Looking to the Horizon

· by · in Astrophysics, Science. ·

Today’s post will be explaining the workings of the Event Horizon Telescope and the recent efforts to capture for the first time an image of the black hole at the center of our galaxy.

The Event Horizon Telescope is a truly global endeavour as it consists of eight radio observatories in six different locations around the world: Spain, Arizona, Hawaii, Mexico, Chile and Antarctica – creating a telescope array as wide as Planet Earth. The set-up is that each telescope points at the black hole at the center of our galaxy, known as Sagittarius A*, and measures the radio waves coming from its direction, collecting more detailed data than we have ever had before. The telescope should achieve a resolution of 50 microarcseconds which is equivalent to being able to see a melon on the moon! Equipped with this resolving power we should be able to image the event horizon of Sagittarius A*, which although being a whopping 20 million km wide is to us but a pinprick in the night sky 26,000 light years away.

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The plan was that the telescopes were all to be turned on for 5 nights between April 5th and April 14th, the exact timings being chosen dependent on the best weather conditions. It can now be confirmed that last night the astronomers operating the sites finished their spell of observations and the data is now in the bank so to speak. Each nights the telescopes generated a total of 2 petabytes of data, which according to a calculation by New Scientist, is enough to store the full genomes of 2 billion people! So, as you can image all this data is going to take a decent old time to process before we can see any results.

Now I may hear you say “Hold on, take an image of a black hole?! But I thought black holes were unable to be seen due to the very nature of things not being able to escape that go beyond its horizon, not even light!” Well right you are, but what astronomers hope to see is the matter that hurtles around the horizon edge, being bent by the intense gravity as it is slowly sucked towards the center of darkness. Even light is bent by the immense gravitational pull so the perimeter of the black hole should glow intensely as the photons (that are just far away enough to avoid being sucked in) spin round and round the horizon. Therefore if our predictions are correct we should see this bright circle of light warped around the shadow within.

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Event horizons have been somewhat of a mythology of science. In fact the existence of black holes was once debated whether to be science-fiction or science-fact, as they were purely a theoretical prediction of Einstein’s general relativity. However in this case seeing really would be believing if the images came out just as the theory predicts them to. Taking things to the next level, if we can get accurate images to actually measure the size of the dark shadow we can test general relativity further as the theory can predict what size the black hole should be dependent on its mass.

However perhaps we’re going to see something different entirely to our predictions. Now this may not be the worst outcome in the world.. in fact it may lead us further along in our attempts to resolve the conflicts between general relativity and quantum mechanics. As it stands the two theories do not fit together and our predictions for the nature of a black hole go no way to resolving this. Often the most extreme environments in nature are the ones which give us the best insights into the rules by which nature plays and the black hole is the most extreme gravitational environment out there. If our observations prove us wrong perhaps it’ll be a push in another more fruitful direction for physics.

Then again, taking history’s track record one should know better than to bet against Einstein. The Event Horizon Telescope should prove that event horizons really exist (else the project might need a re-brand). Now it’s just a question of time and some hard-core data-analysis to get the findings up. The information from all the telescopes – equivalent to the storage capacity of ten thousand laptops – must be physically sent to the telescope’s processing enters in MIT and the Max Planck Institute for Radio Astronomy and to make matters worse the drives from the South Pole site can’t be flown out until the end of winter season there, in November! The technique of combining radio wave signals is known as ‘very long baseline interferometry’ and although it is a common technique amongst astronomers the sheer amount of data in this case is unprecedented. It’s not certain that this initial run by the Event Horizon Telescope will be successful in generating a clear image but the team has plans to conduct repeat observations, extend the network to more sites and eventually into space to work towards an even sharper signal.

So for now all we can do is sit back, relax and let the astronomers do their biz as we await to see for the first time if the mask can pulled off the mysterious character that is the black hole.

49 responses to “Looking to the Horizon”

  1. Thank you Mehki – awesomely ‘coincidental’ timing! This post will be a useful link to close an item I’ve just revamped on scientific peculiarities of the Resurrection of Jesus, as may be ascertained from his burial shroud. (For auto-publication this Sunday – when else, after all).

