Hypothesis: the true story of the universe begins with a big bang, from there includes a non-stellar source of light and that the CMB was born of that source.

Questions:

What experiment do I conduct to try to disprove any or all of that hypothesis? What apparatus would I build? What would the experiment entail? How would I tell my results have disproved the hypothesis?

What prediction could I make about something people have yet to observe? That is, what could we do to check that hypothesis' predictions? Does it even make predictions that are checkable? If so, what are they, or what is one of them?

Just out of curiosity what is the purpose?

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The first principle is that you must not fool yourself - and you are the easiest person to fool.
~~~ Richard Feynman ~~~
It is imperative in science to doubt.
~~~ Richard Feynman ~~~
Common sense is not so common
~~~ Voltaire ~~~

Well, one thing you could check would be the motion of all matter that you could see.

You could also check for background radiation. That would be a second thing.

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"I'm as accurate as any psychic. And I'm a cartoon!" -- Squidward

"Arrrgh, the laws of physics be a harsh mistress!" -- Bender

Auroa,

I can't really run an experiment on all the matter I can see. Does the hypothesis make any particular prediction about that matter that is checkable?

What can I check regarding background radiation?

Spratleyj,

I like skepticism and I don't want to fool myself.

Then perhaps thou shall try the ATM section...

__________________
The first principle is that you must not fool yourself - and you are the easiest person to fool.
~~~ Richard Feynman ~~~
It is imperative in science to doubt.
~~~ Richard Feynman ~~~
Common sense is not so common
~~~ Voltaire ~~~

Well, a first step is to recognise that the BB wasn't proposed yesterday, and that people have been (and continue) to devise tests and experiments since the day it was proposed. The BB is the predominant theory at present because it's predictions have repeatedly been confirmed by experiments and observation, including :
- existence of the CMB
- that the CMB has a black-body spectrum, but with fluctuations
- relative amounts of Hydrogen, Helium and Deuterium
- galaxies look different (younger) the further out you look

In addition (though I'm not sure this counts as a prediction), the age of the universe derived from CMB agrees with other methods of estimation.

So, what further tests/experiments?
Well, a few ideas :
- we've no idea what Dark Matter / Dark Energy are, so it's possible as we learn more about them that they could support or destroy the model (eg. making it impossible for galaxies to form).
- The Large Hadron Collider has been built specifically to examine behaviour at temperatures/pressures not seen since the BB. The behaviour observed could affect the model.

Bottom line, BB is still a falsifiable theory, but it's up to the supporters of other models to make predictions that better match observations before people will switch

To quote Nereid after I posted pretty much the same thing on the ATM section

Not sure what any of these questions have to do with the ATM idea presented in this thread, would you be kind enough to explain, rcglinsk?

Seems to me that these are more appropriate in a (new) Q&A thread ...


For context, the original post was,

"Radiation from Bigbang was from about 13.7 billion years old. It is not from any star"

...and it was presented as a poll where people could vote yes, no or I don't understand.


I responded to Nereid that I thought my questions were the central concerns when answering the poll question, but that I would take up the advice and post the questions in Q&A.

Please elaborate. You sound like you've started off on a great foot, but why do those ratios matter? What is the significance?

Please elaborate on what you mean by "look younger." I wonder how you know what a "young" galaxy looks like, as opposed to an "old" galaxy.

For whatever hypothesis you propose for differentiating when a galaxy is "old" versus "young"

What experiment do I conduct to try to disprove any or all of that hypothesis? What apparatus would I build? What would the experiment entail? How would I tell my results have disproved the hypothesis?

What prediction could I make about something people have yet to observe? That is, what could we do to check that hypothesis' predictions? Does it even make predictions that are checkable? If so, what are they, or what is one of them?

Also, please describe how you know how "far out" galaxies are. You didn't send a space ship with a tape measure after all.

I'm not sure either. What are those other estimations? What is the content of them?

I don't have any idea what dark matter or energy are either. I wonder by what mechanism things I nor you have any knowledge about could support or destroy a model. Please elaborate.

What behavior, theoretical or not, do you refer to? How would it "support" a model?

