Black hole about to be imaged... oh er missis
Discussion
http://www.bbc.co.uk/news/science-environment-3893...
Looks like a world network and a bit of computing power is about to capture Sgr A.
Reading this, it seems why all the hard drives are still expensive?
Looks like a world network and a bit of computing power is about to capture Sgr A.
Reading this, it seems why all the hard drives are still expensive?
Boring_Chris said:
I've been geeking all over these things for ages now. But from everything I've read, they're not going to see a great deal?
I'm not questioning the project, at all. I'd love to know more about what they're expecting to find.
There probably isn't all that much detail to see in the image itself, however it will be a milestone - the first every direct image of a black hole.I'm not questioning the project, at all. I'd love to know more about what they're expecting to find.
It may also allow some of the theories/models to be validated or refined:
1. It will confirm that black holes actually do actually exist and that there is not some other object that we currently dont have an explanation for.
2. That their properties are as expected - the image may allow direct measurement of the event horizon for example.
3. May reveal some details of any accretion disk (size, speed, shape, orientation, gravitational distortion of the light etc) - further validating/refining the models and properties (e.g. mass of the black hole, effects on the gravitational field etc)
I think that as much as anything it is a test of the system itself. Getting as long a baseline as possible to maximise the angular resolution etc. Like all good science and cutting edge engineering, it will inevitably generate results that weren't expected, flaws and strengths will be found in the system and they will evolve the design, and produce even more results that weren't expected. Hopefully anyway 
It would be great to send a couple of receivers out to the L4/L5 Lagrange points and make a massive synthetic aperture. Catch would be that it wouldn't have good resolving power in the plane of the ecliptic.
It would be great to send a couple of receivers out to the L4/L5 Lagrange points and make a massive synthetic aperture. Catch would be that it wouldn't have good resolving power in the plane of the ecliptic.
Zad said:
I think that as much as anything it is a test of the system itself. Getting as long a baseline as possible to maximise the angular resolution etc. Like all good science and cutting edge engineering, it will inevitably generate results that weren't expected, flaws and strengths will be found in the system and they will evolve the design, and produce even more results that weren't expected. Hopefully anyway
It would be great to send a couple of receivers out to the L4/L5 Lagrange points and make a massive synthetic aperture. Catch would be that it wouldn't have good resolving power in the plane of the ecliptic.
I watch a lot of space documentaries but I have absolutely no fIt would be great to send a couple of receivers out to the L4/L5 Lagrange points and make a massive synthetic aperture. Catch would be that it wouldn't have good resolving power in the plane of the ecliptic.
king idea what you just said. 
Well, in radio telescopes, like optical telescopes, the bigger the "lens" (the aperture) the better. Normally this is just so you can grab as much light (or radio waves) as possible, but there is also another reason. The smallest detail you can resolve increases too. This is nothing to do with the amount of light! Instead, it is a mathematical function of how many wavelengths of light it is across the lens/mirror/dish/aperture.
Unfortunately, radio waves are physically much longer than visible light. Like a million times or more. So in theory you'd need a dish 1 million times bigger to see the same object at the same resolution.
Fortunately, you don't actually need a continuous surface area! So you could have one dish, say, at Jodrell Bank, and another in, say, Cambridge. If you can find some way of connecting them together, then you effectively have a dish with much higher resolution. (The distance between the dishes is called the baseline) Now that's do-able if you are both in the UK, ( https://en.wikipedia.org/wiki/MERLIN ) but if you are all around the world then it is much easier just to synchronise everyone's local system with atomic clocks and record the signal in high resolution.
