Is Krauss looking at this right?

[tar]

tar, an "object as it exists throughout all of time" doesn't disappear behind an event horizon. Events that already have been observed can be taken as fact. They won't be "erased" from one's past knowledge.

 

Scientists avoid this type of confusion by talking about "events" and "event horizons", not about eternal objects. As Iggy pointed out, a galaxy that disappears behind an event horizon was not even always a galaxy. When speaking of events and whether they'll "ever" be visible, there is no confusion between events related to the state of an object after it crosses an event horizon, and events related to past states of the object. It is the events that occur after it crosses an event horizon that will never be visible.

 

Several times in this thread you mention something that is a misunderstanding of what Krauss is saying, and appear on the verge of understanding it. But then you re-assert your belief that Krauss must be wrong anyway, and the opportunity is lost.

 

Krauss could be wrong. The Big Bang model could be wrong. Inflation theory could be wrong. Gravity theory could be wrong. If you already know something is wrong, there's no need to bother understanding it.

 

md65536,

 

Well I do appreciate your posts. And every once in a while, I do almost get it. But its sort of slippery. I think perhaps I am lacking the grey matter, to play with the big boys. Enough stuff to be on the same court perhaps...during practice...but not enough for game day.

 

It seems to me, obvious that the universe is quite immense and intricate, and while an equation can be true and fit reality, it does not seem to me that there is any requirement what-so-ever that reality be bound by the equation.

 

Events in four dimensional spacetime can be plotted and transforms made, but they are gross simplifications of what is really happening. Entities exist, made up of smaller entities, and that make up, with other entities, larger entities. They interact, they grow, they have characteristics, and they break apart or merge into new entities.

 

Many equations deal with "systems", as in how much energy does a system have. I have a problem understanding how this is achieved with a simple equation. Take our galaxy for instance. How can you say how much energy it contains, when its doing the things its doing, at different times? You can't mean anything real unless you can measure the whole thing at once, which you can't. It's too big. And what we see of it, is what it was doing before, if we think of it as events. We have no access to what it is doing now. So already, the activity on the other side of the Milky Way, is not visible to us. Not for 400,000 years.

 

I can not manage that immensity and the consequences. It seems plently incomprehensible enough, just to understand what is happening within our solar system, or for that matter on Earth, or even what is happening within 50 miles of where I sit.

 

And if the universe is currently made up of entities all doing something right now, 13.7 billion years after the Big Bang occurred, I would think that that means, that the universe, as a whole, has not yet done what it is going to do next. All of spacetime has not yet happened. Only the events, up to now, in the universal sense of now. In the Godlike view, I keep referring to. And what makes up our reality, our here and now is the sum total of all the photons that have been absorbed and emitted in the order and manner in which they were, around here, and the entities that have emerged as a result.

 

I do not believe that Krauss can take E=MCsquared and derive from it, a peanut butter cup, nor a human consciousness. He does not know what the universe will be doing in 100 or 500 billion years. And if he does not know that, how can he surmise what it will look like, from here?

 

Regards, TAR2

 

And we can be conscious of time scales and size scales, greater than our lifetimes and the size of our brains. We have a rover on Mars, collectively speaking. Who is to say that given another 13.7 billion years there will not be a collective consciousness that can embrace the Galaxy as one here and now, and recognize the existence of other such consciousnesses.

 

Or have we, in Krauss's prediction, already acheived the ability to know and care about the existence of Galaxies we will never experience? Seems to me, we would not know or care about such things, if we did not belong, already, permanently to the enterprise, in some very real and important sense.

 

Why this does not smell of God to you, is beyond me.

[Iggy]

Iggy,

 

Ok. If Krauss turns out to be correct in his prediction... I would be very much surprised. I think it likely he forgot to take something into consideration.

Like I said a couple times before, you're free to imagine.

 

The model is almost 100 years old. It was created by Friedmann and Lemaitre -- endorsed by Einstein -- solved for accelerated expansion by Sean Carroll and many others, and popularized by Krauss. You're free to imagine that your gut feeling is right and all the greatest minds in physics and cosmology are wrong because they are forgetful.

 

In an odd way, I truly envy the power of imagination it must take to convince a person of that.

[michel123456]

Like I said a couple times before, you're free to imagine.

 

The model is almost 100 years old.

 

usually this kind of argument is used as an attack, not as a support.

 

It was created by Friedmann and Lemaitre

Lemaitre was a priest.

IIRC Friedmann's work supports equally an expanding, contracting or steady state universe. quoting from wiki

The Friedmann–Lemaître–Robertson–Walker (FLRW) metric is an exact solution of Einstein's field equations of general relativity; it describes a homogeneous, isotropic expanding or contracting universe that may be simply connected or multiply connected.

 

and from this other wiki article

Relativity

Friedmann's 1924 papers, including "Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes" (On the possibility of a world with constant negative curvature of space) published by the German physics journal Zeitschrift für Physik (Vol. 21, pp. 326–332), demonstrated that he had command of all three Friedmann models describing positive, zero and negative curvature respectively, a decade before Robertson and Walker published their analysis.

 

This dynamic cosmological model of general relativity would come to form the standard for the Big Bang and steady state theories. Friedmann's work supports both theories equally, so it was not until the detection of the cosmic microwave background radiation that the steady state theory was abandoned in favor of the current favorite Big Bang paradigm

.