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  3. Has anyone thought of putting a telescope in orbit around the Moon? Ironically, it would have to be in orbit to be “stationary”, that is, pointing in a single direction all the time.

    On the Moon’s surface, presumably the dark side, it would be pointing in a rotating fashion as the Moon rotates while travelling around the Earth.

    Come to think of it, the radio-telescopes on Earth have the same problem, and would have to compensate in some fashion to cancel the effect of the Earth’s rotation.

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    • An interesting idea but i’m not sure I see the benefits over having a space based telescope in orbit around Earth which requires a much easier launch mechanism?

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      • The advantage would be using the Moon’s gravity to haul us around a wider orbit that Earth satellites. Now all we’d need to do would be to set up a few more around the other planets and we’d have one heck of a large distance between them creating a really big “lens”. The trick would be coordinating their motion … huh … wait … perhaps if each took its own picture in its own time and then we cut-n-paste, like we did when mapping the Moon.

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  4. Oh hello Long time no see, I was becoming worried!
    Very interesting post, the capacity of ten thousand laptops needs a HUGE patience of the one who will look into it.
    Who will look into it a computer or humans?
    And I thought that the horizon event was a fact not a theory!

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    • Hello! Yes sorry about the silence, we’ve both been rather caught up with work and haven’t had much spare time on our hands, trying our best to get back to normal now though! So I’m no data analysis expert but I believe a lot of the initial processing and reduction will be able to be done by computers then humans will step in when it gets fiddly. Yes common thought, which had me confused too. But actually it’s only the way we understand general relativity and black holes to work but we’re yet to have direct proof for this as so far we have only been able to ‘observe’ black holes through their gravitational pull effects!

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  5. Mind… blown. There have been a few recent depictions of black holes–most notably the one in Interstellar–which look pretty realistic, based on theory at least. It’ll be interesting to see how they compare to real life.

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  6. Thank you for a very informative post. However, I cannot help but to comment on what appear, to me at least, to be a common misperception amongst physicists, which is black holes wallow matter. To my knowledge, general relativity says nothing about matter falling into black holes. In fact, it says nothing about what happens beyond the event horizon of those not so mysterious objects. If anything, it confirms that nothing can fall into a black hole. An observer outside the horizon would view an object falling in as remaining in its position indefinitely – and that is mathematical truth, which is the real truth.
    If one is to rationalise the development of black holes as physical entities, one would arrive at a very simple object which is no more than a hidden star whose sole characteristic, other than its mass, is its exceptionally high spin speed. Then, if one compares its behaviour in space with that of a solid object spinning at high speed in a fluid medium, one would arrive at a very similar equation to that of a black hole.
    A solid object spinning in a fluid develops into a singularity, which is effectively a discontinuity in the medium in which it spins. The singularity is an enveloping void surrounding the object, rendering it unobservable from the outside. Any relatively small object attracted to that singularity by virtue of the spin of the medium in its surroundings would become trapped in that spin and subject to intense radially variable force that would cause it to disintegrate in time, effectively shredding it to its most basic elements.
    The question of how object in space develop spin is essentially a quantum phenomenon that starts at the level of individual protons and how they interact through the fabric of space.

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    • Wait a minute, spin would be an outward rather than an inward force. The inward force is gravity. And I think the time stretch would be part of the stretch of the object as it falls more and more under the influence of the gravitational center. Observers sufficiently outside the center mass would be less affected, but those approaching the center would be stretched by inner parts (feet if falling feet first) of them falling faster than outer parts. At least that’s the image I’ve noticed in the animations over the years.

