Unambiguous detection of individual gravitons, though not prohibited by any fundamental law, is impossible with any physically reasonable detector. The reason is the extremely low cross section for the interaction of gravitons with matter. For example, a detector with the mass of Jupiter and 100% efficiency, placed in close orbit around a neutron star, would only be expected to observe one graviton every 10 years, even under the most favorable conditions. [...]
However, experiments to detect gravitational waves, which may be viewed as coherent states of many gravitons, are underway (such as LIGO and VIRGO). Although these experiments cannot detect individual gravitons, they might provide information about certain properties of the graviton. For example, if gravitational waves were observed to propagate slower than c (the speed of light in a vacuum), that would imply that the graviton has mass [...].
Fascinating! I take it that the question of whether the graviton could have mass is now considered to be well answered in the negative.
"Gravity is a weak force, in the sense that the gravitational force between two protons is about 10^33 times weaker than the electric force between them. And I'm using protons rather than electrons here to make the gravity stronger - with electrons gravity would be almost 10^40 times weaker.
This has various consequences, but one is that gravitational waves are absorbed by matter much less than electromagnetic waves. It would be fun to estimate the amount of energy absorbed by the Earth as this particular gravitational wave came through, but it would be absurdly small. Gravitational waves make neutrinos look like rampaging gorillas."
Rephrasing, and assuming waving commutes with rampaging, gravitons make neutrinos look like WAVES of rampaging gorillas. I'm no physicist but to answer the original question I'd hazard a guess: quite far!
Imho whatever is carrying gravity between masses cannot itself have a mass.
I can't think of an obvious reason the Higgs mechanism wouldn't work for gravitons, but I could be mistaken, it's not exactly the most intuitive area of physics.
Also, keep in mind that the strong force transmits the force between colour charges while also having a colour charge itself, so it isn't entirely inconceivable for the force transmitting the attraction between masses to have a mass.
No clue if a massive graviton would allow for black holes, but it's not entirely sure what black holes even are (especially quantum mechanically). At the very least it's presumably possible for some particles to escape it (e.g. as Hawking radiation).
Forget gravitons, this already exists in pure general relativity. Spacetime is curved around a massive object, and that curvature contains energy. That's just another word for mass, so the curvature itself exerts gravity. This creates more curvature (...etc etc). This is one of the reasons as to why Einstein's equations are nonlinear.
Note that the concept of having mass is separate from the gravity force. Interaction with the Higgs field gives rise to mass, whereas gravitons are the force carrying particle for gravity.
By the way, this is why the strong nuclear force has such a short range. Gravity has infinite range as far as we can tell, so that makes it unlikely that the graviton, if it exists, has mass.
Surely we create gravitons whenever we move a mass just like we create photons whenever we move a body that interacts electromagnetically? Isn't the point that we're constantly exchanging gravitons with all matter as they mediate gravitational attraction.
This also means that between LIGO and ATLAS/CMS, the last few years have screwed in the final screws on two of the big physics advances of the 20th century: quantum field theory and general relativity are now both experimentally complete, and both look nearly unassailed in their correctness. The next steps for physics look increasingly abstruse: understanding the exceptional cases, like black holes, holography, and the fundamentally computational form of the universe. It's an exciting time, and it looks more and more like we're close to the very bottom, since we have to look so far now to find anything outside our models.
Dark matter (about 25%) seems to only interact gravitationally, which means that we've just, today, proven that we have an instrument that could possibly observe it directly. To date, all our evidence for dark matter is indirect--observing the otherwise unexplained behavior of normal matter. Today is the gravitational equivalent to Galileo pointing his first telescope at the night sky.
Dark energy (about 70%) still seems to be a total mystery.
And of course there is our inability to reconcile quantum mechanics with gravity. With each further proof of the correctness of each of those theories, the mystery of their apparent incompatibility deepens.
All of these factors lead me to believe that we may still have a long way to go in our understanding of the physical universe. I hope I'm right.
This is also why I believe it is so important to pursue nuclear energy. If we do invent further theories and experiments, it's likely that they will require even greater energy levels than we can create now, and potentially imply even greater dangers. If we can't learn to manage nuclear physics in a practical, routine way, we'll never have a hope of going beyond it (if indeed there is a "beyond.")