 

 

 

So, paraphrasing:

a model was created 100 years ago by a priest, -- endorsed by Einstein -- solved for accelerated expansion by Sean Carroll and many others, and popularized by Krauss..

Edited September 17, 2012 by michel123456

[Iggy]

Like I said a couple times before, you're free to imagine.

 

The model is almost 100 years old.

usually this kind of argument is used as an attack, not as a support.

It's not an argument, an attack, or support.

 

Lemaitre was a priest.

I am aware. Newton was an alchemist. If you have a point it is lost on me.

 

Lemaitre was the first to solve the FLRW metric from general relativity. He deserves every bit to be mentioned with Einstein, de Sitter, Friedmann, Tolman and all the other great fathers of modern cosmology.

 

IIRC Friedmann's work supports equally an expanding, contracting or steady state universe.

The way you phrased this suggests you don't know that a steady state universe expands. It has been proved many times over that the FLRW solution cannot work with a static universe. Friedmann, Lemaitre, Robertson, and Walker independently discovered the solution.

 

"Friedmann's work", as you say, isn't separate from Lemaitre's work as you seem to be thinking. They were both figuring out the same thing independently.

 

quoting from wiki

The Friedmann–Lemaître–Robertson–Walker (FLRW) metric is an exact solution of Einstein's field equations of general relativity; it describes a homogeneous, isotropic expanding or contracting universe that may be simply connected or multiply connected.

wiki is correct.

 

and from this other wiki article.

Relativity

Friedmann's 1924 papers, including "Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes" (On the possibility of a world with constant negative curvature of space) published by the German physics journal Zeitschrift für Physik (Vol. 21, pp. 326–332), demonstrated that he had command of all three Friedmann models describing positive, zero and negative curvature respectively, a decade before Robertson and Walker published their analysis.

 

This dynamic cosmological model of general relativity would come to form the standard for the Big Bang and steady state theories. Friedmann's work supports both theories equally, so it was not until the detection of the cosmic microwave background radiation that the steady state theory was abandoned in favor of the current favorite Big Bang paradigm

Wiki is again correct. It should be added that the CMB isn't the only falsification of steady state cosmology.

 

So, paraphrasing:

a model was created 100 years ago by a priest,

You wouldn't say "created". You would say "solved" or "discovered". [edit]that was originally my mistake though[/edit] After the publication of general relativity it was inevitable that a metric would be found to describe the whole family of homogeneous solutions. I mentioned Lemaitre because I believe he was the first. Pointing out that he was a priest is pretty weird.

 

-- endorsed by Einstein -- solved for accelerated expansion by Sean Carroll and many others, and popularized by Krauss.

Correct. One could add the name of any cosmologist who has worked with standard cosmology to that paragraph, but my point is only that Krauss' name belongs at the end of the list.

 

 

EDIT:

 

I looked up the dates and I was mistaken. Friedmann did publish it before Lemaitre.

 

I also think I figured out the point you were trying to make. You omitted Friedmann's name when you paraphrased my "it was created by Friedmann and Lemaitre and endorsed by Einstein" comment into "it was created by a priest and endorsed by Einstein..." so your point must be that you don't think the Friedmann equations work with the current accelerated expansion model of standard cosmology (the Lambda-CDM model). That is mistaken. It is perfectly described by the FLRW metric.

 

The point is that the solution is nearly 100 years old. It has been the backbone of cosmology for nearly as long as cosmology has been a hard science. It is, in other words, very well solved and very well understood. To say that its predictions could be mistaken as a result of Krauss' forgetfulness is unreasonable, to put it kindly.

Edited September 17, 2012 by Iggy

[tar]

Like I said a couple times before, you're free to imagine.

 

The model is almost 100 years old. It was created by Friedmann and Lemaitre -- endorsed by Einstein -- solved for accelerated expansion by Sean Carroll and many others, and popularized by Krauss. You're free to imagine that your gut feeling is right and all the greatest minds in physics and cosmology are wrong because they are forgetful.

 

In an odd way, I truly envy the power of imagination it must take to convince a person of that.

 

Iggy,

 

Well I try to look at things from all perspectives, as in what does what I see "mean".

 

For instance here is the portion of an image containing a gaxaly and a super nova in it, cut out of the image captioned below.

 

 

Image Caption: The supernova PTF 11kx can be seen as the blue dot on the galaxy. The image was taken when the supernova was near maximum brightness by the Faulkes Telescope North. The system is located approximately 600 million light years away in the constellation Lynx. (BJ Fulton, Las Cumbres Observatory Global Telescope Network)

 

redOrbit (http://s.tt/1lBZB)

 

Now tell me how something could go from being the size of a white dwarf and its companion (which would be much less than a pixel in this picture) to something that appears to be 10s of thousands of ly across, in a couple of weeks?

 

Even if it was exploding at the speed of light, it would take thousands of years to grow that large.

 

Now I don't know how this image was put together, and color coded and the like, but we are not talking about a thing we can see all at once, we are talking about a galaxy that is probably 300,000 to 500,0000 ly across. Anything that happens in 3 weeks, 600 million ly away, could get no larger then about a 20th of a ly across. (which is much less than a pixel in the above view of a Galaxy)

 

If it was not peer reviewed science that tells me this is a supernova, I would, on general principle think "how could it be something happening on that size scale, so quickly". Nothing can happen faster than the speed of light.

