Modern physics(and engineering) is kind of absurd. And I mean that in a good way. LIGO? I didn't believe at all that it would ever work. Even when they got detections I kinda thought they were chasing their own tails. Now the evidence is pretty much rock solid that the data is real(multiple facilities, correlations with light observations for neutron star mergers, etc).
Then I heard about LISA, which essentially is building this thing in fucking space(different geometry, but same basic concept), with probes somehow orbiting in unison and firing lasers at eachother over ridiculous distances(2.5 million kilometers!). I thought they were raving mad. But pathfinder, the POC, seemed to work, and now they're building the thing. Planned for 2037, but still.
When I heard about this project in a spacetime video a few years ago IIRC, again I thought okay, this is too far. It's never gonna work, there'll be too much noise yadda yadda. And it now it looks they might have done it.
At this point, if physicists say something is possible, I listen no matter how impossible it sounds.
This discovery didn't actually involve LIGO, nor any other feats of impressive physical engineering. It was made by observing neutron stars and finding patterns in their unexpected perturbations.
Neutron star rotation is so consistent that they are used to calibrate atomic clocks[0]. However some of them were glitching and not rotating as expected, but the glitches were consistent between each other. It turns out they aren't actually glitching, but spacetime is being distorted by massive gravitational waves.
Indeed, and part of the magic is knowing jupiters position with a very high precision. Said precision was delivered by the Juno probe in 2016 or so. With that precision we now know the earth position with much more accuracy. The trick is the jupiter and sun orbit around a point outside the surface of the sun. Said point (barycenter) is the point the earth rotates around.
The increased positional accuracy of the earth allows teasing out the distortion from to various pulsars to use the galaxy as a ligo like gravity wave detector.
My physics professor, David Blair, sketched out the design for LIGO and other detectors back ~1980 and the kinds of technology that would first need to be created in order to get there.
The big money and the big builds tend to be in the US (for now, at least, but empires always shift centres over the long time periods) but the ideas come from all over the world.
I watch pretty much all their videos as they come out, and indeed this one was... pretty out there(pun intended). Somehow I have no doubt it'll be built one day.
For now my mind is sufficiently blown by JWST taking spectra of exoplanet atmospheres.
For more materials, measurement, and spacecraft engineering challenges in verifying gravity theory, check out Gravity Probe B [1]. 40+ year effort (spoiler: it confirmed the geodetic and frame-dragging effects of General Relativity).
> how comes they can't get this fusion thing to work?
Fusion energy involves conjuring physics which don’t exist in that form in the known universe. (Stellar fusion happens at lower rates than what we’re targeting. The only reason it works is because stars are so huge.)
Fussion is easy, hyndrogen nukes were detonated decades ago. Ask them about LENR (Low Energy or Lattice Enabled Nuclear Reactor). Cold Fusion topic is reputation-damaging for scientists for decades. I banned multiple times here for "participation in discussion". Now, LENR is used to boost fusors performance by two order of magnitude (for medical purpose).
What do these waves look like as they pass through us? Acoustic-like compression and expansion of particles as molecules temporarily reorient toward a “down” that is ever-so-slightly off from the Center of mass of the Earth?
Also, I assume that these waves are very gentle sinusoids? Could the opposite — a high-amplitude gravitational square wave — be possible? What would it do to the things it passes through?
The gravitational way has a direction (say, z) in which its propagating. Within the plane perpendicular to that direction (x-y), a circular ring of particles will at at one moment experience squeezing in one direction (x) and stretching the perpendicular direction (y). As the wave passes through and you move from the peak of the wave to the trough, the directions reverse, so the first direction (x) stretches and the other direction (y) squeezes. By "stretching" and "squeezing" I mean instantaneous additional (positive and negative) acceleration on top of the (much, much larger) acceleration from the background gravitational field provided by the Earth.
Just as a child can swing their legs at the resonant frequency of a swing to pump up their sinusoidal amplitude, a very weak gravitational wave can pump up a ring oscillator if it's oscillating at the ring's resonant frequency.
