标记档案: 大爆炸理论

宇宙大爆炸理论 – 第二部分

阅读后 论文Ashtekar 量子重力和思考它, 我意识到我的麻烦与宇宙大爆炸理论是. 它更多的是对较细节的基本假设. 我以为我会在这里总结一下我的想法, 以上为我自己的利益比任何其他人的.

经典理论 (包括SR和QM) 治疗空间连续虚无; 因此,长期时空连续. 在此视图中, 存在于连续的空间物体和彼此在连续时间进行交互.

虽然时空连续统这一概念是直观的吸引力, 这是, 充其量, 残缺. 考虑, 例如, 一个旋转体的空. 它预期会遇到的离心力. 现在想象一下,身体是静止的,整个空间旋转周围. 它会不会遇到任何离心力?

这是很难理解为什么会有任何离心力,如果空间是空的虚无.

GR介绍了一个范式转变通过编码重力进入时空从而在本质上动态, 而不是空洞虚无. 因此,, 质量得到沉浸在太空 (和时间), 空间变得代名词宇宙, 和纺纱身体问题变得很容易回答. 是的, 它会经历离心力,如果它是旋转它周围的宇宙,因为它是等效于人体的纺丝. 和, 别, 它不会, 如果它是在刚刚空的空间. 但 “空” 不存在. 在没有质量, 没有时空几何.

所以, 自然, 在大爆炸之前 (如果有一个), 不可能有任何空间, 也确实可以有任何 “之前。” 注意, 然而,, 该Ashtekar文件并没有明确说明为什么必须有一个大爆炸. 它得到最接近的是,BB的必要性产生于重力的空间 - 时间中的GR的编码. 尽管引力的这种编码,从而使时空动态, GR仍然把时空的连续平稳 — 一大败笔, 根据Ashtekar, 这QG整顿.

现在, 如果我们承认,宇宙开始了一次大爆炸 (并从一个小区域), 我们必须考虑量子效应. 时空必须是量化的唯一正确的方式做这将是通过量子引力. 通过QG, 我们希望避免GR的大爆炸奇点, 以同样的方式QM解决了氢原子的无界基态能量问题.

我上面描述的就是我所理解的背后现代宇宙学的物理参数. 剩下的就是数学的大厦建立在这个物质之上 (或甚哲学) 基金会. 如果你对哲学基础没有强烈的意见 (或者如果你的意见与它保持一致), 你能接受BB没有困难. 不幸, 我有不同的看法.

我的看法围绕以下问题旋转.

这些职位可能听起来像无用的哲学沉思, 但我确实有一些具体的 (在我看来,, 重要) 结果, 下面列出.

还有更多的工作需要在这方面做的. 但对于未来几年, 从我的职业生涯定量我的新书合同和压力, 我没有足够的时间来研究遗传资源和宇宙学与应有的严肃性. 我希望要回他们一次传播自己太薄通行证的当前阶段.

宇宙大爆炸理论

I am a physicist, but I don’t quite understand the Big Bang theory. Let me tell you why.

The Big Bang theory says that the whole universe started from a “singularity” — a single point. The first question then is, a single point where? It is not a single point “in space” because the whole space was a single point. The Discovery channel would put it fancifully that “the whole universe could fit in the palm of your hand,” which of course it could not. Your palm would also be a little palm inside the little universe in that single point.

The second question is, if the whole universe was inside one point, what about all the points around it? Physicists would advise you not to ask such stupid questions. 不心疼, they have asked me to shut up as well. Some of them may kindly explain that the other points may be parallel universes. Others may say that there are no “other” 点. They may point out (as Steven Weinberg does in The Dreams of a Final Theory) that there is nothing more to the north of the North Pole. I consider this analogy more of a semantic argument than a scientific one, but let’s buy this argument for now.

The next hurdle is that the singularity is in space-time — not merely in space. So before the Big Bang, there was no time. 遗憾, there was no “前!” This is a concept that my five year old son has problems with. 同样, the Big Bang cosmologist will point out that things do not necessarily have to continue backwards — you may think that whatever temperature something is at, you can always make it a little colder. But you cannot make it colder than absolute zero. 真, true; but is temperature the same as time? Temperature is a measure of hotness, which is an aggregate of molecular speeds. And speed is distance traveled in unit time. Time again. Hmmm….

I am sure it is my lack of imagination or incompleteness of training that is preventing me from understanding and accepting this Big Bang concept. But even after buying the space-time singularity concept, other difficulties persist.

Firstly, if the whole universe is at one point at one time, one would naively expect it to make a super-massive black hole from which not even light can escape. Clearly then, the whole universe couldn’t have banged out of that point. But I’m sure there is a perfectly logical explanation why it can, just that I don’t know it yet. May be some of my readers will point it out to me?

