Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: myuncle on 20/10/2018 12:28:26
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Can they try to detect gravitational waves with powerful microscopes? They could use them everywhere on the planet, isolating them like the LIGO, hanging them from pendulums. The advantage would be that no long pipes are needed. They record footages 24 hours a day, then they analyse the footage, playing back at the exact same moment the GR has been detected by LIGO.
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The best microscopes have about 100,000 times less resolution than LIGO in terms of the smallest change they could see.
Also, the bigger the thing you look at the bigger the effect of the gravity waves.
Ligo looks at a baseline 4 km long. An electron microscope looks at objects about 4mm long.
So the microscope would be about 100,000,000,000 times less sensitive.
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The best microscopes have about 100,000 times less resolution than LIGO in terms of the smallest change they could see.
Also, the bigger the thing you look at the bigger the effect of the gravity waves.
Ligo looks at a baseline 4 km long. An electron microscope looks at objects about 4mm long.
So the microscope would be about 100,000,000,000 times less sensitive.
But can the microscope detect any change in matter? not detecting necessarily vibration, but detecting simply the possible effects that gravitational waves have on liquids, gases, or light?
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What changes do you think gravity waves produce?
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What changes do you think gravity waves produce?
I don't know, if the waves can penetrate the LIGO shell and move the mirrors, maybe a microscope can see the movement of a few atoms.
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Do you have any idea how small the movement is- even for something as big as LIGO?
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A high-energy electron in an electron microscope can see objects close to the size of an atom.
However, this high-energy electron jiggles every atom that it hits, making it impossible to measure any tiny movement due to gravitational waves.
The size of movement they are trying to detect with LIGO is far less than the size of a proton, which is in turn much less than the size of an atom.
- LIGO uses massive mirrors, which are illuminated by laser light.
- The light bounces back and forth around 280 times, for an effective length of over 1,000km.
- Light has a very small and steady pressure on the large mirrors.
- Steps are being taken to improve the sensitivity of LIGO by cryogenically cooling the ends of the tunnel and the mirrors (a technique developed by the Japanese). This will reduce the thermal jiggling of atoms in the mirror, to further increase sensitivity of LIGO.
So I'm afraid that electron microscopes would not be a good tool to search for gravitational waves, due to the interaction of the following two effects:
https://en.wikipedia.org/wiki/Uncertainty_principle
https://en.wikipedia.org/wiki/Matter_wave
PS: Maybe one day, we may be able to produce a coherent beam of high-energy electrons, which would be a good way to measure distances accurately, in a small space. Today's electron microscopes use non-coherent electron beams.
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I messed up the arithmetic in my earlier post.
LIGO will see changes of about 1/10,000 of the size of a proton.
The proton radius is about 10^-15 metres
So the resolution is about 10^-19 metres.
The resolution of a microscope might be 10^-10 metres so the microscope- it it was "fixed" and looking at the end of a bar 4km - the same size as LIGO- would be 1,000,000,000 too "coarse" to see the bar move due to gravity waves.
Since the biggest thing you can actually put in a microscope is about a million times smaller than LIGO, the change in size is also about a million times smaller.
So the microscope fails by a factor of about 1,000,000,000,000,000
LGIO is really good at its job.
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Thanks. Let's say that you want to confirm the results with other equipment around the world. If you suspend something thinner than a mirror maybe is going to move more, and the movement can be a shift in position detected by the microscope? Another question. If you want to build a new observatory, do you need any L shaped pipes? Even if you use another mirror and laser beam, and you compare it with the results shown by LIGO at the same time, in this case two pipes would be unnecessary, because all you have to do is to see the behaviour of the mirror at the same exact time, but on a different world location.
Having said this, I find it too difficult to believe that we can detect gravitational waves or black holes (if they exist).
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If you suspend something thinner than a mirror maybe is going to move more
It seems that you view gravitational waves as a force, and you would expect that this force would move a less massive object more(?).
