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Saanchi
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Could someone please describe the recent LIGO project, gravitational waves and their detection in simple terms. PLEASE.
That sounds like the lottery fallacy: you should not ask what is the probability that someone in particular won the lottery, but what is the probability that anyone won the lottery. You have to compare the probability given with the probability of detecting any kind of gravitational wave event.fizzy said:http://news.cnrs.fr/articles/gravitational-waves-detected
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Benoît Mours, scientific director at the LAPP1 and principal investigator of the Virgo project in France. “According to our verifications, random noise in the form of GW150914 is so unlikely that it would only happen once every 200,000 years.”
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Those kind of odds don't really mean anything in isolation.
How many such annihilation events were happening 1.5bn years ago? What are the odds of us looking at just the right to witness it as the wave shot through the Earth?
To look at the odds the other way around: the chances that we would start looking just as such an event flew past us are so unlikely it must be noise.
fizzy said:How many such annihilation events were happening 1.5bn years ago? What are the odds of us looking at just the right to witness it as the wave shot through the Earth?
Orodruin said:But this is the beauty. We do not necessarily know the rate of these events, but as we have discovered one of them we can use it to estimate the rate. Since statistics is low it will be a rather bad estimate, but it will exclude a zero rate at high confidence.
DrClaude said:That sounds like the lottery fallacy: you should not ask what is the probability that someone in particular won the lottery, but what is the probability that anyone won the lottery. You have to compare the probability given with the probability of detecting any kind of gravitational wave event.
No it is not. We know that there is a rate, just not what it is. We can use the experiment to constrain that rate. This is how science works.fizzy said:Circular logic. We've know we've detected on since the chances of this being random are very small ... therefore we can calculate how many there are ... therefore we can work out what the chances of it happen by chance are ...
Or at least we can be highly confident.Orodruin said:This is why we can now rule out zero signal rate.
I would say this is how we use "rule out" in colloquial speech.mfb said:Or at least we can be highly confident.
Which also rules out the possibility that the universe has a low rate of black hole mergers in favour of a higher rate. There is no inconsistency here.fizzy said:So either the universe is full of black-holes continually annihilating each other and this is to be expected or it the odds of happening are about as improbable as the small chance this was noise.
That would seem like a more logical conclusion. Perhaps 95% of the mass of the universe is black holes popping each other off all the time.Orodruin said:Which also rules out the possibility that the universe has a low rate of black hole mergers in favour of a higher rate. There is no inconsistency here.
There is only one probability at work here. The noise rate is well known as it can be computed from what we know about the detector systems and therefore we can make deductions about the signal rate, which we did not know previously.fizzy said:The short observation time has to affect both probabilities.
Nobody has ever claimed the signal to be improbable, it only is improbable if the signal rate is low. The only claim is that a background event is highly improbable - once every 200000 years. Since you have an event, this let's you constrain the signal rate as the total rate is signal+background. Nobody has stated anything different - I do not think there are any false impressions given unless you misinterpret the quote.fizzy said:My initial point is that just stating one of the improbable events out of context of the other gives a false impression.
Well, a rate of a few mergers per year is not much, if you consider that of the order of 100 supernovae per second (!) happen in the observable universe.fizzy said:So either the universe is full of black-holes continually annihilating each other and this is to be expected
No, certainly not. Where does that number of 95% come from? Please don't make up numbers.fizzy said:Perhaps 95% of the mass of the universe is black holes popping each other off all the time.
Saanchi said:Could someone please describe the recent LIGO project, gravitational waves and their detection in simple terms. PLEASE.
The LIGO discovery on gravitational waves was a groundbreaking moment in the field of astrophysics. It confirmed the existence of gravitational waves, which were predicted by Einstein's theory of general relativity over a century ago. This discovery has opened up a new window for studying the universe and has the potential to revolutionize our understanding of space, time, and the fundamental laws of physics.
LIGO (Laser Interferometer Gravitational-Wave Observatory) uses two detectors, one in Louisiana and one in Washington, to detect gravitational waves. These detectors use a laser beam split into two perpendicular arms, which are several kilometers long. When a gravitational wave passes through the detectors, it causes a minute stretching and squeezing of space-time, which is detected by measuring the interference pattern of the laser beams.
The black holes detected by LIGO were the first direct observations of black holes merging and producing gravitational waves. This was a significant confirmation of Einstein's theory of general relativity, which predicted the existence of black holes and their ability to produce gravitational waves. It also provided valuable insights into the behavior of black holes and their role in shaping the universe.
The LIGO discovery has opened up a new way of observing the universe and has the potential to reveal information about some of the most mysterious objects in the universe, such as black holes, neutron stars, and dark matter. It also allows us to study the universe in a completely different way, providing a deeper understanding of space, time, and gravity.
The LIGO discovery has opened up a new field of research, known as gravitational wave astronomy, which has the potential to reveal new insights into the universe. It could lead to further discoveries of black hole mergers, neutron star collisions, and other cosmic events that produce gravitational waves. It could also help us understand the origin of the universe and potentially lead to the development of new technologies, such as more sensitive detectors, that could detect even fainter gravitational wave signals.