TL:DR; If your radio dish network is 1000x further across, you can resolve detail that is 1000x smaller. So putting some space probes 100M km out in space at nice stable places but a long way away from each other allows you to see tiny things. These stable points are called Lagrange points. There have been orbiting radio telescopes sent up, but so far as I know it was a few years ago now and things have moved on.
http://www.space.com/30302-lagrange-points.html (The Wikipedia one is very sciencey and mathematical)
https://en.wikipedia.org/wiki/Very-long-baseline_i... (The method of connecting all this stuff together)
Here's an interesting little side note. You can pick up precise atomic clocks on Ebay really cheaply, and precision timing systems are relatively trivial to make now, as are liquid nitrogen cooled microwave receivers. I wouldn't be surprised if amateurs were already building interferometer networks like this around the world. Shovelling a hundred GB of data across the globe isn't rocket science any more. Obviously the dishes will be much smaller and not so sensitive, but if there are lots of them all over the world, there could be the potential for some amazing amateur science.
Unfortunately, radio waves are physically much longer than visible light. Like a million times or more. So in theory you'd need a dish 1 million times bigger to see the same object at the same resolution.
Fortunately, you don't actually need a continuous surface area! So you could have one dish, say, at Jodrell Bank, and another in, say, Cambridge. If you can find some way of connecting them together, then you effectively have a dish with much higher resolution. (The distance between the dishes is called the baseline) Now that's do-able if you are both in the UK, ( https://en.wikipedia.org/wiki/MERLIN ) but if you are all around the world then it is much easier just to synchronise everyone's local system with atomic clocks and record the signal in high resolution.
TL:DR; If your radio dish network is 1000x further across, you can resolve detail that is 1000x smaller. So putting some space probes 100M km out in space at nice stable places but a long way away from each other allows you to see tiny things. These stable points are called Lagrange points. There have been orbiting radio telescopes sent up, but so far as I know it was a few years ago now and things have moved on.
http://www.space.com/30302-lagrange-points.html (The Wikipedia one is very sciencey and mathematical)
https://en.wikipedia.org/wiki/Very-long-baseline_i... (The method of connecting all this stuff together)
Here's an interesting little side note. You can pick up precise atomic clocks on Ebay really cheaply, and precision timing systems are relatively trivial to make now, as are liquid nitrogen cooled microwave receivers. I wouldn't be surprised if amateurs were already building interferometer networks like this around the world. Shovelling a hundred GB of data across the globe isn't rocket science any more. Obviously the dishes will be much smaller and not so sensitive, but if there are lots of them all over the world, there could be the potential for some amazing amateur science.
Zad said:
Well, in radio telescopes, the bigger the "lens"...
Great post there Zad, a very good explanation of what is trying to be achieved.The key to all of this is the timing/relativity, I watched the TV prog 'Inside the brain of Einstein' again the other day. It covers all of these issues.
As an aside;
The advances in atomic clocks and stable electronics have been massive over the last couple of years. I've worked in satellite-comms and the guard bands we had to impose due to a satellite phone being directly under the satellite vs one at the 'edge' (NSEW) of the planet were a real issue. That's a c, speed of light issue.
Then there were issues with phones deployed on the same longitude near the poles or near the equator - massive temperature differences and electronic clocking problems again. The satellite is constantly telling the phone to adjust its duty cycle and the ground station is constantly telling the satellite to adjust its duty cycle.
What's also interesting/fascinating is that if the atomic clocks on the GPS satellites weren't constantly corrected (due to the fact they are running faster the Earth based clocks, they are moving through space-time much faster than the Earth bound ground stations), then within 24 hours your GPS position would be about three miles off!
Edited by TheExcession on Saturday 18th February 16:04
Zad said:
Well, in radio telescopes, like optical telescopes, the bigger the "lens" (the aperture) the better. Normally this is just so you can grab as much light (or radio waves) as possible, but there is also another reason. The smallest detail you can resolve increases too. This is nothing to do with the amount of light! Instead, it is a mathematical function of how many wavelengths of light it is across the lens/mirror/dish/aperture.
Unfortunately, radio waves are physically much longer than visible light. Like a million times or more. So in theory you'd need a dish 1 million times bigger to see the same object at the same resolution.