However, just like Earth's gravity, more massive objects feel a greater force of attraction, but this is precisely counterbalanced by the greater inertia of the more massive object. This was the point of Galileo's thought experiment about dropping two masses from the leaning tower of Pisa. Both masses experience the same acceleration, and the same movement.
So there is no advantage in measuring the position of a low-mass object like a single atom, compared to the position of a large mirror. And in fact, measuring the position of a single atom is inherently more uncertain, due to Heisenberg's uncertainty principle.
Plans are under discussion to make the LIGO mirrors even more massive, increased to 160 kg.
https://en.wikipedia.org/wiki/LIGO#LIGO_Voyager
do you need any L shaped pipes?
These large vacuum pipes are very expensive, and very fragile. An earthquake could make them collapse, and the explosive recompression would destroy the facility.
One proposal is to put a gravitational observatory into space, so it doesn't need pipes to contain the vacuum, and it isn't limited by the curvature of the Earth.
See: https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna
Note that this would use an equilateral triangle, rather than an L-shaped detector.
Even if you use another mirror and laser beam, and you compare it with the results shown by LIGO at the same time,
By using two laser beams in the same location, the only information you need to transmit to another location is the very small difference between the two beams when they are recombined.
This signal is confined to the audio band, 20Hz-1kHz, and is a small amount of information to compare.
However, if you were to compare the arrival rates of every photon from the laser, the amount of information to be compared between two sites would be around 1016 bits per second, which is really beyond current communication capabilities.
So comparing two beams at a single site is a significant data reduction technique.
By comparing the phase from 3 widely-separated sites on the Earth's surface (each with an L-shaped antenna), it is possible to determine the polarization and direction of the source. If each site just had a single tube, you would need 6 observatories to make the same analysis.
I find it too difficult to believe that we can detect gravitational waves or black holes
You are in good company.
- Einstein didn't think that gravitational waves would be detectable either, even though they were predicted by his theory. He thought that the effect was just too subtle to be detectable.
- For a long time, Einstein wasn't sure that black holes were a valid interpretation of his theory. He viewed the infinities as a sign that his theory broke down in this region of space.
But why do you find it hard to believe?
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If you suspend something thinner than a mirror maybe is going to move more
It seems that you view gravitational waves as a force, and you would expect that this force would move a less massive object more(?).
However, just like Earth's gravity, more massive objects feel a greater force of attraction, but this is precisely counterbalanced by the greater inertia of the more massive object. This was the point of Galileo's thought experiment about dropping two masses from the leaning tower of Pisa. Both masses experience the same acceleration, and the same movement.
So there is no advantage in measuring the position of a low-mass object like a single atom, compared to the position of a large mirror. And in fact, measuring the position of a single atom is inherently more uncertain, due to Heisenberg's uncertainty principle.
Plans are under discussion to make the LIGO mirrors even more massive, increased to 160 kg.
https://en.wikipedia.org/wiki/LIGO#LIGO_Voyager
do you need any L shaped pipes?
These large vacuum pipes are very expensive, and very fragile. An earthquake could make them collapse, and the explosive recompression would destroy the facility.
One proposal is to put a gravitational observatory into space, so it doesn't need pipes to contain the vacuum, and it isn't limited by the curvature of the Earth.
See: https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna
Note that this would use an equilateral triangle, rather than an L-shaped detector.
Even if you use another mirror and laser beam, and you compare it with the results shown by LIGO at the same time,
By using two laser beams in the same location, the only information you need to transmit to another location is the very small difference between the two beams when they are recombined.
This signal is confined to the audio band, 20Hz-1kHz, and is a small amount of information to compare.
However, if you were to compare the arrival rates of every photon from the laser, the amount of information to be compared between two sites would be around 1016 bits per second, which is really beyond current communication capabilities.
So comparing two beams at a single site is a significant data reduction technique.
By comparing the phase from 3 widely-separated sites on the Earth's surface (each with an L-shaped antenna), it is possible to determine the polarization and direction of the source. If each site just had a single tube, you would need 6 observatories to make the same analysis.
I find it too difficult to believe that we can detect gravitational waves or black holes
You are in good company.
