Astrophysics and Cosmology - Discuss the Universe here

[Chronaut]

 

Thank you for the detailed reply, chron. I do remember some of that
now that you mention it. The only thing I can reply to that is that Lazar did have multiple witnesses who saw the craft in flight, unless of course they are all lying, and that as you mentioned, our knowledge is limited even though we think "we" know a lot. I say we because I'll admit I don't.  I think the best part of your response is that people should consider the gravity waves that were detected similarly to the distortion you'd experience on the crest of an ocean wave as opposed to a light wave, right?  However, I'm still trying to wrap my mind around this... you could easily say that light is a distortion in the electromagnetic ocean, no?

I'm sure I'm showing more ignorance here, but you mentioned the conservation of energy... wasn't there a new space drive recently proven to break that very law? I apologize for not having that drives name on the tip of my tongue, and I'm on my cell so it's hard to look up while responding to this.

I’m glad I could offer some food for thought on the subject â€" as you can probably tell I love digging into stuff like this: it’s interesting and you can learn as much from studying a false scientific assertion as you can from studying an established one, because both cases always leads back to the experimental evidence and the mathematics.  And sometimes the hoaxes lead to unexpected insights about unrelated matters, like black program security operations in this case.

There’s footage of the flight demonstrations that Lazar took Leer and Knapp et al. out there to see â€" I remember watching it; it must still be around somewhere online.  I don’t think that was a lie at all, per se.  In fact it supports my interpretation that Lazar is a covert operative working under a cover story:  I think his story was scripted for him, and that Lazar coordinated with his handlers to provide those flight demonstrations to get Knapp and others interested in popularizing the story.  Notice that those craft didn’t exhibit any of the radical flight characteristics that defy conventional aerospace technology â€" the trademark hairpin moves and sudden leaps between low and high velocity.  They moved like conventional aircraft; perhaps a drone with a bright light source perhaps â€" you can see the effect of inertia on the slowly arcing turns, and in the rising and descent trajectories:  this was not a “inertia-defying” craft, as so many have witnessed elsewhere.  Notice that the bright object in the footage also doesn’t wobble around like he described.  He also never said anything about the ufo glowing when it operated, so why does the craft in the footage glow?  Because it was a staged farce, imo.

It’s difficult to envision gravitational wave distortion with words alone, because it’s quadrupole (and octupole etc) radiation, which is nothing like the longitudinal waves or transverse waves that we’re all familiar with â€" check out the nice animations they have here, and you’ll see how they oscillate as they move along an axis perpendicular to your computer screen:  https://en.wikipedia.org/wiki/Gravitational_wave

And you must be thinking of the dreaded “EM Drive” â€" that naughty little microwave cavity that keeps fooling experimentalists into thinking that there’s some kind of new motive principle at work.  The reckless leaps of logic I’ve seen in the popular press about that thing are so wildly out of control that it beggars the imagination.

Honestly, I’d be thrilled if it did any of the stuff that people claim about it.  Nothing would make me happier than to suddenly discover that one or more of the sacrosanct pillars of modern physics had been reduced to ashes overnight.

But preliminary tests demonstrating outrageously tiny forces are notorious for turning out to be experimental error, and there’s no reason to suspect that this will turn out to be any different.  I don’t know if you remember Dr. Martin Tajmar’s claims of detecting a “gigantic” gravitational frame dragging effect in a cryonic chamber using a rotating superconductor a few years ago, but in that case we had a very bright and highly qualified physicist working with some great equipment to test a theoretically viable concept and employing a rigorous range of controls, publishing peer-reviewed papers about the effect that had heads turning around the world…and it turned out to be eddy currents in the surrounding vapor…oops.

Robert Shawyer’s “EM Drive” is an asymmetrical microwave oven that supposedly violates the conservation of momentum (and maybe energy too, idk) by exploiting a new theoretical effect that’s never been described mathematically but allegedly has something to do with either a vacuum fluctuation reaction force (which has somehow heretofore eluded detection and defies known physics) and/or a quantum gravity effect dozens of orders of magnitude stronger than general relativity defines at that energy, and doing something that GR can’t explain.  Or it’s just a thermal effect from heating an asymmetrical metal box to several hundred degrees using copper power cables that tend to distort at high currents.

