Open thread, Apr. 10 - Apr. 16, 2017

relativistic mass

That's not a very useful concept, because it's nothing but the total energy measured in different units. It only has a name of its own for hysterical raisins. A much more useful concept is the invariant mass, which is the square root of the total energy squared minus the total momentum squared (in suitable units), which (as the name suggests) is the same in all frames of references; in particular, it equals the total energy in the frame of reference where the total momentum is zero. Nowadays when people say "mass" they usually mean the invariant mass, because it makes more sense to call the relativistic mass "total energy" instead.

I don't like this solution.

But it's the standard way the luminosity distance is defined.

There is nowhere the speed of light to be seen there.

Units with c = 1 are used in the formulas.

OTOH, the "curvature of space" they mention, is not very necessary in our flat space.

Space alone is flat (within measurement uncertainties), but space-time is curved, because space expands with time.

But the Lorentz factor would be needed here.

It's not the easiest way to treat objects moving with the Hubble flow...

Not only for the time dilatation factor, by which the energy output is to be reduced - but also for the relativistic mass increase by the same factor.

Yes, there are two (1+z) factors, one because fewer photons are emitted per unit time because "time was slower back then" (I know, not a very clear way to put it) and one because each photon is redshifted. The luminosity distance is defined with one (1+z) factor so that when you divide by its square you get (1+z)^-2.

And for the length contraction as well!

No, because we're talking about the total luminosity of the galaxy -- if its length is contracted and its luminosity density is increased by the same factor, nothing changes.

That's the real problem, I think.

What do you mean? It's not like this is an open question in cosmology. The implications of the FLRW metric have been well known for decades.

It's all baked into z.

z is defined based on frequency change but the frequency change must also be the amount it appears to be slowed down, since e.g. you could measure the number of peaks in a light wave coming from a galaxy as a measure of time.

For the benefit of others: in making this post Thomas is I expect motivated by my responses to his post here:

https://protokol2020.wordpress.com/2013/09/06/embarrassing-images/#comments

In an edit to my last comment, Thomas wrote:

you must get an apparent slowdown proportional to the ratio of frequencies, because the frequency is itself a measurement of time.

That is NOT true AT ALL! Time dilatation IS NOT linear. NOT AT ALL.

And what about blue shift galaxies? Do you think they speed up their internal clock?

I will not approve such comments anymore. You have to know the basic stuff.

In reply about the blue shift galaxies: they will indeed appear to be sped up from our perspective. Something moving toward us is slowed down in our reference frame by time dilation, but also appears sped up because light takes less and less time to get here. As with redshift, both of these effects are baked into z, so the final (apparent) speedup is what you get from z.

I really like the idea, but agree that it is sadly not the right thing here. It would be a fun addition to an Arbital-like site.

Hmm, so some of this sounds like I may misunderstand the terminology of academic philosophy. I'm trying to learn it, but I generally lack a lot of context for how the terminology is used so I largely have to go with what I find to be the definitions suggested by summary articles as I find I want to talk about some subject. In many cases I feel like the terminology is accidentally ignoring parts of theory space I'd like to point to, though I'm not sure if that's because I'm confused or academic philosophy is confused. Yet it seems to be the primary shared language I have available for talking about these subjects other than going "full-Heidegger" and being deliberately subtle to hide my meaning from all who would not bother to do the work to think my thoughts.

On some particular points:

I agree that we only know through experience, but your reference to how this cashes out in physical terms suggests that we might mean something different by knowing through experience. That is, I do not disagree that in fact this is how it cashed out. But the fact that it does, is a fact that we learned by experience, and from the point of view that we had before those experiences, it could have cashed out quite differently.

Sure, I only included the physical explanation because I wanted to be clear that I'm talking about a fundamental kind of thing here by "experience" and not, say, the common use of the word "experience". Unfortunately existing phenomenology lacks, from what I can tell, a rigorous way of talking about experience as generic information transfer.

I think there is conclusive proof of such a structure: some things are not other things (take any example you like: my desk is not my chair), and this is a fact that does not in any way depend on me. If it depended on me, then we could say this is my way of knowing, not the structure of the world, and essentialism might turn out to be false. But as it is, it does not depend on me, and this proves that the world has a structure on which its existence logically depends.

This is one such case where maybe the terminology fails me. Perhaps the existentialist/essentialist divide is not the one I mean. I want to separate those theories that conflate ontology, especially teleological aspects of ontology, with metaphysics from those that view them as separate. Once we have them separate, then we seem to be able to talk about idealism and realism from a perspective of structure creates reality or reality creates structure (i.e. ontology determines metaphysics or metaphysics determines ontology). It is this latter latter case I mean to be in: ontology, which is necessarily discovered only through experience) is the lens through which we can try to discover metaphysics, but metaphysics is ultimately about the stuff that exists prior to the understanding of its structure, and that there is literally nothing you can say about reality except through the lens of ontology because you have no other way to know the world and make sense of the experience of it.

In fact, overall you seem to me to be asserting a position like that of Parmenides

I'd say Parmenides has the same flavor as me, although I'd have to do some heavy interpretation to make what evidence we have of his position fit mine.

