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Roger Penrose claims our Universe has been through multiple Big Bangs

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Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#231

Post by slowmovintarget »

sangnoir wrote: post #228
slowmovintarget wrote: post #111

Earlier quoted context omitted.

That's the point. Penrose's ideas are worth taking seriously because they are directly in line with his field of expertise, and there are means supplied in his papers to rule the ideas out (predictions that should hold true on data we are able to measure). This was a contrast, not an analogy.

What data do we have from the time before the big bang?

His papers present things to look for in the current cosmic microwave background that would be evidence. In other words, data we have access to.

He's made some claims that these "circles" have been found, as some colleagues of his are working on making such observations. Those "circles" have not been independently verified, however, nor is it yet possible to rule out process error in the data, or the observations calculated from the data.

The CMB should show cold spots from evaporated black holes that have expanded to several arc-seconds in diameter. It requires very sensitive survey data, though.

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#232

Post by bazoom42 »

GalenErso wrote: post #44
bazoom42 wrote: post #39

Earlier quoted context omitted.

Does the child abuse bother you?

Yes. It's not going to erode my faith, since I'm loyal to Christian values and principles more than any individuals, but the things some of these people in power have done are unacceptable, immoral, and fundamentally un-Christian, and they should be held accountable.

As a non-religious person, it is hard to grasp the mindset where one can denounce the abuse in words, but in actions support the institution which perpetrated the abuse and protected the abusers. But I understand faith is not rational.

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#233

Post by mr_mitm »

likeabbas wrote: post #230
mr_mitm wrote: post #227

Earlier quoted context omitted.

> There’s also solutions to FTL travel that don’t have to violate causality. Space itself is expanding faster than light. But you can't use expansion of space to move matter or to travel. You could even argue that distant galaxies aren't even moving at all, they just appear to do so because the distance between them and us increases. Comparing velocities of distant objects in curved spacetime is tricky in general.

The Alcubierre drive gets around this by bending the spacetime around a craft so that portion of space is moving and not the craft through space. And beyond that, traversable wormholes aren’t completely ruled out yet

Yes, I will happily concede that time travel and FTL is possible with wormholes. I would even buy into Novikov's self-consistency principle to avoid paradoxes.

However, to manipulate spacetime like that, we'd have to control massive quantities of an never observed type of energy. Like, on the order of the mass of the galaxy, or at least solar masses. And constructing a wormhole between A and B will still take longer than light travels between the endpoints, so I'm not exactly holding my breath.

The Alcubierre drive (assuming it's feasible) will still violate causality though, and the self-consistency principle does not apply, so I'm convinced that's a bust.

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#234

Post by arp242 »

wswope wrote: post #131
truculent wrote: post #14

IANAP - why are these ideas so controversial? The article seems to suggest he has some (potentially) supporting evidence, and I don't have an intuition for how damning the counter-argument is ("This would necessitate making all particles lose mass as the universe gets old." Again, IANAP and physics can get weird).

Since I haven’t seen anyone else mention this bit of context elsewhere in the thread: Penrose gets a bit of side-eye in the physics community because of his metaphysical beliefs on consciousness. (Specifically, that quantum effects in tubule proteins of the brain produce special nondeterministic effects that constitute our conscious essence, and true consciousness is impossible without this nondeterministic fount of…

> He’s clearly a smart guy… but also has some hot takes.

I'm good with that as Penrose is very clear where the uncontroversial science ends and the hot takes begin; he doesn't try to "peddle" anything. "Here is my hot take and this is the TRUTH" is something I have problems with, "here's my hot take a lot of people will disagree with, but I think it may be true because [...]" isn't; and is often even valuable even if the hot take turns out to be wrong, because it exposes shortcomings, omissions, or other things that are not yet entirely clear.

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#235

Post by likeabbas »

mr_mitm wrote: post #233
likeabbas wrote: post #230

Earlier quoted context omitted.

The Alcubierre drive gets around this by bending the spacetime around a craft so that portion of space is moving and not the craft through space. And beyond that, traversable wormholes aren’t completely ruled out yet

Yes, I will happily concede that time travel and FTL is possible with wormholes. I would even buy into Novikov's self-consistency principle to avoid paradoxes. However, to manipulate spacetime like that, we'd have to control massive quantities of an never observed type of energy. Like, on the order of the mass of the galaxy, or at least solar masses. And constructing a wormhole between A and B will still take longer…

Our prevailing theory of quantum mechanics is QFT which suggests that there aren’t actually any individual particles, but fields that experience excitations which act like individual particles. If we find that gravity is also just a field and gravitons are excitations within the field, who’s to say that perhaps every excitation in that field is entangled in some sort, and to create a traversable wormhole to the other end of the galaxy, we only need to impact the gravitons around us?

