What was the Big Bang

[Subduction Zone]

Whatever.

Relax, it is not that big of a deal. You kept trying to claim that I did not understand the Big Bang when it becomes more and more obvious that you are the one whose understanding is lacking. You could always try to learn instead of simply denying my claims and not supporting your claims properly.

One of the reasons that links are needed is that the mistakes that a person may make can be illustrated with their own links. Unsupported quotes are worthless. I demonstrate this quite often to Christians by the fact that the Bible says at least 12 times that "there is no god". Without a link to the source of the quotes one cannot know what was really meant. Spoiler alert, they do not support the non-existence of God.

 

[Polymath257]

Would you please tone down your obnoxious arrogance.

Yes, open and closed are now commonly used as a reference to the curvature of the universe. But what happened to the issue of the open and closed expansion in your so-called "outdated" definition. Are you saying that's no longer a meaningful fact? Where is your link to the why the definition was changed and how that relegated the ultimate fate of the universe to irrelevancy.

Actually, open and closed expansion and open and closed curvature of the universe are both issues that still apply--although the former is now essentially settled, and they may turn out to be interrelated.

There isn't an 'open and closed' curvature. There is positive curvature, negative curvature, and flatness. In the presence of a non-zero cosmological constant, all of these are possible even in the case of an accelerating expansion rate.

 

[Polymath257]

Absolutely not. Expansion is accelerating and is passing through superluminal speed at the visible limit of the universe which invisible because of it. What we have to learn is how our local universe is embedded in a non-local (locationless/timeless) ether or Quantumland. The standard model of an open universe does not account for expansion continuing to accelerate beyond light speed.

Yes, actually, it does so quite nicely. that is simply the definition of a Hubble radius.

 

[Polymath257]

Once again, they have measured the curvature of our universe. To the best ability to measure it is flat. I did provide a link to support that claim. Do you need some more? Since it is flat as far as we can see that means that even at light speed you will never "curve back" on yourself. The universe continues to expand and due to the expansion and not actual motion light will never get that far. The universe can expand faster than the speed of light since that is not "motion" in the classical sense.

The difficulty here is that any error bars at all on 'flat' (i.e, zero curvature) will allow both positive or negative curvature.

What we *can* say is that *if* space is positively curved, then the 'return distance' is orders of magnitude larger than the Hubble radius.

 

[Thermos aquaticus]

The difficulty here is that any error bars at all on 'flat' (i.e, zero curvature) will allow both positive or negative curvature.

What we *can* say is that *if* space is positively curved, then the 'return distance' is orders of magnitude larger than the Hubble radius.

It's curious that I am not seeing any future NASA missions looking at this question. There are at least two that will look at dark matter and dark energy, but none for the curvature of space. Are you aware of any planned space missions or Earth based observatories looking at this question?

 

[Subduction Zone]

The difficulty here is that any error bars at all on 'flat' (i.e, zero curvature) will allow both positive or negative curvature.

What we *can* say is that *if* space is positively curved, then the 'return distance' is orders of magnitude larger than the Hubble radius.

That is why I did include a qualifier. From my understanding the rate of expansion, along with the minimal size of our universe, makes the return trip of a ray of light out of the question, even if the universe has a positive curvature. Is that correct?

 

[Subduction Zone]

It's curious that I am not seeing any future NASA missions looking at this question. There are at least two that will look at dark matter and dark energy, but none for the curvature of space. Are you aware of any planned space missions or Earth based observatories looking at this question?

The curvature of the universe was measured by a careful analysis of the Cosmic Background Radiation. So any work that refined the observation of the radiation should increase our knowledge of the curvature of the universe.

 

[Thermos aquaticus]

The curvature of the universe was measured by a careful analysis of the Cosmic Background Radiation. So any work that refined the observation of the radiation should increase our knowledge of the curvature of the universe.

Like Polymath says, it is nearly impossible to determine if the universe is truly flat. It's kind of like experiments that try to measure the mass of a photon. The best that they can do is put an upper limit on the mass of a photon because we are limited by the sensitivity of the instrument. The same would apply to the flatness of the universe.

 

[Subduction Zone]

Like Polymath says, it is nearly impossible to determine if the universe is truly flat. It's kind of like experiments that try to measure the mass of a photon. The best that they can do is put an upper limit on the mass of a photon because we are limited by the sensitivity of the instrument. The same would apply to the flatness of the universe.