For what it's worth we thought the same thing a little over 100 years ago. We just had to figure out a few pesky things like blackbody radiation and physics would be all wrapped up.
You forgot about dark matter.
And the devices required to probe Plank length/mass/energy are way beyond even our imagination.
But yes, it's the fringes that we'll find new physics. It's not unlike the late 19th century when newtonian + E&M seemed to account for all there was to know.
There hardest thing in fundamental physics right now is to know what questions to ask. We've got answers that work for a lot of the biggest ones that the last 100 years have been spent developing and exploring.
That's been going on for a few hundred years now.
Well, we know that both theories are "wrong" in the sense that they give nonsense answers if you ask them the wrong questions. It's just that all of those questions are well beyond our ability to test experimentally.
Am I reading this correctly, that shortly after the detector came online we just happened to observe the exact moment a billion years ago that two black holes collided?
Was that extremely coincidental? Or do these events happen all the time, and so if it wasn't those two black holes it would be two others?
I should add that there are lots of selection biases and educated guesses in all of this, too. The signal from BH-BH mergers is louder and easier to detect from larger distances. At the same time, NSs are probably more common than BHs, but it's not really clear whether there are more NS-NS binaries than BH-BH binaries because NSs receive kicks from the supernova when they are born but BHs (probably) do not. This may have the effect of blowing apart many nascent NS-NS binaries but leaving the BH-BH binaries intact.
I guess you could count one looong wave as a series of one-time events/measurements, but it could as well be a loooong interference.
Also, have read today that this discovery backs inflationary theory, how so?
It seems highly unlikely that they could say a specific bh-bh merger was the cause. It seems implied they are triangulating the source, with two detectors?
Interested to know what they were shooting for when they spun this experiment up.
Counterintuitive, but yes. Because it happened billions of years ago, it happened a long long way away. The sphere of objects billions of years away/ago is far larger than those closer to us. So such a detector should be detecting exponentially more very old objects than new ones. Given the rarity, I would expect nearly all detected events to have happened long long ago in galaxies far far away.
Also, models point to such events being more common in the distant past where there were more black holes (primordials) floating around than there are now.
The article makes it sound like the detection of these waves is just a quick one-time blip though. I'd expect something as big as black holes merging to generate more longer lasting waves than just a quick blip. What is the period of these waves?
No they don't. There is a law known as [Huygens' principle](https://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_princi...) which says that when a disturbance at a particular point creates a wave, that wave only propagates on an outwards-expanding sphere that is centered at that point of disturbance, and does not produce any effect on the interior of that sphere. This was originally formulated for light waves, but it also holds for other kinds of waves, such as sound waves or, in this case, gravitational waves. What this means is that when you look at something that's far away you see a sharp image of exactly what happened there a short time ago (the time it had taken the light to reach you), whereas if the principle did not hold, each light source would have a small "echo" after it which would blur the image.
However, one of the reasons Huygens' principle holds is that the waves are propagating over three dimensions. In contrast, water waves only propagate over two dimensions, so Huygens' principle fails. That is why ripples continue to emanate from a spot even long after the disturbance there is over. More generally, Huygens' principle holds whenever the number of dimensions is odd and fails whenever the number of dimensions is even.
[Note: I may be wrong on why Huygens' principle fails for water waves. Water waves are actually pretty complicated compared to other kinds of waves and I am not knowledgeable in all the subtleties.]
From the article, no one knows: "Black holes, the even-more-extreme remains of dead stars, could be expected to do the same, but nobody knew if they existed in pairs or how often they might collide. If they did, however, the waves from the collision would be far louder and lower pitched than those from neutron stars."
Here's a better article:
http://www.newyorker.com/tech/elements/gravitational-waves-e...
This is right. Soon we'll have a much more precise value for "all the time!"
Possibly stupid question: Given how far away it was, and that the inverse square law applies, would the effect of these waves be visible on the human scale if we were closer? We can see the effects of the compression of spacetime with LIGO after all, so presumably we could?
LIGO measures wave amplitude, as far as I can tell, which goes down linearly with distance (unlike wave energy, which goes down quadratically, since it's proportional to square of the amplitude). So we could expect to see an effect about a billion times bigger.