Exactly square gravitational waves are of course not possible, just as for electromagnetic waves. (They would have infinite energy at the corners.) But in principle you could get a close approximation. However, spacetime is incredibly stiff, and I think all the known real-world sources produce pretty smooth waves. I presume most violent events are mergers of existing black holes, and essentially always result from a smooth in-spiral rather, say, a sharp collision event. This is what the "chirp" signal looks like to the LIGO detector:
The effects of a square wave would be roughly as you would expect: instead of smoothly pumping up an oscillator, it would give it a sharp kick, just as with electromagnetism.
> Just as a child can swing their legs at the resonant frequency of a swing to pump up their sinusoidal amplitude, a very weak gravitational wave can pump up a ring oscillator if it's oscillating at the ring's resonant frequency.
So is it possible that a passing gravitational wave could initiate some natural process that otherwise might have not happened?
Acoustic waves propagate through what are essentially elastic deformations of the material they travel through. Can gravitational waves be thought of as propagating by elastically deforming spacetime?
If this analogy holds, then can it be taken further? Acoustic waves dissipate their energy insofar as they trigger plastic deformation in a material. Could gravitational waves plastically deform... spacetime itself? Or would they just be deforming the material? Or is gravitational energy not dissipated into other forms of energy at all?
"However, spacetime is incredibly stiff, and I think all the known real-world sources produce pretty smooth waves."
In English, why does stiffness correlate to smooth waves? What does stiff spacetime mean? I'd have thought a square wave would be "stiff" as it's quite the opposite of smooth.
Thank you for that! As an EE and radio enthusiast, I feel like I have a fairly good grasp of how gravitational waves behave from that description. The way in which the mechanics of these different energies all sort of share characteristics is rather beautiful.
Could you set up massive pendulums to convert this gravitational wave energy into mechanical energy? Would such a device diminish the strength of the wave downstream?
I recommend looking into LIGO and other similar experiments. They use laser interferometry to accurately measure the distance between two points, to an extreme degree. From LIGO's website:
Gravitational waves cause space itself to stretch in one direction and simultaneously compress in a perpendicular direction. In LIGO, this causes one arm of the interferometer to get longer while the other gets shorter, then vice versa, back and forth as long as the wave is passing. The technical term for this motion is "Differential Arm" motion, or differential displacement, since the arms are simultaneously changing lengths in opposing ways.
As described above, as the lengths of the arms change, so too does the distance traveled by each laser beam. A beam in a shorter arm will return to the beam splitter before a beam in a longer arm--as the wave passes, each arm oscillates between being the shorter arm and the longer arm. When they arrive back at the beamsplitter (where they re-merge), the light waves no longer meet up nicely; they are out of phase. Instead, they shift in and out of alignment for as long as the wave is passing.
>*Gravitational waves cause space itself to stretch*
Please ELI5 specifically and empiracally what "Space Itself" actually is.
Would it be possible to build a 'galactic clock & Compass' - a "clock" to the regular pulses of a pulsar and the galactic direction the pulsar is in relation to the terrestrial compass (magnetic) on earth...?
What is the pulsar with the most reliable timings?
It's not so much that you see a slightly different "down," but that space itself is changing such that the distance between e.g. your head and feet is (very) slightly altered.
The two descriptions are equivalent. By the equivalence principle, the wave looks locally like neighboring bodies see different directions of down (and also slightly different strengths of the force of gravity in that direction).
Dumb, but earnest question: if space itself changes, how can the distance change? What is the distance a measure of, if not space itself? What's the yardstick, speed of light?
The gravitational waves we detect are transverse waves. Longitudinal gravity waves have been proposed, discarded, and proposed again, I’m not sure what their current theoretical status is.
I was wondering if these waves could affect our brains, even subtly. Maybe cause a reaction in one part of one cell that tips the balance between a neuron firing or not.
Thanks for the link. I had issues with the WaPo article, but that tongue-in-cheek joke with dead-pan delivery wasn't one of them. Fortunately another commenter called it out as a joke as well.
Imagine if we could take advantage of the time-space potential/differences between gravitational areas to "skip" large parts of space. We would have to have a very precise gravity map, but could also get huge gravity potential boost!