I just think a little prudence is called for â€" let’s at least see a peer-reviewed paper or two before we start throwing out the most rigorously proven conservation laws known to physical science.

[Chronaut]

Can a gravitational wave cause another object to move?  (don't laugh...)

That's not a dumb question at all - I think you're asking if gravitational waves can "push" an object, like light and water waves can push an object, i.e. transfer linear momentum to an object.

It's not a dumb question because it's not what we detected and it's not obvious from looking at the weird dynamics of a gravitational wave, which only seems to distort bodies in directions perpendicular to the wave's motion (that's what we detected, the distortion perpendicular to the direction of travel).  And since it's a distortion in spacetime itself, it's hard to imagine how such a wave could transfer linear momentum to a body.  But it can, and in fact when some black holes collide, they get thrown from the centers of their host galaxies by the ostensibly asymmetrical pulse of gravitational radiation they emit on impact:
https://en.wikipedia.org/wiki/Gravitational_wave#Energy.2C_momentum.2C_and_angular_momentum_carried_by_gravitational_waves

[Coffeeman]

 
I’m glad I could offer some food for thought on the subject â€" as you can probably tell I love digging into stuff like this: it’s interesting and you can learn as much from studying a false scientific assertion as you can from studying an established one, because both cases always leads back to the experimental evidence and the mathematics.  And sometimes the hoaxes lead to unexpected insights about unrelated matters, like black program security operations in this case.

There’s footage of the flight demonstrations that Lazar took Leer and Knapp et al. out there to see â€" I remember watching it; it must still be around somewhere online.  I don’t think that was a lie at all, per se.  In fact it supports my interpretation that Lazar is a covert operative working under a cover story:  I think his story was scripted for him, and that Lazar coordinated with his handlers to provide those flight demonstrations to get Knapp and others interested in popularizing the story.  Notice that those craft didn’t exhibit any of the radical flight characteristics that defy conventional aerospace technology â€" the trademark hairpin moves and sudden leaps between low and high velocity.  They moved like conventional aircraft; perhaps a drone with a bright light source perhaps â€" you can see the effect of inertia on the slowly arcing turns, and in the rising and descent trajectories:  this was not a “inertia-defying” craft, as so many have witnessed elsewhere.  Notice that the bright object in the footage also doesn’t wobble around like he described.  He also never said anything about the ufo glowing when it operated, so why does the craft in the footage glow?  Because it was a staged farce, imo.

It’s difficult to envision gravitational wave distortion with words alone, because it’s quadrupole (and octupole etc) radiation, which is nothing like the longitudinal waves or transverse waves that we’re all familiar with â€" check out the nice animations they have here, and you’ll see how they oscillate as they move along an axis perpendicular to your computer screen:  https://en.wikipedia.org/wiki/Gravitational_wave

And you must be thinking of the dreaded “EM Drive” â€" that naughty little microwave cavity that keeps fooling experimentalists into thinking that there’s some kind of new motive principle at work.  The reckless leaps of logic I’ve seen in the popular press about that thing are so wildly out of control that it beggars the imagination.

Honestly, I’d be thrilled if it did any of the stuff that people claim about it.  Nothing would make me happier than to suddenly discover that one or more of the sacrosanct pillars of modern physics had been reduced to ashes overnight.

But preliminary tests demonstrating outrageously tiny forces are notorious for turning out to be experimental error, and there’s no reason to suspect that this will turn out to be any different.  I don’t know if you remember Dr. Martin Tajmar’s claims of detecting a “gigantic” gravitational frame dragging effect in a cryonic chamber using a rotating superconductor a few years ago, but in that case we had a very bright and highly qualified physicist working with some great equipment to test a theoretically viable concept and employing a rigorous range of controls, publishing peer-reviewed papers about the effect that had heads turning around the world…and it turned out to be eddy currents in the surrounding vapor…oops.

Robert Shawyer’s “EM Drive” is an asymmetrical microwave oven that supposedly violates the conservation of momentum (and maybe energy too, idk) by exploiting a new theoretical effect that’s never been described mathematically but allegedly has something to do with either a vacuum fluctuation reaction force (which has somehow heretofore eluded detection and defies known physics) and/or a quantum gravity effect dozens of orders of magnitude stronger than general relativity defines at that energy, and doing something that GR can’t explain.  Or it’s just a thermal effect from heating an asymmetrical metal box to several hundred degrees using copper power cables that tend to distort at high currents.