Might I say as an aside, I'm all for smashing things together at high speeds; regardless of the pure scientific discovery that might come of it.

Why?

RobA,

Shoot, I think I might have been unclear.

In the last post you said,

I meant "why?" to refer to both claims, "BB is ... a falsifiable theory," as well as "it's up to supporters of other models to make predictions that better match observations before people will switch."

The BB says that the initial energy would have congealed into individual particles - protons, aka Hydrogen ions (later to become Hydrogen atoms). As the universe cooled, some of these would have collided together, sometimes sticking together to form Helium and Deuterium (and some Lithium). For various reasons, nothing heavier would have been formed , which was a BIG problem for the BB until Hoyle (who, coincidentally, always hated the BB) figured out that heavier stuff would have been formed inside stars. Stars also generate negligible amounts of Helium (compared to expected BB quantities), and would consume any deuterium.

So, basically all the Hydrogen, Helium and Deuterium we can see would have come from the BB. But - and this is the thing - we also know from experiments here on Earth how likely Hydrogen is likely to fuse into Helium/Deuterium. Applying that to expected conditions post BB means we can calculate how much Helium and Deuterium would have been formed from the primordial Hydrogen.

This was first calculated by Gamow, who came up with (IIRC) 75% Hydrogen, 20% Helium, and 5% Deuterium. This was from first principles, before observations were possible.


Take a look at the Hubble Ultra Deep Field, and this article. Younger galaxies have a number of features, like they're much smaller, more irregularly shaped, etc. From the HubbleSite:

Back to work - I'll get to the rest later

Hi RobA,

What are the precise predictions? 75.00 +/- .01? What observations do you refer to when you say there is agreement? In your mind, what level of agreement is necessary to make the ratio matter?

What does the BBT theory predict as to ratios of hydrogen, helium and deuterium in relation to each other element of the periodic table? Is there a similar level of agreement? As in within the same, I will assume very small, error bars?

Should agreement matter if it only relates to hydrogen, helium and deuterium; even if there is no agreement in relation to the other elements?

Also, your articles refer to "young" as defined by models of what young means. I was more asking about what those models said and what they were based on.

Please though, remember the other questions:

How is the big bang a falsifiable theory?
Why would one believe it solely because no one has offered a better theory?
What are the other measures of the age of the universe you refer to?
How does one know how "far out" a galaxy is?

Hi rcglinsk

I'm not very knowledgeable on astrophysics (thats why I read Q & A), but as for why BB is the dominant theory, this is because it is the 'best fit' for the observable phenomena. That doesnt mean its ideal, or that sometime in the future a new theory wont replace it. No-one is saying you have believe it, but it is the "best fit" at this point in time.

Simple. Take one universe, and...

Essentially, you can't. What the LHC and similar experiments are trying to do is to duplicate conditions, albeit on a very small scale, as they existed at the beginning, making observations, and either substantiating our current understanding, or leading the way to how things might be different than how we've extrapolated them to be.

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rcglinsk

Good questions, terrible thread

You want to know astrophysics. The whole thing.

You are doing this inefficiently (yes, I'm an economist).

Embark on a physics degree is my advice.

The easiest way is to go back in time and see how the universe looked like in the beginning, or build your own universe.

To simplify it, big bang states one thing, that the universe started from a very small point of space, and expanded. The falsify it, you'd have to show that the universe is not always expanding (for example, its size fluctuates). Just contracting won't do, since it could be the big crunch.

Well, yes and no. If there is no better theory, it meant this this one is the best, currently. It had been build upon by decades of observational evidence. If someday, somehow, a better theory came up, that could explain all that Big Bang can, and explain all that Big Bang couldn't, it'll supersede Big Bang. Note though, if it is something that Big Bang can absorb, then the Big Bang theory will be modified, instead of being replaced.

I might recommend some reading over at wikipedia. It is explained in more detail, and provides more link.

I recommend this page(wikipedia again). Again, I do not have the sufficient knowledge to explain in more detail.

Let's wait until someone knowledgeable enough comes in..