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#236

Post by GoblinSlayer »

jbotz wrote: post #207
GoblinSlayer wrote: post #204

Earlier quoted context omitted.

Because universe is a physical structure, not mathematical, e.g. you can't define things into existence.

Is it? Says who? This is an untirely unfalsifiable assumption. I personally don't share it. "It from bit"[0], I say, mathematics is fundamental, physical reality is just our perception of the underlying math. [0] Title of a paper by John Wheeler. Can't find it right now, but if you google "it from bit" you'll find a lot of commentary on it.

Found commentary on "it from bit". It looks like an attempt to resurrect antirealism (participatory universe). The reason why antirealism was buried is because there's too much realism in quantum physics, so it won't fly.

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#237

Post by imbnwa »

schiffern wrote: post #162
sidcool wrote: post #154

The concept of infinity seems impossible to me in physical world. It's a great mathematical concept to model our understanding. Just like imaginary numbers. I cannot imagine anything being infinite in the physical world. I find the simulation hypothesis more probable than Universe being infinite. Space and Time is not infinite. It may be Gazillions of centuries old, but not infinity. It can't be.

>infinity seems impossible to me "Me," in this case, is a microcontroller that evolved to move muscles on a primate body effectively. Do we have any reason to believe such a system should be capable of grasping the true nature of the universe? After all, it's far outside the design spec!

>"Me," in this case, is a microcontroller that evolved to move muscles on a primate body effectively.

Distinction between brain and body not really a thing though, yeah?

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#238

Post by tcmart14 »

sitkack wrote: post #153
tcmart14 wrote: post #148

Earlier quoted context omitted.

Yea, that is my understanding. He does call it a crazy theory, but its a whole different kind of crazy that most people think of. I've listened to him talk about it and yea, when you actually listen to him you get the vibe of, "its an interesting idea that the math can't really prove or disprove, it may not be right, but it is an interesting thought experiment." I would say it is a step below Fred Hoyle. For those wh…

Should we entertain unfalsifiable theories?

I should have also been a little more specific with the "the math doesn't prove or disprove it" as in, "the math as it currently stands does not prove or disprove it." Which is true of a lot of theories in physics. There is a possibility and the math and experimentation isn't there yet to decide if the theory is correct or not. Not that the math will never come, but the equations are not there today.

To answer the question, within reasonable limits, yes. If it is a thought experiment to provoke looking at a problem a different way, it could be useful. While Fred Hoyle's steady state theory didn't hold much water, using it as a basis to analyze certain problems, he was able to held figure out Nucleosynthesis. The problem is knowing the reasonable limits. Like, don't let it consume your entire life's work and use it as a means to analyze a problem from a different angle.

In context of Roger Penrose, it may be illuminating. Right now, I imagine most are trying to solve the problem starting at the big bang and working backwards. Penrose is essentially trying to pick some arbitrary potential solution and asking, "if this is true, what else must be true" and seeing if he can work his way forward to the Big Bang or not.

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#239

Post by tcmart14 »

GoblinSlayer wrote: post #214
namaria wrote: post #209

Earlier quoted context omitted.

There is no historical record of such controversy. It's an easy question to answer with basic astronomy and geometry. The controversy is a modern manufacture and the cartoon trope of old timey misconceptions about the shape of Earth is not based on evidence. Those in a position to ask the question have always been in a position to reach the obvious answer.

Do you want to say that people didn't believe in flat earth?

I would say, if you go back 2,000 years, most people probably never considered the question or cared. The ones who did were a small number of intellectuals. At some point, there probably was a debate among those. The peasants out in the field? Didn't know and probably didn't care and didn't matter.

Re: Roger Penrose claims our Universe has been through multiple Big Bangs

#240

Post by ajkjk »

likeabbas wrote: post #224
simonh wrote: post #210

Earlier quoted context omitted.

Just to nitpick, the Casimir effect only produces negative pressures relative to the vacuum energy. They're not truly negative. Just in case anyone reading that misunderstands. Also 'violates causality' is an awful lot to unpack, and is glossing over so much nuance that I don't think it's really a meaningful thing to say. For example violation of the Bell inequalities does not rule out superdeterminism, and that has…

You left one portion out of the explanation of the Casimir effect > The Casimir effect shows that quantum field theory allows the energy density in certain regions of space to be negative relative to the ordinary vacuum energy, and it has been shown theoretically that quantum field theory allows states where the energy can be arbitrarily negative at a given point.[57] Many prominent physicists such as Stephen Hawking…

Well it's not that weird to say "no, FTL travel is impossible" compared to the alternative "FTL travel is possible". The prevailing theories clearly say it's not; why would scientists proclaim anything contrary to that? Of course they want as much as anyone to prove the current theories wrong, but it would still be negligent to go around saying anything other than what the theories actually say to the laypeople.
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