The detected effect was a change in metric of one part in 6e20 if I'm not mistaken: (4e-3 * (diameter of proton))/4km based on the article's claim of "four one-thousandths of the diameter of a proton". So at one light year distance we could expect an effect of one part in 6e11.
Not really visible on the human scale, seems to me. You could detect it easily with something like the Mössbauer effect, I expect. Your typical lab bench laser interferometer has errors on the order of 1 in 1e6 as far as I can tell, so probably wouldn't be able to pick this up.
Disclaimer: I could be totally off on what a lab bench laser interferometer can do. I'm pretty confident in the rest of the numbers above.
So, inverse square that explosion... 1 light year is about 10^16m, so we square that and get 10^32m, so we're now talking about ... 10^15 J.
So, unless my maths is all off (which is possible), if this happened about a light year away, whoever's on the side facing towards the blast wouldn't get to observe very much because they'd feel as if a 1kt nuke just went off above their head. Not a great way to start the day.
Chances are it would wipe out life on Earth too, through the ensuing side-effects like lighting the atmosphere on fire, sterilising half the planet, significantly heating up the oceans, possibly even stripping part of the atmosphere away, etc.
For a great novel based around a strikingly similar premise to what was just observed (and the main reason I even bothered to calculate this), Diaspora by Greg Egan is a fantastic book.
Which was the order of predictions I'd read, years back, but egads. Considering how much larger that is than a supernova, I'd be concerned to have such an event happen in this galaxy...
H-----L-------s
s
/|\
/ | \
L-----H
Too bad, you had me excited for a moment at the thought of faster than light travel.
Let's say a gravitational wave compresses space. To someone inside that compressed space, there should be no noticeable difference. Light will still flow the same way through the compressed space at the same speed relative to the compression. Matter will behave identically, because both light and matter are part of the fabric of that space. As I understand it, the only way the mirror lengths could change is if space is created or destroyed.
If that doesn't make sense, consider the 2d analogy of drawings living on paper. Assume also that light moves only along the surface of the paper. If you bend the paper, the light will bend with it. But when you bend the paper, the creatures living on the paper can't know it's bent. The fabric of the paper is still identical. Even if some of the paper gets compressed in one direction, it will still have the same amount of particles, so any light travelling through there will hit the same amount of resistance. And stretching the paper, even if you're a drawing on the part being stretched, would have no effect. A 2d creature looking at something 1 foot away, even if the paper is stretched to 10 feet, won't see any difference, because the fabric light travels through is also stretched.
The only way I can see this making sense is if light travels independent of the fabric of space, but it's my understanding that light travels through it, not independent of it?
"According to the equations physicists have settled on, gravitational waves would compress space in one direction and stretch it in another as they traveled outward."
LIGO is two sets of 2 L-shaped antennas spread far apart on the globe, so that we can compare the compression of space in orthogonal directions and measure the very short delay between the gravitational wave hitting the first detector followed by the second. In this case, that difference was 7 milliseconds, which is also consistent with the speed of gravitational waves (also the speed of light)
At first glance, I'd guess that this discovery only strengthens that conclusion: even a small deviation from GR might well change the detailed behavior of an immensely high curvature situation like a black hole merger, and what we saw seems to have been a spot on match for the GR-based models.
I am unfamiliar with modern alternatives to comment.
The system is quite complex and full of exotic objects, so ordinary real world intuition is a poor guide. And the laws are couched in a mathematical language that is also foreign to our everyday world.
Yet, predictions can be made and tested. It's an intellectual puzzle like "what does this very tight loop do?", or "how does the Y combinator work?" -- but in a different arena.
Now, as a full-time software engineer and part time jack of all trades, I appreciate stuff like this experiment and the work of Space X and others much as I appreciate good engineering. It's a difficult problem to solve. So many disciplines had to cooperate to grant us some small insight into the inner workings of our universe. It's marvelous, and makes me feel like a kid again.
We (as in, species) just observed a phenomenon that's related on a fundamental way to any form of matter, doesn't matter(no pun intended) if it is space or not.
... and I shudder to think that more often than not, anything I code in C/C++ will segfault on first run.
To my mind, it'd be roughly like trying to triangulate an earthquake in France with three sensors in a 1mm^3 cube in NYC (scale is probably way off, I definitely didn't do the math).
