Quote from: 2552 on 02/03/2013 12:08 pmNew on Arxiv from Heidi Fearn and James F. Woodward: Experimental Null test of a Mach Effect ThrusterThe thrust was in the micronewton range... i.e., the weight of a single grain of salt! So it's highly probable that the thrust was due to convection currents, or even the earth's magnetic field, rather than a new form of physics.
New on Arxiv from Heidi Fearn and James F. Woodward: Experimental Null test of a Mach Effect Thruster
I'm trying to understand Woodward's theory and I have trouble following a few equations. Could I discuss them here or should I open a thread?
...If this is the case, then a stronger level of microwaves should be emitting from the larger end of the cavatron than from the side or the bottom...
Just a note - you're describing Shawyer's EM-Drive specifically. Woodward's M-E drive is a completely different animal...
Hello,there's a thought experiment concerning propulsion I'd like to present. Imagine two objects with different mass in free space, being apart 1ly. They are connected by an ideal rope of negligible mass. As is known, space is expanding at a rate of about (21.25km/s)/Mly or (2.125cm/s)/ly. Since the amount of space between the objects is increasing and the rope prevents the objects from moving apart, they experience a net diametral force, each pulling on the other object.Is my assumption correct, that the object with more mass pulls stronger on the object with less mass (since both objects are being moved with their local space-time section) and thus the less mass-rich object moves away from a nearby free observer? Wouldn't this also be a propellantless propulsion, or am I missing something?Best regards
It's my understanding that the expansion only happens between galaxies, and that the gravitational fields of the mass within galaxies stop them from expanding. This makes sense, as otherwise the galaxies would be getting more diffuse over time, and I believe that's not observed.So, ISTM your thought experiment would only work in inter-galactic space.This may also be a "Maxwell's Demon" type system - what provides the force to stop the two masses from moving apart?cheers, Martin
Quote from: MP99 on 03/24/2013 11:33 amIt's my understanding that the expansion only happens between galaxies, and that the gravitational fields of the mass within galaxies stop them from expanding. This makes sense, as otherwise the galaxies would be getting more diffuse over time, and I believe that's not observed.So, ISTM your thought experiment would only work in inter-galactic space.This may also be a "Maxwell's Demon" type system - what provides the force to stop the two masses from moving apart?cheers, MartinIt's the normal EM binding forces within the rope that holds the rope matter together. I know, the thought experiment is a bit.. let's say, "impractical". But in principle, what I described should happen. Do you see something other bothering you besides the immense length of the "ideal rope" ?
Edit:I did some math regarding the possible diffusion of galaxies. 1ly is ~9.5*10^12km. A galaxy with diameter 1Mly should experience a spacial expansion of ~21.25km/s as viewed from one outer edge to the other. It follows that to expand that galaxy outwards for one additional lightyear, it would take 1ly/(21.25km/s) = ~4.449*10^11s or about 14*10^8 years. Would this be even measurable with our current means? I mean, how old are the oldest images of distant galaxies (or even our own)? Only a regular comparison and incredible precision measurements could prove or disprove it, IMO. I smell an open issue
What's that rope made of? Perhaps a carbon nanotube fibre?It will end up incredibly massive, and negate the "negligible mass" part of your thought experiment. Also, what stops the rope / fibre from stretching? I would guess that any stretch impulse would travel down the rope at the speed of sound (in the medium), which is massively slower than light. Alternatively, the stretching of space may stretch the rope itself until it reaches a limit where it refuses to stretch further.These are the sort of "real world" details which eventually demonstrated the fallacy of Maxwell's Demon.Also, as I say, I'd read in an old New Scientist article that space only experiences expansion where the rate of expansion is greater than the rate of collapse caused by any local gravitational field.Quote from: Xpl0rer on 03/24/2013 11:46 amEdit:I did some math regarding the possible diffusion of galaxies. 1ly is ~9.5*10^12km. A galaxy with diameter 1Mly should experience a spacial expansion of ~21.25km/s as viewed from one outer edge to the other. It follows that to expand that galaxy outwards for one additional lightyear, it would take 1ly/(21.25km/s) = ~4.449*10^11s or about 14*10^8 years. Would this be even measurable with our current means? I mean, how old are the oldest images of distant galaxies (or even our own)? Only a regular comparison and incredible precision measurements could prove or disprove it, IMO. I smell an open issue There are images of galaxies going back about 10x your calculated timescale (universe is ~14x10^9 years, and there are images of galaxies within fraction of first billion years).I can't guess whether the effect would be visible - or not!cheers, Martin
Quote from: MP99 on 03/24/2013 11:33 amIt's my understanding that the expansion only happens between galaxies, and that the gravitational fields of the mass within galaxies stop them from expanding. This makes sense, as otherwise the galaxies would be getting more diffuse over time, and I believe that's not observed.So, ISTM your thought experiment would only work in inter-galactic space.This may also be a "Maxwell's Demon" type system - what provides the force to stop the two masses from moving apart?cheers, MartinIt's the normal EM binding forces within the rope that holds the rope matter together. I know, the thought experiment is a bit.. let's say, "impractical". But in principle, what I described should happen. Do you see something other bothering you besides the immense length of the "ideal rope" ?Edit:I did some math regarding the possible diffusion of galaxies. 1ly is ~9.5*10^12km. A galaxy with diameter 1Mly should experience a spacial expansion of ~21.25km/s as viewed from one outer edge to the other. It follows that to expand that galaxy outwards for one additional lightyear, it would take 1ly/(21.25km/s) = ~4.449*10^11s or about 14'108 years. Would this be even measurable with our current means? I mean, how old are the oldest images of distant galaxies (or even our own)? Only a regular comparison and incredible precision measurements could prove or disprove it, IMO. I smell an open issue .Best regards
Imagine a distant galaxy on the edges of the visible universe. The matter in the galaxy possesses momentum which contributes to the absolute momentum of the visible universe. If space expansion between two points gets greater than the speed of light, then the galaxy finally leaves our personal universal event horizon - and with it its momentum. From our POV, the momentum of the system "universe" seems to change (i.e. part of it is seemingly lost), because space expansion becomes greater than the speed with which information can be transferred (speed of light). One moment we know the "countable" momentum is X, the next moment it becomes X-N.