- Einstein didn't think that gravitational waves would be detectable either, even though they were predicted by his theory. He thought that the effect was just too subtle to be detectable.
- For a long time, Einstein wasn't sure that black holes were a valid interpretation of his theory. He viewed the infinities as a sign that his theory broke down in this region of space.
But why do you find it hard to believe?
Thanks for your patience, I am not a scientist or a student, just curious about it. Why I don't believe it? Because I find it so hard to believe that these gravitational waves came from so far away, they managed to overcome so many galaxies, they haven't been deflected by any star, they managed to reach our planet, they managed to penetrate the atmosphere, penetrate silently the LIGO shell, and finally, they somehow managed to move this mirror, heck, what a journey! I find it hard to believe that there were no other possible explanations, like a malfunction, like a small quake, like a bird pecking the pipe, or aeroplanes. Another reason why I am not convinced, it is because these waves came apparently from the collision of two black holes, they awarded a nobel prize for the gravity waves discovery, but nobody has ever been awarded for the black holes detection? Isn't the so-called scientific community putting the cart before the horse? If you claim that you detected black holes or GW, you are not exactly rediscovering the wheel, you are making a big claim, and big claims require big evidence. I think the evidence we have so far is interesting, I don't ignore it, but at the same time I find it very weak. For example what's the strong evidence of the black hole? The gas clouds spinning very fast around them? Ok, very interesting again, but is it enough to claim the existence of a black hole?
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Thanks for your patience, I am not a scientist or a student, just curious about it. Why I don't believe it? Because I find it so hard to believe that these gravitational waves came from so far away, they managed to overcome so many galaxies, they haven't been deflected by any star, they managed to reach our planet, they managed to penetrate the atmosphere, penetrate silently the LIGO shell, and finally, they somehow managed to move this mirror, heck, what a journey!
Yet you have no problem believing that light and other forms of radiation from galaxies billions of light-years away can make it to our telescopes? Such a journey would be even easier for gravitational waves to make, as they can travel through clouds of dust, stars and planets without being absorbed.
I find it hard to believe that there were no other possible explanations, like a malfunction, like a small quake, like a bird pecking the pipe, or aeroplanes.
The GW150914 event was detected by two different detectors within the same second, one in Washington state and one in Louisiana. The GW170817 event was likewise detected by two detectors (one in Louisiana and one in Italy). Not only that, but the source of that particular gravitational wave event was also detected via electromagnetic radiation by the Fermi and INTEGRAL spacecraft and found to be the collision of two neutron stars. Can you explain how a malfunction, earthquake, bird or airplane can affect multiple detectors thousands of miles apart at virtually the same time?
Another reason why I am not convinced, it is because these waves came apparently from the collision of two black holes, they awarded a nobel prize for the gravity waves discovery, but nobody has ever been awarded for the black holes detection? Isn't the so-called scientific community putting the cart before the horse? If you claim that you detected black holes or GW, you are not exactly rediscovering the wheel, you are making a big claim, and big claims require big evidence. I think the evidence we have so far is interesting, I don't ignore it, but at the same time I find it very weak. For example what's the strong evidence of the black hole? The gas clouds spinning very fast around them? Ok, very interesting again, but is it enough to claim the existence of a black hole?
The signature of a black hole-black hole collision has a very specific appearance according to theory and was predicted many years in advance of the first gravitational wave detection itself. I have a book written in the early 90's describing just that. Perhaps I'll quote it when I get back home and can get a look at it again.
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it so hard to believe that these gravitational waves came from so far away, they managed to overcome so many galaxies, they haven't been deflected by any star, they managed to reach our planet,... they managed to penetrate the atmosphere, penetrate silently the LIGO shell..., heck, what a journey!
Let me tell you about an even more extraordinary telescope: Ice Cube, at the South Pole.
It monitors for particles that have passed through the entire width of the Earth, and has recently uncovered its first point source.
These particles that can pass through the diameter of the Earth: Neutrinos.
Another particle that can also easily pass through the entire diameter of the Earth: Gravitons (and coherent waves of them: Gravitational Waves).
