Gravity Waves Detected?
rjo__
Posts: 2,114
cnn.com/2016/02/11/us/gravitational-waves-feat/index.html
The headline says that gravity waves have been detected and that they prove Einstein's theory.
You can't prove a theory... you can only disprove it.
Let's try a gedunken thunken.
If two astronauts leave Earth traveling in opposite directions at 1/2+1/3 the nominal speed of light... how do they age relative to each other and to an observer on Earth?
The headline says that gravity waves have been detected and that they prove Einstein's theory.
You can't prove a theory... you can only disprove it.
Let's try a gedunken thunken.
If two astronauts leave Earth traveling in opposite directions at 1/2+1/3 the nominal speed of light... how do they age relative to each other and to an observer on Earth?
Comments
The theory is a bunch of maths. The maths predicts that something will be so. Years later we find that measurement shows that is so. Does that "prove" the correctness of the theory? In all cases, everywhere, for all time? No. It's pretty damn impressive though!
The thing is, if I understand correctly, Einstein came up with his general relativity thing. He then found a solution to the GR equations that predicted black holes and gravity waves. Einstein did not like this solution and rejected the idea of black holes. All that business about event horizons and singularities was not to his liking.
Similarly his GR predicted that the universe would be unstable. Either collapsing under its own gravity or expanding forever. Einsein did not like that idea either and bodged a fiddle factor into GR to make the universe stable.
Well, turns out that nature indicates that their are black holes and the universe is expanding.
So Einstein had the maths right but did not like what it predicted on a few occasions.
For example... if one assumes that gravity can decay without affecting momentum... you can get an expanding universe. Or if one assumes that photons decay... over very long periods... you can get a red shift everywhere.
In science, there is no proof. Science only makes progress by proving ideas to be wrong... not the other way around.
Thanks Heater
Newton comes up with his law of universal gravitation. Just an equation. It seems to agree with measurement. It predicts things like planetary orbits and so on. BUT he makes no claim to explain what gravity actually is or why it works that way. He had quite a poetic way to say that which sadly I don't remember.
On the other hand, Einstein seems to have arrived at relativity by "thought experiment". First he thought through how things must be, then he had a devil of a job for years getting the maths to describe his thoughts.
On a third hand, quantum mechanics seems to be a bunch of rules pulled out of somebodies butt that happens to fit experiment very well and has been used to predict many things very accurately. Nowhere does anyone have any idea why the bizarre rules of QM should be so. It just works.
Another thought provoking question...
If time is linear and always moving forward (never backwards) and it is possible to speed up time and slow down time. Then it is also possible to create a "wrinkle" by speeding up time in one area, but slowing time in another area. The analogy here is a car with one wheel moving faster than the other. Eventually you are going to make a circle. So is it possible to create a "circle in time" or an anomaly in time that repeats? And wouldn't that count as going backwards in time?
Next time you have a Déjà vu moment, consider that you might have been in a time loop.
An interesting assertion. As Heater suggests, Einstein came up with gr to explain how gravity works. The ideas were utterly new. Since then, people have tried and tried to prove gr wrong, but no one has done so. Would you argue that because no part of the theory has been disproved, no progress has been made?
Years ago I found a book... I will do doubt remember the title
and author later tonight... anyway the guy took the math... made a few
different assumptions... cannot remember which and actually
found that the available experimental science supported his assumptions
better. I was not really qualified to fully understand what I was reading,
but I had a friend, who held 4... count them... 4 chairs at the U of illinois.
I gave a copy of the book to him. He agreed to read it and concluded that nothing that the fellow was saying was wrong... It did not mean that he was right, just that he was not stretching
the truth.
I personally believe that gr is fundamentally wrong, because of the central equation...
which to my mind comes from a mistaken assumption about the conservation of energy.
I don't think there is any way around it.
Beau,
It is more fun to question the nature of reality itself... it gets us no further, but it is fun.
What happens if everything that we know is a mere reflection of what exists on the spiritual plain...
everything. Imagine that we look up and see stars in a cold universe, but it is only because we exist behind a veil that obscures the deeper reality. What is time in such a reality and why do we care so much about it? Beats me, but it must reflect a real issue:)
I cannot see why life does not exist in a plasma only that it would be vastly different and that time would have a different scale... ergo biology? Is that why we exist? To solve problems on a different time scale. We really cannot know... but it sure seems like there is more to this than meets the eye:)
Yes and NO of course not. In terms of a rational dialectic at the theoretical level, we seem to be stuck. If I were Piaget I would be warning of a coming epistemologic crisis. But I am not.
Google... crisis in physics.