Could we? Is there math that supports this? Wouldn't this require taking some, and then not losing it when the wave passes? I don't see much happening with the earth, as it's experiencing them, so I assume the "extraction" process would be significant and unique.
I was taught that all items fall at the same speed, due to the gravitational constant.
With these waves, does that mean that items will fall at ever so slightly differing speeds, as depending on the size of the wave there is a pull in the other direction, and the constant is slightly off?
And OT, but related: Since every item has a gravitational pull related to its mass, would a bigger item fall ever so slightly faster than a small one, as it is pulling itself to Earth in addition to Earth pulling it down.
No, gravitational waves do not affect the equivalence principle and do not change the gravitational constant. They are waves of change in the geometry of spacetime; freely falling objects show these spacetime geometry changes by changes in their relative motion.
Well in both your questions it depends on how you define speed. It is commonly understood to be the first derivative of position, or the quotient of distance divided by a time-span. But how do you define and measure distance and time-spans? Which reference frame do you use?
Also, the things falling in a vacuum at the same speed thing is a common misconception. The two arguments usually are that the mass of one body can be canceled out in both equations or that splitting a body into two won't make its halves fall slower.
To answer the question: Given all bodies have the same size, a constant distance to and mass of the reference body (usually earth) and everything starting at rest with no relative speed heavy and light bodies do experience the same acceleration, but a heavy body will collide sooner than a light body. Did it "fall faster"?
This is all firmly outside my technical discipline, but aren't there some theories that faster-than-light travel might be achieved by bending spacetime around a spacecraft, as opposed to trying to propel the spacecraft through space?
I really want to emphasize that this is entirely speculation, but is it possible that these gravitational waves could be the "ripples" produced in the wake of such faster-than-light travel, the same way a boat travelling through a body of water leaves ripples in the water behind it?
In the video, they mention that the models we have for FTL (by bending spacetime) wouldn't generate ripples in this way. We could however detect ripples from a really massive ship accelerating really really quickly.
> Whereas the original discovery spotted waves originating from the collision and merger of two star-sized black holes, the most likely source of the latest finding is the combined signal from many pairs of much larger black holes — millions or even billions of times the mass of the Sun — slowly orbiting each other in the hearts of distant galaxies. These waves are thousands of times stronger and longer than those found in 2015, with wavelengths of up to tens of light years. By contrast, the ripples detected since 2015 using a technique called interferometry are just tens or hundreds of kilometres long.
Seems like they probably know where these are coming from. I imagine, like your boat analogy, that we can observe massive natural oceans swells and wouldn't notice the wake of a boat as it moves across the ocean.
from a layman's perspective, this sounds crazy cool that they were able to "see" this in the data. seems like one of those things that would be easy to miss from being scoped in and only discoverable after zooming back out. waaaaay out.
Do they require a long list of impossible things to work? Also yes!
There are entirely valid solutions in general relativity which allow for an object in a pocket of spacetime with other spacetime warped around it in such a way that, more or less, space is moving but not the object.
However achieving the arrangement of spacetime to make this happens requires many things which are impossible, aren't known to exist, or require something like all the energy in the Universe to achieve.
Also there are no valid known solutions that transition from normal space to this special spacetime arrangement, so it could only exist if it always existed.
So it comes down to: we're pretty sure such things are not actually possible but we know where to look and what problems to solve if it were. Occasionally we see a paper which removes some of the impossible things from the list.
It's one of those "unlikely but maybe someday" kinds of things.
"I understand how the engines work now. It came to me in a dream. The engines don't move the ship at all. The ship stays where it is and the engines move the universe around it." ―Cubert Farnsworth
Theoretically it's impossible to travel through space at or more than speed of light. But space itself can move faster than light speed, and a warp drive would help something similar that you mentioned. That is possible theoretically. But the amount of energy or mass it needs is very high and no current technology (or in foreseeable future) can achieve it. So FTL remains a dream.
My hunch based on nothing is that we will achieve FTL no earlier than 2250.
It's fun to imagine the species in x-hundred years. My college physics professor once told us that in 500 years, physics professors will still teach Maxwell's equations in the format he was showing us. And honestly, I think he's right.
