• universeness
    2.3k
    DE isn't worn by particles. Its a property of space that pushes matter away from each other.Landoma1

    Doesn't help me, as QFT suggests there are no particles, just field excitations which can be labeled such for the purposes of scientific calculations. Is energy a 'property of space?' Why do some forms of it 'push' and others 'pull.' I don't expect you to have answers as science does not know what energy is. I don't think the term 'space' is currently understood much beyond the terms 'expansion' or '3D volume.' I am merely airing some of my confusions.
  • Landoma1
    38


    Well, in a sense graviton field oscillations do the trick. Gravitons can travel in higher dimension. Which could be the reason it's so weak. But for a philosophy forum this is too much, I guess. You could ask on a physics forum.
  • Landoma1
    38
    as science does not know what energy isuniverseness

    Science doesn't know?

    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.
  • universeness
    2.3k
    Science doesn't know?Landoma1

    Are you indicating surprise at the fact that science does not yet have all the answers?

    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 expansionLandoma1

    What point are you making?
  • Landoma1
    38
    What point are you making?universeness

    That the total energy is not zero.

    Energy is motion. Half mass times velocity squared. Or mass times SoL squared.
  • noAxioms
    1k
    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
    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.

    As Landoma1 says, dark energy doesn't dilute with expansion, but matter does, so as we expand, the density of matter drops, as does its total percentage.
    AT_7e_Figure_27_01.jpg
    About 6 billion years ago the dark energy and total matter balanced and expansion was linear. It has been accelerating from that 'stop' ever since.

    And no, I'd not be able to explain vacuum energy better than the sites you visit.

    Wayfarer's advise and post this as a question on quora.
    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.

    I’m no authority on physics but I’m interested in the philosophical implications.Wayfarer
    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.

    science does not know what energy is.universeness
    Science is in the business of predicting what something does, and not so much declaring what something is.

    That the total energy is not zero.Landoma1
    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.
  • universeness
    2.3k
    The numbers, as I know them, is 68% dark energy, 32% matter and a smidge of radiation.noAxioms

    I don't get those numbers, if 68% is undetectable dark energy then where is the detectable energy like electromagnetism? Not part of the 32% matter I assume?

    so as we expand, the density of matter drops, as does its total percentage.noAxioms

    Yep, I get that but not the individual density within galaxies as they are gravitationally bound.
    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? or is this factor insignificant to the 'big picture.?'

    Is there an equivalence, such as dark e = dark m dark c squared?

    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 therenoAxioms

    I appreciate the advice but I tend to pay most attention to those on quora who declare their qualifications but I still look for confirmation and dissension on places like the physics stack exchange and on youtube offerings from the established cosmology/physics community. I like to read the 'crank' stuff on quora as well as it's good to see the ways in which skewed thinking can operate. It helps me better recognise it in myself.

    Science is in the business of predicting what something does, and not so much declaring what something isnoAxioms

    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 want to predict what a system does, absolutely, but I don't want to see the universe as a black box I can never peer inside of. I want to know its inner workings and so does science imo. I think science does seek to know what something IS.
  • universeness
    2.3k
    a moving rock will slow over timenoAxioms

    Surely this is not true in a frictionless vacuum, like space. If you push a rock in space it will go on forever unless it meets something along its path.
    Sean Caroll makes this very point, when he describes motion that does not need a sustaining cause.
  • Agent Smith
    6.2k
    physics is philosophy — Landoma1

    PhD?
  • noAxioms
    1k
    if 68% is undetectable dark energyuniverseness
    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.

    where is the detectable energy like electromagnetism? Not part of the 32% matter I assume?
    Part of the 5% baryonic matter, the only energy that participates in EM.

    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?
    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.
    Matter is definitely destroyed (converted to radiation) via nuclear combustion.

    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.
    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.

    "in a cosmological frame, ... a moving rock will slow over time"
    — noAxioms
    Surely this is not true in a frictionless vacuum, like space.
    universeness
    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).
  • universeness
    2.3k
    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 argumentnoAxioms

    So its affects are detectable, ok I see the distinction.

    Part of the 5% baryonic matter, the only energy that participates in EMnoAxioms

    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.'

    I had to put back the context you took outnoAxioms
    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.
  • noAxioms
    1k
    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
    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 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. If it goes into a black hole, it stays there and adds its energy to the black hole's mass.