 

Regards, TAR2

[JohnStu]

I've seen that video at least 7 times and I've read his book.

 

Yes, I think he is on the right path.

 

If we zoom in a cake, we see weird looking landscapes. Then we zoom in more, we "see" organic molecules. Then we zoom in more, oh, look an electron. Then we zoom in more, we might "see" nucleus of an electron?

[Iggy]

Iggy,

 

Well I try to look at things from all perspectives, as in what does what I see "mean".

 

For instance here is the portion of an image containing a gaxaly and a super nova in it, cut out of the image captioned below.

 

 

Image Caption: The supernova PTF 11kx can be seen as the blue dot on the galaxy. The image was taken when the supernova was near maximum brightness by the Faulkes Telescope North. The system is located approximately 600 million light years away in the constellation Lynx. (BJ Fulton, Las Cumbres Observatory Global Telescope Network)

 

redOrbit (http://s.tt/1lBZB)

 

Now tell me how something could go from being the size of a white dwarf and its companion (which would be much less than a pixel in this picture) to something that appears to be 10s of thousands of ly across, in a couple of weeks?

 

Even if it was exploding at the speed of light, it would take thousands of years to grow that large.

 

Now I don't know how this image was put together, and color coded and the like, but we are not talking about a thing we can see all at once, we are talking about a galaxy that is probably 300,000 to 500,0000 ly across. Anything that happens in 3 weeks, 600 million ly away, could get no larger then about a 20th of a ly across. (which is much less than a pixel in the above view of a Galaxy)

 

If it was not peer reviewed science that tells me this is a supernova, I would, on general principle think "how could it be something happening on that size scale, so quickly". Nothing can happen faster than the speed of light.

 

Regards, TAR2

The brighter a blurry point source of light the larger it appears. It is, however, not uncommon to see lateral superluminal motion like this graph shows. Is this a new topic?

Edited September 18, 2012 by Iggy

[tar]

Iggy,

 

Well perhaps lateral superluminal speeds is another topic, maybe it is not, I don't know anything about it.

 

My point is, the large size that the supernova obtains in several short weeks, is not possible, in the context of the immense galaxy it took place in. Its "apparent" size, must have something to do with how and when the light waves/photons make the 600 million ly trip to our instruments, and how it "looks" when it gets here.

 

What I am trying to envision, and understand, is when and why we call something currently existing.

 

For instance, I read that our galaxy produces 1 to 2 supernovae in a hundred years. I don't think this is accurate.

 

If we, here on Earth, see a supernova that occurred inside our Galaxy every 100 years, and the stars in our Galaxy are an average of say, 150,000 ly from us, one could suppose that there could be 15 thousand super novas that have already occurred in our galaxy, that we have not yet experienced on Earth. The 5 week long light event of each supernova that has occurred in our Galaxy, but has not yet reached the Earth, is currently existant and "on its way" toward the Earth.

We don't consider it "happening" until we witness it.

 

Likewise with the super nova we see "happening" in the Galaxy 600million lys from us. If the close side of that Galaxy is 600million lys from us, the far side is say 600.3 million lys from us, which would mean we need to watch the darn thing for 300,000 years, to log every super nova that occurred in that Galaxy, 600million years ago. And we would have to only count ones we saw that came from deeper within the Galaxy, the appropriate distance to match with our 600million year ago focus moment. And so on.

 

Point being, that Krauss cannot speak about what the universe will look like from here in 100 billion years, as if the condition of the universe can be seen all at once. We are currently NOT seeing what the universe is like at the moment. We are seeing what is was like, before. My feeling is, that now, we cannot see any further than 13.7billion lys, and when we look there, we see portions of the universe just becoming transparent to photons, a few hundred thousand years old and millions of degrees hot. In 100 billion years, we will probably be able to see things 100 billion light years away, that happened when those portions of the universe were a few hundred thousand years old and millions of degrees hot.

 

Regards, TAR2

 

And of course, everything inbetween, at its appropriate age.

Edited September 20, 2012 by tar

[Iggy]

My point is, the large size that the supernova obtains in several short weeks, is not possible, in the context of the immense galaxy it took place in. Its "apparent" size, must have something to do with how and when the light waves/photons make the 600 million ly trip to our instruments, and how it "looks" when it gets here.

You had the same reasoning with Krauss. You don't understand something so you assume it's wrong.

 

The supernova is a point source... meaning the angle its physical size subtends in the sky is much smaller than a pixel of the image you posted. It doesn't show up as a single extremely bright pixel because that isn't how cameras and telescopes and astronomy work.

 

Point sources show up as blurry disks (just like the image you posted) because of atmospheric turbulence and diffraction in the telescope. Astronomers call them seeing disks and their size depends on the atmosphere, the telescope, brightness, exposure time, and it can be calculated with the 'point spread function' or the 'point smear function'... I don't remember... this is tedious.

 

Post 55 represents a problem with your reasoning. Your answer to standard cosmology was to post an unrelated astronomy picture and basically say 'I don't understand this astronomy picture so I assume cosmology is wrong'. It's like hearing a Spanish phrase that you can't figure out and therefore assuming that something is wrong with Spanish and all the native speakers are talking wrong.