Somethings we will do the same way for hundreds of years, like the wheelbarrow will still exist in 500 years as it has for likely the previous 5,000.
Otoh, I doubt we will be going faster than light this millenium.
'space' isnt a substance that can move at any speed.
What's meant by the claim that 'space moves faster than light' is that extremely distant objects are moving away from each other, relative to each other, 'faster than light' -- which is permitted, so long as that distance can never be bridged by light.
The claim amounts to, in other words, that the universe is so large that we can compare objects at distances greater than those light could travel between them, and if we do that, they travel faster than light.
This is an "illusion in measurement" more than anything else. Nothing is travelling faster than light.
Yeah the only energy source that can produce enough energy to power an Alcubierre drive (warp drive) that humanity has ever even conceived is a matter-antimatter reactor. But we don’t even fully understand matter, much less antimatter, and are pretty far from that. 2250 at the earliest is not an unreasonable estimate.
This video might help understand where mass comes from and how to potentially modulate it, because mass can be thought of as bound energy creating voids in the gluon field:
The Higgs mechanism affects electrons, not quarks, and is only responsible for about 1% of matter's mass. Most mass comes from the binding energy between quarks, which creates flux tubes between quark-antiquark pairs. If we add more energy to pull quarks apart, eventually the total energy added exceeds the mass-energy equivalence of another quark-antiquark pair, so a new pair gets created from the vacuum. I believe this is related to the Casimir effect, but IANAP (physicist).
Keep in mind that the mass-energy equivalence also applies to time. So like in the movie Interstellar, when they go down to the water planet, gravity is so high that time passes slower for them than the guy in the orbiting ship. In other words, the ship sees the landing craft move slower and slower as it approaches the surface. This difference in the speed of time near a gravity well is what slows the inner edge of a satellite slightly more than the outer, curving it along the path of the orbit, which from the satellite's perspective feels like a straight line at that velocity, because it's weightless and feels no other acceleration other than tidal force. So if someone could move large amounts of energy into a confined space with some kind of flux capacitor (is this a pun? I don't even know anymore), they could slow time there and create a virtual mass through mass-energy equivalence by E=mc^2. If they did it in front of the satellite, it would begin to increase in velocity towards that mass. So this is sort of a warp drive mechanism, although I don't know how you'd confine it, and the energies involved would be planet-scale to achieve 1 g of acceleration like near the Earth.
Also if someone made a closed loop where electron-positron pairs were sent one way, then their energy was used to create quark-antiquark pairs sent the other way, there might be a 1% imbalance in mass due to the Higgs mechanism, which would add momentum to the loop opposite the direction of the heavier stream. Although due to conservation of momentum, I suspect that this wouldn't actually happen, because any momentum above light pressure should get lost to heat/entropy/etc. But it would be a fun experiment to try. The same experiment would also work just sending light energy photons one way and matter-antimatter pairs back the other way, but I've never seen a proof as to why this would or wouldn't beat light pressure. This would be a reactionless rocket, not a warp drive.
If there's a gravity field like a gluon field, just with slightly different rules, then I don't see why it couldn't be modulated. In fact, I think that the dark matter strands connecting galaxies are densities where perhaps something like slowed neutrinos or axions collect and slow time. They could even be places where gravity "flows" along eddies left over from the Big Bang, although this seems strange to us because gravity normally only flows into gravity wells. There's also currently no explanation for the Hubble constant in the expansion of the universe, so perhaps something is creating space over time. So I don't see why space couldn't be created behind a craft to push it forward. We just don't know how.
There are so many unexplored interactions like this, that I don't think any physicist can confidently say that warp drives, reactionless rockets and folding space are impossible. Which means that I give it 50/50 odds that some kind of sci-fi space engine will be invented within the next few decades, probably starting with a reactionless drive like the EmDrive, which (if it works) uses resonance to time the interaction of microwaves with the rebound of atoms in an asymmetric field, similar to the Biefeld-Brown effect explored by Thomas Townsend Brown in the 1920s, which was later found to just be an electrohydrodynamic (EHD) effect:
Unfortunately only physicists are privy to the mental associations which allow thought experiments like this. Textbooks leave us mainly theory and equations, not insights or abstractions. Physics formulas are like trying to understand the behavior of an app from its assembly language. So in a very real way, academic gatekeeping prevented almost everyone from contributing. For every divergent thinker like Einstein, there are 100 convergent thinkers who judge skeptically and crush ideas into oblivion.