    Ok, I just didn't understand the significance of 'cosmological frame.'
    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.

    Cosmological coordinates, as I'm using them, typically refers to comoving coordinates with proper distances, as opposed to comoving coordinates with comoving distances, which is yet another way of assigning values to distant events.

    I can get into more detail, but let's just pick an example of the most distant known galaxy *: 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.

    You see all kinds of distances to super-distant objects posted on the web, but in the absence of a coordinate system or some other statement of in what way the quoted figure was computed, the statement is meaningless. Clue: Distances to things is often not expressed in either of these methods called light-travel time, which is not a valid method at all. There's been articles written why that's the worst possible choice.


    * I suspect J-Webb telescope is going to break the record for spotting an even more distant object. CMB doesn't count, it not being an object.
  • universeness
    2.3k
    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 momentumnoAxioms

    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.

    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

    All info in a black hole will eventually come back out via Hawking radiation so it doesn't stay there forever.

    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 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. I do have some a little knowledge of 'comoving coordinates,' 'an expanding metric,' which takes the rate of expansion into account when considering the motion of an object such as a galaxy through space. Is this 2.3c motion for this 'furthest away galaxy,' not part of the 'eternal inflation' idea? I am probably not using the correct terminology here but I am more interested in getting the basic proposals correct without worrying too much about terminology/nomenclature.

    Yeah. GO J-Webb and the re-start of the LHC! Exciting times!
  • Metaphysician Undercover
    10.2k
    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.
  • universeness
    2.3k
    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

    But does energy actually move? A human 'Mexican wave' looks like movement in the horizontal but its actually each individual human moving up and down in the vertical,
    Same with water waves, it's just undulating water until it meets land and the breaker wave 'falls over' or crashes into the land. If QFT is correct and particles are field excitations then particle movement would be similar undulations, would they not? So energy inertia would be a change in velocity due to some underlying quantum effects/fluctuations happening within field structures.
    My thinking is probably inaccurate and too simplistic here. No doubt, I would greatly benefit from a much deeper delve into areas like classical mechanics and comparing it with quantum mechanics. Another entry on my wish list.
  • Alkis Piskas
    1.1k
    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!!
  • Jackson
    1.8k
    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

    I have no problem reading it and I am not a subscriber.
  • Alkis Piskas
    1.1k
    I have no problem reading it and I am not a subscriber.Jackson
    Good that you can. I can't.

    This is what I get:
    https://pasteboard.co/xQcRnLsIb06Y.jpg
  • EricH
    416
    If I had to make a guess, I'd say that you visited NY TImes sometime in the past (could be years ago) and just forgot about it.

    I could be wrong, but the way these things usually work is that the website stores the # times you visited - but this is stored on your browser cache. Try clearing your browser cache and see if that works.
  • Alkis Piskas
    1.1k

    Thanks for the tip. My browser's cache is cleared everytime it closes. It's impossible that NY Times remembers me.
    Bah, simply, there are perverse minds. Some more than others. These ones have no parallel! :smile:
  • noAxioms
    1k
    Speaking of the most distant galaxy.
    This topic apparently referenced GN-z11, which held the most-distant record for a long time, with a redshift of 11.09.
    It was broken last April where data collected from other telescopes found one at z=13.6 or so.
    JWST now is going to break that record on a regular basis. It has found one at z=16.7, and even more distant objects are likely to be found. It is detecting light beyond the redshift ability of say Hubble.

    My comment here was about the z=11 one.
    It highlights the differences between coordinate systems.
    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

    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
    Fine.
    In inertial coordinates, the z=11 light was emitted from ~2000 mpc away and the galaxy is currently around 4100 mpc away.
    In comoving coordinates, the light was emitted around 750 mpc away and the galaxy is currently around 9500 mpc away.

    The new record holder isn't much further away, and the light from it was emitted from even closer than 750 mpc away (proper distance at the time).

    Is this 2.3c motion for this 'furthest away galaxy,' not part of the 'eternal inflation' idea?
    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.

    Yeah. GO J-Webb and the re-start of the LHC! Exciting times!
    Yea, I seem to be reading articles regularly about new records being broken. Glad it survived the mishap with the 'rock'.
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