Tag Archives: big bang theory

Big Bang Theory – Bölüm II

After reading a paper by Ashtekar on quantum gravity and thinking about it, I realized what my trouble with the Big Bang theory was. It is more on the fundamental assumptions than the details. I thought I would summarize my thoughts here, more for my own benefit than anybody else’s.

Classical theories (including SR and QM) treat space as continuous nothingness; hence the term space-time continuum. Bu görünümde, objects exist in continuous space and interact with each other in continuous time.

Although this notion of space time continuum is intuitively appealing, it is, at best, incomplete. Consider, Örneğin, a spinning body in empty space. It is expected to experience centrifugal force. Now imagine that the body is stationary and the whole space is rotating around it. Will it experience any centrifugal force?

It is hard to see why there would be any centrifugal force if space is empty nothingness.

GR introduced a paradigm shift by encoding gravity into space-time thereby making it dynamic in nature, rather than empty nothingness. Böylece, mass gets enmeshed in space (ve zaman), space becomes synonymous with the universe, and the spinning body question becomes easy to answer. Evet, it will experience centrifugal force if it is the universe that is rotating around it because it is equivalent to the body spinning. Ve, yapamaz, it won’t, if it is in just empty space. Ancak “empty space” doesn’t exist. In the absence of mass, there is no space-time geometry.

Bu yüzden, doğal, before the Big Bang (if there was one), there couldn’t be any space, nor indeed could there be any “before.” Note, Ancak, that the Ashtekar paper doesn’t clearly state why there had to be a big bang. The closest it gets is that the necessity of BB arises from the encoding of gravity in space-time in GR. Despite this encoding of gravity and thereby rendering space-time dynamic, GR still treats space-time as a smooth continuum — a flaw, according to Ashtekar, that QG will rectify.

Şimdi, if we accept that the universe started out with a big bang (and from a small region), we have to account for quantum effects. Space-time has to be quantized and the only right way to do it would be through quantum gravity. Through QG, we expect to avoid the Big Bang singularity of GR, the same way QM solved the unbounded ground state energy problem in the hydrogen atom.

What I described above is what I understand to be the physical arguments behind modern cosmology. The rest is a mathematical edifice built on top of this physical (or indeed philosophical) vakıf. If you have no strong views on the philosophical foundation (or if your views are consistent with it), you can accept BB with no difficulty. Ne yazık ki, I do have differing views.

My views revolve around the following questions.

These posts may sound like useless philosophical musings, but I do have some concrete (and in my opinion, important) results, listed below.

There is much more work to be done on this front. But for the next couple of years, with my new book contract and pressures from my quant career, I will not have enough time to study GR and cosmology with the seriousness they deserve. I hope to get back to them once the current phase of spreading myself too thin passes.

Big Bang Theory

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. Kötü hissetmeyin, 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” makas. 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. Üzgünüm, there was no “önce!” This is a concept that my five year old son has problems with. Yine, 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. Gerçek, gerçek; 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?

Ikinci, 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, bana, 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.
  • Ayrıca, 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. Iyi, 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, görünüşte. 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. Fizikte, 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. Bana, 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 (görmezden, for the moment, my favorite question — neyin gerçek olduğunu?) But popular writers have embraced it. Örneğin, 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.

Evren – Boyut ve Yaş

Ben onlar hakkında bir galaksiyi bulundu okuduğumda beni rahatsız oldu bu soru haberi 13 milyar ışık yılı uzakta. Bu ifadenin Benim anlayış: Bir mesafede 13 milyar ışıkyılı, Bir galaksi vardı 13 milyar yıl önce, şimdi ondan ışığı görebilecek şekilde. Bu evren, en azından olduğu anlamına olmaz 26 milyar yaşında? Bu galaksi hakkında almış olmalı 13 göründüğü yerde milyar yıl ulaşmak için, ve ondan ışık başka almalıdır 13 milyar yıl Bize ulaşmak için.

Soruma cevap, Martin ve Swansont (Ben varsayalım kim akademik phycisists vardır) Benim yanılgıları işaret ve aslında daha fazla bilgi edinmek için bana sor. All I asimile olduğumda cevap verilecektir, o görünür! 🙂

Bu tartışma, Big Bang teorisi üzerine Yazımın başlangıcı olarak yayınlanmıştır, Bir veya iki gün içinde geliyor.

