DE isn't worn by particles. Its a property of space that pushes matter away from each other. — Landoma1
as science does not know what energy is — universeness
Science doesn't know? — Landoma1
What if the total energy in the universe is not zero? This is the case for gravity. The amount of matter energy indeed equals the amount of gravitational potential energy. But there is expansion — Landoma1
What point are you making? — universeness
The numbers, as I know them, is 68% dark energy, 32% matter and a smidge of radiation. Of that 32% matter, about a sixth is normal matter and the rest is dark matter.So does the dark energy effectively add to the positive 'push' of the 5% matter content of the universe? So that the totality of energy from the vacuum > 0.
There is also the issue of dark matter? Does that proposed 95% of all 'matter' not also not add to the positive push and gravitational pull of the vacuum? — universeness
I hesitate to use quora since they've no mechanism to propagate better answers to the top. There is a lot of very wrong info on quora. I look things up on say physics stack exchange, but don't have an account there.Wayfarer's advise and post this as a question on quora.
That's pretty much my purpose in delving into the phyiscs. I want to know it well enough to glean the implications, but not so well that it's critical that I learn tex.I’m no authority on physics but I’m interested in the philosophical implications. — Wayfarer
Science is in the business of predicting what something does, and not so much declaring what something is.science does not know what energy is. — universeness
No so sure that is meaningful. For one, most kinds of energy are not conserved in a cosmological frame. In the absence of a net force, a moving rock will slow over time. Light energy drops as expansion stretches out its wavelength. But negative energy also tends towards zero, so you can't know if total energy is on the rise or not, or maybe is always zero.That the total energy is not zero. — Landoma1
The numbers, as I know them, is 68% dark energy, 32% matter and a smidge of radiation. — noAxioms
so as we expand, the density of matter drops, as does its total percentage. — noAxioms
I hesitate to use quora since they've no mechanism to propagate better answers to the top. There is a lot of very wrong info on quora. I look things up on say physics stack exchange, but don't have an account there — noAxioms
Science is in the business of predicting what something does, and not so much declaring what something is — noAxioms
a moving rock will slow over time — noAxioms
Dark energy is detectable, else it would not be part of our theories. It isn't directly detectable, but neither is any other force/energy by that argument.if 68% is undetectable dark energy — universeness
Part of the 5% baryonic matter, the only energy that participates in EM.where is the detectable energy like electromagnetism? Not part of the 32% matter I assume?
Birth and death of stars doesn't create or destroy matter. Stars are made of pre-existing matter. Trivial amounts of matter are formed by processes like pair production, but such matter isn't long lived.New 'matter' is also created is it not? new stars, new galaxy formations, does this not also add to the density per unit area of space or is it balanced by star deaths etc?
Agree. That's why I'm here, and not just on the science sites. I'm a moderator on one science site, but I mostly have to deal with cranks and spammers.I know what you mean but I think science makes a great effort to explain what IS, and rightly so. This will always be demanded of science imo.