The fact that this is true and we have seen the explosion of scientific advances is not
a contraction. It proves that despite our theoretical deficiencies, we have developed solid methodologies. But science does depend on more than solid methodoloogy... it does depend on theory... and there are serious problems with our theories.
That is serious progress! Our confidence level in our current understanding is very high now. Our tech is very capable now too, bolstered by that understanding.
Something will break. We just need to keep turning the crank on it all, and funding that work matters.
What is needed now are more kinds of thought experiments, from the Einstein point of view.
Feynman would add that we could also use more creative guesses.
Nobody knows why inertia is yet, for example.
If I were to "guess" at where new physics may come from, Einstein fashion, it's a thought associated with inertia, linking it somehow like he did space time.
If I were to guess in Feynman style, it's going to be some new kind of particle, like understanding the Higgs is not atomic, but the start of understanding of new fields, etc... found either by emperical or inferential means.
Both may converge on the same thing too! We know the Higgs is, for example. We don't know what it means yet, not like we do other more mature aspects of the physics.
Meanwhile, there is a lot of known physics that has yet to be applied as broadly as it could. Not sexy like new physics, but still really important. Materials is white hot right now, for a great example of applied physics really paying us off big.
And in that sea of stuff, someone will see something that doesn't quite jive... and it all starts to crack, and we get somewhere new.
If there is a crisis at all, it's the understandable worry that another advance on the order of Einstein may not come for some time. For them, it makes sense. They want to pry reality apart and look at how it works, and they want to do that right now, while they are here to see it. Can't blame them one bit. Hope the funding is there.
For most of us, there is a lot of exciting science playing out in our lives right now. Good times.
Maybe.
I do not believe that for a minute. That may actually be true for a very large subset of humans, and for sure this human. I'm fine with that. The better ones can explain it to me when they get there.
I read somewhere recently that each generation has an overall greater IQ. And we know exemplary humans just happen from time to time too.
What I see is humans connected and empowered like never before. Another one of us will have that unique insight, and now, more than ever, we actually stand a chance of not having it lost as we have so many times before.
New physics will come. I believe that absolutely.
This was hard for me as a kid, and one teacher sorted it nicely.
Newton arrived at understanding, for example. We were able to validate that by observation and experiment and confidence grew, until it didn't.
Nature is the authority.
Science is how we arrive at better understanding. There is always better understanding.
Good as it gets.
We don't really know anything, and that's the difficult part. We do understand and we do have degrees of confidence in that understanding.
Newton level understanding, for example, is still as good as it ever was. It's applicable where confidence is high. As we find we cannot realize confidence, we also know there is the potential for new understanding
All we really can do is understand if we do this, nature does that, until nature doesn't.
And that is science. It's not ever a proof, just understanding.
We have yet to actually know a darn thing, but we do have understanding.
That distinction isn't often discussed in lay circles, and I've always thought it should be.
So, that teacher ended up turning the idea of school on its head for me! We go to school, and do science, etc.. to understand better. We don't do it to actually know anything at all.
Yes I was about to post much the same.
In some philosophical, logical, rational way a theory can never be proved, only disproved. This happens, people put forward ideas, do the maths, predict some outcomes. Then the experiments get done and the predicted outcomes don't occur and/or some other weird ting happens instead. Poof goes that theory.
On the other hand good theories have been demonstrated to make good predictions. We could say that does not "prove" them correct but...
In the whole history of physics good theories have never been proved wrong. Once they have been demonstrated to work they have continued to work. Good theories have never been over thrown and replaced. Newtonian mechanics is still as valid today as it ever was. Yes we find it breaks down in extreme conditions but it is still all working as well as it ever did.
Now. It could happen that nature changes it's mind one day. Perhaps f = ma suddenly becomes f = 2ma. Then people in the future or in a different place would conclude Newton is wrong. Maybe, but Newton was still correct in it's time.
However, there is a problem with nature changing. It may on very large scales of time. Tough to test. We lack ideas and we lack technology.
That idea is troublesome. Such a change would render us unable to exist!
I like to think nature is constant, but infinitely complex, and I like to think that, because it means there is always better understanding possible, and that means the possible isn't bounded.
There will simply always be better understanding. Science is progress and the future. If we do the work, we get the reward, simple as that.
So yes, assumptions are everything. Like, let's assume that energy and momentum is conserved. Let's assume information is never lost. Let's assume physical processes work by minimizing "action". These principals, assumptions if you like, guide the maths in the right direction. You might have to elaborate on that "mistaken assumption about the conservation of energy". As far as I know the conservation of energy is still a rock solid principle in physics. With the additional idea that energy and mass are the same thing.
In what way is GR fundamentally wrong? The announcement of the detection of gravity waves is yet another confirmation of it's accurate predictive power. Pretty much 100 years after it was used to make the prediction of gravity waves, amazing?