I just think a little prudence is called for â€" let’s at least see a peer-reviewed paper or two before we start throwing out the most rigorously proven conservation laws known to physical science.

Thanks for shitting up one of the more consistently interesting threads with conspiracy theory bullshit. Are you one of Jackstar's alts?

[Chronaut]

Hey Agent : Orange - do you have any idea how the linear momentum component of gravitational radiation can be transferred to a distant body?  It's pretty clear, and fascinating, how gravitational radiation can "kick" an inspiralling system out of a galaxy (described in the passage below), but I don't understand how that momentum gets absorbed by other bodies at a distance to accelerate them away from the source.  Any thoughts?

"One interesting effect that emerges from the higher-order studies of binary inspirals is that gravitational radiation carries away net linear momentum, hence the center of mass of the system moves in an ever-widening spiral. We can understand this as follows (following an idea of Alan Wiseman). In an unequal-mass binary, the lower-mass object moves faster. As the speed in orbit becomes relativistic, the gravitational radiation from each object becomes beamed, with the lower-mass object producing more beaming because it moves faster. Therefore, at any given instant, there is a net kick against the direction of motion of the lower-mass object. If the binary were forced to move in a perfect circle, the center of mass of the system would simply go in a circle as well. However, because in reality the orbit is a tight and diminishing spiral, the recoil becomes stronger with time and the center of mass moves in an expanding spiral. Note that by symmetry, equal-mass nonspinning black holes can never produce a linear momentum kick, and that if the mass ratio is gigantic the fractional energy release is small and therefore so is the kick. For nonspinning holes, the optimal ratio for a kick is about 2.6.

This process is potentially important astrophysically because if the final merged remnant of a black hole inspiral is moving very rapidly, it could be kicked out of its host stellar system, with possibly interesting implications for supermassive black holes and hierarchical merging. There have therefore been a number of calculations of the expected kick. It has turned out that these are very challenging. The primary reason is that most of the action is near the end, when the black holes are close to each other and simple approximations to the orbit are inaccurate. Analytic calculations (recent examples include Favata, Hughes, and Holz 2004; Blanchet, Qusailah, and Will 2005; Damour and Gopakumar 2006), suggest that the kick due to inspiral from infinity to the ISCO is minimal, but that the final plunge could produce interesting speeds. In the last three years there has been tremendous progress in numerical relativity, and at this stage one can say that the kick can be estimated with decent accuracy for any orientation, mass ratio, and spin magnitude. The real stunner turned out to be that with spin axes in the orbital plane, one can end up with kicks of nearly 4000 km/s!! That's larger than the escape speed from any galaxy.
https://www.astro.umd.edu/~miller/teaching/astr498/lecture25.pdf

[Chronaut]

Can a gravitational wave cause another object to move?  (don't laugh...)

I'll have to amend my earlier answer gabrielle - it looks to me like the octupole and higher order radiation that carries linear momentum away from an inspiralling system comprised of unequal mass bodies, can only be absorbed by a system that also possesses an octupole moment.  So gravitational waves can't "push" just any body - only a body or system with the right properties could absorb that linear momentum and get pushed away from the source of the radiation.

A really interesting question with some very complex dynamics

[gabrielle]

I'll have to amend my earlier answer gabrielle - it looks to me like the octupole and higher order radiation that carries linear momentum away from an inspiralling system comprised of unequal mass bodies, can only be absorbed by a system that also possesses an octupole moment.  So gravitational waves can't "push" just any body - only a body or system with the right properties could absorb that linear momentum and get pushed away from the source of the radiation.

A really interesting question with some very complex dynamics

That's ok Chronaut.  I was just trying to stump you.     
so now I have to look up another ten words and go back to the library.  I really appreciate your answer.  It might take me a while to comprehend what you said.

[Richard Groyper]

Can a gravitational wave cause another object to move?  (don't laugh...)

What kind of object? Space/time, quantized particles, quarks, atoms? Other gravitational waves, maybe... Unlikely anything with mass would be my guess. It's a brand new discovery. "Do not  know at this time" - would be an accurate statement.