 

It's conspiracy theory thinking.

 

What I am trying to envision, and understand, is when and why we call something currently existing.

 

For instance, I read that our galaxy produces 1 to 2 supernovae in a hundred years. I don't think this is accurate.

It is accurate. It's not very precise, but it is perfectly accurate.

 

If you don't understand when events happen because signal delay is confusing you I strongly suggest learning to make a spacetime diagram. I'm serious about this. If you knew how to make a spacetime diagram it would simplify and clarify these issues you keep talking about.

 

If we, here on Earth, see a supernova that occurred inside our Galaxy every 100 years, and the stars in our Galaxy are an average of say, 150,000 ly from us, one could suppose that there could be 15 thousand super novas that have already occurred in our galaxy, that we have not yet experienced on Earth. The 5 week long light event of each supernova that has occurred in our Galaxy, but has not yet reached the Earth, is currently existant and "on its way" toward the Earth.

I think you mean 15 hundred, but yes, of course, supernovae have happened which we haven't yet seen on earth.

 

We don't consider it "happening" until we witness it.

No. The supernova and the observation are two separate events that happen at separate times. If a supernova at distance d is observed at time t then it happened at t-d/c.

 

Likewise with the super nova we see "happening" in the Galaxy 600million lys from us. If the close side of that Galaxy is 600million lys from us, the far side is say 600.3 million lys from us, which would mean we need to watch the darn thing for 300,000 years, to log every super nova that occurred in that Galaxy, 600million years ago. And we would have to only count ones we saw that came from deeper within the Galaxy, the appropriate distance to match with our 600million year ago focus moment. And so on.

That's right. If you want to witness all of the simultaneous events of a single moment in the galaxy you have to watch it for 300,000 years (or whatever the radial length divided by the speed of light is). Ok... if a group of people 100 meters deep in their ranks all simultaneously shoot a paintball at you and the paintballs go 20 meters / second then you have to stand still for 5 seconds if you want to be shot by every paintball. The radial length divided by the speed. 100 meters divided by 20 meters/second, or, in the example you give, 300,000 lightyears divided by 1 lightyear/year.

 

Why are you mentioning this? Are you trying to learn it? Is it obfuscation?

 

Point being, that Krauss cannot speak about what the universe will look like from here in 100 billion years, as if the condition of the universe can be seen all at once.

In other words, you don't understand how standard cosmology can predict future observations without seeing the universe all at once therefore it must be wrong.

 

We are currently NOT seeing what the universe is like at the moment. We are seeing what is was like, before.

It's like telling a mechanic "this is the engine" or telling a pilot "this is the wing". Good for you for knowing that.

 

Please, learn to make a spacetime diagram. Open up a topic on it... not for arguing, but for learning. It would be very much worth your time.

[michel123456]

The brighter a blurry point source of light the larger it appears. It is, however, not uncommon to see lateral superluminal motion like this graph shows. Is this a new topic?

 

I agree to make "lateral superluminal motion" a new topic.

 

I'd thought that "lateral" motion for light is not observable. We don't see the light that does not come to us. We only catch the photons that hit our eyes (or our instruments) so that "lateral motion" for light (or superluminallight) is a kind of peculiar concept to me.

Please enlight me.

Edited September 22, 2012 by michel123456

[tar]

Iggy,

 

You say this and you know it's true. "No. The supernova and the observation are two separate events that happen at separate times. If a supernova at distance d is observed at time t then it happened at t-d/c."

 

And its understood and agreed upon by everybody, including me. It makes sense. But my problem has always been, from the first, trying to figure out what it means. What is t. What is d. What is c. What are these symbols signifying in reality. They are representatives of what reality is doing, they are not reality itself.

 

Let's take t for instance. We have the time an event happens, and we have the time the photons emitted at the event, (a separate time) reach our instruments. Already we have two different times, and only one t in the equation.

 

Then we have d, which has changed due to the expansion of space in the t between the t of the emission event and the t of the reception event. Changed from what to what and when, is not yet set, it is a different distance at one t and the other, which means the distance had to be all the other distances between the two events, at all the separate ts between.

 

Then we have C which is constant? Constantly traveling a changing d in a changing t?

 

I am left with no hook to hang my hat on. I do not know what it means, that space is expanding. It seems to require that C means something different at each t between, and therefore has many different characters, not just one constant one.

 

But you are right. These thing have all been figured out. All the dts and dds and C just being put at 1=d/t. Dimensions dropped conviently out, to get a "clear" picture of what is going on. If I were to only understand how to draw a spacetime diagram it would become clear to me. Perhaps. Perhaps not.

 

There is here and now, which is the perspective from which we view the universe.

There is the universe that we view.

There is the model of the universe that is held in Krauss' head and written in the formulae and diagrams of spacetime.

 

However smart and capable a person becomes, the model will never be more accurate than the universe itself. You cannot outthink the universe.

 

Regards, TAR2

 

P.S. We get a three d slice of the universe every moment, and another in the next moment. Every body and everything gets this, and has been getting it, and storing it, for the last 13.7 billion years.

In a hundred billion years, the situation will be similar, in that everybody, and everthing will have been collecting and storing these 3D slices, for 100 billion years worth of moments. And each here and now in that future universe, will be able to see a 100 billion years into the past. I doubt that Krauss can predict what this will look like. That is why I question whether he is looking at this right.