It is well known that GR breaks down on very small scales. Where quantum mechanics rules.
Might be. Might not be. Nice idea but so far we have no evidence of the existence of any such spiritual plain. So there is nothing to talk about. No predictions that can be derived from the idea. Physics and science in general is about things we can measure and reason about. This may well be driven be some weird "spiritual plain" but so far the idea has no use.
Anyway, I have been wanting to do exactly that experiment with a Prop for ages. Do you have any schematics and diagrams of your setup?
I was recently listening to some physicist discussing the question of whether the human race might reach the limit of it's comprehension. That we will just not be smart enough to make progress understanding the way things work past some point.
His argument was that, yes that is a distinct possibility, but he sees no sign that we are even close to the edge yet. Why? Because he still sees today that young guys and girls in their 20s are still able to make major contributions to theoretical physics and mathematics. If, he says, we were coming to the end of the line we would expect the youngsters to have to study for longer and longer before they could make a meaningful contribution. Until it takes so long that they have gone senile and can't make any progress. This is not happening yet.
Information must be embodied by something. Remember the discussion about surface area a while back?
That something will be governed by the laws of physics, including conservation of energy.
Without this being true, information is something apart from our reality.
Here's a mind bender that just happened to me while thinking about this: Math. It contains truths that are distinct from the physical world. Square root of two, would be one of those. So, information itself must be embodied by something, but that which it represents doesn't have to be. My head hurts!
I'm gonna go write some PASM this morning.
That makes way too much sense. Classic physicist. Love it.
This week's announcement is a good example. Until the 80's (IIRC), gravitational waves were an interesting prediction, but not much more than that since there was no way to test the idea. Then a couple of people found a binary pulsar, and along with all of the advances in electronics and computing that had happened over many decades, now there was a way to test GR. They looked at how the system was spinning down, the behavior matched prediction, and they shared a Nobel. More importantly, now there was justification for spending a lot of money on attempts to directly observe gravitational waves. A really, really hard thing to do, and it took a couple of decades, but by continuing to push the technology the LIGO team was finally successful. Now we know they are real, that GR provides the mathematical tools to interpret the observations, and suddenly we have a completely new way of studying reality. Whenever that happens, new stuff follows.
When Galileo pointed his telescope at the sky it was the beginning of a very long string of discoveries. When Jansky discovered cosmic radio emissions, the same thing happened. When we sent instruments above the atmosphere to collect photons with wavelengths both shorter and longer than visible light, it happened again. So it will be with gravitational waves. And while it will never be easy to detect them, the technologies will get better and sensitivity will improve. A few decades ago we were limited to photons to study the universe. Then came neutrinos, and now gravitational waves, (and probably other things I'm forgetting) and new physics will result. And that's also one reason why young people can still come up with new breakthroughs. The generation behind them put some new tools in their hands. It's always happened, and it will continue to happen, at least for the foreseeable future.
The famous Leonard Leonard Susskind as defined the number of bits as "The number of yes/no questions you have to answer to fully describe the state of a system" This fits with our computer science notion of bits, when you have two memory cells that can be on or off you only need to ask two "Is it on or off" questions to determine the state of your memory.
He has also talked about how much information is stored in black holes. Well, how do you add a single bit of information to a black hole? You drop a photon into it. The smallest amount of information (and energy) you can add to a black hole is when the photons wave length equals the black hole's radius. Any small and quantum mechanics indicates it cannot be absorbed by the black hole.
But then there is the notion that information is "the number of degrees of freedom of a system". Which gets us back to the classical physics ideas of entropy.
All these definitions are the same of course. Yep. I'm still keeping myself awake at night thinking about it. When you drop those bits, photons, into a black hole you are adding energy to the black hole.
The energy of a photon is E = hc / λ.
But energy is mass because E = mc².
But the radius of a black hole is proportional to its mass: r = 2Gm/c²
But the surface area is proportional to it's radius: A = 4πr²
So we see that the surface area of a black hole is proportional to the amount of information in it.
And then, we see that the maximum amount of information we can get into a volume of space is limited by it's surface are, exceed that and it collapses into a black hole. Poof there goes your information, you can't retrieve it later!
It gets better...Physicists like Nima Arkani-Hamed are now arguing that because of all of the above an entire system, like the universe, can be described by mathematics that only operates on it's surface. Time and space are no longer the fundamental things we should have in our equations. "space-time has to go" as Nima says.
All this comes under the name "Holographic Principle".
I agree, there is no crisis of understanding. Perhaps for slightly different reasons.
The argument is that the laws of physics might just be to hard for us dumb humans to understand past a certain point. A kind of "understanding event horizon" that we cannot get through.
