Metaphysics in astronomy: The myth of expanding "space".

[alokmohan]

We are all becoming ARP.But every Tom ,Dick and Harry is not Arp.Dont care to treat your thesis as ARP.Read more about dark energy,

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>To imply that the space itself is stretching implies that the vacuum of space has some kind of substance, eg, aether or the like.<p><hr /></p></p></blockquote><br /><br />I don't think scientists are suggesting that the vacuum of space has substance, per se, at least not in the way that matter does. They are referring to the geometry of the entire Universe.<br /><br />OTOH, the phenomenon of frame dragging and things like gravity wells suggest that indeed there is a real "thing" -- something somewhat akin to the old concept of an aether but a bit different, because it does not seem to be a universal coordinate frame. And there is some evidence that spacetime may be more than just geometry -- namely, gravitational lensing. It's peculiar stuff. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[SpeedFreek]

If the <i>"fabric of space"</i> isn't stretching, how do we explain the observation that a SN1a type supernova with a redshift of z=2 has <b>twice the duration</b> of a SN1a supernova with a redshift of z=1?<br /><br />The idea that space is expanding would explain the apparent redshift-distance relationship, the angular-diameter distance <b>and</b> the time-dilation of more distant supernova of a type that are theorised to always have the same absolute duration.<br /><br />So we see supernovae that, at a redshift-distance of z=1 always last the same length of time. At twice that redshift-distance, they always last twice as long.<br /><br />The simplest explanation is that the light has been "stretched" by that amount during its journey. If the supernova that emitted that light lasted 20 days, but when we receive the light it comes in over 40 days, it seems logical to conclude that the light has been stretched by a factor of 2 during its journey.<br /><br />If we then observe that the wavelength of that light has been changed by the same factor, it adds even more weight to the explanation.<br /><br />So it seems like the space that the light was moving through was stretching as that light travelled, which stretched the light that was travelling through it.<br /><br />Then we observe that the dimmest most redshifted galaxies actually look quite close when we measure their angular-diameter - they look to have been only 2-3 billion light years away when they emitted that light, but as their light is the dimmest it seems like it has been travelling for the longest. If they have a redshift of z=7, if their light has been stretched by a factor of 7, then the radius of the universe has increased by that factor since they emitted their light.*<br /><br />We have confirmed redshifts for galaxies up to z=7 and as of yet unconfirmed redshifts of up to z=15.<br /><br />This simple idea seems to be able to explain the vast majority of our observations (although there are always exceptions that <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[franontanaya]

Sorry, here comes the ignorant of the town.<br /><br />So, basically, what's the weak point in thinking that galaxies were closer before because less time had passed after the explosion of a cosmic egg that threw them in all directions, and that their light was dimmer and slower (that's it, thru a denser medium) as the past space was dustier and it just cleared as the dust cloud expanded? <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

The big-bang is not theorised to have happened as an "explosion" of matter, coming from one point in space, for if it were, that point would be <b>here</b>. Our observations tells us that (apart from the galaxies in our local, gravitationally bound group) all galaxies are speeding away from <b>us</b>, so if there were an "explosion" from a cosmic egg, we just happen to be at the epicentre!<br /><br />The rest of your idea sounds like "tired light" to me, apart from the slowing down of the light. We have no mechanism in science (apart from the metaphysical idea of cosmic expansion) that can slow down light so it takes twice as long to receive it as emit it, whilst <b>also</b> stretching the wavelength of light by a factor of 2.<br /><br />How would your concept stretch the wavelength of the light <b>and</b> slow it down? Gravity doesn't slow light, it only stretches the wavelength. Dust in space might dim light, but not slow it down.<br /><br />By the time that the early galaxies formed, we can see empty black space in between them. You propose that there was some "medium" in space that slowed light when the early galaxies formed and yet when we look back to that epoch we see galaxies that look similar to more recent ones, with space similar to more recent space in between them. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[vandivx]