Gravitational wave observatories on different sides of the Earth are able to triangulate the source of a single gravitational wave event, because gravitational waves travel at the speed of light, and travel through the Earth (or a star) as if it wasn't there. Penetrating a vacuum tube is trivial, by comparison.
See: https://en.wikipedia.org/wiki/IceCube_Neutrino_Observatory
I find it hard to believe that there were no other possible explanations, like a malfunction, like a small quake, like a bird pecking the pipe, or aeroplanes.
One of the reasons that the two US detectors were placed at opposite sides of the 50 states is so that earthquake waves, waves pounding on the beach, lightning, passing aeroplanes and angry birds could all be ruled out.
- P-Waves in an earthquake travel at 5-8 km/second, clearly distinguishable from gravitational waves at 300,000km/sec.
- The gravitational wave detectors are surrounded by earthquake monitors, that measure the precise direction and strength of any seismic disturbances (eg an approaching truck).
- The mirrors are suspended from an elaborate vibration-isolation platform, using both passive and active techniques. (A few years ago, I had the opportunity to examine some of these devices at one of the first gravitational wave observatories, in Gin-Gin, Western Australia - now a museum.)
- A bird pecking on the vacuum tube would transfer no sound through the vacuum inside the tube, and no vibration through the isolation systems.
- The frequency of the gravitational waves is the same at all locations, and changes in the same characteristic way over time
- As Kryptid says, the waveform matched the predictions quite well, allowing astronomers to extract information like the mass of the black holes, their radius, the mass of the final black hole, and even how misaligned their rotation axes were.
- In fact, they matched the charts that I saw at Gin-Gin quite well, years before they were actually detected.
Isn't the so-called scientific community putting the cart before the horse? If you claim that you detected black holes or GW...
I think that the scientific community did things in the correct order:
1) Try to detect gravitational waves: Eventually succeeded, after trying for many years
2) Try to detect:
2a) black holes colliding (done)
2b) neutron stars colliding (done)
2c) Black hole colliding with a neutron star (not yet)
2d) Neutron star about to experience a starquake (not yet)
2e) Asymmetrical supernovas (not yet)
2f) Gravitational Waves left over from the Big Bang (not yet)
2g) Supermassive black holes: Will require a newer space-based gravitational wave detector with much better low-frequency response (although some pulsar-based measurements may get there first)
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Creating a light source or radio waves is something we can do everyday, and play with them in our room, it doesn't require any leap of faith. Gravitational waves is something totally new, we can't generate them in our room, it's like comparing apples vs oranges.
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There is a possibility that Bose Einstein Condensates could be used in space to detect gravitational waves.
https://phys.org/news/2018-10-bose-einstein-condensate-space.html?utm_source=nwletter&utm_medium=email&utm_campaign=weekly-nwletter
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What changes do you think gravity waves produce?
I don't know, if the waves can penetrate the LIGO shell and move the mirrors, maybe a microscope can see the movement of a few atoms.
Atoms are always moving and randomly too. What you're suggesting is impossible. An electron microscope cannot detect individual atoms either. A tunneling electron microscope can but it doesn't show motion of atoms.
Ligo detects waves in spacetime, something a microscope can't do. And the wavelengths its designed to detect are much larger than can be detected by a microscope.
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Creating a light source or radio waves is something we can do everyday, and play with them in our room, it doesn't require any leap of faith. Gravitational waves is something totally new, we can't generate them in our room, it's like comparing apples vs oranges.
So what is your argument here? If we can't create it ourselves, we have no reason to believe that it exists?
I'm still waiting for you to explain the coincidences of multiple detectors having a fluke at the same time.
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we can't generate them in our room
Yes, we can.
However the ones we create are far too weak to observe.
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Gravitational waves is something totally new, we can't generate them in our room, it's like comparing apples vs oranges.
We can't generate energy from controlled nuclear fusion in our room - and still won't after the $US20 Billion ITER is constructed.
But that doesn't stop the Sun from shining
See: https://en.wikipedia.org/wiki/ITER