I would argue that the human race passed that event horizon hundreds of years ago already. It used to be that the entire knowledge and understanding of the human race could be absorbed by a single human brain. We are well past that point. We are many and we specialize, no individual can possibly absorb it all.
But still we make progress...
"Anyway, I have been wanting to do exactly that experiment with a Prop for ages. Do you have any schematics and diagrams of your setup?"
I used an He-Neon laser tube with a logic level gate on the HV side I had modified. It was originally used for a gun sight. The modification was to gate the high voltage directly powering the laser tube so I had better control of turning it On or Off.
The receiver was a generic IR LED but I was using it in capacitive mode (<-- reverse biased) So I could apply a sensitive auto gain / auto biasing circuit similar to this one .... (but it used a derivative single transistor configuration ... See further below)
IR Heartbeat detector circuit: (Two Transistor)
http://forums.parallax.com/discussion/149216/demo-ir-heartbeat-detector
In the circuit below replace the 10uF cap with the reverse biased IR receiver and connect the Emitter of the first stage transistor directly to ground. You shouldn't need the Op-Amp or any part of the remainder of the circuit, the collector output should be sufficient.
Long range passive RFID Receiver circuit: (Single Transistor)
http://www.kit-start.com/RFID Receiver/RFID receiver_html_mf57f20d.jpg
The output was taken and filtered through a schmitt trigger inverter ... 74HCT14 with ALL unused inputs tied to ground.
In software I would simply "enable" or "disable" the laser and time the pulse change.
BTW) In reference to my Earlier post ... We just had a 5.1 Magnitude Earthquake minutes ago !!!
http://earthquake.usgs.gov/earthquakes/eventpage/us20004zy8#general_region
Whoa what? A helium neon laser, switching the HT? I was imagining that kind of thing would be really slow. A foot is a nano-second right?
Luckily we have diode lasers now. The HT supply on my HeNe laser melted down by the way.
Thanks for the circuit suggestions.
Hope those passing gravity waves are not causing to much grief.
.... I used what I had available ... the diode laser's beam spread was too great. The He-Neon had a divergence of about the size of a tennis ball at 1/2 mile. I'm not sure that a diode laser will go that tight. It least not any of the ones that I have. The current was only about 10mA on the He-Neon while the voltage was about 1kV DC
Edit: "The high voltages needed (10kV to start laser emission and 1-2kV to maintain it.)" ... Actually my gate modification was just modulating the beam at 1kV ... the receiver circuit is sensitive to change, so the modulation was easily detected.
Sure. Einstein came up with GR, but I read that the LIGO paper has over a thousand coauthors. Many of those probably worked on the technology instead of the physics, but they were still a necessary part. I think many of the projects on the LHC involve even larger groups, but that's just another adaptation for tackling harder problems. Maybe the crisis will come when we run out of interested people.
Yes, there is a habit now to put the names of anyone contributing to such a project onto the resulting papers.
Rather like the endless credits they put on the end of movies. Although I don't think they go as far as listing the caterers, carpenters and toilet cleaners like the do on Hollywood movies
I seem to remember the the figure of 6000 contributors to just one of the detectors in the LHC. Whatever figure it is it's huge. That worries me some times.
People could lose interest if we get overrun by the creationists, intelligent designers, and followers of other crack pot religions. Then it's back to the dark ages for the human race.
Also, if the human population suddenly dropped significantly. We would not have enough people to understand all the technology we rely on now.
I kind of miss my old HeNe laser. Built from a kit from Maplin Electronics circa 1995. It had a nice aluminium box a bit over a foot long and a nice PCB for the voltage doubler PSU you had to build up. Worked a treat until the transformer melted. Seems that was a common fault.
That's when I discovered cats love to chase the red dot of a laser. Which is all the rage on the net now a days I believe.
The first time I ever saw a laser pointer it was my electronics prof. wielding a HeNa laser at the blackboards. About 1976.
First and second authors carried most of the weight.
Last name in the list very likely managed and directed the overall research, including securing funding.
That is by convention and is not universally true, but useful to know.
You are giving away the secrets of the scientific brotherhood now. You will be showing us their secret hand shake next
Certainly, but I don't think that's a bad thing. When the new work could not have happened without new technology, and that technology is the work of a large team, did they not make a critical contribution? Or when a paper consolidates a large dataset from many sources, what else can you do but list all the contributors? Probably many of those people are in the situation that they need to show productivity, so courtesy dictates that they be listed as a coauthor. Big Science leaves little choice but long lists of contributors. Still, the first couple of people and maybe the last are the ones everyone looks at, and with good reason. Having been one of those names buried in the middle, I can both appreciate the courtesy yet still understand why those names are mostly ignored.