I'm just an armchair warrior full of derivative ideas who has never invented anything, who would love to run experiments like these. But just like you the reader, I'll spend the rest of my life making CRUD apps to make rent because billionaires have all the money, instead of getting to be like Dr. Gillian Taylor in Star Trek IV, suddenly able to explore every possibility under the freedom of UBI. That was a joke, but not really.
>The Higgs mechanism affects electrons, not quarks
It effects both. The LHC produces Higgs particles through the annihilation of top-antitop pairs, which works because the top quark couples strongly to the Higgs field.
I understand the gist of this research: pulsars emit radio waves at regular frequencies, so by monitoring radio waves received from pulsars in the sphere surrounding us, we can measure correlated anomalies in their frequencies and infer that they were caused by large gravitational waves that effectively changed the shape of the transmission medium. That makes sense.
But this is not measuring the gravitational wave itself. It's measuring the change in trajectory of the radio signals that are "riding" the wave. In the ocean analogy, it would be as if we were surrounded by a circle of floating turrets that each emitted floating darts at regular intervals in all directions. Then we would measure the time it took the darts to reach us, and from that we could infer the size of the waves the darts encountered along the way. But we never actually see the waves, only the darts.
So my question is: how can we tell the difference between one really big wave, and many really small waves that would sum to the same effect? In other words, we know there is some waveform(s) that changed the velocity vector of the radio signal. But if there are multiple arrangements of waves that would produce the same change in signal, how do we pick the right arrangement?
The timing of a single pulsar would not be reliable enough to detect gravitational waves. Instead, each collaboration monitors an array of dozens. As a result, they have found a signature called the Hellings–Downs curve, which predicts how, in the presence of gravitational waves coming from all possible directions, the correlation between pairs of pulsars varies as a function of their separation in the sky.
Not sure it answers your question but my impression is they simulate results of all possible effects and then see which one(s) the data correlates with. So if there are multiple causes that could produce identical effects then I doubt they could distinguish between them.
That makes intuitive sense. So I guess the more pulsars we measure, the more accurately we can disambiguate between different possible waveforms.
It reminds me of EEG (brain wave) measurement: a hairnet with 256 electrodes will have higher resolution than one with 128 electrodes (ignoring all the issues with interference of the skull).
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When I heard about this project in a spacetime video a few years ago IIRC, again I thought okay, this is too far. It's never gonna work, there'll be too much noise yadda yadda. And it now it looks they might have done it.
At this point, if physicists say something is possible, I listen no matter how impossible it sounds.
Neutron star rotation is so consistent that they are used to calibrate atomic clocks[0]. However some of them were glitching and not rotating as expected, but the glitches were consistent between each other. It turns out they aren't actually glitching, but spacetime is being distorted by massive gravitational waves.
[0] https://gizmodo.com/scientists-use-spinning-neutron-stars-to...
The increased positional accuracy of the earth allows teasing out the distortion from to various pulsars to use the galaxy as a ligo like gravity wave detector.
My physics professor, David Blair, sketched out the design for LIGO and other detectors back ~1980 and the kinds of technology that would first need to be created in order to get there.
The big money and the big builds tend to be in the US (for now, at least, but empires always shift centres over the long time periods) but the ideas come from all over the world.
https://www.uwa.edu.au/Profile/David-Blair
If you think LISA is mad this will blow your mind.
For now my mind is sufficiently blown by JWST taking spectra of exoplanet atmospheres.
[1] https://einstein.stanford.edu/TECH/technology1.html
Fusion energy involves conjuring physics which don’t exist in that form in the known universe. (Stellar fusion happens at lower rates than what we’re targeting. The only reason it works is because stars are so huge.)
Also, I assume that these waves are very gentle sinusoids? Could the opposite — a high-amplitude gravitational square wave — be possible? What would it do to the things it passes through?