Edited September 22, 2012 by tar

[md65536]

If I were to only understand how to draw a spacetime diagram it would become clear to me. Perhaps. Perhaps not.

I suppose we may never know, then...

 

And every once in a while, I do almost get it. But its sort of slippery. I think perhaps I am lacking the grey matter, to play with the big boys. Enough stuff to be on the same court perhaps...during practice...but not enough for game day.

I've been thinking about this earlier comment of yours.

 

You're wrong. You don't lack the grey matter to understand this (I'm assuming no brain damage or anything like that), but perhaps you lack a proper attitude? It's a good excuse though, if you don't want to learn about this, to say you're incapable. But I've seen examples of people who've overcome greater challenges than perhaps any of us here will ever know, including those who've taken online courses for no reason besides self-improvement, and excelled against the odds. I doubt many who learn something difficult begin by believing they're unable to. I doubt many who believe they're incapable ever try.

 

 

 

I've been thinking about this in terms of an analogy (even though my last one didn't work I'll try again).

Imagine that cosmology is like a cruise ship, which is designed by many people, and no one person can focus on every single detail of the entire ship. So you may study some particular aspects of it, and end up with a particular combination of knowledge that no one else has, which may perhaps even make you an expert on that. And you may find a small flaw in the ship, something like "Deck 10-forward is not wheelchair accessible", perhaps a detail missed by someone looking at only the big picture.

 

You may even discover something big that was overlooked by everyone else, such as "If this collided with an iceberg, it would likely rip through the hull!"

 

By analogy, what you're doing in this thread is like saying "The cruise ship can't float, because it's made of metal." And then it's explained that it can, and you say "Well even so, there are so many details to a cruise ship that something must have been overlooked, so I still think it can't float."

 

 

Anyway, back to cosmology... experts on this don't get that way just by thinking about it. They learn about it. What is your source for the information you're posting in this thread? Perhaps you can request a better resource (a book or web site) to learn about it.

 

P.S. We get a three d slice of the universe every moment, and another in the next moment. Every body and everything gets this, and has been getting it, and storing it, for the last 13.7 billion years.

In a hundred billion years, the situation will be similar, in that everybody, and everthing will have been collecting and storing these 3D slices, for 100 billion years worth of moments. And each here and now in that future universe, will be able to see a 100 billion years into the past. I doubt that Krauss can predict what this will look like. That is why I question whether he is looking at this right.

 

 

Yes, Krauss is assuming that information will be lost. For example, we don't know what a particular dinosaur might have observed when looking up at night. We have no way of accessing that information... it is lost. It's a fairly safe assumption too, because even if say 100 billion years from now all of our information was somehow still preserved, there will still be other places, and other times, where that information is not possibly accessible. Krauss is making a very coarse prediction.

[Iggy]

I agree to make "lateral superluminal motion" a new topic.

 

I'd thought that "lateral" motion for light is not observable. We don't see the light that does not come to us. We only catch the photons that hit our eyes (or our instruments) so that "lateral motion" for light (or superluminallight) is a kind of peculiar concept to me.

Please enlight me.

I was talking about this. I didn't see your topic.

 

---

 

 

Iggy,

 

You say this and you know it's true. "No. The supernova and the observation are two separate events that happen at separate times. If a supernova at distance d is observed at time t then it happened at t-d/c."

 

And its understood and agreed upon by everybody, including me. It makes sense. But my problem has always been, from the first, trying to figure out what it means. What is t. What is d. What is c.

In the sentence I wrote t is the time of the observation, d is the distance between the observation and the supernova, and c is the speed of light.

 

What are these symbols signifying in reality. They are representatives of what reality is doing, they are not reality itself.

 

Let's take t for instance. We have the time an event happens, and we have the time the photons emitted at the event, (a separate time) reach our instruments. Already we have two different times, and only one t in the equation.

There was no second variable for time and there was no equals sign in the sentence I wrote because I wrote "the supernova happened at" in their place.

 

[math]t_S = t_O - \frac{d}{c} [/math]

 

ts is the time of the supernova, to is the time of observation. Are you trying to make this sensible to you, or are you trying to make it appear less sensible to others?

 

Then we have d, which has changed due to the expansion of space in the t between the t of the emission event and the t of the reception event. Changed from what to what and when,

The equation I gave ignored expansion.

 

The galaxy was closer at the time of the supernova than it is at the time of the observation. If you want to calculate how much closer find the redshift (z = 0.045) and solve:

 

[math]d_S = \frac{d_O}{1+z} [/math]

 

If the galaxy is 600 million lightyears when it is observed, like you said, then it was 574 million lightyears when it was emitted (at the time of the supernova). This is no more exciting than calculating the distance of a car diving away from you.

 

If you really want to learn this stuff I'm afraid internet postings aren't a good way to pick it up, and believe it or not, you aren't going to poke a hole (to borrow MD's analogy) in standard cosmology by asking elementary questions.

 

is not yet set, it is a different distance at one t and the other, which means the distance had to be all the other distances between the two events, at all the separate ts between.

 

Then we have C which is constant? Constantly traveling a changing d in a changing t?

Do you really want me to explain the function of c in the solutions of general relativity?