However, the error ellipse will probably be quite larg, and given that they come from cosmological distances it's unlikely that they would be anything but isotropically distributed (like gamma ray bursts are).
Now estimating the distance is a different matter.
There is a third one (VIRGO) near Pisa, Tuscany - a French/Italian collaboration.
Unfortunately it was not online for this event.
There is also one being built in Tokyo, and another being planned in India.
https://en.wikipedia.org/wiki/Evolved_Laser_Interferometer_S...
One is to compare the arrival time at each of the detectors and infer direction from the speed-of-light delay.
Another option is to measure the difference in relative strength between each of the detectors. I'm assuming the detectors aren't uniformly sensitive; perhaps they're most sensitive to waves travelling in a direction parallel to one arm of the detector and perpendicular to the other, and completely insensitive to waves that are perpendicular to both (i.e. it would affect them both the same and cancel out, or perhaps not affect either of them at all). With multiple detectors at right angles to each other, you can get a pretty good idea which way it came from.
Combining the two methods could give you greater accuracy, and also help to rule out spurious signals that are not gravity waves.
This makes me wonder what you would see if you had a sufficiently accurate directional gravity wave detector and let it run for a long time. Sooner or later, you'd get an actual image, like a telescope.
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102
I'd say the true importance of this discovery is in successfully creating an experimental apparatus to detect what was previously almost universally agreed to probably exist but thought to be nearly impossible to detect. What's truly exciting isn't proving Einstein right, but the possibilities of what we'll be able to to detect with this apparatus in the future. So it's the team that built the apparatus which truly deserves the credit today.
But what happens to them? Is there any way to turn them back into matter? If not, then at some point, will all matter in the universe end up as gravitons?
Also, if an object moving through space creates gravitational waves, doesn't that violate the law that states that a non-accelerating object will not lose/gain any energy? Because if you have to emit gravitons as you move in space, and emitting them requires energy or matter expenditure, then an object moving through space will slowly lose all it's mass?
In other words, if two bodies are moving relative to one another, one emits G-Waves, and one detects them. Are the waves at the detector doppler shifted in frequency by the relative velocities?
Beautiful.
If this happened in the centre of the Milky Way, we're about 25k light years away.
Let's say 2 1 million solar masses black holes merged there... and they also gave off about 3/60 of their mass as radiation, that's about 100'000 solar masses being radiated 25k light years away.
Using my calculation in the other post, we're talking 10^52 Joules. Across a distance of 25'000 light years, or about 10^20 metres, that's then decreased by 10^40 (inverse square) so we're left with about 10^12 Joules...
Which is good news! If that happened in the Milky Way, we would probably survive it - though we'd definitely notice some strange atmospheric effects...
Maybe it's the psychology of how we (fail to) deal with different scales. Discovering new, larger, more wonderful places in the Universe doesn't make the Earth any smaller or less wonderful than it is. Our brains might "zoom out" our mental map to fit these new places in, which makes us appear smaller, but in fact it's our horizons that have grown.
According to https://en.wikipedia.org/wiki/Books_published_per_country_pe... there were nearly 200,000 books published in the UK in 2011. That doesn't make the works of Shakespeare insignificant.
On the other hand, it's nice to know the world really does appear to be boundless. I mean in terms of the possible.
We aren't much, but we are here and it's a pretty awesome experience.
Maybe we need to be here, otherwise what is the point?
I like to think there are others too, thinking thoughts like we are. Maybe that is necessary too. Maybe nobody has reached a point in their development for more, or contact to make sense.
I find our time here and now bittersweet. So much is yet to be experienced and understood. But, then again, here and now isn't all bad. We have great science, new frontiers opening up all the time. Our stories of the future are fantastic, and there is still a lot of magic and wonder about us, the world, reality...
We may not see the best. In fact, I say none of us will, but right now is never dull.
I feel like we are just beginning to get a real grasp on reality. That seems powerful and exciting. We could have lived in much darker, harder, ignorant times.
These times may be seen that way too, or they may be a peak, with a decline to come. Nobody knows, and I like it that way.
It depends on how you look at it. You are taking a pessimist's view on things that the universe is so large and we are so small that we don't matter. If you take an optimists's view on things you'll discover that we do matter and learning new things increases our significance.
