Live data from Hacker News

A wandering black hole caught feeding on the run

phys.org

1–10 of 26 posts

Re: A wandering black hole caught feeding on the run

#4
While the conclusions of the observation are interesting, what really stood out to me was the observations themselves. That black hole is 20 million light years away, in another galaxy! And we have multiple high enough resolution observations to conclude how the gas orbits the black hole and gets dragged along behind it. That's nuts.

Re: A wandering black hole caught feeding on the run

#6

While the conclusions of the observation are interesting, what really stood out to me was the observations themselves. That black hole is 20 million light years away, in another galaxy! And we have multiple high enough resolution observations to conclude how the gas orbits the black hole and gets dragged along behind it. That's nuts.

What blows my mind is that 20 million light years also means that what we're observing something that happened 20 million years ago. We're looking into the very distant past, at something that might well no longer exist.

Turn that around and there well could be other lifeforms observing the Earth with dinosaurs roaming around on it. Perhaps observing the impact of a giant meteor onto the earth.

The light of that meteor impact on Earth is still roaming the universe. If only we could travel faster than that light.

Re: A wandering black hole caught feeding on the run

#7

While the conclusions of the observation are interesting, what really stood out to me was the observations themselves. That black hole is 20 million light years away, in another galaxy! And we have multiple high enough resolution observations to conclude how the gas orbits the black hole and gets dragged along behind it. That's nuts.

What blows my mind is that 20 million light years also means that what we're observing something that happened 20 million years ago . We're looking into the very distant past, at something that might well no longer exist. Turn that around and there well could be other lifeforms observing the Earth with dinosaurs roaming around on it. Perhaps observing the impact of a giant meteor onto the earth. The light of that met…

What is even more crazy is that we can actually look as far as the beginning of the universe just because of how long it takes for particles from the other side of the universe to reach us.

Re: A wandering black hole caught feeding on the run

#8

Earlier quoted context omitted.

What blows my mind is that 20 million light years also means that what we're observing something that happened 20 million years ago . We're looking into the very distant past, at something that might well no longer exist. Turn that around and there well could be other lifeforms observing the Earth with dinosaurs roaming around on it. Perhaps observing the impact of a giant meteor onto the earth. The light of that met…

What is even more crazy is that we can actually look as far as the beginning of the universe just because of how long it takes for particles from the other side of the universe to reach us.

I’m not a science person but I think I understand the crux of what you’re saying here - have a question though: are those particles finite? And those are light particles, right? Is the number of those particles increasing the longer they travel?

Sorry if questions don’t make sense…

Re: A wandering black hole caught feeding on the run

#9
post #8

Earlier quoted context omitted.

What is even more crazy is that we can actually look as far as the beginning of the universe just because of how long it takes for particles from the other side of the universe to reach us.

I’m not a science person but I think I understand the crux of what you’re saying here - have a question though: are those particles finite? And those are light particles, right? Is the number of those particles increasing the longer they travel? Sorry if questions don’t make sense…

The commenter is referring to the Cosmic Microwave Background (CMB). Whilst most of the universe is a dark void, if you tune a radio to a certain frequency, there's a faint, static buzz in the microwave part of the spectrum. It is heard no matter which direction you point the dish. This is a left-over from the Big Bang and started out as light but due to the expansion of space, the wavelength has increased, and that's why it's now received in the microwave part of the spectrum. There are lots of great explainers on the CMB and the history of its discovery is entertaining too. One of the easier concepts in cosmology, and one of the most important.

Re: A wandering black hole caught feeding on the run

#10

While the conclusions of the observation are interesting, what really stood out to me was the observations themselves. That black hole is 20 million light years away, in another galaxy! And we have multiple high enough resolution observations to conclude how the gas orbits the black hole and gets dragged along behind it. That's nuts.

What blows my mind is that 20 million light years also means that what we're observing something that happened 20 million years ago . We're looking into the very distant past, at something that might well no longer exist. Turn that around and there well could be other lifeforms observing the Earth with dinosaurs roaming around on it. Perhaps observing the impact of a giant meteor onto the earth. The light of that met…

  > What blows my mind is that 20 million light years also means that what we're observing something that happened 20 million years ago.
Well... Not really. It took the entirety of the book A Brief History Of Time to even grasp a cusp of this, so I know I won't convince you in a short HN comment, but "now" is the collection of events that currently affect us. Due to causality, events outside our light cone have not occurred yet. They have no more influence than does an egg falling off the counter that has yet to hit the floor. The egg breaks only when it hits the floor - events only occur in our reference frame when they could affect outcomes in our reference frame. C is the propagation of causality, the fact that light travels at that speed in a vacuum doesn't affect that.
Post reply on HN