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RegisteredUsername

Gee, to the hundredth of a percent ?? Well, Ned Wright's Tutorial says 24% by mass, give or take 0.5%. Turns out my memory WILDLY overestimated the Deuterium, which comes in at around 0.01%

I refer to things like these. Figuring out what the universe contains is an ongoing effort, not just one set.

The fact that these observations give around 23% to 26% Helium, rather than, say, 1% or 5%, is IMHO a darned good match :P

As per my previous post, the BB model says NOTHING above Lithim was produced in the BB (so yes, VERY small error bars ! )

[quote=rcglinsk;1336074]

Please though, remember the other questions:

Like any other theory, data could come in tomorrow that would blow it away. As I mentioned earlier, we have no idea what 95% of the universe is comprised of. Discoveries in that area could affect the model. Further, the BB is greatly dependent on Quantum Gravity. How that turns out, together with discoveries from the LHC and others, can knock it.


I can't improve on RegisteredUsername's answer to that one

Again, take a look at Ned Wright's Tutorial

Those galaxies were in the Hubble Ultra-Deep Field. That picture was the result of Hubble staring at the emptiest piece of sky for a 1 MILLION second exposure - that's over 10 days solid ! EVERYTHING in that picture is a LOOOOOONG way away !

RobA has answered that quite well, and if you just keep asking it in different forms, eventually you will be taught all of astrophysics-- that's a tall order.
This seems to be your fundamental issue, I dare say. But anyone is free to "believe" whatever they choose. Contrary to popular belief, physics theories are not intended to create belief. They are intended to unify, organize, and predict, observations. Period, that's what they do. What you believe about them, in terms of their fundamental ontology (the primitive elements that the theories assume exist), is up to you.

Indeed, there is essentially no major physics theory that has not seen substantial reconstruction of its fundamental ontologies over the course of science's advances. Belief in the ontology of our theories is a luxury that we all avail ourselves of, essentially for convenience and satisfaction, but it is no required aspect of the theory. The real question is not why would you choose to believe it, but rather, why would you choose to believe something else?
Some of the age measures that the Big Bang theory unifies, when one
appends dark matter and dark energy (required to unify other observed effects) include:
--the dynamical age imprinted in the Hubble flow
--the age of the oldest stars, based on evolutionary models
--the amount of heavier elements produced in stellar nucleosynthesis
--the history of galaxy and supermassive black hole formation
In short, the age of everything that we have seen is happening on grand scales in the universe.
We never know how "far out" anything is. Distance is also a theoretical construct, used to unify and organize another whole class of observations. We take local observations of distance we use in our everyday lives, and extend them out into space using the "ladder of distance scales". This "ladder" is another example of how we unify concepts that work in the laboratory with concepts that work as consistently in the rest of the cosmos.

Again, believe what you will, but the unifying power of the approach of science is well documented. Sometimes it leads to principles and technology we rely on every day, and other times it is just science applied to things that are far away and have little direct effect on us.

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There are two kinds of delusions, the obvious kind that clearly don't work, and the insidious kind that clearly do.

rcglinsk, if memory serves correctly, we've discussed something like this before, haven't we?

The extreme digest version (well, one such version) goes something like this:

Why is cosmology a science? Because astrophysics is a science.

Why is astrophysics a science? Because physics is a science.

Why is physics a science? So, this discussion is, fundamentally, about what 'science' is (in the last century or three)?

Perhaps if you could distill your questions into these key aspects?

* where do you see the biggest disconnect between cosmology and astrophysics?

* ditto, between astrophysics and physics?

* ditto, wrt your view of science and that you infer from what you read?
To take just one of your specific questions, than can be answered within the framework of the relevant part of science ...

As Ken G and RegisteredUserName have already noted, 'distance' in cosmology (and astrophysics) is something that differs from the vague, absolute idea many of us form from our intuition.

This HTML version of a short paper may be quite illuminating and informative wrt 'distance' (has more meat than the wikipedia page RUN cited): Distance Measures in Cosmology

Concerning the primordial abundance of the light nuclides (1H, 2H, 3He, 4He, 7Li). Detailed studies of BBN (Big Bang Nucleosynthesis) make testable predictions about the abundance of these, relative to the number of 'relict' photons (in the CMB), at the time nucleosynthesis stopped. No surprise that astronomers have done a great deal of research on estimating these abundances! Several have been estimated using at least two independent techniques. And the results are consistent with LCDM models.

