Oh, thanks Christian. I haven't read it yet, but it looks extremely interesting. Not sure how it fits in until I read it, but it's encouraging that he appears to take seriously the idea that, at the other side of a black hole, there is ... something, emerging somewhere (and somewhen).
Hi Julian! A question I’ve had about the Evolved Universe model but didn’t want to go back and comment on an old post: in this model, black holes in one universe are the big bangs of the offspring universes—more black holes, more offspring. Does this not imply that each of the offspring universes has less total mass, by a huge factor? At some point do you run into a mass limit as you divide up the available mass into more and more offspring? Or am I missing something?
Nathan! Lovely to see you here. And I'm delighted you asked that particular question, because by a happy coincidence I just answered it, in a post I haven't quite finished (but plan to put up soon). But yeah, it's a question that I think occurs to a lot of people when they first read about these ideas. (It certainly occurred to me). I've seen Lee Smolin asked it a couple of times at lectures and conferences. Luckily for the theory, it's got a simple answer: you can make a universe out of nothing, because all the positives and negatives in our universe (all the positive and negative electric charges; all the positive mass energy and negative gravitational energy...) net out to zero. In particular , mass energy and gravitational energy cancel out, so the net mass/energy of our universe is, we now assume, very likely zero. So you could make our entire universe from nothing at all... If you don't believe me, let me hand over to the great Stephen Hawking, who gave a nice explanation in straightforward language in his book Brief Answers to the Big Questions...
"The laws of physics demand the existence of something called 'negative energy'. To help you get your head around this weird but crucial concept, let me draw on a simple analogy. Imagine a man wants to build a hill on a flat piece of land. The hill will represent the universe. To make this hill he digs a hole in the ground and uses that soil to dig his hill. But of course he’s not just making a hill—he’s also making a hole, in effect a negative version of the hill. The stuff that was in the hole has now become the hill, so it all perfectly balances out. This is the principle behind what happened at the beginning of the universe.When the Big Bang produced a massive amount of positive energy, it simultaneously produced the same amount of negative energy. In this way, the positive and the negative add up to zero, always. It’s another law of nature. So where is all this negative energy today? It’s in the third ingredient in our cosmic cookbook: it’s in space. This may sound odd, but according to the laws of nature concerning gravity and motion—laws that are among the oldest in science—space itself is a vast store of negative energy. Enough to ensure that everything adds up to zero."
Maybe I'll take a guess at this. I kind of suspect that's a way in which our Newtonian understanding of things might not work. Conservation of mass works well within the universe, but it probably is not the case when big bangs are involved.
Hi Patrick! Yeah, you are right, for the reasons I outlined above to Nathan. It's counterintuitive, from where we are standing inside what feels like a Newtonian world where mass is conserved, but universes themselves can in fact come from nothing...
Glad you’re so excited about the new data & providing us an interpretation for it!!! Usually, I would caution one to be wary of confirmation bias when reviewing new data, but in this case the data lines up well enough with the hypothesis given prior that it really qualifies more as a successful hypothesis test. I wouldn’t tell someone that predicted a rock would fall then dropped the rock that it was confirmation bias, now would I? Doesn’t rule out flaws in the original hypothesis of course, but I think this simply gives more room for refinement than anything!
I’m especially curious about fixed mass limitations and what we may learn in that direction. Going by pure intuition here, I imagine each child universe will have some small fraction of the mass available to the parent universe, which would lead to exponentially larger structures going up and exponentially smaller structures going down. Would these early-universe-structures tell us otherwise? We’re seeing unfathomably massive amounts of rotational energy: could that be passed on in substantial enough volumes that the amount of mass needed to populate a universe is negligible?
(My bad if this was already discussed; I’m reading random articles as I go.)
Just read about this and wondered if you had thoughts about how it fits (or not) with evolved universes;
https://www.theguardian.com/books/2023/oct/30/white-holes-inside-the-horizon-carlo-rovelli-review-black-hole-quantum-physics
Oh, thanks Christian. I haven't read it yet, but it looks extremely interesting. Not sure how it fits in until I read it, but it's encouraging that he appears to take seriously the idea that, at the other side of a black hole, there is ... something, emerging somewhere (and somewhen).