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      • First, I must apologise for the lengthy response, which I felt necessary to explain what I meant. I agree with you Marven, in that spin generates an outward (centrifugal) force, which is what causes a star to expel the surrounding medium, leading to the development of a singularity (discontinuity) in the fabric of space around it. However, if we agree with general relativity’s definition of gravity as the warping of space, we must accept that space is, or contains, a physical medium that can be warped and as such, it can influence the motion of all objects occupying it. And because it is physical, it must be subject to some warping limit.
        The warping of space must reach some critical limit after which it is torn or ruptured around the star’s atmosphere, where the effect of gravity and spin are at maximum. Therefore, the combination of gravity in the star’s surroundings (gravitational field), which become the event horizon and the star’s spin speed cause a discontinuity to develop around the star. If I may add here, a black hole does not trap light due to its intense gravity, because light travels at constant speed regardless of gravity, though gravity could cause it to change direction. What terminates light in a black hole is the discontinuity in the fabric of space.
        The stretching of objects falling towards the event horizon of a black hole is due to the intense increase in the rate of warping of space time, which is what I referred to as the shredding of objects, and is usually referred to as spaghettification of objects falling into black holes.

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      • Personally I don’t think space or time are actually “warped”. I think that’s an example of a missing “as if”, as in “it is AS IF space is being warped”. All we’ve got is the objects and the forces between them.

        For example, if you took a ship from NY to London, it may take a couple of weeks. But if you took a plane, it takes less than a day. It is AS IF the distance between them was shortened.

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    • Thanks physicalrealityblog for your comment. However I’m afraid we disagree on a few points. I’ve written a post on falling into a black hole and what an observer watching from a safe distance would view and what an infalling observer would experience. The post is called ‘Black Holes #1: Falling In‘ The infalling observer, unless you subscribe to the firewall point of view, would notice nothing different when passing the horizon and carry on through to the center of the black hole. Regarding singularities, they are points which are mathematically indescribable and a solid spinning object in a fluid is quite easily mathematically modelled using mechanics and fluid dynamics. One must also remember our classical notion of objects spinning in space has nothing to do with the quantum mechanical property ‘spin’. Joe wrote a post on ‘Quantum Numbers‘ which explains this nicely. Thank you for your comment and interest here at RTU!

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      • Thank you so much for responding to my above comment and for referring me to other relevant posts Mekhi. My intention was not to dispute the validity of general relativity. To the contrary, my intention is to remove the misconceptions attached to it by misinterpretation. I feel uneasy about the claim that there exist places in the universe in which the laws of physics do not apply, for that puts the theory in trouble.
        Furthermore, the concept of a singularity being infinitely small, or a theoretical point, means that all black holes should be of the same size. However, we know that is not the case, and that if we have a choice as to which one we fall into, we should opt for a large one 🙂 Therefore, there is some misunderstanding in the current interpretations of the nature of black holes as singularities. Singularities, be them mathematical of physical, after all, mathematics is the modelling of physics, are mere discontinuity in an otherwise well-defined domain.
        Regarding the applicability of the mathematics of fluid mechanics to the behaviour of objects in space and the existence of singularities in both cases, there are numerous research papers available on the internet confirming that, some of which have been published very recently. For starts, they both use PDE.
        My refers to the rotation of solid object in a fluid as analogy to the behaviour of black holes is not to imply that the objects themselves constitute singularities, although by being of a different material makes them as such, but that at very high spin speed a spinning object in a fluid medium generates a discontinuity in high speed circular flow around itself. That discontinuity would not have the same property as the fluid around it and therefore the equations applying to the fluid would not apply there, hence the common statement that the laws of physics breakdown at a singularity.
        As to the subject of quantum spin, I shall be publishing a post in perhaps two three months, in which I shall explicitly define quantum spin number in terms of the mass distribution in matter particles.

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  7. Pingback: Event Horizon Telescope | The Saganist·

    • I have had a little read myself, and to me there is a confusion between light and other sources of electromagnetic radiation. The argument goes something along the lines of perhaps the universe is filled with some kind of particle which absorbs light and makes it look dark. The universe however is already filled with “light” it just isn’t light that our eyes can detect – but the cosmic microwave background is just that, it’s electromagnetic radiation permeating the universe in all directions we can observe. Your argument would have to follow that there is something blocking visible light to humans but not the microwave background – which seems implausible to me, if that makes sense?