If you get a chance, I think time spent reading up on this would be well spent ... how astonishing is it that a model (LCDM) with but a handful of free parameters can not only account for all the billions of datapoints concerning the CMB, but also produce consistent estimates of the abundances of the these nuclides ... throughout the observable universe!

There is one fly in the ointment: the Li abundances estimated don't match those predicted, within the relevant error bars. YMMV, but I think this is saying more about the way the primordial 7Li abundance is estimated, from the various observations, than pointing to a hole in the LCDM models (the nuclear cross-sections are very tightly constrained, so essentially no room to move there). It's a fascinating story; for example, this is the only isotope for which there are three 'creation' processes at work: BBN, stellar nucleosynthesis, and via cosmic ray collisions ('spallation') (there are also, of course, 'destruction' processes at work). So the observed, contemporary, abundance of 7Li is the result of all three creation (and destruction) processes at work over ~13 billion years ... and the corollary is that to estimate the primordial abundance, you need to model these over the history of the universe since the end of the time of BBN. That's tricky.

You clearly know very little about the Big Bang Theory, and there is nothing wrong with that. And you are generally skeptical - nothing wrong with that, either. But you are questioning the theory as if those who have developed it are idiots, as in questions like the following:

Does it even make predictions that are checkable?

I have a suggestion for you: You should assume that scientists - astrophysicists, cosmologists, astronomers, et al. - are clever. From the content of your questions, I can tell you that these scientists are more clever than your wildest imagination.

You wonder about the other elements of the periodic table and why their ratios aren't predicted in the BBT like hydrogen and helium. Well, as RobA mentioned twice, no element heavier than lithium could have been fused during the first 3 minutes. There was not enough time because the universe was rapidly expanding, and therefore cooling very quickly. Fusion requires very high temperatures - particles moving very rapidly - to slam positively charged protons together and make them stick. (This is all worked out very rigorously using quantum theory and observations from high-energy particle accelerators.) So there was a very small window of time when the temperature was right for hydrogen to fuse, resulting in a certain amount of helium and very small quantities of deuterium and lithium. Then the window closed. The temperature cooled beyond a certain level, and no more fusion could occur. End of story.

Well, fortunately, that wasn't the end of the story. When things cooled down enough so that everything wasn't in thermal equilibrium, about 400,000 years later, gravity started pulling these gasses together, creating stars and galaxies, etc. THE STARS are what created the other elements. Large stars go through a whole cycle of element creation. As the lighter elements are fused and used up, gravity contracts the star, making it hot enough so that heavier and heavier elements are fused. Stars heavier than a certain mass will then explode at the end of their life, and all those elements (plus heavier ones fused in the explosion) will be sent out into the galaxy.

It is very well supported that this is the only way that the elements that make up this planet and almost everything on it, including the carbon, etc. in your body, could have been formed. (I blew me out when I heard Carl Sagan say this in his TV series Cosmos over 30 years ago. This explanation is very solid, and after 30-40 years, there is simply no viable alternative explanation. Until you hear otherwise, this is it. Get used to it.)

I suggest learning about the Big Bang Theory first, and then if you still have any skeptical questions, I'm sure someone on this board will answer them with glee and fervor.

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Why, yes, of course it does.

Research something called "red shift".

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"Arrrgh, the laws of physics be a harsh mistress!" -- Bender

I'll add to that. We observe the "local" universe and measure its contents, in matter and energy. We then apply the FRW solutions of GR (what falls out on the adopted constraints of isotropy and homogeneity) to tell us how the matter/energy density evolve as a function of time. We run it backward and can predict that the proton/neutron density, at the time in which nucleosynthesis was converting some of the protons and all of the neutrons into deuterons, helium (3He and 4He) plus Lithium, was no where near high enough to allow the triple-alpha process (3 x 4He --> 12 C) to create carbon to occur. Why? Because that process is virtually a 3-body collision that involves unstable 8Be and an excited state of 12C. It therefore occurs only within the very high density cores of stars that are late in life, but could not occur at any significant level in the early universe. When you couple that with the fact that nucleon masses of 5 and 8 are unstable, the early expanding, cooling universe presented a bottle neck in the production of the elements. Setting aside the elements Be, B (which also likely have significant or predominant contributions from cosmic ray spallation) stars created the rest of the periodic table.

