Live data from Hacker News

Emergent Gravity and the Dark Universe

arxiv.org

21–30 of 85 posts

Re: Emergent Gravity and the Dark Universe

#21

Also, a simple explanation for the layman: http://www.alphagalileo.org/ViewItem.aspx?ItemId=169788&Cult...

Thanks for the layman link... I started reading and encountered a concept I didn't understand so I googled it. Then, I encountered another concept I didn't understand and google that, again and again, until I was several pages deep and only on the second sentence of the paper's description. TIL I don't know as much as I thought.

Re: Emergent Gravity and the Dark Universe

#22
post #15

So I too love the idea that we don't need dark matter to explain all the gravitational effects we observe in the universe. However, is it just me or does the falsification of this seem a bit sketchy: if we find a dark matter particle...then my theory is false. That's a bit like saying...oh yeah if we find a different way to unify general relativity and quantum mechanics...then String Theory is false. It seems like th…

Remember that these people use a language that might sound similar to common english, but words have different meaning and it is much more precise. No reading between the lines.

He gave an example of what would falsify his theory, that is all.

Re: Emergent Gravity and the Dark Universe

#23
post #9

Earlier quoted context omitted.

> even though we've supposedly observed [gravitons] now Source? Or are you saying that the existence of gravitational waves constitute a proof of the existence of gravitons, due to wave/particle duality? I'm not a physicist, but all I thought we had detected were gravitational waves.

> the existence of gravitational waves constitute a proof of the existence of gravitons, due to wave/particle duality I always thought this is the case. But IANAP either. Could anyone with actual knowledge chime in?

No, a gravitational wave has mass (carries mass is more accurate), but a graviton does not. They are not two aspects of the same thing.

Re: Emergent Gravity and the Dark Universe

#24

Like others have mentioned I'm not sure what happens now to the gravity waves we've detected.

I'm not convinced we have in fact detected gravity waves. From our point of view merging black holes would not move due to time dilation, but the waves detected are modeled after black holes without time dilation.

Although it's possible we detected a wave from a different source, not a black hole.

Re: Emergent Gravity and the Dark Universe

#25
In the summary, it says that these theories are "best understood in Anti de Sitter space...". I thought current observations ran against a spacetime that had a negative curvature. Are they just saying the math is easier in that geometry, but that it still applies to flat (or ever-so-slightly-positively curved) spacetime? Or are they arguing in favor of a "saddle-shaped" universe?

Re: Emergent Gravity and the Dark Universe

#28

In the summary, it says that these theories are "best understood in Anti de Sitter space...". I thought current observations ran against a spacetime that had a negative curvature. Are they just saying the math is easier in that geometry, but that it still applies to flat (or ever-so-slightly-positively curved) spacetime? Or are they arguing in favor of a "saddle-shaped" universe?

The ADS in 'ADS/CFT correspondence' stands for 'anti-de Sitter'. Any time you read someone talking about 'information on the boundary' of a bulk space, that's usually what they're working with.

I'm sure there's a way to transform everything to a de Sitter space, but i'm neither a mathematician nor a physicist, so I don't know how it's done...

Re: Emergent Gravity and the Dark Universe

#29
post #13

I'm currently reading The Confusion [0] and just got through Leibniz's explanation of monadology [1][2]. Summarized very very briefly, the idea is that every particle in the universe is a sort of computational device, and their actions/reactions are determined by their "perception" of all the other particles in the universe. Does this research suggest that he may have been semi-correct?? [0] https://en.wikipedia.org/…

Frankly, I'd be surprised if anything ever suggested that Leibniz's colorful metaphysics was correct, even or incorrect.

Leibnizian monads are unextended and unable to act on one another (from §1 and §7 of the Monadology), which is to say that they're non-physical. On the other hand, as they're somehow supposed each to have a complete picture to the world (§56), they imply some form of non-locality. Which is to say that they're some very spooky things.

The thing that comes closest to Leibniz's monadology is the idea that the world is a simulation running inside a computer. But Leibniz's idea was more like that there is an arbitrarily large number of computers running the same simulation, while some of them also run artificial intelligences which just watch the simulation unfold.

Which is an idea I think can be fairly described as "completely nuts".

Re: Emergent Gravity and the Dark Universe

#30
post #23

Earlier quoted context omitted.

> the existence of gravitational waves constitute a proof of the existence of gravitons, due to wave/particle duality I always thought this is the case. But IANAP either. Could anyone with actual knowledge chime in?

No, a gravitational wave has mass (carries mass is more accurate), but a graviton does not. They are not two aspects of the same thing.

In a quantum field theory, a wave implies a force carrying particle, does it not?
Post reply on HN