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      • Hello Joseph, thank you for your reply. I didn’t know you could read Mekhi’s posts!!
        So let me make sure I understood what you said: Electromagnetic radiation (such as the cosmic microwave background ) is a kind of light which cannot be perceived with our own eyes, found everywhere in the universe. Am I right?
        If so, my idea is that the effect of some unknown particle which composes a subject (such as dark matter) has a role to play in the darkness of the sky. If the Electromagnetic radiation is similar to the real microwave radiation, I don’t see how we could count it as “light”, as we don’t heat our food with “light”. So is it possible to test if this dark matter or some other entity is actually darkening the universe?

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      • Yes exactly, spot on on em radiation. Electromagnetic radiation is indeed the same as real microwave radiation and we do very much heat our food with light! Okay I am being a little silly – electromagnetic radiation is a disturbance in an electromagnetic fields. The frequency depends on what can detect it and its nature – very low frequencies are microwaves, very high frequencies are infra-red. In the middle, we have a range of frequencies the human eye can detect – this is what we have dutifully dubbed light. So you see the universe is only dark in the sense that it is devoid of radiation that can be detected by the human eye – but that only makes it dark to a human, it does not make it devoid of electromagnetic radiation if that makes sense

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      • Yes I understand, thanks. But what makes this dark colour? It could have been pink or yellow. You may say that black holes absorb light, but the colour remains, no?

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      • It isn’t a dark colour, it just does not poses the quality you see as colour. So when something appears red to you, the object has absorbs all the colours except the frequencies of light which we identify as the colour red. Colour is something which we see, so only visible light can produce colour. If however we could detect with our eyes electromagnetic radiation in the other ends of the spectrum then that too would have something we would identify as a colour. So light and colour are the same thing

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      • Thanks it helped a bit, but the question is still there. Why is the space between galaxies or between sources of light, black? Why not grey? I understand that colours come

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      • Sorry sent it before I finished, I understand that colours come from light, but why darkness no?

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      • Colours don’t just come from light – colours are light. There is no such thing as a red jumper – there is just a jumper that allows only red light to reflect off its surface. Mix all the colours of light and you have white light. When you don’t have light, your eyes cannot detect anything and therefore your brain cannot create an image – an absence of light gives you nothing, or darkenss. We must of course be careful not to confuse humans not being able to see something with there being nothing there.

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      • You brain shows you what your eyes detect – they are light receptors. So where there is no visible light, there is nothing to be received therefore you don’t see anything. There is of course other kinds of radiation – this is how we can use say thermal imaging devices to see when our eyes fail us.

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      • I don’t want to be a pain in the neck but, why the eyes detect darkness when there is no light? I’m sorry if I’m not clear enough but the thing is if there is no light and the eyes can’t see anything like when someone is blind, why does our brain interpret that as black, such as the darkness of space

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      • The eyes don’t detect darkness they detect nothing – which is what you perceive as darkness. That would of course be total total darkenss (i.e. no lgiht at all). Black is the colour of an object which absorbs all of the colours of visible light – i.e. what you can assume to be the same as no light.

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      • Ohhhh, ok! So the darkness we see in a dark room is not the same as the black colour? So nothingness is perceived by the brain as black. And the dark sky is actually the same thing?! If I got it right, please tell me so.
        And thank you very much for your time and explanations.

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      • Very very close! the only slight subtlety I would add is that black isn’t a colour – it is no colour. So true black and darkenss are the same… the main difference is that most objects you call black are not true black, they reflect some of the light. If you google blackest materials in the world, you see some amazing materials where they absorb so much light that you can’t even really make out the shape. So black and nothingness is the same because black isn’t a true colour, it is no colours which is the same as nothingness!

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      • Thank you so much, I’ll look into it tonight. So how come that we make “black” colour out of three different ones? Is it by chance?

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      • No not at all – if you take each of the colors of light and mix them, you have one colour that absorbs everything but red, one that abosrbs everything but green etc so you end up with a mix that absorbs pretty much everything – black. This won’t of course be total total black, ususally a sludgy grey

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      • Thanks, I understand everything now. I’m writing a new post on the topic, you may read it tonight if you want. And if there is anything wrong in it, please just let me know.
        Have a nice day.

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      • It’s like when we turn off the lights, and we stay in a pitch black room. Why is it so?

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