I can't draw a conclusion about this myself from what you have said: perhaps you could compare yourself e.g. statements about ethics and statements about money, which are clearly intersubjective. I find it hard to imagine someone who is really and truly non-realist about money: that is, who believes that when he says, "I have 50 dollars in my wallet," the statement is strictly speaking false, because he actually has just a few pieces of paper in his wallet, and much less than 50. But perhaps this is no different from the fact that it is hard to accept that people who claim to be moral non-realists, actually are so.

I'd say there's nothing so special about talking about ethics versus money other than they have differences in meaning and purpose for us, i.e. teleological differences. There is a useful sense in which I can say "I have 50 dollars in my wallet" or "murder is bad" but this is also all understood through multiple layers of structure heaped on top of reality that, without interpretation via experience, would have no meaning. Perhaps "truth" has a broader meaning than I think in academic philosophy, but it seems to me if we're talking about ways of experiencing the experience of reality then we've left the realm of what most people seem to mean by the word "truth". But perhaps this is a definitional dispute?

Because it doesn't seem right to me to create something that will kill off all of humanity even if it would have higher utility.

There are (I feel confident enough to say) 7 billion plus of us actually existing people who are NOT OK with you building something to exterminate us, no matter how good it would feel about doing it.

So, you claim you want to maximize utility, even if that means building something that will kill us all. I doubt that's really what you'd want if you thought it through. Most of the rest of us don't want that. But let's imagine you really do want that. Now let's imagine you try to go ahead anyway. Then some peasants show up at your Mad Science Laboratory with torches and pitchforks demanding you stop. What are you going to say to them?

I'm actually very familiar with freedom of speech

Freedom of speech applies, in the US, to the relationship between the government and the people

You seem to be mistaken about your familiarity with the freedom of speech. In particular, you're confusing it with the 1st Amendment to the US Constitution. That's a category error.

elitist tone

LOL. Would you assert that you represent the masses?

it's stunning lack of detail gave me no insight whatsoever

A stunning example of narcissism :-P Hint: it's not all about you and your lack of insight.

Can you at least try to articulate why you believe this? When you make a statement like this with very few arguments, in response to a genuine question, it doesn't matter if you feel the post you're responding to is incredibly misguided or based on poor understanding. It's simply condescending to respond this way.

No, I don't think so. A short answer does not implicitly accuse the question of being stupid or misguided.

It was a simple direct question. I have a simple direct answer to it without much in the way of hedging or iterating through hands or anything like that.

If someone asks you "vanilla or chocolate?" and you're a chocoholic, you answer with one word and not with a three-page essay on how and why your love for chocolate arose and developed.

Now your question of "why?" could easily lead to multiple pages but tl;dr would be that I like freedom, I don't like the Ministry of Truth, and I think that power corrupts.

why you felt it was worthy?

I would offer a guess that the upvotes say "I agree" and not "this was the most insightful thing evah!" :-)

We're talking about "should", the normative approach. A private entity can do a lot of things -- it doesn't mean that it should do these things.

Freedom of speech is not just a legal term, it's also a very important component of a civil society.

Lumifer didn't say anything about enforceability. E.g. the boy scouts have the right (as a private group, if you accept that a group with the U.S. president as their figurehead is in fact private) to disallow membership based on gender, sexual orientation, or religion. That doesn't mean it is right for them to do so. One should expect that in a civilized society groups like the boy scouts shouldn't discriminate based on things like sexual orientation. But that doesn't necessarily imply that there should be regulatory action to enforce that.

Likewise, Facebook should be a public commons where freedom of speech is respected. But that doesn't mean I'd call for regulatory enforcement of that.

You shouldn't uncritically ingest all the crap the media is feeding you. It's bad for your health.

in times of war

So we are at war with Russia? War serious enough to necessitate suspending the Constitution?

All of the information submitted to Wikileaks was real. Even if it came from Russia it was nothing to do with Fake News.

I agree there is a big danger of slipping down the free speech slope if we fight too hard against fake news, but I also think we need to consider a (successful) campaign effort of another nation to undermine the legitimacy of our elections as an act of hostile aggression,

You know, your campaign against fake news might be taken slightly more seriously if you didn't immediately follow it up by asserting a piece of fake news as fact.

I've just been skimming the wiki page on Russian involvement in the US election.

SecureWorks stated that the actor group was operating from Russia on behalf of the Russian government with "moderate" confidence level

The other claims seem to just be that there was Russian propaganda. If propaganda and possible spying counts as "war" then we will always be at war, because there is always propaganda (as if the US doesn't do the same thing!). The parallels with 1984 go without saying, but I really think that the risk of totalitarianism isn't Trump, its people overreacting to Trump.

Also, there are similar allegations of corruption between Clinton and Saudi Arabia.

Right, the chain has one more step, but still: if people start unsubscribing from Facebook, then money goes elsewhere and so does advertisers.

You're looking only at the walled garden of institutions inside a democracy. But if you look at past history, authoritarian governments or muddled legal situations (say some global corporations), you'll find out that as long as the structure of power is kept intact, people in power can do pretty much as they please with little or no backlash.

As for fake news, the most reliable way to tell is whether the piece states information as verifiable fact, and if that fact is verified.

Verified by whom? There is a long history of "facts verified by official sources" turning out to be false.

That means if you have an investigative reporter with non-public sources, that's fake news because the other side has no access to his non-public sources?