Slashdot Mirror
Global Internet Telescope Tops Hubble's Resolution
satorchi writes "
The Arecibo Observatory
together with the
European VLBI Network have used the internet to make a
real-time transatlantic synthesis telescope. Data from the individual telescopes was transfered via the internet, and processed in real time by the central processing station at the Joint
Institute for VLBI in Europe. 9 terabits were transfered during the 20 hour experiment, and the resulting synthesised telescope had a resolution of 20 milliarcseconds, about 5 times better than the Hubble Space Telescope (HST). This level of detail is equivalent to picking out a small building on the surface of the Moon!"
we can look for the place where the moon landings took place to finaly debunk all those sceptics ?
How heavily has this impacted the transatlantic Internet communications, during these 20 hours ?
Trolling using another account since 2005.
Does anybody have an idea about the cost of such a telescope (if you where to build a new one) compared to the Hubble?
Maybe a space based replacement for Hubble isn't needed...
TC - My Photos..
Oh, no room for Bender, huh? Fine! I'll go build my own lunar lander, with blackjack and hookers. In fact, forget the lunar lander and the blackjack. Ahh, screw the whole thing!
-- look sir droids...
9 terabits were transfered...
Yes, but how many Libraries of Congress is 9 terabits equivalent to?
.: Max Romantschuk
The monolith factory.
bkd
The title of this story is stupendously moot. It's like saying "oil tanker carries more weight than freight train". Yes, I'm sure it does. It also doesn't go across land.
Very similarly, this is an antenna (radio astronomy) not a telescope (optical astronomy).
Even if it were a telescope, it would still be limited by atmospheric distortions (hence why you'd want one in space).
And even if it were a telescope in space, you'd probably end up with WEBB - which lacks sensors in many of the ranges that Hubble does cover.
All of the above lead up to at least two results...
1. Less scientific data
and, arguably more important as it drives the public's opinion/enthusiasm/taxpaying-willingness/etc.
2. Far less pretty pictures.
I suggest doing a search for Hubble on Slashdot and reading the +5 Insightful/Informative posts, as many of them go into detail as to why many of the proposals simply aren't a replacement for Hubble, and why it either should stay up - or a proper replacement be built.
Such as the 1:4:9 monolith?
Escher was the first MC and Giger invented the HR department.
The comparison between Hubble's and Arecibo's resolution is misleading. The hubble telescoope operates in the viewable spectrum of light, while Arecibo and VLBI do radio astronomy. Radio waves are several magnitues longer, so it's even more difficult to get the same resolution. But since the frequencies are lower, too, it is possible to synchronize several telescopes using interferometry.
Interferometry is done at ESA's VLT with up to four telescopes and mirrors with a precision of about 10nm in the viewable spectrum, at a distance of about 100m. But here, we have a distance of several thousand kilometers, so the signals are digitalized and put together at the computer. This is difficult because it's really hard to synchronise the time -atom clocks are not precise enough. Hence the synchronisation is done "so that it fits best", not using any precise clock. (I don't think this is any easier to do, kudos to the scientists at arecibo and VLBI!)
Comparing a synthesised radio telescope (as was done here) with the Hubble is like comparing apples and oranges. It is MUCH harder to generate these kind of high-resolution pictures in visible as it is in radio.
For instance, if I were to use the VLBI technique in optical wavelengths, and if I had conditions where atmospheric turbulence wasn't affecting the image (as happens with radio), I would produce 20 milli arcsecond resolution with telescopes less than 10 metres apart, as opposed to telescopes on different continents!
Ground-based telescopes using adaptive optics surpassed Hubble years ago in terms of resolution. Prior to adaptive optics, atmospheric turbulance dictated a ground-based telescope's resolution (how close two objects can be and still be distinguished as "separate objects"). The advent of adaptive optics and telescope interferometry as largely solved the problem with the atmosphere so that resolution continues to increase with mirror size or in the case of multiple telescopes in an interferometer setup, the size of the baseline.
Ground-based telescopes have a number of clear advantages in addition to high resolution: they're easily upgraded/repaired and they cost far less than a Shuttle launch.
That said, space-based telescopes still have some advantages over their larger ground-based counterparts: first, they're obviously not subject to day and night but the big advantage is that a space telescope can observe in wavelengths that would be blocked by the Earth's atmosphere.
They're complimentary technologies.
The Hubble Space Telescope Project. This is an excellent guide to the 'scope and instrumentation on board the Hubble.
http://www.busyweather.com/
The principle involved is the same principle which has been used for some decades now in radio interferometry: the data (consisting of the electric field as a function of time) from several radio telescopes are recorded (with timestamps) and then sent to a correlator which combines the signals. This means that in contrary to optical interferometry, the interference is not realised in real time, but `simulated' afterwards in a computer.
The difference is in the way the signals are transported; they used to record the data on magnetic tape drives, which are still used but are more and more being replaced with hard disks. Apparently they have now also started to use the Internet to transport the data.