Fortunately, you don't actually need a continuous surface area! So you could have one dish, say, at Jodrell Bank, and another in, say, Cambridge. If you can find some way of connecting them together, then you effectively have a dish with much higher resolution. (The distance between the dishes is called the baseline) Now that's do-able if you are both in the UK, ( https://en.wikipedia.org/wiki/MERLIN ) but if you are all around the world then it is much easier just to synchronise everyone's local system with atomic clocks and record the signal in high resolution.
TL:DR; If your radio dish network is 1000x further across, you can resolve detail that is 1000x smaller. So putting some space probes 100M km out in space at nice stable places but a long way away from each other allows you to see tiny things. These stable points are called Lagrange points. There have been orbiting radio telescopes sent up, but so far as I know it was a few years ago now and things have moved on.
http://www.space.com/30302-lagrange-points.html (The Wikipedia one is very sciencey and mathematical)
https://en.wikipedia.org/wiki/Very-long-baseline_i... (The method of connecting all this stuff together)
Here's an interesting little side note. You can pick up precise atomic clocks on Ebay really cheaply, and precision timing systems are relatively trivial to make now, as are liquid nitrogen cooled microwave receivers. I wouldn't be surprised if amateurs were already building interferometer networks like this around the world. Shovelling a hundred GB of data across the globe isn't rocket science any more. Obviously the dishes will be much smaller and not so sensitive, but if there are lots of them all over the world, there could be the potential for some amazing amateur science.
Can you use the Earth's orbit to increase the effective size (in one direction only admittedly) so acquiring the data over 6 months (assuming the image doesn't change much in that time) would increase the resolution along one axis?Unfortunately, radio waves are physically much longer than visible light. Like a million times or more. So in theory you'd need a dish 1 million times bigger to see the same object at the same resolution.
Fortunately, you don't actually need a continuous surface area! So you could have one dish, say, at Jodrell Bank, and another in, say, Cambridge. If you can find some way of connecting them together, then you effectively have a dish with much higher resolution. (The distance between the dishes is called the baseline) Now that's do-able if you are both in the UK, ( https://en.wikipedia.org/wiki/MERLIN ) but if you are all around the world then it is much easier just to synchronise everyone's local system with atomic clocks and record the signal in high resolution.
TL:DR; If your radio dish network is 1000x further across, you can resolve detail that is 1000x smaller. So putting some space probes 100M km out in space at nice stable places but a long way away from each other allows you to see tiny things. These stable points are called Lagrange points. There have been orbiting radio telescopes sent up, but so far as I know it was a few years ago now and things have moved on.
http://www.space.com/30302-lagrange-points.html (The Wikipedia one is very sciencey and mathematical)
https://en.wikipedia.org/wiki/Very-long-baseline_i... (The method of connecting all this stuff together)
Here's an interesting little side note. You can pick up precise atomic clocks on Ebay really cheaply, and precision timing systems are relatively trivial to make now, as are liquid nitrogen cooled microwave receivers. I wouldn't be surprised if amateurs were already building interferometer networks like this around the world. Shovelling a hundred GB of data across the globe isn't rocket science any more. Obviously the dishes will be much smaller and not so sensitive, but if there are lots of them all over the world, there could be the potential for some amazing amateur science.
Its amazing how important obscure "small" errors become when you get projects of this size. I know that with GPS satellites, you don't just adjust for the satellite's speed, but also the gravity gradient between the sats and the receiver. I mean, who knew that gravity had a measurable effect on a radio signal! Well, me, but I had to do an M.Sc to find that out.
You can use an orbit to simulate an aperture (ooer missis again) in some ways, but the amount of time is huge, and it limits some of the fancy processing you can do with interferometry. Indeed, the very early predecessors to the GPS system (called Transit) used the movement of the satellites across a longer period of time to calculate your position.
You can use an orbit to simulate an aperture (ooer missis again) in some ways, but the amount of time is huge, and it limits some of the fancy processing you can do with interferometry. Indeed, the very early predecessors to the GPS system (called Transit) used the movement of the satellites across a longer period of time to calculate your position.
Reading with interest. Fascinating stuff. I was aware of the bit about timing but that was probably from some science show.