 

I am left with no hook to hang my hat on. I do not know what it means, that space is expanding.

Your confusion doesn't make the model any less reliable.

 

I doubt that Krauss can predict what this will look like. That is why I question whether he is looking at this right.

Right. You can't understand it. You can't picture it. So, you doubt anyone else can. You must realize how absurd that sounds.

Edited September 22, 2012 by Iggy

[tar]

Iggy,

 

I suppose that is my problem. I do not know what is being intentionally ignored, and what is being looked at wrong (as in ignoring the reality of the situation).

 

But you are right, I have a personality difficulty, in that I don't seem to be able to fully trust another's take, if it appears to me, that they have left something out of consideration.

 

And I do not have a particular source of my information. I put together everything I have read and heard about, and viewed and try to figure out what it means. Understanding, that whatever model of the universe I arrive at, is a miniture, analog model of what actually exists, that represents but does not duplicate, the world and universe that I have been informed of.

 

Interesting that you used the steamship analogy to depict that no one person could plan and build and consider every aspect, without trusting others to do their part correctly. Just saw a show last night on the secrets of NYC, and how the rivers and streams and tidal estuaries and such were built over and how landfill and sunken ships were used to turn river into real estate and streets, subways built and pump systems and such, ingenious and grand in design and execution. So many peices, so many parts, constantly changing, being repaired, redesigned, maintained and torn down and rebuilt. Each achievment built on the countless efforts and ideas of all who came before. And at every point, you had a city, and you still have a city, and the one is different from the other, in a zillion ways, and the same, in another zillion.

 

I could not build and maintain a city by myself. Just visit it, and enjoy its wonders.

 

I think the same goes for the universe. Its too big and too old and too constantly changing, to freeze in a formula. Unless of course, you know what it is, you are ignoring, and know it is just a gross simplification you are imagining, that does not actually do the universe any justice.

 

But if one is to distrust one's own model, but trust the model reached by consensus, I am not sure, where the innovations and breakthroughs are supposed to come from.

 

You say that the formula for a galaxy moving away from you, is no different than figuring a car receeding from you. I don't agree. The car, when its close and when its far, is those varying distances, at checkable, unified times, that can be stepped back from, and checked and seen as sequential, unified nows. In the case of the galaxy, there is not a way to see both here and there, at the same time. Thus there is a large question as to the current status of that galaxy, and what one is calling an object, and what one is calling an event, and a severe question in my mind, of when somebody is matching models and when somebody is matching their model to reality. What is lost to us, is not necessarily lost to the universe. And what is true about the universe is many things and times at once.

 

For us to see that galaxy today, and see it tomorrow, requires that the photons from that galaxy that inform us of its size and shape and activity, are already embedded, in sequence and consistently, in the space between Earth and that Galaxy. And what that Galaxy looked like, to us, yesterday, is embedded in the space behind us (if we are facing the galaxy in question) a light day away. That "object" exists everywhere within 13.7billion light years of its actual location.

 

In a hundred billion years, I predict that "object" will exist everywhere within 100 billion lightyears of its current location.

 

And the universe will not be lost to our location.

 

Regards, TAR2

[Iggy]

Iggy,

 

I suppose that is my problem. I do not know what is being intentionally ignored, and what is being looked at wrong (as in ignoring the reality of the situation).

 

But you are right, I have a personality difficulty, in that I don't seem to be able to fully trust another's take, if it appears to me, that they have left something out of consideration.

 

And I do not have a particular source of my information. I put together everything I have read and heard about, and viewed and try to figure out what it means. Understanding, that whatever model of the universe I arrive at, is a miniture, analog model of what actually exists, that represents but does not duplicate, the world and universe that I have been informed of.

 

Interesting that you used the steamship analogy to depict that no one person could plan and build and consider every aspect, without trusting others to do their part correctly. Just saw a show last night on the secrets of NYC, and how the rivers and streams and tidal estuaries and such were built over and how landfill and sunken ships were used to turn river into real estate and streets, subways built and pump systems and such, ingenious and grand in design and execution. So many peices, so many parts, constantly changing, being repaired, redesigned, maintained and torn down and rebuilt. Each achievment built on the countless efforts and ideas of all who came before. And at every point, you had a city, and you still have a city, and the one is different from the other, in a zillion ways, and the same, in another zillion.

 

I could not build and maintain a city by myself. Just visit it, and enjoy its wonders.

 

I think the same goes for the universe. Its too big and too old and too constantly changing, to freeze in a formula. Unless of course, you know what it is, you are ignoring, and know it is just a gross simplification you are imagining, that does not actually do the universe any justice.

 

But if one is to distrust one's own model, but trust the model reached by consensus, I am not sure, where the innovations and breakthroughs are supposed to come from.

It sounds like that was a reply to md65536's post.

 

You say that the formula for a galaxy moving away from you, is no different than figuring a car receeding from you.

No, I wouldn't have said that.

 

For us to see that galaxy today... That "object" exists everywhere within 13.7billion light years of its actual location.

For me to feel the sun's rays means I'm inside the sun. Hearing my words in your head means your name is Iggy. My dog has been alive for 6 years so he has visited Alpha Centauri.

 

I think I've learned better than to try and convince you otherwise.

