10 ms·
I didn’t realize until recently that supermassives and classic black holes are formed differently. https://en.wikipedia.org/wiki/Supermassive_black_hole https:
by melling 7y ago
I didn’t realize until recently that supermassives and classic black holes are formed differently.
https://en.wikipedia.org/wiki/Supermassive_black_hole https://en.wikipedia.org/wiki/Supermassive_black_hole
It’s also fun to remember that this event happened 26,000 years ago.
- kickopotomus 7y ago> It’s also fun to remember that this event happened 26,000 years ago. This is one of my favorite (but also the most daunting) things about space. It is so awesome (and bizarre) that we can essentially observe the past. In this case, the event occurred sometime around when humans were figuring out how to make baskets[1]. [1]: https://en.wikipedia.org/wiki/Timeline_of_human_prehistory https://en.wikipedia.org/wiki/Timeline_of_human_prehistory
- pacala 7y agoAlternatively, the present is the weighted average of past causal influences. This event had no causal influence over the humans figuring out how to make baskets. From Earth perspective, the event just happened.
- ggggtez 7y ago>weighted average No, the averages ignore input order. Reality is order dependent.
- DecoPerson 7y agoSo a photon emitted/reflected by some human weaving a basket may have just interacted with the Milky Way's supermassive black hole!
- bouncycastle 7y ago...and a gamma ray burst from some distant galaxy that will strike Earth sometime in the future causing a great catastrophy could have already happened while the human was putting on the finishing touches on the basket.
- deleted 7y ago[deleted]
- JohnJamesRambo 7y agoI really like this thought.
- BurningFrog 7y agoYou might not be ready for this, but: The past is the only thing we can observe!
- lioeters 7y agoHmm, isn't the present the only thing we can observe? All the past we see is whatever effect left over now.
- ddingus 7y agoLatency between perception or measurement and reality insures we are always behind. The info has to take time to travel.
- bojo 7y agoWell, to be incredibly pedantic, it takes time for the light being reflected off of things to reach your eyes and be processed by your brain, so you are always observing the past even if it isn’t remotely perceivable :)
- lioeters 7y agoGood point, I did think about the latency after I posted the comment. (Apparently about 13ms between photons hitting the eyes and the brain recognizing it.) Would the statement stand if it were updated to say, "The (presentMoment - latency) is the only thing we can observe"? Perhaps "experience" instead of "observe" would have fit better - although, experience by definition is only in the present, otherwise it would be a memory. Then a counter argument might be: everything is memory, even the current moment being experienced. I suppose that sliver of "now" might be infinitesmal, approaching zero..
- kickopotomus 7y agoYeah but that's being rather disingenuous. 99.9% of the time, the time difference between when an event occurs and when we perceive it is negligible. In situations on the universal scale, it is incredible to know that no matter what, we will only be able to see the distant past (thousands to millions of years) for most other celestial bodies.
- bgeeek 7y agoAnd some of them fish that were around then are... well, still fish. Not sure I like the reference of humans in the example :)
- Aperocky 7y agoStrictly speaking, it happened _now_ in our own timeline, whether it happened 26K years in the past for the blackhole is a mystery as everyone gets their own timeline and we have no idea (read: can only reasonably conjecture) what the future timeline for that black hole is until it gets to us.
- slg 7y ago>whether it happened 26K years in the past for the blackhole is a mystery Wouldn't it have occurred much less than 26,000 years ago from the perspective of the black hole due to time dilation caused by the difference in gravitational potential of the blackhole compared to us?
- xadhominemx 7y agoNo, it happened 26,000 years ago in our time frame as well
- candiodari 7y agoI don't get how that works. 26,000 years ago it would have been FAR outside of our "light cone". In other words it was completely beyond anything that affected our world. Only recently that changed. So doesn't it make sense that it only became part of reality yesterday ? And therefore to say that it happened yesterday. The famous supernova of 1572 AD also very much didn't happen anywhere close to 1572 AD.
- Legogris 7y agoSo let's say you travel at the speed of light towards that event. When you arrive, 26,000 years later, would you then say the event happened 26,000 or 52,000 years ago? If the former, have you just travelled 26,000 years into the past, or did time stand still for 26,000 years from your perspective? I'd argue your clock has still moved forward 26,000 years. If we would take a snapshot of the Universe VM spacetime at the current moment at the start of the event, the "now" in time would have to correspond to the current state for every other location if you want it to be useful and not only intuitive.
- tyrust 7y ago>It’s also fun to remember that this event happened 26,000 years ago. Tweet from the author saying this, in case anyone else was looking for a citation: https://twitter.com/quantumpenguin/status/1160708885260328960 https://twitter.com/quantumpenguin/status/116070888526032896...
- belorn 7y agoIn comparison, when we look at the sun it is 8m and 20s in the past and the moon 1.3s.
- antognini 7y agoThe Wikipedia article says this, but for those who just read the comments, the formation of supermassive black holes (SMBHs) is very much an open problem! There are two main theories here: 1. You have a collection of black holes that formed from stars in a very dense cluster at the nucleus of the Galaxy early in its life that all merged to form an intermediate mass black hole, which then grew into a SMBH. 2. An intermediate mass black hole formed directly from the direct collapse of a large gas cloud and then grew into a SMBH. But even the better known case of the formation of stellar mass black holes is still not well understood!
- MichaelDickens 7y ago> 2. An intermediate mass black hole formed directly from the direct collapse of a large gas cloud and then grew into a SMBH. Based on my limited understanding of cosmology, wouldn't the gas first form a star, and not form a SMBH until the star's nuclear reaction became too weak?
- andrewflnr 7y agoPut enough mass in the right radius and fusion can't do jack about it. Over a large enough area, IIRC it doesn't actually take a very high density, so it never has to reach a point where it can fuse before the event horizon forms.
- Anarch157a 7y agoI recall someone calculating that a sphere of gas with a radius equal to Neptune's orbit, with the same density of air at sea level would mass 4 million solar masses. That means if we filled thw Solar system with air, it would form a SMBH.
- a1369209993 7y agoNot if the gas cloud is large enough. Small gas clouds (white dwarfs, neutron 'star's) produce enough presure from particle degeneracy to support themselves against gravity, medium clouds (stars) need active heating (from fusion) to keep gas particles moving fast enough to remain far enough apart to avoid forming a black hole, and for sufficiently large clouds even having the gas particles moving at the speed of light wouldn't be enough to avoid forming a black hole.
- hgl 7y agoI wonder if there exists a sci-fiction that talks about how human beings detect something disastrous happened to Sgr A* and realize that happened 26,000 years ago then try to leave the Milky Way in panic.
- ridgeguy 7y agoYes, there is. But it isn't humans who first discover our galaxy's core explosion, but Pierson's Puppetteers (1). Fun stories by Larry Niven in his "Known Space" series. (1) https://en.wikipedia.org/wiki/Pierson%27s_Puppeteers https://en.wikipedia.org/wiki/Pierson%27s_Puppeteers