[Agent : Orange]

I'll have to amend my earlier answer gabrielle - it looks to me like the octupole and higher order radiation that carries linear momentum away from an inspiralling system comprised of unequal mass bodies, can only be absorbed by a system that also possesses an octupole moment.  So gravitational waves can't "push" just any body - only a body or system with the right properties could absorb that linear momentum and get pushed away from the source of the radiation.

A really interesting question with some very complex dynamics

That's right, they are emitted from specific configurations and interact with specific configurations. The wave equation that comes from the weak field limit looks just like any wave equation (ie, Maxwell) and so they have energy density, etc and can also have an analogue of an energy-density and momentum (Poynting) vector as well. This means they carry energy and momentum with them. The only difference is the waves are based on tensors rather than vectors, so the two index character of them means they have quadrupole character. Very interesting.
Article on GW energy-momentum (Poynting) vector here for those interested: http://arxiv.org/pdf/gr-qc/9801095.pdf
All that comes from the fascinating weak field GR expansion which looks just like Maxwells equations with mass and mass currents in place of charge and charge-current: https://en.wikipedia.org/wiki/Gravitoelectromagnetism
You can form a wave equation from these weak fields too, just like you can with Maxwell, and you get back a gravitational wave equation as you might expect. This wave equation then gives the speed of propagation as the speed of light. So it's an interesting result.

[Chronaut]

That's right, they are emitted from specific configurations and interact with specific configurations. The wave equation that comes from the weak field limit looks just like any wave equation (ie, Maxwell) and so they have energy density, etc and can also have an analogue of an energy-density and momentum (Poynting) vector as well. This means they carry energy and momentum with them. The only difference is the waves are based on tensors rather than vectors, so the two index character of them means they have quadrupole character. Very interesting.
Article on GW energy-momentum (Poynting) vector here for those interested: http://arxiv.org/pdf/gr-qc/9801095.pdf
All that comes from the fascinating weak field GR expansion which looks just like Maxwells equations with mass and mass currents in place of charge and charge-current: https://en.wikipedia.org/wiki/Gravitoelectromagnetism
You can form a wave equation from these weak fields too, just like you can with Maxwell, and you get back a gravitational wave equation as you might expect. This wave equation then gives the speed of propagation as the speed of light. So it's an interesting result.

Niccce - this Menezes paper is gonna keep me company tonight =)  Most people aren't aware of the beautiful analogy between electric charge and "gravitational charge" and all of the wonderful parallels they share with magnetism and radiation, when the magnitude of the gravitational field is in the weak field limit.  Apparently Robert Forward wanted to build a toroidal gravitomagnetic inductor to experiment with possible propulsion applications in mind.  I wonder if we'll be able to harness plasma to try that out someday.  Iirc there's an open question about gravitational field symmetry with a mass current simultaneously flowing in both minor and major axis rotation.

I still love to peruse Robert Forward's inspiring papers on gravitation and experimental frontiers for antigravity research and the baffling physics of negative mass - you've probably read all that stuff but I though I'd mention them for anyone interested in this kind of thing.

[Agent : Orange]

Niccce - this Menezes paper is gonna keep me company tonight =)  Most people aren't aware of the beautiful analogy between electric charge and "gravitational charge" and all of the wonderful parallels they share with magnetism and radiation, when the magnitude of the gravitational field is in the weak field limit.  Apparently Robert Forward wanted to build a toroidal gravitomagnetic inductor to experiment with possible propulsion applications in mind.  I wonder if we'll be able to harness plasma to try that out someday.  Iirc there's an open question about gravitational field symmetry with a mass current simultaneously flowing in both minor and major axis rotation.

I still love to peruse Robert Forward's inspiring papers on gravitation and experimental frontiers for antigravity research and the baffling physics of negative mass - you've probably read all that stuff but I though I'd mention them for anyone interested in this kind of thing.

When I first read about the gravitational Meissner effect I was really impressed. Since then I've always kept an eye out for strange optics or other obscure E&M that might have an analogue in weak field GR. It's just such a nice way of finding parallels between E&M and gravity I think it's very underappreciated and it bothers me it's not much known outside of GR circles.

[Chronaut]

That's ok Chronaut.  I was just trying to stump you.     
so now I have to look up another ten words and go back to the library.  I really appreciate your answer.  It might take me a while to comprehend what you said.