第二, what’s with dark matter and dark energy? The Big Bang cosmology has to stretch itself a bit with the notion of dark energy to account for the large scale dynamics of the observed universe. Our universe is expanding (or so it appears) at an accelerating rate, which can only be accounted for by assuming that there is an invisible energy pushing the galaxies apart. Within the galaxies themselves, stars are moving around as though there is more mass than we can see. This is the so called dark matter. Although “dark” signifies invisible, to me, it sounds as though we are in the dark about what these beasts are!

The third trouble I have is the fact that the Big Bang cosmology violates special relativity (SR). This little concern of mine has been answered in many different ways:

  • One answer is that general relativity “trumps” SR — if there are conflicting predictions or directives from these two theories, I was advised to always trust GR.
  • 除了, SR applies only to local motion, like spaceships whizzing past each other. Non-local events do not have to obey SR. This makes me wonder how events know whether they are local or not. 好, that was bit tongue in cheek. I can kind of buy this argument (based on curvature of space-time perhaps becoming significant at large distances), although the non-scientific nature of local-ness makes me uneasy. (During the inflationary phase in the Big Bang theory, were things local or non-local?)
  • Third answer: In the case of the Big Bang, the space itself is expanding, hence no violation of SR. SR applies to motion through space. (Wonder if I could’ve used that line when I got pulled over on I-81. “Officer, I wasn’t speeding. Just that the space in between was expanding a little too fast!”)

Speaking of space expanding, it is supposed to be expanding only in between galaxies, not within them, 显然. I’m sure there is a perfectly logical explanation why, probably related to the proximity of masses or whatnot, but I’m not well-versed enough to understand it. In physics, disagreement and skepticism are always due to ignorance. But it is true that I have no idea what they mean when they say the space itself is expanding. If I stood in a region where the space was expanding, would I become bigger and would galaxies look smaller to me?

Note that it is necessary for space to expand only between galaxies. If it expanded everywhere, from subatomic to galactic scales, it would look as though nothing changed. Hardly satisfying because the distant galaxies do look as though they are flying off at great speeds.

I guess the real question is, what exactly is the difference between space expanding between two galaxies and the two galaxies merely moving away from each other?

One concept that I find bizarre is that singularity doesn’t necessarily mean single point in space. It was pointed out to me that the Big Bang could have been a spread out affair — thinking otherwise was merely my misconception, because I got confused by the similarity between the words “singularity” and single.

People present the Big Bang theory in physics pretty much like Evolution in biology, implying the same level of infallibility. But I feel that it is disingenuous to do that. 对我来说,, it looks as though the theory is so full of patchwork, such a mathematical collage to cook up something that is consistent with GR that it is hard to imagine that it corresponds to anything real (无视, for the moment, my favorite question — what is real?) But popular writers have embraced it. 例如, Ray Kurzweil and Richard Dawkins put it as a matter of fact in their books, lending it a credence that it perhaps doesn’t merit.

Universe – Size and Age

I posted this question that was bothering me when I read that they found a galaxy at about 13 billion light years away. My understanding of that statement is: At distance of 13 billion light years, there was a galaxy 13 billion years ago, so that we can see the light from it now. Wouldn’t that mean that the universe is at least 26 billion years old? It must have taken the galaxy about 13 billion years to reach where it appears to be, and the light from it must take another 13 billion years to reach us.

In answering my question, Martin and Swansont (who I assume are academic phycisists) point out my misconceptions and essentially ask me to learn more. All shall be answered when I’m assimilated, it would appear! 🙂

This debate is published as a prelude to my post on the Big Bang theory, coming up in a day or two.

Mowgli 03-26-2007 10:14 PM

Universe – Size and Age
I was reading a post in http://www.space.com/ stating that they found a galaxy at about 13 billion light years away. I am trying to figure out what that statement means. 对我来说,, it means that 13 billion years ago, this galaxy was where we see it now. Isn’t that what 13b LY away means? 如果是这样的, wouldn’t that mean that the universe has to be at least 26 billion years old? 我的意思是, the whole universe started from one singular point; how could this galaxy be where it was 13 billion years ago unless it had at least 13 billion years to get there? (Ignoring the inflationary phase for the moment…) I have heard people explain that the space itself is expanding. What the heck does that mean? Isn’t it just a fancier way of saying that the speed of light was smaller some time ago?
swansont 03-27-2007 09:10 AM

Quote:

Originally Posted by Mowgli
(Post 329204)
我的意思是, the whole universe started from one singular point; how could this galaxy be where it was 13 billion years ago unless it had at least 13 billion years to get there? (Ignoring the inflationary phase for the moment…)

Ignoring all the rest, how would this mean the universe is 26 billion years old?

Quote:

Originally Posted by Mowgli
(Post 329204)
I have heard people explain that the space itself is expanding. What the heck does that mean? Isn’t it just a fancier way of saying that the speed of light was smaller some time ago?