I think somebody has already posted this link, but I'll do it again. We can make detailed computations of H:2H:4He:3He:6,7Li ratios from the first several minutes of the big bang, and these depend on the present Hubble parameter, and measurements of the present baryonic (protons + neutrons) matter density in the universe, as averaged over sufficiently large volumes of space. Both of these observable parameters have other, independent consequences on other observables (such as the fluctuation power spectrum of the cosmic background radiation, and the collapse of structure much later to form galaxies and galaxy clusters, and ...).

This is a very brief overview of the current evidence for the Big Bang.

That line of reasoning has always struck me as a form of:

http://www.csun.edu/~dgw61315/fallacies.html

So the issue is whether there is a prima facie case for accepting the big bang theory. I think the questions I posed go to the heart of that issue.

To truly test big bang we need the same conditions. No Space or Time, these have to be absent to replicate BBT. Then we have to wait for all the mass and energy of the Universe to appear in a flash out of nothing. When this happens we can observe how sub atomic particles become plasma and then stars and galaxies.

What's confusing me is how all that amounts to a prima facie case that there was a big bang. Everyone on this thread and all the science papers writers talk about it as if it were a real thing. It's like the alpha-omega self sustaining dynamo. People talk about that happening in the earth and making our magnetic field, but any time someone tries to make a magnetic field without electric current or a bar magnet in a laboratory it doesn't work. I meant the questions to find out what people think the prima facie case for the big bang is. If you know the prima facie case for the self sustaining dynamo I'd be all for hearing that as well.

I think you are correct. That's kinda the heart of my concern with the big bang theory. We have no readily available way to know whether we are wrong.

Here's what I wrote in an earlier post (extract):

"Why is physics a science? So, this discussion is, fundamentally, about what 'science' is (in the last century or three)?"

It seems, rcglinsk, that you are asking about the extent to which certain forms of logic are applicable, or used (or both), in modern science or not.

Is that so?

This is yet another angle on the question "What is science?"

In this case, it concerns circumstances that cannot be replicated at will, such as the Great Vowel Shift (in linguistics, in the history of the English languages), the origins of the Great Depression (in economics), the causes of the P-T great extinction (in geology, etc), and so on.

I think the mistake you, and rcglinsk, are making is to focus on one particular theory (or set of theories) in one branch of science (cosmology) ... your questions surely concern the nature of science (not the BBT).

This is weird. I feel like I posted a reply to the observation issue a moment ago but don't see it. Was a long day at work...

Anyway, I think most people who say observation would not mean an estimation of how things were 13 billion years ago. Especially because arriving at those numbers requires applying a lot of other theories. For example the theories of how galaxies formed or how stars produce heavy elements.

Nereid explained it pretty well,

Spaceman Spiff,

When you talk about the "local" universe's matter and energy content, are you including dark matter or dark energy? And if not, how does one arrive at a matter content for the milky way galaxy?

Correct me if I'm wrong but all we can readily measure is rotational velocities of visible objects. That can tell us about a centripetal force, but it cannot tell us if that force is 100% gravity allowing a conversion to mass.

RobA,

What data could come in tomorrow and blow the theory away? What would that data say? How would it falsify the theory?

Also, you mentioned the hubble deep field and how the movement of those galaxies on the horizon is nearly imperceptible. Is that not true for any stellar object a sufficient distance away? Doesn't that only set a minimum distance and not say much about the particular distance?

That's odd. I've never thought of logic as having forms which are applicable in some settings but not others. Granted, you might not want to try logic when negotiating with a two year old. "Because I said so" is not a logical argument, but it's the right one for the situation. Are you saying one's logic should change from scientific topic to scientific topic?