Nice work - I had to scratch my head on that one for awhile =P  To put it a bit more simply, the gravitational radiation that carries linear momentum (the "pushing" force) only comes from systems like a neutron star spiraling into a black hole.  So only a system like that, or with the same basic properties, can absorb that radiation and get pushed away.  It's just another level of complexity than the stuff we're used to in ordinary life, because as Agent : Orange explained, gravitation isn't based on the nice easy vectors (arrows basically) that we all know and love; it's based on tensors, which are a higher order of complexity.

[Chronaut]

When I first read about the gravitational Meissner effect I was really impressed. Since then I've always kept an eye out for strange optics or other obscure E&M that might have an analogue in weak field GR. It's just such a nice way of finding parallels between E&M and gravity I think it's very underappreciated and it bothers me it's not much known outside of GR circles.

Gravitational Meissner effect - that's a gem ;

Ever see Lockheed Martin's patent US5929732A, "Apparatus and method for amplifying a magnetic beam"?
https://patents.google.com/patent/US5929732A/en

If you can focus a magnetic field into a beam using other magnetic fields, it must be possible to focus a gravitational field into a beam as well.  Tractor beam, monsieur?

[zeebo]

Thanks. Time to read up about Hawking Radiation.

Me too.  We're always told nothing can escape the e. horizon and yet apparently something does and that's why black holes can eventually 'evaporate'.  Is this one of those squishy places where quantum and gravity theories don't quite gel with each other?

[Agent : Orange]

Me too.  We're always told nothing can escape the e. horizon and yet apparently something does and that's why black holes can eventually 'evaporate'.  Is this one of those squishy places where quantum and gravity theories don't quite gel with each other?

Nothing actually escapes the horizon with Hawking radiation. Since the vacuum is always bubbling with assorted quantum bric-a-brac, particle pairs are always popping out of the vacuum, annihilating one another and returning to the vacuum. These quantum fluctuations are required to have zero energy to balance nature's books. Such fluctuations occur all the time, even in empty space. Of course these particle-antiparticle pairs are fluctuating in the spacetime near black holes too. If one member of the pair (it doesn't matter which one) falls into the black hole, then it's partner no longer has anything to annihilate with and provided it is outside the event horizon it can escape. Since the escaping particle has mass (energy), it means it's partner must have negative mass (energy) within the black hole. This will annihilate some of the black hole mass and pay the mass debt for its partner.

To an outside observer it looks like the black hole emitted a particle and shrunk a tiny bit.

In fact there's nothing special about the event horizon, in GR it looks just like any other part of spacetime with finite curvature. You can even pick coordinates in which the horizon doesn't show up at all. It's only to us distant observers who are using particularly obvious coordinates that see an event horizon. An astronaut falling into a black hole, for example, doesn't notice anything special as he crosses the event horizon, but an observer outside the black hole won't ever hear anything more from his increasingly reddening after image.

[Agent : Orange]

Gravitational Meissner effect - that's a gem ;

Actually a beautiful result for such a short paper:
http://arxiv.org/abs/hep-th/9603077
He even finds an estimate for the maximum neutron star radius from the coherence length, which is in the ballpark with calculations from detailed equations of state. So it is quite an interesting paper for me. 

Ever see Lockheed Martin's patent US5929732A, "Apparatus and method for amplifying a magnetic beam"?
https://patents.google.com/patent/US5929732A/en

If you can focus a magnetic field into a beam using other magnetic fields, it must be possible to focus a gravitational field into a beam as well.  Tractor beam, monsieur?

haha!
That's a great idea.
A bit harder to set up with mass quadrupoles since we will basically need to replace each fixed dipole with a black hole binary system. We will also need to keep them insulated from one another somehow so they don't turn into one giant N-body problem mess.

Minor technical hurdles. Because, do you know what's better than a lab scale tractor beam?
A solar system scale tractor beam!

Alternatively, would make a great "cosmic lighthouse" for anyone only interested in finding species that have the capability of detecting gravitational waves.

[Chronaut]

Actually a beautiful result for such a short paper:
http://arxiv.org/abs/hep-th/9603077
He even finds an estimate for the maximum neutron star radius from the coherence length, which is in the ballpark with calculations from detailed equations of state. So it is quite an interesting paper for me. 