<blockquote><font class="small">In reply to:</font><hr /><p>Space itself is nothingness, really. It is not composed of anything. It is a void. How a void can do anything but exist is beyond me.<br /><br />To imply that the space itself is stretching implies that the vacuum of space has some kind of substance, eg, aether or the like.<br /><br />So it looks like physics isn't much past the aether stage, with expanding spacetime being a backdoor aether.<br /><br />Otherwise, space must be a void of nothingness which positive matter, ie, something, is defined. Very simple.<p><hr /></p></p></blockquote><br />void cannot exist, the abstract concept of void signifies total negation of 'something' which condition (or mode of existence) is metaphysical impossibility<br /><br />-----------<br /><br />the thread poster seems to have contempt for metaphysics, witness the thread title "Metaphysics in astronomy: The myth of expanding "space"." - in his mind expanding space is something pulled out of one's hat and so he labels such idea 'metaphysics' which term he employs to express his contempt <br /><br />now metaphysics is a science that underlies all of physical sciences which ultimately rest on it and stand or fall with its validity, all science whatever rests on some underlying metaphysical assumptions, one can't get away from that no matter what and only choice here is whether ones' metaphysical assumptions are valid or not<br /><br />metaphysics deals with the most basic assumptions, it supplies most basic framework with which one starts out doing physical science and as such it shouldn't be regarded with contempt (like MM does here)<br /><br />your idea that void exists and that it can't do anything but exist is your metaphysical assumption and if you should actually prove to be wrong on this count all your science relating to it will be affected - it will carry into all your science work and poison it at the fundamental level essentially invalidating or at least partially crippling it in the process <div class="Discussion_UserSignature"> </div>

 

[franontanaya]

<blockquote><font class="small">In reply to:</font><hr /><p>Our observations tells us that (apart from the galaxies in our local, gravitationally bound group) all galaxies are speeding away from us<p><hr /></p></p></blockquote><br /><br />Well, the universe we see is equally older in all directions as seen from Earth. So, if 1 billion years ago it was generally dustier, everything we see around us at 1 billion light years around will be more heavily filtered and that could give us the impression that the light shift is Earth-centric, when it would be only a matter of how much time it took that light to reach us. <br /><br />About speed of light, we know about something that 'slows' it, which is moving through a non empty medium, and something that can 'modify' its movement, which is gravity. Again, I would feel more confortable with a relation between the perceived slow down of light and something we know already that modifies the movement of light.<br /><br />I.e.: As light travels through the non perfect vacuum of space it's pulled and pushed by gravity and interferenced by the medium, so small chaotic changes in direction and speed would blur the time of arrival of the whole sequence of signals as much as it took it to reach us. The time of arrival of light from the whole sequence of closer novas would be more similar to the real timespan, while on farther novas we need to wait a bit longer to receive the lazy photons that danced more on the gravity waves during their travel. <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

It would have to be something a lot more substantial than "dust" to slow it by the amount that light from distant SN1a is time-dilated. Gravity doesn't slow light, it just changes the wavelength or direction. Also, <b>only</b> the gravity of the emitter and the receiver shifts the apparent wavelength. If it passes into and out of a subsequent gravity well, the wavelength is shifted one direction on the way in as much as it is shifted the other direction on the way out. So light from a distant source, passing through an area of high gravity during its journey, will not be slowed or have had its apparent wavelength changed by that area of high gravity when that light finally reaches us.<br /><br />When light hits dust, it tends to illuminate it or make it glow as the light is re-emitted, with very little delay. For dust to account for even a doubling of duration would need a <b>lot</b> of dust, and it might have to account for the duration being stretched by a factor over over 10! I'm not sure dust can act like a medium in this way. <br /><br />But the clincher is that for dust and gravity to account for the time-dilation <b>and</b> the redshifting of the wavelength, the gravity of the emitter and the receiver would have to affect the wavelength of the light by <b>exactly the same factor</b> as the dust slowed it during its journey, for the two factors to correspond when we receive it... so.. not very likely, is it? <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[alkalin]

<font color="yellow">It seems we have to wait for better data for the time-dilation of type 1a supernovae before we can be sure it is in conflict with the Lambda-CDM model, but it is looking a bit dicey for sure!</font><br /><br /><br />Are all supernovas of a certain type all identical? I seriously doubt it. How confident can we be that these supernovas even look the same type after light has been modified due to matter in space? Do we have enough statistics on numerous distant supernovas to tell us that there is a difference in duration due to how far away they are?<br /><br />How confident can we be that treating the information from a galaxy is the same as we would treat local star spectra? What happens to galaxy light as it is being continuously modified by matter in space? <br /><br />I think the issue is how is the light from a very distant galaxy separated with precision from the light of a supernova in that galaxy. Does this lack of light separation provide the clue as to why distant supernovas appear to have a longer duration?<br />

 

[SpeedFreek]

No, all types of supernovae are not identical, when of a certain type, they are not all considered as "standard" candles. Only SN1a are considered to have the same absolute magnitude and duration, as they burn for a similar time at a similar redshift, with a similar brightness. Nearly all the SN1a data analysed so far seems to fit the same "curve", but the exceptions do throw up some questions. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[alokmohan]

I fully agree.