Also I wonder, in this form as humans, can anyone really comprehend what this all means, beyond the Math and experimental confirmations?
What if we are living in a simulation, and just being played?
Wherever we went on earth we've colonized quickly. If we can do that to space, universe might be our backyard.
Sorry I am not vary knowledgeable on the topic.
Beyond that, I guess I'd say that this particular signal doesn't feel like that much of a surprise: we were already pretty confident that if a black hole binary were to merge, a signal more or less like this would be an expected result. The scientists were evidently surprised that their very first signal was so strong (this one was even borderline detectable by the previous version of LIGO), which may teach us something, but it's not revolutionary.
On the other hand, there is now a way to see dark matter. That could enable a lot of new astronomy.
In the future this will get better when VIRGO in Italy and KAGRA [2] in Japan come online. Then we will have 4 independent detectors which will be able to verify that same signal is observed at the same time.
Obviously of course given the transient nature of what is being observed once the merger has occurred it will very rapidly stop producing gravitational waves so we will not be able to measure the same event again.
https://dcc.ligo.org/public/0122/P150914/014/LIGO-P150914_De...
[0] http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116...
Was he indeed always right on his theories for phenomenons before they could be proved by experiments; or is that the case that we only hear about when he is proved right?
Of course, being Einstein, he was again on the right side of the argument when the universe was much later discovered to be accelerating, again requiring a cosmological constant (or some similar fudge factor).
Today, most physicists accept the spooky action at a distance rather than the idea that QM is incomplete.
Bohr's argument in the discussion was a bit of a mess and I couldn't pull anything out of his rebuttal to EPR other than an assertion that QM behaves the way it does and not to pay any attention to the man behind the curtain. Its a very philosophical argument with very little scientific content and he just proposes that the QM math is correct because its correct, as far as I can tell.
EPR made a logical cogent argument. It was based on the philosophical principle of the locality of physics. They translated that into the mathematics of Quantum Mechanics and proposed a simple experimental test. Later that was refined by Bell and tested experimentally by Aspect and others. It was the Einstein-Podolsky-Rosen paper that laid the groundwork of how to test the non-locality/hidden-variables of QM though.
EPR moved the scientific discussion forwards much more than Bohr did, but it turns out the test they proposed showed that the position they favored was incorrect.
Also Einstein was arguing first and foremost that physics must be _local_. That's in opposition to the "spooky action at a distance" bit that he didn't like. Since local hidden variables are ruled out then he really was proven "wrong".
TL;DR I think Bohr's argument is rubbish, and Einstein's is solid, but the Universe is a bitch and doesn't care...
Or, put another way, is the speed of light only a constant because we measure it in constant gravity?
Any effect of gravitational fluctuations in spacetime on the speed of light is a bit like a car driving on a race track that has treadmills scattered around it pointing in various directions and speeds. The car's speedometer will always read the same value because it's measuring the speed of its tires on whatever it's driving on.
http://gmunu.mit.edu/sounds/sounds.html has a bit more info on why scientists tend to use the sound analogy when talking about gravitational waves.
[1] Maybe not entirely true, we have convincing evidence of some extra-solar dust reaching earth too..
This device just acts like a gigantic hearing device. Except it's not pressure waves, but the fabric of the universe which reverbates.
Note that the frequency of the signal is indeed in the audible range.
Anyway, I was a bit irritated of this same phrase, but because I tought radio astronomers had been listening to skies for quite some time now.
Whatever they have detected or calculated is something else.
And here's more detailed from PBS Space: https://www.youtube.com/watch?v=gw-i_VKd6Wo
" On 14 September 2015, while Drago was on the phone with a LIGO colleague in Italy, his pipeline sent him an email alert—of which he receives about one each day—telling him that both LIGO detectors had registered an “event” (a nonroutine reading) 3 minutes earlier, at 11:50:45 a.m. local time. It was a big one. “The signal-to-noise ratio was quite high—24 as opposed to [the more typical] 10,” he says."
The coalescing holes pumped 50 times more energy into space this way than the whole of the rest of the universe emitted in light, radio waves, X-rays and gamma rays combined.
Actually, in each transformation there is an explosion and part of the mass goes away (try to not be very close). So the total mass in the final black hole is smaller than the mass in the initial stars, the rest are debris forming a nebula or something around the black hole.