 

Thus there is a large question as to the current status of that galaxy, and what one is calling an object, and what one is calling an event, and a severe question in my mind, of when somebody is matching models and when somebody is matching their model to reality.

(...)

In a hundred billion years, I predict that "object" will exist everywhere within 100 billion lightyears of its current location. And the universe will not be lost to our location.

Again you say in different words that you have large questions in your mind and the universe is surprising, complicated, and difficult to model, and therefore the definitive predictions of well supported science are wrong and the definitive predictions of your gut feeling are right.

 

I'm sure there's nothing more to be said. The answer to the opening post is that Krauss is correctly conveying the predictions of cosmology. It is a straightforward solution of the Friedmann equation using the parameters of standard cosmology.

[tar]

Iggy,

 

OK, I'll be quiet. We will just have to wait a hundred billion years to see how it turns out.

 

Regards, TAR2

[michel123456]

I'm sure there's nothing more to be said. The answer to the opening post is that Krauss is correctly conveying the predictions of cosmology. It is a straightforward solution of the Friedmann equation using the parameters of standard cosmology.

 

Yes.

And my comment on that was that if Krauss is right (as it looks), then the current cosmology model is most probably wrong.

It is not conceivable (IMHO) that we currently live a privileged period of the Universe, a period so special that allows us to observe the Universe in a different way than future generations on future planets would observe. To me, there MUST be nothing special in our position in space (cf cosmological principle) and in time: IOW there is no privilege to our position in spacetime.

Edited September 24, 2012 by michel123456

[zapatos]

Yes.

And my comment on that was that if Krauss is right (as it looks), then the current cosmology model is most probably wrong.

It is not conceivable (IMHO) that we currently live a privileged period of the Universe, a period so special that allows us to observe the Universe in a different way than future generations on future planets would observe. To me, there MUST be nothing special in our position in space (cf cosmological principle) and in time: IOW there is no privilege to our position in spacetime.

Every time is a privileged time as the universe is constantly changing. I see the universe (slightly) different than my father did. You could just as easily say that future generations on future planets are the ones who are privileged as they will observe the universe in a different way than past generations on past planets.

[Iggy]

Iggy,

 

OK, I'll be quiet. We will just have to wait a hundred billion years to see how it turns out.

 

Regards, TAR2

Nonsense!

 

Another 999 billion years of argument and I'm sure I'll have you convinced with time to spare.

 

 

 

---

 

 

Yes.

And my comment on that was that if Krauss is right (as it looks), then the current cosmology model is most probably wrong.

It is not conceivable (IMHO) that we currently live a privileged period of the Universe, a period so special that allows us to observe the Universe in a different way than future generations on future planets would observe. To me, there MUST be nothing special in our position in space (cf cosmological principle) and in time: IOW there is no privilege to our position in spacetime.

Then... you deny all of cosmology, no? You disbelieve the big bang, for example? There is too much evidence that the observable universe was extremely hot and dense about 14 billion years ago to be seriously scientifically disputed.

 

'There is nothing new under the sun' seems like a predisposed impulse people have. If it weren't for those meddling scientists the philosophers would have gotten away with it too!

[tar]

Iggy,

 

You have me convinced that many people smarter than me have thought this through, and have a pretty good idea of what is going on, and the math to back it up. I will yield, and not try to confuse the issue with idle muses.

 

But, and its a big but, I think it would be prudent to consider that as smart as we are today, there is bound to be smarter people in a hundred years, that have built their world and their models on the shoulders of those who toil today. And it seems a bit premature to call the final score, from where we stand.

 

If I may shift the goal posts a bit, I do not think the final pronouncement of scientists 100 years ago, worked out to be the final word in science, and it seems sort of short sighted from an objective viewpoint, considering the size and age of the universe, that any one of us, would be unquestionably right about ANY prediction of an "endgame" that the universe is bound for. We truely do not know what that will look like. Nor have we a way to verify any such prediction. AND we do not know the nature of the eyes that will be looking, when that time comes.

 

Regards, TAR2

 

After all, we are children of the universe. We evolved in its presence, and we are capable, without instruments, of seeing and remembering the stars. Perhaps with instruments and the ability to reach above the scattering atmosphere, and given a longer lifespan, much longer than a hundred years, an organism might just be able to sense a wavelength the length of the galaxy, and NOT consider space empty at all. Perhaps.

Edited September 25, 2012 by tar

[michel123456]

Then... you deny all of cosmology, no? You disbelieve the big bang, for example? There is too much evidence that the observable universe was extremely hot and dense about 14 billion years ago to be seriously scientifically disputed.

 

'There is nothing new under the sun' seems like a predisposed impulse people have. If it weren't for those meddling scientists the philosophers would have gotten away with it too!

That's not my fault!

 

The cosmological principle is:

"the working assumption that observers on Earth do not occupy an unusual or privileged location within the universe as a whole, judged as observers of the physical phenomena produced by uniform and universal laws of physics."

 

Now, if you analyze "location within the universe as a whole" you can say that the word "location" does not describe a point in space, but an event in spacetime.

And that's it!

Edited September 25, 2012 by michel123456

[Iggy]

That's not my fault!

 

The cosmological principle is:

"the working assumption that observers on Earth do not occupy an unusual or privileged location within the universe as a whole, judged as observers of the physical phenomena produced by uniform and universal laws of physics."