The speed of light is an inherent part of atomic structure, in the fine structure constant (alpha). If c was changing, then the patterns of atomic spectra would have to change. There hasn’t been any confirmed data that shows that alpha has changed (there has been the occasional paper claiming it, but you need someone to repeat the measurements), and the rest is all consistent with no change.

Martin 03-27-2007 11:25 AM

To confirm or reinforce what swansont said, there are speculation and some fringe or nonstandard cosmologies that involve c changing over time (or alpha changing over time), but the changing constants thing just gets more and more ruled out.I’ve been watching for over 5 years and the more people look and study evidence the LESS likely it seems that there is any change. They rule it out more and more accurately with their data.So it is probably best to ignore thevarying speed of lightcosmologies until one is thoroughly familiar with standard mainstream cosmology.You have misconceptions Mowgli

  • General Relativity (该 1915 theory) trumps Special Rel (1905)
  • They don’t actually contradict if you understand them correctly, because SR has only a very limited local applicability, like to the spaceship passing by:-)
  • Wherever GR and SR SEEM to contradict, believe GR. It is the more comprehensive theory.
  • GR does not have a speed limit on the rate that very great distances can increase. the only speed limit is on LOCAL stuff (you can’t catch up with and pass a photon)
  • So we can and DO observe stuff that is receding from us faster than c. (It’s far away, SR does not apply.)
  • This was explained in a Sci Am article I think last year
  • Google the author’s name Charles Lineweaver and Tamara Davis.
  • We know about plenty of stuff that is presently more than 14 billion LY away.
  • You need to learn some cosmology so you wont be confused by these things.
  • Also a “singularity” does not mean a single point. that is a popular mistake because the words SOUND the same.
  • A singularity can occur over an entire region, even an infinite region.

Also thebig bangmodel doesn’t look like an explosion of matter whizzing away from some point. It shouldn’t be imagined like that. The best article explaining common mistakes people have is this Lineweaver and Davis thing in Sci Am. I think it was Jan or Feb 2005 but I could be a year off. Google it. Get it from your local library or find it online. Best advice I can give.

Mowgli 03-28-2007 01:30 AM

To swansont on why I thought 13 b LY implied an age of 26 b years:When you say that there is a galaxy at 13 b LY away, I understand it to mean that 13 billion years ago my time, the galaxy was at the point where I see it now (which is 13 b LY away from me). Knowing that everything started from the same point, it must have taken the galaxy at least 13 b years to get where it was 13 b years ago. 所以 13+13. I’m sure I must be wrong.To Martin: 你是对的,,en,还有更多的这种思路的不仅仅是暴和AGN飞机,,en,续集本文,,en,讨论了一些含义,,en,但这部续集太投机得到发表在什么像样的杂志,,en,我跟我的日常工作太忙,担心这些事情,,en,但是我希望要回物理学,,en,并且可能还要理念,,en,在几年,,en,干杯,,en, I need to learn quite a bit more about cosmology. But a couple of things you mentioned surprise mehow do we observe stuff that is receding from as FTL? 我的意思是, wouldn’t the relativistic Doppler shift formula give imaginary 1+z? And the stuff beyond 14 b LY awayare theyoutside” 宇宙?I will certainly look up and read the authors you mentioned. 谢谢.
swansont 03-28-2007 03:13 AM

Quote:

Originally Posted by Mowgli
(Post 329393)
To swansont on why I thought 13 b LY implied an age of 26 b years:When you say that there is a galaxy at 13 b LY away, I understand it to mean that 13 billion years ago my time, the galaxy was at the point where I see it now (which is 13 b LY away from me). Knowing that everything started from the same point, it must have taken the galaxy at least 13 b years to get where it was 13 b years ago. 所以 13+13. I’m sure I must be wrong.

That would depend on how you do your calibration. Looking only at a Doppler shift and ignoring all the other factors, if you know that speed correlates with distance, you get a certain redshift and you would probably calibrate that to mean 13b LY if that was the actual distance. That light would be 13b years old.

But as Martin has pointed out, space is expanding; the cosmological redshift is different from the Doppler shift. Because the intervening space has expanded, AFAIK the light that gets to us from a galaxy 13b LY away is not as old, because it was closer when the light was emitted. I would think that all of this is taken into account in the measurements, so that when a distance is given to the galaxy, it’s the actual distance.

Martin 03-28-2007 08:54 AM

Quote:

Originally Posted by Mowgli
(Post 329393)
I will certainly look up and read the authors you mentioned.

This post has 5 或 6 links to that Sci Am article by Lineweaver and Davis

HTTP://scienceforums.net/forum/showt…965#post142965

It is post #65 on the Astronomy links sticky thread

It turns out the article was in the March 2005 issue.

I think it’s comparatively easy to readwell written. So it should help.

When you’ve read the Sci Am article, ask more questionsyour questions might be fun to try and answer:-)