(And, as the other commenter said, gravity is too weak.)
Consider that major galaxies (apparently all of them?) have a massive black hole at the center, yet those galaxies aren't collapsing in on themselves.
That is one of the more routine feats of engineering involved.
Does this mean an actual truck, a vehicle? Did they accidentally hurt someone?
I liked this quote: The future for the dark side looks bright.
Could someone explain ?
Basically, I want to understand how it's possible to measure a distance change on the femtometer scale.
For comparison, the wave that was detected is claimed to be "four one-thousandths of the diameter of a proton". That's about 7e-18 meters, on a baseline arm length of 4 km, so about one part in 6e20 -- about 175,000 times stronger than the waves Earth's orbit produces. And that was about 40x as strong as minimal sensitivity on LIGO, according to the article ("can detect changes in the length of one of those arms as small as one ten-thousandth the diameter of a proton").
Obviously if we were closer to the black hole collision we'd see much stronger waves. But you really do need very massive bodies accelerating very much (or equivalently orbiting very fast) to produce something that's detectable by LIGO over interstellar distances at all. The key part from this article is that the orbital period was about 1/250 of a second at the end; compare to Earth's orbital period. Going back to the formula given in the above Wikipedia entry, the frequency dependence is hiding in the "1/r" factor for the amplitude. 1/r is proportional to w^{2/3} (though it's not clear to me whether that's still true in a general-relativistic treatment; it's true enough for the Earth's orbit), which tells you how the wave amplitude scales with frequency...
As others have said, intensity (power per unit area) decreases according to the same inverse square law that governs most effects due to localized sources in three dimensions of space. In this case, you're looking at a distance of over a billion light years, and then squaring it: that's a pretty enormous "per unit area"!
But gravity itself is also a tremendously weak force compared to the others. That may seem surprising at first, but it becomes pretty clear when I point out that a cheap little refrigerator magnet exerts enough force to overcome the gravitational pull of an entire planet right beneath it. Gravitational waves are pretty much just ripples on the top of that already tiny force.
Distance. A billion light-years is a very long distance, and the inverse-square law applies.
I don't think anyone has combined them as you suggest though!
Well, if you observe a meaningful, non-natural gravity wave signal, you know that you've discovered not merely another technical situation (which you'd know if you detected the same thing in radio waves), but a phenomenally advanced one.
So, if not an advantage, there is at least a meaningful difference.
We've known gravity waves existed since the Hulse-Taylor pulsar, so just observing them for the first time is not nearly as interesting as the science to come in the next decade. Advanced LIGO is a powerful new tool that will open up exciting new observations.
This is just understanding at present. That, in itself is worth it.
As that understanding develops, and our tech advances, engineering may be able to apply it in useful ways, maybe object detection above a specified mass? New ways to visualize things?
One "application" is to serve as a ruler to measure out tech with. The limits are there, putting these observations just within reach.
Now that we have some confirmation, we also have the metrics as well as the compelling new science that may arise from all of this as a strong motivation to advance.
It's like being able to detect color for the first time. At first we understand what color is, then we refine, and after iterations, engineering, experiments, we get to a place where we see it all in color.
Applications will follow.
These waves being confirmed are like a new sense. Crude, but real. We can now follow this new perception to its conclusion, just as we have many other things.
We don't always know what that conclusion will be, or the form an application may take, but we do know we won't actualize any of it if we don't do the basic, hard, expensive work needed first.
Indirectly from the technology they had to develop to measure this, possibly something specially due to the precision they needed to measure this.
But that's the NYT I guess.
Iirc the idea would be that inferometers would be used to test things like that.
I don't think we (humanity) will achieve warp drives, though, I do support the attempt.
Actual paper here: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116...
Oh no you didn't.
1. Theory predicts gravitational waves when massive objects collide and that the gravitational waves would have an effect that could be measured by the experimental instruments.
2. The experimental instruments measure something.
3. This is considered proof that massive objects collided.
4. Therefore gravitational waves exist.
To reframe my skepticism, the experiment measures something. The conclusion as to what it measures, however, is unsupported by statistical inference or direct experience of a causal phenomenon. That's not to say that what the phenomena measured -- the earth resonating -- is uninteresting or unimportant or even inconsistent with the theory of gravitational waves.