Very simply, this aperture synthesis experiment is not the same as being able to resolve a house on the moon, unless the house was emitting radio waves. Optical aperture synthesis is harder, but it has been done, at COAST, among others.
Owl tried to think of something wise to say, but couldn't.
Suppose that you wanted to detect a very faint object. You could aim your telescope at a given point in the sky for a couple of hours each night. You could integrate the image over a six month period. That should give you a baseline of 186 million miles never mind a paltry couple of thousand miles.
One of my favorite experiments is to take a sine wave buried under about 20 dB of noise. By integrating over a long enough period, the signal emerges beautifully. (of course it has zero bandwidth) The neat thing about this is that your detector only has to resolve one bit; you still get a nice sine wave out. This should work for detecting dim stars and I'd be suprised if they didn't do it. Do they? Any astronomers out there?
Interferometric telescopes can drastically increase the resolution as compared to single-tube telescopes.
Having two scopes one mile apart, as far as resolution is concerned, is equivalent to having a single one-mile-wide mirror (in essence; the previous poster is correct in his argument about atmospheric distortions & other problems).
The problem is that the amount of light collected is still based solely on the sum of the surface areas of the mirrors-- not the effective area.
If not enough light (or radio waves, in this case) is collected to trigger the CCDs, the object throwing out the radiation simply won't be detected.
Incidentally, the Keck telescopes in Hawaii work this same way, but with a much shorter baseline. It helps that, at two miles above sea level, they're above much of the atmosphere, and that they both have fairly large mirrors to begin with.
For more information about how they work, Google lists plenty of resources.
Allegedly real newspaper headline from 1998:
Man Struck by Lightning Faces Battery Charge
we computer guys think we're geeky, but these stargazers make us look like a bunch of high school jocks.
It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the last vestiges of control of our public school system from decent, God-fearing Americans (as if any further evidence was needed! Daddy's Roommate? God Almighty!)
.45 and a .38 Special! And when they detect you with a firearm, their computers cross-reference the address to figure out your name, and then an enormous database housed at Berkeley is updated with information about you.
Documentaries such as Enemy of the State have accurately portrayed the elaborate, Byzantine network of surveillance satellites that the liberals have sent into space to spy on law-abiding Americans. Equipped with technology developed by Handgun Control, Inc., these satellites have the ability to detect firearms from hundreds of kilometers up. That's right, neighbors... the next time you're out in the backyard exercising your Second Amendment rights, the liberals will see it! These satellites are sensitive enough to tell the difference between a Colt
Of course, this all works fine during the day, but what about at night? Even the liberals can't control the rotation of the Earth to prevent nightfall from setting in (only Joshua was able to ask for that particular favor!) That's where the "moon" comes in. Powered by nuclear reactors, the "moon" is nothing more than an enormous balloon, emitting trillions of candlepower of gun-revealing light. Piloted by key members of the liberal community, the "moon" is strategically moved across the country, pointing out those who dare to make use of their God-given rights at night!
Yes, I know this probably sounds paranoid and preposterous, but consider this. Despite what the revisionist historians tell you, there is no mention of the "moon" anywhere in literature or historical documents -- anywhere -- before 1950. That is when it was initially launched. When President Josef Kennedy, at the State of the Union address, proclaimed, "We choose to go to the moon", he may as well have said "We choose to go to the weather balloon." The subsequent faking of a "moon" landing on national TV was the first step in a long history of the erosion of our constitutional rights by leftists in this country. No longer can we hide from our government when the sun goes down.
There's a Mercedes gap too. I want one and can't afford one, but it's not government's job to do anything about it.
Here's some math to explain what a resolution of 20 milliarcseconds really means.
:)), that is.
1 arcsecond = 1/3600 degrees
Therefore, 20 milliarcseconds = 20/3600000 degrees = (20/3600000)/360*2pi radians
Delta = arctan(diameter/distance)
where Delta stands for angular diameter. This formula is the basic definition of angular diameter. (Note : This formula automatically implies that the units of angular diameter are same as the unit of a plane angle, i.e. radian/degree)
Taking tan function on both sides we get
tan Delta = diameter/distance
Since resolution of the telescope is (20/3600000)/360*2pi radians we get
tan ((20/3600000)/360*2pi) = diameter/distance.
Now,
tan ((20/3600000)/360*2pi) = 9.69627362*10^-8,
This means that
9.69627362*10^-8 = minimum diameter/distance
which can be restated as
distance*9.69627362*10^-8 = minimum diameter
By substituting distance as required, we can obtain the diameter of the smallest observable object at that particular distance.
For example, taking (mean) earth-moon distance as 385,000 km we get
minimum diameter for an object on the moon to be observable = (385,000*9.69627362*10^-8) km = 0.0373306534 km = 37.3306534 m (approx.)
All math was done using Google's calculator and all formulae/definitions are from Wikipedia.
Disclaimer : I may have misinterpreted/misued the formulae so the above results are open to mistakes.
Mod this up anyway, I'm sure somebody will find my mistakes, if there are any (I hope not