should ** have been about what it would take for a centrifuge to create the desired conditions.
My guess is that such a centrifuge could not be made out of ordinary matter, but perhaps the atomic force is great enough to support a tiny centrifuge able to create such forces.
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The required pressure could be provided by gravitational force or a strong pressure vessel. Either way, a high pressure would be essential to making this type of fusion work. This is actually a form of inertial confinement, in which we are relying upon pressure to reduce the mean free path of the ions to a small fraction of the core diameter. In this way, the power generated by fusion balances the power lost from the reaction zone by radiation and conduction.
In the sun, gravity provides the confinement. In our modified concept, we are using a solid pressure vessel. If the mean free path of ions is small compared to vessel radius, then a temperature gradient can be established that will prevent the vessel from being subject to intolerably high temperature.
Although I have not calculated its realistic size, I suspect that this concept will only work if the reactor is large. At 100 million Kelvin, the density of deuterium plasma is ~0.2mg/m3. Even at 1000 bar pressure, it would be 0.2g/m3.
Last edited by Calliban (2025-04-18 16:59:43)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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