Yep, understanding error bars is an important part of science. I have also seen some abuse error bars by trying to make a measurement that was less than the minimal error of a method. One could conceivably measure the universe and find that it does have a positive or negative curvature beyond the error of measurement, but if the universe truly is flat no matter how well we can measure it there will always be a margin of error that could go either positive or negative.

 

[Thermos aquaticus]

Yep, understanding error bars is an important part of science. I have also seen some abuse error bars by trying to make a measurement that was less than the minimal error of a method. One could conceivably measure the universe and find that it does have a positive or negative curvature beyond the error of measurement, but if the universe truly is flat no matter how well we can measure it there will always be a margin of error that could go either positive or negative.

During the summers I have helped train undergrads in the lab. One of their tasks is to create a Powerpoint that contains their hypotheses, data, and conclusions of the research projects they have done over the summer. I don't know how many times I have asked, "Where are the error bars?", when looking over their presentations. Thankfully, some undergrads have taken a stats based science class, but it is illustrative of how often statistics are ignored by the lay public.

 

[`mud]

It's spherical, it's flat, it's boundless, it's finite !
Compared to what ??
Contained by what ??
Encapsulated by what ???

 

[Ben Dhyan]

Since you can only travel at subluminal speeds and the universe is expanding at greater than the speed of light when measured across the expanse of the universe you will always be heading into new space.

Please assume FTL travel, so where does the traveler end up, at the edge of the universe or back where they started from?

 

[Polymath257]

It's curious that I am not seeing any future NASA missions looking at this question. There are at least two that will look at dark matter and dark energy, but none for the curvature of space. Are you aware of any planned space missions or Earth based observatories looking at this question?

Well, the Weber scope should supply useful information in that regard. People are still crunching the data from the Planck mission also. And the dark matter and dark energy studies both feed into questions concerning whether there are deviations from the standard model.

The trick is to constrain the models via the data and then read off the curvature. Nothing directly measures overall curvature. It has to be calculated from measurements of density and the size of the cosmological constant (if it is constant, that is). So the data constrains the different parameters that lead into the curvature calculation.

 

[Polymath257]

Please assume FTL travel, so where does the traveler end up, at the edge of the universe or back where they started from?

At this point, we do not know. It is still *possible* that space is finite in extent.

But, for that matter, even if space is negatively curved or flat, it is *still* possible that it is finite. This is a mathematical possibility that is often ignored by physicists, although some are beginning to investigate this.

 

[Polymath257]

The curvature of the universe was measured by a careful analysis of the Cosmic Background Radiation. So any work that refined the observation of the radiation should increase our knowledge of the curvature of the universe.

Yes, although supernova studies for the rate of acceleration of the expansion are also relevant.

 

[Polymath257]

That is why I did include a qualifier. From my understanding the rate of expansion, along with the minimal size of our universe, makes the return trip of a ray of light out of the question, even if the universe has a positive curvature. Is that correct?

I haven't gone thorugh the calculations when there is a non-zero cosmological constant, but with a zero value, the time to 'go around' a finite universe was double the time until a Big Crunch. My guess is that a similar result would hold even with a CC in the sense that the expansion acceleration would overpower any attempt to circumnavigate.

 

[Ben Dhyan]

At this point, we do not know. It is still *possible* that space is finite in extent.

But, for that matter, even if space is negatively curved or flat, it is *still* possible that it is finite. This is a mathematical possibility that is often ignored by physicists, although some are beginning to investigate this.

Why is it not possible for this possible finite universe in 'flat' space to be generally described verbally, or graphically?

 

[Ben Dhyan]

A flat 2 dimensional surface can be curved (by gravity say) into the shape of a sphere. It has no edge, it is finite but unbounded, and if you walk in one direction, you will return to your starting point because it is finite. It's the same principle for the universe only in with 3 dimensions being warped into a finite but unbounded space. You can add to that the element of expansion, in both the 2D and 3D models.

Your post does not address my point, the point is you stated that 'we don't know is there is an edge to the universe'. Now it follows logically if it does have an edge, than the finite universe in unbounded space does not exist. Iow, we don't know if there is a finite universe in unbounded space, if we did, we would know there is not an edge to the universe...and vise versa.

 

[gnostic]

No, this would only be true if the universe was closed. The universe to our best measurements is flat or open. Your statement goes with the now largely discarded thought of a universe that goes through endless series of Big Bangs and Big Crunches.

Otherwise known as the oscillating universe model, cyclical universe model, or the Big Bounce.

 

[james blunt]

Why is it not possible for this possible finite universe in 'flat' space to be generally described verbally, or graphically?

There you go and by ''flat'' they mean isometric.