341–350 of 525 posts
Can someone explain in layman terms: If graviton particles or gravity waves travel at light speed, how does this information escape the event horizon?
It doesn't. It escapes from outside the event horizon. The event horizon is the dark area in the middle.
I am not trying to throw cold water on this, but I have some questions. This ted talk has a very basic explanation of how they constructed this image. I was curious if anyone with image interpolation experience could weigh in on the method. https://www.youtube.com/watch?v=P7n2rYt9wfU When she first starts explaining their method around 8:00m in, I was initially very skeptical of this result because she said that they…
With interferometry, you're getting an incomplete sampling of the Fourier transform of the sky image, and if you just invert the samples, you get what we call a "dirty" image.
But you know your sampling of the Fourier plane exactly, since that's just a function of the projected baselines between every pair of telescopes during the observation, so you can create a "dirty beam" - now all you have to do is remove the effects of the dirty beam from the dirty image. Of course, that's a deconvolution problem, and given that you don't have all the information - you sampled it - it can never be exact.
But it can be very good! There are very sophisticated radio synthesis image deconvolution algorithms, including CLEAN and Maximum Entropy. For Maximum Entropy methods, you can apply a Bayesian prior on your images - most of the time, the prior we apply is a blank sky (seriously!) but if we have other constraints that we can use (e.g., the approximate size of the region with extended emission), Bayes tells us that we would be remiss not to use it.
If you look at this image [1] from Paper IV [2], we show the image results from different techniques on different observing days. Those are the inputs to what is the "consensus image" - you can check how close they all are to each other.
Does that make sense...?
[1] https://iopscience-event-horizon.s3.amazonaws.com/2041-8205/... [2] https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85
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I wonder how important time is in collecting these data? Because if 6 months isn’t an issue, then the array size could be expanded in one axis to the diameter of Earth’s orbit around the sun, no?
The collecting time is important, but mainly to 1) sample the rotation of the Earth in the Fourier space for better angular resolution and 2) for raising your overall signal-to-noise ratio is the image (but the one released is already pretty good, so not much improvement can be done there unless you're trying to go for the faint features in the image). Unfortunately, you can only do interferometry with simultaneous m…
We seem to need a big radiotelescope on the moon then? That should give simultaneous measurement on a much larger baseline?
Higher resolution official release seems to be: https://www.nsf.gov/news/special_reports/blackholes/download...
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That's also not even wrong. You can't see why? Let's say we're imagining what Uranus would look like. I draw a picture, and say it should look like a "fuzzy Jupter." But you ask, why should it look that way? Do you have a reason? And I say you should be confident, but don't provide an argument. By the end, I start talking about how it might look like Saturn. Then I come along and say, "it should be obvious the fuzzin…
Are you upset that the Veritasium video didn't explicitly spell out for you that this black hole is very far away, so the first image of it ever is basically certain to be fuzzier than IMAX fidelity computer simulations used in a Hollywood movie? I think you're being very silly.
Earlier quoted context omitted.
Are you upset that the Veritasium video didn't explicitly spell out for you that this black hole is very far away, so the first image of it ever is basically certain to be fuzzier than IMAX fidelity computer simulations used in a Hollywood movie? I think you're being very silly.
What? You obviously didn't read what I wrote.
You're ranting about Saturn and Jupiter for some reason. Why don't you calm down and look at page eight of the paper that Veritasium video was based on: https://ve42.co/luminet "Image of a spherical black hole with thin accretion disk Astronomy and Astrophysics, vol. 75, no. 1-2, May 1979, p. 228-235"
Look at that last image, and squint at it until it gets fuzzy. Lo and behold, a fuzzy coffee mug stain!
Perhaps it was a mistake for him to make the focus of the video on the physics of black holes, rather than the limitations of state of the art radio interferometry... but I don't think so.
I'm wondering if there is a way to do it with holograms (since they preserve phase information): take holograms of the object from opposite sides of the earth and then combine them offline. There are some papers in this direction:
https://hal.archives-ouvertes.fr/hal-00654840/document
(spy satellites probably already do it...)
Good video that correctly predicted the image and describes why it looks the way it does [1]. TL; DR The dark area is the entire surface of the event horizon, including the side facing away from us, plus some more due to photons missing the event horizon "directly" being drawn in. One side is brighter due to its being Doppler boosted. [1] https://www.youtube.com/watch?v=zUyH3XhpLTo
One day we may even connect millions of smartphones to observe various interesting space phenomena.