Mowgli 03-26-2007 10:14 PM

Evren – Boyut ve Yaş
I was reading a post in http://www.space.com/ stating that they found a galaxy at about 13 milyar ışık yılı uzakta. Ne ifadesi anlamına gelir anlamaya çalışıyorum. Bana, Bu demektir 13 milyar yıl önce, Şimdi bunu görmek bu nerede galaksi oldu. Değil ne LY 13b uzak araçtır? Eğer öyleyse, Bu evrenin en azından olması gerektiğini ifade etmem 26 milyar yaşında? Demek istediğim, Tüm evren bir tek noktadan başladı; nerede olduğunu, bu galaksi nasıl olabilir 13 milyar yıl önce vardı sürece en azından 13 milyar yıl oraya? (Şu an için enflasyonist faz almamak…) Ben insanların uzay kendisi genişleyen olduğunu açıklamak duydum. Halt Bu ne anlama geliyor? Işığın hızı bir süre önce küçük olduğunu söyleyerek sadece bir meraklısı bir yol değil mi?
swansont 03-27-2007 09:10 AM

Alıntı:

Originally Posted by Mowgli
(Posta 329204)
Demek istediğim, Tüm evren bir tek noktadan başladı; nerede olduğunu, bu galaksi nasıl olabilir 13 milyar yıl önce vardı sürece en azından 13 milyar yıl oraya? (Şu an için enflasyonist faz almamak…)

Geri kalan her şey almamak, nasıl bu demektir evrendir 26 milyar yaşında?

Alıntı:

Originally Posted by Mowgli
(Posta 329204)
Ben insanların uzay kendisi genişleyen olduğunu açıklamak duydum. Halt Bu ne anlama geliyor? Işığın hızı bir süre önce küçük olduğunu söyleyerek sadece bir meraklısı bir yol değil mi?

ışığın hızı atom yapısının doğal bir parçasıdır, ince yapı sabiti (alfa). C değişiyordu ise, Daha sonra atom spektrumları desenleri değiştirmek zorunda kalacak. Alfa değiştiğini gösteren herhangi bir teyit veriler olmamıştır (Bunu iddia sıra kağıt olmuştur, ancak ölçümleri tekrarlamak birine ihtiyacım var), ve geri kalanı hiçbir değişiklik ile tüm tutarlı.

Kırlangıç 03-27-2007 11:25 AM

Onaylamak veya sözü swansont pekiştirmek için, zamanla değişen c dahil bazı saçak veya standart dışı kozmoloji var spekülasyon ve (veya alfa zaman içinde değişen), ama değişen sabitler şey sadece alır daha fazla hüküm out.I've aşkın bir süredir izliyor 5 yıl ve daha fazla kişi bakmak ve herhangi bir değişiklik olduğunu görünüyor AZ muhtemel delilleri incelemek. Onlar data.So ile daha doğru bir şekilde ekarte bunu göz ardı etmek muhtemelen en iyi “ışığın değişen hızı” biri kadar kozmoloji, standart ana kozmoloji ile iyice tanıdık.Sen yanılgılarını Mowgli var

  • Genel Görelilik (the 1915 teori) Özel İ koz (1905)
  • Eğer bunları doğru anlamak Onlar aslında çelişmeyen, SR sadece çok sınırlı bir lokal tatbik kabiliyetine sahiptir, çünkü, tarafından uzay geçeceğinden gibi:-)
  • GR ve SR çelişir seem Wherever, GR inanıyorum. Daha kapsamlı teori.
  • GR çok büyük mesafeler artırabilir oranı üzerinde hız sınırı yok. Sadece hız sınırı YEREL şeyler üzerinde (Eğer yakalamak ve bir foton geçemez)
  • Yani biz ve c daha hızlı bizden uzaklaşıyorsun olan şeyler gözlemlemek DO olabilir. (Bu kadar uzakta, SR geçerli değildir.)
  • Bu benim geçen yıl bence bir Sci Am makalesinde açıkladı
  • Google yazarın ismi Charles Lineweaver ve Tamara Davis.
  • Biz daha şu anda daha fazla şeyler bol hakkında bilmek 14 milyar LY uzak.
  • 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 the “big bang” model 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 (hangi 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. Bu yüzden 13+13. I’m sure I must be wrong.To Martin: Haklısın, I need to learn quite a bit more about cosmology. But a couple of things you mentioned surprise me — how do we observe stuff that is receding from as FTL? Demek istediğim, wouldn’t the relativistic Doppler shift formula give imaginary 1 z? And the stuff beyond 14 b LY away – are they “outside” the universe?I will certainly look up and read the authors you mentioned. Teşekkürler.
swansont 03-28-2007 03:13 AM

Alıntı:

Originally Posted by Mowgli
(Posta 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 (hangi 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. Bu yüzden 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.

Kırlangıç 03-28-2007 08:54 AM

Alıntı:

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

This post has 5 veya 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 read—well written. So it should help.

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