The Astronomy Thread

Tripamang said:

On the topic of chemical rockets, don't those top out at fairly low numbers in terms of max speed? I always thought your max speed was limited to how quickly the exhaust leaves the rocket.

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Dandain said:

Tuco hates dreaming, he need capitalistic motivations in reasonable timeframes.

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abstract said:

Abstract
It is proposed that gravitational fields may be interpreted as a variation in the relative available driving power (Watts) of the
Electromagnetic, Zero-Point Field (ZPF). It is shown that variations in the relative available power are covariant with variations in the
coordinate speed of light as measured by a distant observer in unaltered space-time. Gravitational time dilation and length contraction
may then be interpreted as a loss of driving power from the ZPF. It is hypothesized that the loss of power is due to increased radiative
damping of matter, resulting from an increase in the local relative energy density which promotes this process. The relative radiative
damping factor affects the relative ground state energy of the quantum mechanical harmonic oscillator such that, the mean-square
fluctuations in matter reproduce the behavior attributed to, and resulting from variations in the space-time metric of General Relativity
(GR). From this principle, all of the variations observed by a distant observer that occur due to gravity, or space-time curvature under
GR may be reproduced from the variable relative damping function acting on the harmonic oscillator. What is presented herein, is an
engineering model for quantum gravity that puts gravity in the hands of engineers, who will understand this process and will potentially
advance artificial gravity and anti-gravity technology from pure speculation, to achievable endeavors in our lifetime.

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abstract said:

In the Engineering Model of Quantum Gravity, [1] gravity results from a loss of power in a quantum oscillator, caused by a gradient in the relative Damping Factor. This paper demonstrates that the EM Drive theory of operation, may be analogous to a man-made gravitational field gradient, inside the frustm. Please review [1] for a full description of the Model, to fully understand the derivation to follow.

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crackpotkiller said:

Lots of wrongness in this (full report which he cites at the bottom, which I will pick apart here and by extension will debunk the OP), and vaguness and evidence of a lack of knowledge of the field of gravitation including facts and terminology.

• The idea of gravitational field as a refractive index is not really a popular or useful notion. It doesn't tell you anything useful and is not something I've ever heard from cosmologists or astrophysicists.
  
  
• Talking about the polarizable vacuum model of gravity is already points off since a.) we know GR works better than ever thanks to gravitational wave observations, b) the idea itself is nonsense as I'm sure has been pointed out here before.
  
  
• Dealing with 1 space and 1 time dimension is not usually called "two dimensions" in Relativity, it's usually referred to as "1+1 dimensions"
  
  
• His definition of refractive index is almost completely arbitrary. Since he (re)defines it as the ratio of the root of the metric elements (which is not the same as some fraction of the speed of light) done in a flat spacetime, which he says he's working in, the metric should be the Minkowski metric. This is all 1 along the diagonal (except the 00 component, the signs depend on whether you use the East or West Coast metric). This means his refractive index K should always be 1 - i.e. no refractive index (or a vacuum one). Nor does he talk about any sort of perturbation to the Minkowski metric, or even mentions the Minkowski metric for flat spacetime. That's a red flag. He also doesn't even bother to mention other metrics commonly learned in a basic GR class, like the Schwarzchild metric.
  
  
• By talking about the speed of light and "refractive index" around some spacetime, he seems to be trying to reinvent gravitational lensing, or aspects of it. This is already well described in GR.
  
  
• He talks about the zero point field, but doesn't actually define it, or say what he thinks it is. Since he claims he's talking about QED this should be particularly relevant.
  
  
• He brings out the tired and continuously debunked notion that one can absorb energy from the vacuum state. You cannot. It is not a free energy source. Then immediately cites Putoff, the founder of Stochastic Electrodynamics (SED). This was an idea that has a little interest in the mid 90s but quickly died out, especially since more precise tests of QED have been done and the theory holds up fantastically.
  
  
• He says equations from QED will be used then goes into SED. Which is unfounded, and another big red flag.
  
  
• He claims electrons have a natural frequency. They do not.
  
  
• He calls his equations 14-16 (in the full report) fluctuations, but they are not really. They are just expectation values of some things he's claiming are measurable.
  
  
• He claims his expectation values for position, velocity and acceleration connect quantum mechanics to gravity. They do not. They can be defined in quantum mechanics and have no connection to gravity whatsoever.
  
  
• He introduces a damping factor and claims the power radiated from a charged particle is damped and that one can interpret this as a curvature in spacetime (or connected to it). Aside from his calculations being based a a more or less debunked (and more or less relegated to crackpot land) theory - SED, this is sort of irrelevant. Speaking quite generally and broadly, any non-zero energy in GR can curve spacetime. It will come into the T00 component of the stress-energy tensor in GR. For example, could you talk about on person standing on a bed using the formalism of GR? Yes. But it won't tell you anything new or interesting since the effects of GR will be so small they will be completely negligible.
  
  
• He also asserts from this damping of power that the speed of light will change (assuming you're in the vacuum of space) due to eqn. 21. It will not. This would violate one of the postulates of Relativity. He just gets this idea from his ad hoc equation for power scaled by a factor of his "refractive index". In fact something this profound would have been measured already from the many telescopes and lab tests we have done.
  
  
• He goes on to claim that his equations are consistent with GR but does no calculations in GR or quotes any results. What's worse is that he wanted to talk about the quantum harmonic oscillator but didn't even bother to quote any results from that (except for the ground state energy), which you could have taken from an undergraduate text on QM.
  
  
• His connection between QM and gravity is simply that a "refractive index" that he dubiously defines using a flat (supposedly) metric is connected with a harmonic oscillator that radiates and is damped. It is this damping which he uses to try and draw similarities with GR (again without actually providing any concrete motivation). This is more like reasoning by analogy than it is a serious theory on quantum gravity. Nothing about the well tested theories of QED or GR really come in and he uses a debunked theory to do it all.
  
  
• Even worse he brings out the tired and wrong idea that the zero point field can be used to extract power. It cannot.
  
  
• He also claims to explain why gravity have a negative energy density (it doesn't in all practical and physically realizable scenarios, and he doesn't even do any calculations from GR to show this).

I'm not going to bother with the rest. This is based on a mountain of misunderstanding, wrong ideas, and debunked theories.

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Scoresby said:

I've always thought an interstellar ark (or arks) would be the way for us to reach other stars. It would take thousands of generations, and in all likelihood the end-product would not be the same species as modern human due to significant environmental pressures, but the tech probably isn't far off from this being possible. The hardest challenge is how in the hell do you get even the minimum viable population of people together in a space ship designed to live and die for ages without someone getting butt-hurt and starting a war and compromising the vessel you are on, killing off the group. We (as a people) are the greatest threat to our own existence and also likely the limiting factor for our ability to get out of our solar system.

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