I started reading it last night and couldn’t tear my eyes away until I was finished â€" riveting, inspired and concise.  A gravitational analogue to a superconductivity phenomenon had never crossed my mind…I love when that happens =P

A bit harder to set up with mass quadrupoles since we will basically need to replace each fixed dipole with a black hole binary system. We will also need to keep them insulated from one another somehow so they don't turn into one giant N-body problem mess.

Celestial configurations make for elegant thought models to explore applied gravitational principles, but my optimistic futurist temperament favors the dream of one day attaining bench-top experimentation and application â€" one of the things I love about Robert Forward’s papers on the subject.  Joseph Weber also dares to envision laboratory gravitational wave experimentation in the “Generation of Gravitational Waves” chapter of his book General Relativity and Gravitational Waves:
https://books.google.se/books?id=lgDDAgAAQBAJ

In fact just a few weeks ago an ambitious but presently attainable experimental setup was described by André Füzfa in Physics Review D for generating a gravitational field, in his paper “How current loops and solenoids curve space-time”:
http://arxiv.org/abs/1504.00333

Because the thing is, if you’ve ever seen a ufo in flight, or accept the performance characteristics and physics analyses by folks like NASA aeronautical scientist Paul Hill (author of Unconventional Flying Objects, 1995), somebody (perhaps a lot of somebodies) has mastered gravitational field technology in craft no larger than 30’ x 20’.  So it can be done.  Somehow.  And a gravitational field propulsion system opens to the door to manned interstellar spaceflight, which would change everything.

Honestly, I think it’s likely that quite a few of the reported sightings are nothing more than flight demonstrations, sending the simple and tantalizing message:  “look at this; this can be done…you can do this…figure it out.”

Alternatively, would make a great "cosmic lighthouse" for anyone only interested in finding species that have the capability of detecting gravitational waves.

That’s a cleverly selective idea; I’m just not sure that we should be sending out any beacons…because when I look at human behavior, and extrapolate that to advanced exosolar intelligences, I think there’s a high probability that quite a lot of sentient alien beings out there are really incredibly terrible people  :/

[TigerLily]

My brain hurts. I was trying to understand Science again.
I just watched "How the Universe Works" on "The First Second ".  It boggled my mind

[TigerLily]

Would you guys please stop being so fascinating.  I am trying to get some work done over here!  Honestly, this is the most interesting stuff I have read in a long time. Thank you all for this discussion and for taking the time to answer questions so thoughtfully.  I am sure I not the only non-scientist reading this and trying to follow. THANK YOU.

Right behind you, G  . This is my first day stopping here. Fascinating discussions.

[Chronaut]

My brain hurts. I was trying to understand Science again.
I just watched "How the Universe Works" on "The First Second ".  It boggled my mind

I see science as the realization of genuine magic:  understanding the invisible mechanisms that reality obeys, to manifest your will and imagination, and achieve the boldest dreams of the human mind.

It's not an easy subject, but every step toward greater understanding offers new tools and capabilities to master the world around you.  And one of these days, some brilliant scientician is going to throw open the door to the stars, and we'll sail through the cosmos like the gods of ancient legend.

....if the howling headcases don't blow up the foundations of global civilization before we get there, that is...

[SciFiAuthor]

That’s a cleverly selective idea; I’m just not sure that we should be sending out any beacons…because when I look at human behavior, and extrapolate that to advanced exosolar intelligences, I think there’s a high probability that quite a lot of sentient alien beings out there are really incredibly terrible people  :/

There's actually a school of thought within exobiology that concludes that in order for a species to become technologically advanced and spread out into the universe they must necessarily be aggressive. You don't become a type III civilization if you're not thoroughly awful.

[gabrielle]

Right behind you, G  . This is my first day stopping here. Fascinating discussions.

TL..is it just me, or does the explanation of how a gravitational wave moves seem sort of like a contraction?   ( getting ready to duck and hide)

[GravitySucks]

TL..is it just me, or does the explanation of how a gravitational wave moves seem sort of like a contraction?   ( getting ready to duck and hide)

You mean like real ones like "Let's" or irregular ones like "can't" or "won't"?

[gabrielle]

You mean like real ones like "Let's" or irregular ones like "can't" or "won't"?

As in....a mother giving birth.  A real one.   