Yet, I don't find the possibility of a geophysical cause -- i.e. that the earth maintains consistent dimensions at a sub-atomic scale -- the many orders of magnitude less likely than gravitational waves necessary to reach a conclusion. In particular, I find natural fluctuation to be more likely because the experiment acknowledges its existence.
For a point of comparison, consider the Perihelion precession of Mercury that provides evidence in support of general relativity. The theory was used to predict the results of an observable event. The experimenters trained their telescopes at a particular location and particular time and observed phenomena consistent with a prediction based on the theory. The same is true of the Higgs. In both cases the experiment is of the form "when X, I will observe Y."
The reasoning here is:
If X, then Y.
Y, therefore X.
(1) It simply fails to understand the scientific method, which is empiricism, not mathematical/logical proof. Scientific evidence is essentially failed disproof, not logical proof.
(2) It mischaracterizes the nature of the prediction, which includes not merely that something will be measured, but that a particular pattern will be measured.
(3) It proposes unspecified "geophysical causes" as an alternate explanation, but there was no pre-existing geophysical model which predicted the pattern observed. (Any after-the-fact geophysical -- or other -- alternative explanation which explains the observed pattern would also need to perform differently on some other test to be verifiably different, and then we could do the test to distinguish the source.)
(4) It misstates the reasoning to contrast it with other experiments, this is exactly "when X, I will observe Y" (where X is "I construct detectors of a particular type in more than one location" and Y is "I will periodically detect particular patterns of signals on those detectors -- not just one of them alone -- which the model predicts will be produced by collisions of massive, distant objects.")
Lower two graphs are predicted waveform in event of binary system coalescence. Upper waveform left and right are observed events at each LIGO facility.
Consider furthermore that the event was observed at each facility with the appropriate lightspeed time offset, and that the wave directionality of the event was lateral and not radial from the center of the earth or some other point as would be expected from a "geophysical" cause.
Furthermore I find it highly unlikely that multiple theoretical and applied physicists would come to apparently total agreement on the significance of these findings and simply overlook the gaping logical fallacy you imply.
That said, it sounds like they did a lot more work to eliminate sources of error than you may be aware of. OTOH if seismic resonance was causing the correlation, there would probably be more time between the events at the two facilities.
Scientists will try to poke holes in these results while further experiments will try to corroborate them. Meanwhile laypeople will be introduced to more oversimplified and counterproductive ways to think about this stuff. Business as usual.
1. Theory predicts a very specific and recognizable class of gravitational wave patterns for likely sources, whose details are determined by a small number of parameters that correspond to meaningful physical quantities (specifically, two masses and a distance; I don't know if there are any more than that).
2. Two independent experimental instruments measure a wave pattern that (apart from some low-level noise) is an excellent match to one of the predictions. Fitting the model to match the specific data, the resulting parameters have entirely plausible astrophysical values.
3. This is considered an example of a theory making a specific, novel prediction that is later confirmed by experiment: pretty close to the classic definition of the scientific method.
4. Therefore, the experimental data has provided strong support for the premises of the theory being tested: both its prediction of gravitational waves and its detailed dynamical predictions for the source scenario matching the observations.
Maybe I'm misunderstanding something in your argument, but I don't see any circularity here. What about this process isn't precisely the way that science is supposed to work?
Someone comes up with a theory that's mathematically simple, beautiful, and consistent. That's great, but we don't consider it "correct" until it actually predicts something novel and we verify the prediction holds experimentally.
That's your "Y, therefore X".
In this case I don't know if your skepticism is warranted.
1st: Paper said that the waves are redshifted to a certain degree (it's in the abstract) [1], ergo 1.3 billion light-years away in space-time. I'm not thinking you want to be so fundamentally skeptical.
2nd: It's in Wikipedia now https://en.wikipedia.org/wiki/Binary_black_hole#Observation so it's pretty much fact.
You may choose to believe 1st or 2nd piece of evidence.
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[1] https://dcc.ligo.org/public/0122/P150914/014/LIGO-P150914_De...
That's not what the detector measures. RTFA.
Why are we surprised at gravitational waves when 2 black holes collided?
This is less "wow, look at what an unexpected result we found!" and more that we finally managed to measure something we've been looking for.
