So earlier today I watched Sabine hassenfelder the physicist from Germany indicate that any kind of wormhole travel or FTL is strictly unlikely. What I'd like to ask is, whether all the work that's done today for creating commercial nuclear fusion is more or less likely, than using the same technology to develop fusion plasma rockets to travel much more swiftly within the solar system? Our fusion plasma rockets the lower hanging fruit, versus commercial nuclear fusion? Thanks!
It is possible for a binary star system to interact with a third star so there is an exchange. We do normally expect binary star systems to have similarly oriented angular momenta.
This is an interesting result. To compute this would have been tough. This is a case of a Robinson-Trautman twisting solution or a twisting type N. The addition of the two angular momenta results in the occurrence of angular momenta perpendicular to the initial angular momenta. This can be seen in with the classical group [L_i, L_j] = ε_{ijk}|L|^2 n_k, for n_k a unit vector. This means there is the emission of angular momentum in the gravitational radiation. The calculation was most likely done numerically.
LC
On Thu, Jan 13, 2022 at 1:37 PM Brent Meeker <meeke...@gmail.com> wrote:> Kudos to whomever did the calculation for this. But I would have thought that most collisions would be misaligned in both spin axes and impact plane. The Sun's spin axis isn't aligned with the Milky Way's axis of rotation, so I had assumed most stars have randomly directed spin axes.Stars do have random axis of rotations in general but not if you're talking about double stars, and the sun is rather unusual in being only a single star, most stars are double stars, and they were created at the same time from the same rotating cloud of gas and dust and thus have similar axis of rotation, so when the resulting stars turned into Black Holes they would also have similar axes. And indeed most of the Black Hole mergers so far detected by gravitational waves have been of that sort, but not this one, that's what makes it so unusual. This system must've been formed by two stars that formed at different places at different times but then got close together and somehow went into orbit around each other.John K Clark See what's on my new list at Extropolisqbj
Brent
On 1/13/2022 3:49 AM, John Clark wrote:
For the first time a sort of gravitational wave rocket has been found. By re-examining the data from the LIGO and Virgo gravitational wave observatories researchers report on January 6 they have detected the merger of 34 and 29 solar mass Black Holes that resulted in a Black Hole of about 62 solar masses with about one solar mass being converted into gravitational waves. What makes this merger unusual is that it was not symmetrical, the axis of spin of the 2 black holes were not aligned with each other and neither was aligned with the axis of orbit around each other. This would indicate that the 2 stars that form them (assuming these 2 large Black Holes were actually formed from the corpses of dead stars) were not born in an isolated system but probably came from a denser environment like a globular cluster. Even more interesting is that the misalignment of the spins means that the gravitational waves emitted were not emitted symmetrically, and gravitational waves carry some linear momentum. So the resulting 62 Solar mass Black Hole must've received a pretty substantial kick causing it to move pretty fast, and that's just what the researchers found, because of that kick the huge 62 solar mass Black Hole started moving at least 700 km a second and probably closer to 1500. It's probably moving fast enough to escape whatever galaxy it was in.
> So earlier today I watched Sabine hassenfelder the physicist from Germany indicate that any kind of wormhole travel or FTL is strictly unlikely.
> What I'd like to ask is, whether all the work that's done today for creating commercial nuclear fusion is more or less likely, than using the same technology to develop fusion plasma rockets to travel much more swiftly within the solar system? Our fusion plasma rockets the lower hanging fruit, versus commercial nuclear fusion? Thanks!
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> This surely can't be done anytime soon. My suspicion is that new discoveries of profound impact will wait until we can build better equipment, as Freeman Dyson state long ago.
frt
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https://bigthink.com/starts-with-a-bang/no-warp-bubble/
The Casimir vacuum provides the energy conditions required for the warp drive. The negative vacuum can be a source for hyperbolic geometry for exotic structures such as wormholes and warp drives. This experiment employed the Casimir vacuum and came up with results that appear suggestive of a warp bubble. This does not though mean we have conclusive evidence of one. There are some other reasons to maintain a skeptical perspective on this.
The Alcubierre warp bubble is probably only stable for sub-light speed. If it is set above the speed of light it has particle horizons that causally separate the bubble. This means it is not stable, for Unruh-like radiation occurs.
This may lead to deep questions. for the vacuum energy is related to the moduli of curves, such as in the Poincare disk and half-plane, and this is also in some ways related to the moduli of gauge symmetry. Each curve bounds a region, thinking in 2-dimensions, and this region is associated with entropy and curvature. For this to work the vacuum has to be stable, which means it is Virasoro or CFT_2 or more. I think this imposes this limit on the warp bubble as being sub-light speed.
This warp bubble might exist, and for various reasons it would be a fascinating development for the foundations of physics. This is not to say I think we will be using this for spaceships, at least not at all soon. These DARPA results are suggestive, but actual experiments will have to rise to what might be called the 5-σ level. I am rather skeptical of this however, even though if this is real it would pave the way for a major probe of the quantum vacuum.
As for fusion, just getting a fusion powerplant is a big hurdle to jump. The Chinese have made an announcement of a fusion device that sustained 15 million K temperatures for 100 or a 1000 second. I cannot remember which. This has a long way to go, and as the joke goes, 20 years from now fusion power will still be 20 years in the future. As for a space power or propulsion, that is far out. We still do not have fission powered space systems or propulsion, and fusion will be far more difficult. The Chinese system is fairly large and the ITER program involves a really large reactor. Space based systems need to be small and as low mass as possible.
LC
> Clear back in 1974 the British Interplanetary Society did a paper where the ORION effect would be better fulfilled by Daedalus which would detonate thousands of deuterium-tritium pellets using electron beams. Same principle using many micro-detonations.
> Orion itself gives me the willies,
> if only because we'd have to stop it in an Newtonian manner, say when Dyson and company arrived to view Saturn's rings close-up.
> For fast interplanetary travel, there needs to be a motivator