[Richard Groyper]

Right behind you, G  . This is my first day stopping here. Fascinating discussions.

TL..is it just me, or does the explanation of how a gravitational wave moves seem sort of like a contraction?   ( getting ready to duck and hide)

The human brain is able to concieve the creation universe, time, and space. It's a lonely feeling, at least when I think about it, I tend to end up feeling that way...

Our natural desire to explore as a species is very strong. We are always trying to look past the horizion. Always trying to grab what's just out of reach. Why?

[FearBoysWithBugs]

TL..is it just me, or does the explanation of how a gravitational wave moves seem sort of like a contraction?   ( getting ready to duck and hide)

If you stick around this thread, you're going to find a lot of stuff like that.  We're familiar with physics as it presents itself in our daily lives.  We are so conditioned by our daily experiences that our brains automatically reject certain notions such as the ones you encountered with gravity waves.

Consider this: in theory, if you got into a space ship and drove forward in a straight line at the speed of light, eventually you would re-arrive at your starting point (MANY years later, but put that aside for now).  Now, how can THAT be?  You went in a straight line, never turned, how did it happen?

We ask those questions because we are familiar with a 3D world, and the results seem counter-intuitive.  But...think of this.  A 2D man sits on the surface of the earth, in his little car, and drives forward in a straight line.  What happens?  Eventually he re-arrives at his origin point, and he's as baffled as we are in our 4D experience.  He doesn't have familiarity with that third dimension,  that the world is round and it is possible to travel forward in a straight line and re-arrive at the origin point.  So he doesn't understand what happened, just like we would not intuitively understand what happened in our spaceship.

I would encourage you to join in the discussion and not worry about looking like a noob.  Believe me, we ALL started there!  When you think about it regularly and it becomes more familiar, some of the confusion ebbs. but the wonder of it all remains, and that makes it worth the trouble. 

[Chronaut]

Consider this: in theory, if you got into a space ship and drove forward in a straight line at the speed of light, eventually you would re-arrive at your starting point (MANY years later, but put that aside for now).  Now, how can THAT be?  You went in a straight line, never turned, how did it happen?

That would be true if we lived in a closed universe (a universe where gravity would eventually re-collapse the universe), and I've always loved that model.

But the 2014 results of the Baryon Oscillation Spectroscopic Survey (BOSS) Collaboration show that the observed universe has zero curvature within an accuracy of 1%, which indicates that it’s topologically flat and infinite, so if you head out in any given direction you won’t end up where you started after all:

“Our results are consistent with an infinite universe.”
http://newscenter.lbl.gov/2014/01/08/boss-one-percent/

[Richard Groyper]

That would be true if we lived in a closed universe (a universe where gravity would eventually re-collapse the universe), and I've always loved that model.

But the 2014 results of the Baryon Oscillation Spectroscopic Survey (BOSS) Collaboration show that the observed universe has zero curvature within an accuracy of 1%, which indicates that it’s topologically flat and infinite, so if you head out in any given direction you won’t end up where you started after all:

“Our results are consistent with an infinite universe.”
http://newscenter.lbl.gov/2014/01/08/boss-one-percent/

Don't forget about expansion. Dark energy is actually excelerating the expansion. Can't beat that with straight light speed. Need a device fold space/time. It's the only way.

[FearBoysWithBugs]

That would be true if we lived in a closed universe (a universe where gravity would eventually re-collapse the universe), and I've always loved that model.

But the 2014 results of the Baryon Oscillation Spectroscopic Survey (BOSS) Collaboration show that the observed universe has zero curvature within an accuracy of 1%, which indicates that it’s topologically flat and infinite, so if you head out in any given direction you won’t end up where you started after all:

“Our results are consistent with an infinite universe.”
http://newscenter.lbl.gov/2014/01/08/boss-one-percent/

It was an illustrative example, where the laws are lenient.  Hush up, Oprah.

[Chronaut]

It was an illustrative example, where the laws are lenient.  Hush up, Oprah.

Oprah?  I've been called a lot of things, but dude, that's harsh... ;

[TigerLily]

TL..is it just me, or does the explanation of how a gravitational wave moves seem sort of like a contraction?   ( getting ready to duck and hide)

the Big Birth Pang  (Childless myself but have witnessed and heard many a detailed horror story of the miracle of birth to agree)