The gravitational way has a direction (say, z) in which its propagating. Within the plane perpendicular to that direction (x-y), a circular ring of particles will at at one moment experience squeezing in one direction (x) and stretching the perpendicular direction (y). As the wave passes through and you move from the peak of the wave to the trough, the directions reverse, so the first direction (x) stretches and the other direction (y) squeezes. By "stretching" and "squeezing" I mean instantaneous additional (positive and negative) acceleration on top of the (much, much larger) acceleration from the background gravitational field provided by the Earth.
Here's a visualization:
https://www.researchgate.net/publication/313828462/figure/fi...
Just as a child can swing their legs at the resonant frequency of a swing to pump up their sinusoidal amplitude, a very weak gravitational wave can pump up a ring oscillator if it's oscillating at the ring's resonant frequency.
Exactly square gravitational waves are of course not possible, just as for electromagnetic waves. (They would have infinite energy at the corners.) But in principle you could get a close approximation. However, spacetime is incredibly stiff, and I think all the known real-world sources produce pretty smooth waves. I presume most violent events are mergers of existing black holes, and essentially always result from a smooth in-spiral rather, say, a sharp collision event. This is what the "chirp" signal looks like to the LIGO detector:
https://www.youtube.com/watch?v=TWqhUANNFXw
The effects of a square wave would be roughly as you would expect: instead of smoothly pumping up an oscillator, it would give it a sharp kick, just as with electromagnetism.
So is it possible that a passing gravitational wave could initiate some natural process that otherwise might have not happened?
If this analogy holds, then can it be taken further? Acoustic waves dissipate their energy insofar as they trigger plastic deformation in a material. Could gravitational waves plastically deform... spacetime itself? Or would they just be deforming the material? Or is gravitational energy not dissipated into other forms of energy at all?
In English, why does stiffness correlate to smooth waves? What does stiff spacetime mean? I'd have thought a square wave would be "stiff" as it's quite the opposite of smooth.
Gravitational waves cause space itself to stretch in one direction and simultaneously compress in a perpendicular direction. In LIGO, this causes one arm of the interferometer to get longer while the other gets shorter, then vice versa, back and forth as long as the wave is passing. The technical term for this motion is "Differential Arm" motion, or differential displacement, since the arms are simultaneously changing lengths in opposing ways.
As described above, as the lengths of the arms change, so too does the distance traveled by each laser beam. A beam in a shorter arm will return to the beam splitter before a beam in a longer arm--as the wave passes, each arm oscillates between being the shorter arm and the longer arm. When they arrive back at the beamsplitter (where they re-merge), the light waves no longer meet up nicely; they are out of phase. Instead, they shift in and out of alignment for as long as the wave is passing.
https://www.ligo.caltech.edu/page/what-is-interferometer
https://en.wikipedia.org/wiki/LIGO
Please ELI5 specifically and empiracally what "Space Itself" actually is.
Would it be possible to build a 'galactic clock & Compass' - a "clock" to the regular pulses of a pulsar and the galactic direction the pulsar is in relation to the terrestrial compass (magnetic) on earth...?
What is the pulsar with the most reliable timings?
There’s nothing to really see as such.
In a major discovery, scientists say space-time churns like a choppy sea
https://www.washingtonpost.com/science/2023/06/28/gravitatio...
(Archived: https://archive.is/AmRvg)
[0] https://news.ycombinator.com/item?id=36514521
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I was taught that all items fall at the same speed, due to the gravitational constant.
With these waves, does that mean that items will fall at ever so slightly differing speeds, as depending on the size of the wave there is a pull in the other direction, and the constant is slightly off?
And OT, but related: Since every item has a gravitational pull related to its mass, would a bigger item fall ever so slightly faster than a small one, as it is pulling itself to Earth in addition to Earth pulling it down.
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Deleted Comment
Also, the things falling in a vacuum at the same speed thing is a common misconception. The two arguments usually are that the mass of one body can be canceled out in both equations or that splitting a body into two won't make its halves fall slower.
To answer the question: Given all bodies have the same size, a constant distance to and mass of the reference body (usually earth) and everything starting at rest with no relative speed heavy and light bodies do experience the same acceleration, but a heavy body will collide sooner than a light body. Did it "fall faster"?