 

Now, if you analyze "location within the universe as a whole" you can say that the word "location" does not describe a point in space, but an event in spacetime.

And that's it!

That interpretation would be inconsistent with general relativity, so you'd have to disbelieve GR too. The usual interpretation is,

 

It follows from the cosmological principle that all points in space ought to experience the same physical development, correlated in time in such a way that all points at a certain distance from an observer appear to be at the same stage of development. In that sense, the spatial conditions in the universe must appear to be homogeneous and isotorpic to an observer at all tiems in the future and the past.

<...>

The supposition of the cosmological principle leads to Alexander Friedmann's standard models of cosmological evolution...

 

The Little Book of Time

[tar]

Iggy,

 

Would it also be appropriate to, using that principle, and the knowledge of the expansion of the universe, suggest that no body which we presently see could be in an earlier stage of development, if we were to view that body later? And correlarily suggest that any body that we presently see, will be sensable later at an appropriately redshifted collection of wavelengths? And that as one body is viewed over very long periods of time (on the scale of millions and billions of years) visible wavelengths will become microwave, and microwave radio waves, gamma waves x-rays, x-rays ultraviolet, then visible, infrared, then microwave, then radio waves?

 

If these things are obvious and true, and viewing a single body is in real time, if it is close, but longer wavelengths as the expansion of the universe carries it away from us (and us from it), then there seems to be only the possibility that the viewed developement of a distant body must be in slowed motion, as the redshift increases.

 

And since we now can see the extremely hot locations in space that are in the stage of development of having just become transparent to photons, at z=1000, and coming to us at radio wave lengths, there should be areas of the universe between here and there at the stages of development, that have not yet formed galaxies?

 

Would these areas of space, between Z=10 and Z=1000, not develop into galaxies, before our eyes, as billions of years pass? And would not the distance of the cosmic background radiation increase porportionately to our own age, as the billions of years pass, here? Until we see to the outer edge of the universe, at which point the hot soup itself would begin to age, slowly, developing into darkness and then, much later, early quasars and such?

 

Regards, TAR2

Edited September 26, 2012 by tar

[Iggy]

Iggy,

 

Would it also be appropriate to, using that principle, and the knowledge of the expansion of the universe, suggest that no body which we presently see could be in an earlier stage of development, if we were to view that body later?

Objects appear more developed tomorrow than today if that's what you mean.

 

And correlarily suggest that any body that we presently see, will be sensable later at an appropriately redshifted collection of wavelengths?

Depends what you mean by sensible. Observability becomes a practical problem.

 

And that as one body is viewed over very long periods of time (on the scale of millions and billions of years) visible wavelengths will become microwave, and microwave radio waves, gamma waves x-rays, x-rays ultraviolet, then visible, infrared, then microwave, then radio waves?

yes

 

If these things are obvious and true, and viewing a single body is in real time, if it is close, but longer wavelengths as the expansion of the universe carries it away from us (and us from it), then there seems to be only the possibility that the viewed developement of a distant body must be in slowed motion, as the redshift increases.

time dilated. yes.

 

And since we now can see the extremely hot locations in space that are in the stage of development of having just become transparent to photons, at z=1000, and coming to us at radio wave lengths, there should be areas of the universe between here and there at the stages of development, that have not yet formed galaxies?

right

 

Would these areas of space, between Z=10 and Z=1000, not develop into galaxies, before our eyes, as billions of years pass?

yes

 

And would not the distance of the cosmic background radiation increase porportionately to our own age, as the billions of years pass, here?

It is proportional if you express the age of the universe in conformal time and the distance in comoving distance. Infinitely far in the future the comoving distance to the CMB will be about 60 billion lightyears (one third larger *in comoving distance* than it is now).

 

In other words, infinitely far in the future there will be 1.3 times as many galaxies as there are now between us and the CMB. Of course, both those galaxies and the CMB will be redshifted beyond observability exactly like things are when they fall into a black hole.

 

Until we see to the outer edge of the universe, at which point the hot soup itself would begin to age, slowly, developing into darkness and then, much later, early quasars and such?

The outer edge of the universe?

 

The distance to the CMB approaches a comoving distance of 60 Glyrs as time approaches infinity. If you watch the mass that is currently emitting CMBR over the next billion years you'll see it develop into galaxies.

 

Making sense of the diagrams on this page would be well worth your time.

[michel123456]

That interpretation would be inconsistent with general relativity, so you'd have to disbelieve GR too. The usual interpretation is,

It follows from the cosmological principle that all points in space ought to experience the same physical development, correlated in time in such a way that all points at a certain distance from an observer appear to be at the same stage of development. In that sense, the spatial conditions in the universe must appear to be homogeneous and isotorpic to an observer at all tiems in the future and the past.

<...>

 

 

I agree completely with the above.

 

The supposition of the cosmological principle leads to Alexander Friedmann's standard models of cosmological evolution...

 

And disagree with the above.

If the universe "must appear to be homogeneous and isotropic to an observer at all times in the future and the past", then it is consistent with my previous statement that says:

"It is not conceivable (IMHO) that we currently live a privileged period of the Universe, a period so special that allows us to observe the Universe in a different way than future generations on future planets would observe. To me, there MUST be nothing special in our position in space (cf cosmological principle) and in time: IOW there is no privilege to our position in spacetime."