I had to put back the context you took out. Newton's laws (the rock moves at the same speed forever, what Carroll is talking about) works in an inertial metric, but not an expanding one. It's why no galaxy has a peculiar velocity (speed relative to the cosmic frame) much greater than a couple percent of c, despite the fact that they usually have something pulling (accelerating) them in some preferred direction. Virgo cluster is our most significant influence, and our peculiar motion (the motion of our local group relative to that cosmic frame) is indeed in that direction, but that motion is slowing as Virgo grows further away. Our local group will never reach even that, let alone the bigger masses like the Great Attractor or the much more massive Shapley Attractor, all in more or less the same direction, or the Dipole Repeller in the opposite direction giving us a push. All that force in the same direction and yet we're slowing (relative to that cosmic frame)."in a cosmological frame, ... a moving rock will slow over time"
— noAxioms
Surely this is not true in a frictionless vacuum, like space. — universeness
Dark energy is detectable, else it would not be part of our theories. It isn't directly detectable, but neither is any other force/energy by that argument — noAxioms
Part of the 5% baryonic matter, the only energy that participates in EM — noAxioms
Ok, I just didn't understand the significance of 'cosmological frame.' I thought all reference frames are 'cosmological' as they exist within the Cosmos. But I see now you are referring to the largest frame there is, the cosmic or universal frame. How galaxy clusters influence the motion of each other etc.I had to put back the context you took out — noAxioms
We seem to be talking past each other. 'Matter' has mass, and is the Magenta line in the pic I posted a few posts up. A sixth of that matter is Baryonic matter, which means, via mostly the EM effect, you can see and feel it. The rest of it is dark matter which you can neither see nor feel since it does not interact with the EM field.I assume that massless photonic energy is part of the 32% matter you mentioned. I think I just got sidestepped by the label 'matter' placed next to the 32% as I assumed matter to mean 'has mass.' — universeness
I'm speaking of a different coordinate system. Inertial frames can be used, but technically the laws of inertial frames only apply to Minkowskian (flat) spacetime, and on the whole, the universe isn't Minkowskian.Ok, I just didn't understand the significance of 'cosmological frame.'
I don't know what you mean by 'massless photonic energy'. Perhaps you mean the radiation (the blue line in the pic. It arguably has mass since it has momentum — noAxioms
It arguably has mass since it has momentum. If it goes into a black hole, it stays there and adds its energy to the black hole's mass. — noAxioms
In inertial coordinates, (in Earth's inertial frame) that galaxy cannot move faster than c (per special relativity) and is moving away from us at about 0.98c. The light we see was emitted from about 6 billion light years (GLY) away, and it is currently about 13.5 GLY away.
In comoving coordinates (an expanding metric), that same galaxy is currently about 31 GLY away, is receding at about 2.3c (technically a rapidity, not a velocity), and the light that we see now was emitted only about 2.5 GLY proper distance from here — noAxioms
I think we are talking past each other a little but it's just nomenclature issues I think.
My physics level is 1st-year uni plus some online courses I completed but its not even graduate standard.
Photons(photonic), massless, energy (packets), radiation, yes. Energy has a mass equivalence but it does not have mass. — universeness
The trick of modern physics, energy has inertia, without mass. But we need to be careful not to confuse the inertia pf energy with the inertia of mass. — Metaphysician Undercover
I got the ridiculous message, i]"You’ve reached your limit of free articles. Already a subscriber? Log in."[/i]. What is my limit??? I guess, zero. Because it's the first time I opened this page and even visited nytimes.com!! Why don't they say simply "You must be a subscriber to read articles" or even more silmply, just ask me to log in! Yes, even reknown places like New York Times can be ridiculous.
OK, this may be off topic, but one should not refer to articles which, in order to be read, one must subscribe to a website!! — Alkis Piskas
Good that you can. I can't.I have no problem reading it and I am not a subscriber. — Jackson
In inertial coordinates, (in Earth's inertial frame) that galaxy cannot move faster than c (per special relativity) and is moving away from us at about 0.98c. The light we see was emitted from about 6.5 billion light years (GLY) away, and it is currently about 13.5 GLY away.
In comoving coordinates (an expanding metric), that same galaxy is currently about 31 GLY away, is receding at about 2.3c (technically a rapidity, not a velocity), and the light that we see now was emitted only about 2.5 GLY proper distance from here — noAxioms
Fine.I have heard of GLY as a billion light years. Its not a unit I have ever used.Parsecs and its kilo or mega multiples is more familiar. — universeness
No, it isn't something specific to eternal inflation. With regular inflation (just a bang, with no inflation still going on anywhere), you still get this same metric. The metric does include dark energy, without which there would be no acceleration of expansion, and the scalefactor would be everywhere negatively curved.Is this 2.3c motion for this 'furthest away galaxy,' not part of the 'eternal inflation' idea?
Yea, I seem to be reading articles regularly about new records being broken. Glad it survived the mishap with the 'rock'.Yeah. GO J-Webb and the re-start of the LHC! Exciting times!
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