Working on a roof once and there was a GPS receiver, wonder why the hell you need to know where the building is. Then it twigged, something needed clocking. At least that is what I put it down to.
Working on a roof once and there was a GPS receiver, wonder why the hell you need to know where the building is. Then it twigged, something needed clocking. At least that is what I put it down to.
This is the bit I am not sure about. If I look at a black hole, I see the edge? That emanates a lot of energy and can be seen, we hope. However, if I look at the black hole from another point in a 34D universe, I see the edge and a lot of energy escaping. Why is the whole thing not lit up like a christmas tree or will all this be found out?
According to the BBC article, the EHT team predict it will look like this:
http://www.bbc.co.uk/news/science-environment-3893...
What we will actually "see" though, is anyone's guess. I suppose a lot will depend on the local conditions. It may be that the black hole just swallows all the matter, or it may spin off in a disc. I suppose it is possible that the matter is hitting it in a stream, and the non-captured stuff may form a single fan. Or, like the missions to the comet or Pluto, produce results that nobody at all predicted. That's the fun of science
Regarding the bit about a building with a GPS antenna on it, yes, they are great precision (and cheap!) frequency sources. You can use a £5 GPS module to "discipline" a £5 quartz crystal oscillator (no, not with black leather and a whip) and the result is a signal source that is very close indeed to that of an atomic clock. A typical use might be a digital "quasi-synchronous" radio system that uses several transmitters to cover an area.
Another is to produce Differential GPS. Put simply, you know the building is fixed, so any apparent movement in the received position is an error. You broadcast this to other stations (over radio usually) and they subtract this location error off their calculated position. Hey presto, a much more accurate location.
If you have the right GPS system, you can measure continental drift with it. In some places such as Australia, the amount of drift is over 7cm a year and may cause problems in some applications such as self driving vehicles (mostly ploughing tractors at the moment).
http://www.bbc.co.uk/news/science-environment-3893...
What we will actually "see" though, is anyone's guess. I suppose a lot will depend on the local conditions. It may be that the black hole just swallows all the matter, or it may spin off in a disc. I suppose it is possible that the matter is hitting it in a stream, and the non-captured stuff may form a single fan. Or, like the missions to the comet or Pluto, produce results that nobody at all predicted. That's the fun of science
Regarding the bit about a building with a GPS antenna on it, yes, they are great precision (and cheap!) frequency sources. You can use a £5 GPS module to "discipline" a £5 quartz crystal oscillator (no, not with black leather and a whip) and the result is a signal source that is very close indeed to that of an atomic clock. A typical use might be a digital "quasi-synchronous" radio system that uses several transmitters to cover an area.
Another is to produce Differential GPS. Put simply, you know the building is fixed, so any apparent movement in the received position is an error. You broadcast this to other stations (over radio usually) and they subtract this location error off their calculated position. Hey presto, a much more accurate location.
If you have the right GPS system, you can measure continental drift with it. In some places such as Australia, the amount of drift is over 7cm a year and may cause problems in some applications such as self driving vehicles (mostly ploughing tractors at the moment).
Same link I started with. 
I think the artists impression, a ubiquitous one and simple, had me thinking about edges and how we see them from different points. What we see as an edge will be someone else looking on face on. We look on face on and someone else is seeing our face on as an edge.
Roll on April.
Re GPS. Thanks.
I think the artists impression, a ubiquitous one and simple, had me thinking about edges and how we see them from different points. What we see as an edge will be someone else looking on face on. We look on face on and someone else is seeing our face on as an edge.
Roll on April.
Re GPS. Thanks.
ash73 said:
Just been watching this presentation by Prof Andy Fabian, he discovered black holes emit incredibly low frequency sound (54 octaves below middle C, with a frequency of 10 million years) which propagates interstellar gas and influences the surrounding galaxy:
https://youtu.be/yheZOkPwagc
On a typical piano your left arm would need to be 9m long to reach the note!
Interesting. They should be able to image something then.https://youtu.be/yheZOkPwagc
On a typical piano your left arm would need to be 9m long to reach the note!
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