Deleted Comment
I still don't understand, why would the heavy body collide sooner if they have the same acceleration (and starting at rest)?
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This is all firmly outside my technical discipline, but aren't there some theories that faster-than-light travel might be achieved by bending spacetime around a spacecraft, as opposed to trying to propel the spacecraft through space?
I really want to emphasize that this is entirely speculation, but is it possible that these gravitational waves could be the "ripples" produced in the wake of such faster-than-light travel, the same way a boat travelling through a body of water leaves ripples in the water behind it?
https://www.youtube.com/watch?v=QMFLcmsjOBg
In the video, they mention that the models we have for FTL (by bending spacetime) wouldn't generate ripples in this way. We could however detect ripples from a really massive ship accelerating really really quickly.
I feel like a quasi-expert on these subjects because of it. lol
Seems like they probably know where these are coming from. I imagine, like your boat analogy, that we can observe massive natural oceans swells and wouldn't notice the wake of a boat as it moves across the ocean.
from a layman's perspective, this sounds crazy cool that they were able to "see" this in the data. seems like one of those things that would be easy to miss from being scoped in and only discoverable after zooming back out. waaaaay out.
Do they require a long list of impossible things to work? Also yes!
There are entirely valid solutions in general relativity which allow for an object in a pocket of spacetime with other spacetime warped around it in such a way that, more or less, space is moving but not the object.
However achieving the arrangement of spacetime to make this happens requires many things which are impossible, aren't known to exist, or require something like all the energy in the Universe to achieve.
Also there are no valid known solutions that transition from normal space to this special spacetime arrangement, so it could only exist if it always existed.
So it comes down to: we're pretty sure such things are not actually possible but we know where to look and what problems to solve if it were. Occasionally we see a paper which removes some of the impossible things from the list.
It's one of those "unlikely but maybe someday" kinds of things.
It would be like being hit by a tsunami and wondering if a cruise ship caused it.
But on a galactic scale.
"I understand how the engines work now. It came to me in a dream. The engines don't move the ship at all. The ship stays where it is and the engines move the universe around it." ―Cubert Farnsworth
https://futurama.fandom.com/wiki/Dark_Matter_Engine
https://www.youtube.com/watch?v=1RtMMupdOC4
My hunch based on nothing is that we will achieve FTL no earlier than 2250.
I see you too have been forced to give PMs estimates when you don't understand the problem.
Somethings we will do the same way for hundreds of years, like the wheelbarrow will still exist in 500 years as it has for likely the previous 5,000.
Otoh, I doubt we will be going faster than light this millenium.
What's meant by the claim that 'space moves faster than light' is that extremely distant objects are moving away from each other, relative to each other, 'faster than light' -- which is permitted, so long as that distance can never be bridged by light.
The claim amounts to, in other words, that the universe is so large that we can compare objects at distances greater than those light could travel between them, and if we do that, they travel faster than light.
This is an "illusion in measurement" more than anything else. Nothing is travelling faster than light.
https://m.youtube.com/watch?v=Ztc6QPNUqls
The Higgs mechanism affects electrons, not quarks, and is only responsible for about 1% of matter's mass. Most mass comes from the binding energy between quarks, which creates flux tubes between quark-antiquark pairs. If we add more energy to pull quarks apart, eventually the total energy added exceeds the mass-energy equivalence of another quark-antiquark pair, so a new pair gets created from the vacuum. I believe this is related to the Casimir effect, but IANAP (physicist).
Keep in mind that the mass-energy equivalence also applies to time. So like in the movie Interstellar, when they go down to the water planet, gravity is so high that time passes slower for them than the guy in the orbiting ship. In other words, the ship sees the landing craft move slower and slower as it approaches the surface. This difference in the speed of time near a gravity well is what slows the inner edge of a satellite slightly more than the outer, curving it along the path of the orbit, which from the satellite's perspective feels like a straight line at that velocity, because it's weightless and feels no other acceleration other than tidal force. So if someone could move large amounts of energy into a confined space with some kind of flux capacitor (is this a pun? I don't even know anymore), they could slow time there and create a virtual mass through mass-energy equivalence by E=mc^2. If they did it in front of the satellite, it would begin to increase in velocity towards that mass. So this is sort of a warp drive mechanism, although I don't know how you'd confine it, and the energies involved would be planet-scale to achieve 1 g of acceleration like near the Earth.