Hi Julian! A question I’ve had about the Evolved Universe model but didn’t want to go back and comment on an old post: in this model, black holes in one universe are the big bangs of the offspring universes—more black holes, more offspring. Does this not imply that each of the offspring universes has less total mass, by a huge factor? At some point do you run into a mass limit as you divide up the available mass into more and more offspring? Or am I missing something?
Nathan! Lovely to see you here. And I'm delighted you asked that particular question, because by a happy coincidence I just answered it, in a post I haven't quite finished (but plan to put up soon). But yeah, it's a question that I think occurs to a lot of people when they first read about these ideas. (It certainly occurred to me). I've seen Lee Smolin asked it a couple of times at lectures and conferences. Luckily for the theory, it's got a simple answer: you can make a universe out of nothing, because all the positives and negatives in our universe (all the positive and negative electric charges; all the positive mass energy and negative gravitational energy...) net out to zero. In particular , mass energy and gravitational energy cancel out, so the net mass/energy of our universe is, we now assume, very likely zero. So you could make our entire universe from nothing at all... If you don't believe me, let me hand over to the great Stephen Hawking, who gave a nice explanation in straightforward language in his book Brief Answers to the Big Questions...
"The laws of physics demand the existence of something called 'negative energy'. To help you get your head around this weird but crucial concept, let me draw on a simple analogy. Imagine a man wants to build a hill on a flat piece of land. The hill will represent the universe. To make this hill he digs a hole in the ground and uses that soil to dig his hill. But of course he’s not just making a hill—he’s also making a hole, in effect a negative version of the hill. The stuff that was in the hole has now become the hill, so it all perfectly balances out. This is the principle behind what happened at the beginning of the universe.When the Big Bang produced a massive amount of positive energy, it simultaneously produced the same amount of negative energy. In this way, the positive and the negative add up to zero, always. It’s another law of nature. So where is all this negative energy today? It’s in the third ingredient in our cosmic cookbook: it’s in space. This may sound odd, but according to the laws of nature concerning gravity and motion—laws that are among the oldest in science—space itself is a vast store of negative energy. Enough to ensure that everything adds up to zero."
Here's Wikipedia's entry on a zero-energy universe, which gives the history of the idea: https://en.wikipedia.org/wiki/Zero-energy_universe
So, yeah, there is no constraint on reproduction. A universe can bang out any number of new universes. Wild, huh?
So it's basically like the virtual particle situation, but on the scale of an entire universe! Wild.
Maybe I'll take a guess at this. I kind of suspect that's a way in which our Newtonian understanding of things might not work. Conservation of mass works well within the universe, but it probably is not the case when big bangs are involved.
Hi Patrick! Yeah, you are right, for the reasons I outlined above to Nathan. It's counterintuitive, from where we are standing inside what feels like a Newtonian world where mass is conserved, but universes themselves can in fact come from nothing...
Glad you’re so excited about the new data & providing us an interpretation for it!!! Usually, I would caution one to be wary of confirmation bias when reviewing new data, but in this case the data lines up well enough with the hypothesis given prior that it really qualifies more as a successful hypothesis test. I wouldn’t tell someone that predicted a rock would fall then dropped the rock that it was confirmation bias, now would I? Doesn’t rule out flaws in the original hypothesis of course, but I think this simply gives more room for refinement than anything!
I’m especially curious about fixed mass limitations and what we may learn in that direction. Going by pure intuition here, I imagine each child universe will have some small fraction of the mass available to the parent universe, which would lead to exponentially larger structures going up and exponentially smaller structures going down. Would these early-universe-structures tell us otherwise? We’re seeing unfathomably massive amounts of rotational energy: could that be passed on in substantial enough volumes that the amount of mass needed to populate a universe is negligible?
(My bad if this was already discussed; I’m reading random articles as I go.)