Also if someone made a closed loop where electron-positron pairs were sent one way, then their energy was used to create quark-antiquark pairs sent the other way, there might be a 1% imbalance in mass due to the Higgs mechanism, which would add momentum to the loop opposite the direction of the heavier stream. Although due to conservation of momentum, I suspect that this wouldn't actually happen, because any momentum above light pressure should get lost to heat/entropy/etc. But it would be a fun experiment to try. The same experiment would also work just sending light energy photons one way and matter-antimatter pairs back the other way, but I've never seen a proof as to why this would or wouldn't beat light pressure. This would be a reactionless rocket, not a warp drive.
If there's a gravity field like a gluon field, just with slightly different rules, then I don't see why it couldn't be modulated. In fact, I think that the dark matter strands connecting galaxies are densities where perhaps something like slowed neutrinos or axions collect and slow time. They could even be places where gravity "flows" along eddies left over from the Big Bang, although this seems strange to us because gravity normally only flows into gravity wells. There's also currently no explanation for the Hubble constant in the expansion of the universe, so perhaps something is creating space over time. So I don't see why space couldn't be created behind a craft to push it forward. We just don't know how.
There are so many unexplored interactions like this, that I don't think any physicist can confidently say that warp drives, reactionless rockets and folding space are impossible. Which means that I give it 50/50 odds that some kind of sci-fi space engine will be invented within the next few decades, probably starting with a reactionless drive like the EmDrive, which (if it works) uses resonance to time the interaction of microwaves with the rebound of atoms in an asymmetric field, similar to the Biefeld-Brown effect explored by Thomas Townsend Brown in the 1920s, which was later found to just be an electrohydrodynamic (EHD) effect:
https://en.wikipedia.org/wiki/Reactionless_drive
https://en.wikipedia.org/wiki/EmDrive
https://en.wikipedia.org/wiki/Biefeld–Brown_effect
Unfortunately only physicists are privy to the mental associations which allow thought experiments like this. Textbooks leave us mainly theory and equations, not insights or abstractions. Physics formulas are like trying to understand the behavior of an app from its assembly language. So in a very real way, academic gatekeeping prevented almost everyone from contributing. For every divergent thinker like Einstein, there are 100 convergent thinkers who judge skeptically and crush ideas into oblivion.
I'm just an armchair warrior full of derivative ideas who has never invented anything, who would love to run experiments like these. But just like you the reader, I'll spend the rest of my life making CRUD apps to make rent because billionaires have all the money, instead of getting to be like Dr. Gillian Taylor in Star Trek IV, suddenly able to explore every possibility under the freedom of UBI. That was a joke, but not really.
It effects both. The LHC produces Higgs particles through the annihilation of top-antitop pairs, which works because the top quark couples strongly to the Higgs field.
But this is not measuring the gravitational wave itself. It's measuring the change in trajectory of the radio signals that are "riding" the wave. In the ocean analogy, it would be as if we were surrounded by a circle of floating turrets that each emitted floating darts at regular intervals in all directions. Then we would measure the time it took the darts to reach us, and from that we could infer the size of the waves the darts encountered along the way. But we never actually see the waves, only the darts.
So my question is: how can we tell the difference between one really big wave, and many really small waves that would sum to the same effect? In other words, we know there is some waveform(s) that changed the velocity vector of the radio signal. But if there are multiple arrangements of waves that would produce the same change in signal, how do we pick the right arrangement?
Not sure it answers your question but my impression is they simulate results of all possible effects and then see which one(s) the data correlates with. So if there are multiple causes that could produce identical effects then I doubt they could distinguish between them.
It reminds me of EEG (brain wave) measurement: a hairnet with 256 electrodes will have higher resolution than one with 128 electrodes (ignoring all the issues with interference of the skull).
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