不知道為甚麼，一直以來始終不以許多人以微中子（Neutrino，大陸翻成中微子）是為暗物質緣由的説法為然。
前不久終於有機會提出自己的看法，或者說是問題。
事情要從一位才女説起。
馬中珮，四十出頭，來自臺灣。麻省理工博士，現任柏克來加大天文物理系教授。自小天縱英才，聰眀絕頂，連業餘嗜好的小提琴都拉過全臺第一。
馬博士在美大放異彩緣於不久前她率領的天文科學團隊發現並證實了人類有史以來找到的最大黑洞，有太陽的一百億倍之大。關於黑洞請參考 黑洞 ─ 宇宙不讓你知道的秘密。 上月初馬博士接受此間華語電視第八臺專訪，半小時的節目中她暢談自己的科研經歷和人生點滴，讓人非常欽羨佩服。
本來這節目一向都接受觀眾叩應進去問問題的，但因節目為事先預錄，所以主持人預告無法接受觀眾電話提問。
我確實有個終生不解的大惑很想打去問問，原先估計光問題本身就得解釋個至少五分鐘，還在琢磨該怎麼問時聽到主持人説不能接聽觀眾電話，頗感失望。
事後我將問題寫成一個電郵，網上找一下找到馬教授的信箱，不假思索便寄了出去，現正等待回電中。
長話短説，我的想法是這樣的：
黑洞等物體若破宇宙三度空間而出其後即不再存在在我人所知所感的空間範圍，而“存在”在我等不可能知悉的其他維度裡，一如汽球上的螞蟻被我們一彈就不再存在在汽球表面，它甚感惶惑，我們則一望即知怎麼回事，毫無希奇可言。
宇宙物質如黑洞等因強重力、高質量“破空而出”後的結果極可能就“徘徊”在我們宇宙附近，只是看不見摸不著，因為它已經不在宇宙“內”。然而線量上它又能到那裡去呢？
這種離開宇宙而去的物體久而久之累積起來數量不無可能極多，畢竟只要質量大於太陽十幾二十倍的星體死亡之後“必定”形成黑洞（黑洞 ─ 宇宙不讓你知道的秘密）。太空中俱備這種“份量”的恆星多至不可勝數，此亦為人類已知之事。 惟有將我們宇宙想像成一個平面(譬如地表，世間萬物都是這地表上的“影子”）才能想像宇宙“外面”是甚麼。這些黑洞在宇宙“外面”逐漸形成某種包覆狀態，一如平原上厚厚的一層濃霧。濃霧離地不遠，但不貼附在地表上。“地表人”不知有霧卻又“但覺有霧”。
所謂的暗物質現今唯一所知也不過就是星群或銀河系旋轉速率高過總體質量所容許之可能，由此懷疑必有不眀物質及其引力參與，星群或銀河系方才有可能不至飛散開去；除此之外人類實一無所知。
我不懷疑這“額外引力”是為事實，我只懷疑這額外引力根本不是宇宙任何物質造成的，也就是說，我懷疑這些強大引力來自上述那層“濃霧” — 破宇宙之空他去的黑洞等在第四度空間對我們“遙引”。
一如佈滿浮萍的池塘裡一個旋渦轉得飛快，浮萍跟著猛轉不已，你很容易就猜得到浮萍本身根本無此“能耐”，而是底下大量水流使然。
換言之，沒有甚麼暗物質，有的僅僅是正常物質，只是我們看不見摸不著，因為它們已在宇宙外。在宇宙外是因為它們撕裂了空間，一如肥皂膜上的一顆小石子扯破肥皂膜掉出去，肥皂膜隨即迅速癒合；小石子還是小石子，只不過“不見了” — 對肥皂膜上的居民而言，他們那裡知道肥皂膜還有“外面”。撕裂空間是因為無限大的重力扭曲四度時空至後者無可承受 — 確是“時空中無可承受之重”。
以上所述必然牽涉到一個根本問題：重力是甚麼？
這問題的答案恰好也是我們最、最、最欠缺的，甚至可以大膽說是唯一還不知道的。我敢說萬有引力的問題一旦解決，宇宙所有一切奧秘包括暗物質、暗能量等都將一次全部解決。
人類已知之“標凖模型”延用近百年來“屢試不爽”（神子、希格場、標準模型、相對量子論 ─ 人類的努力、挫折、與希望），可是還無法解釋重力（萬有引力）。牛頓只發現如何計算，未能解釋萬有引力。愛因斯坦用相對論的張量給予 modelize，可以更精確計算也經實驗證實，卻無法適用於特殊情況如黑洞。如果相對論加量子論能完全解釋重力，我們早就已經完全瞭解黑洞了，但事實並非如此。 我問馬教授的倒不是這臆想的答案，因為我知道這問題離答案還遠得很，起碼幾百年。我想知道的是在物理學界有沒有這麼種想法，這個研究方向，還有這整個論述（好吧就“臆想”）有無漏洞。畢竟所根據的許多並非已知事實，有些只是理論初步證明“不無可能”（例如空間的裂變、癒合）。
以下是我的電郵原文：
Dear Dr. Ma,
I first heard of you as soon as you and your team found the largest black hole and the news spread swiftly. When I saw you on channel 26 "Talk Tonight" my wife and I instantly signed ourselves up as members of your fans, which I believe is growing by the day. We adore your son dearly when we saw him "conducting" in a video you provided. He is so cute and lively, instantly reminded us of our son when he was at the same age. Congratulations on such a high level of accomplishment in just about every aspect one can imagine. You are indeed the pride of my countrymen.
I have an important (to me) question to ask during your interview in the show, but unfortunately it wasn't live. I found your email address in Wikipedia so I decided to give it a try. I am a engineer, not a scientist, so my question may appear dumb, but it lingers for years in my mind and has bugged me for a long time.
I am wondering if and when a black hole implodes to its singularity, the latter itself actually tears up our 3-D space and got "dropped out" of the space of our universe. Using a 2-D membrane (analogy of a 2-D space) it is not difficult to imagine such occurrences. In such a case, the black hole can be thought of as being existent, only no longer in our 3-D space (and/or time for that matter), yet with its gravity felt throughout.
I got this concept because in Bryan Greene's famous book (and TV program) "The Elegant Universe" he mentioned how in the string theory our space can be torn apart and re-healed by itself, he also described how he and others "proved" such a possibility, using the famous (and amazingly successful) Mirror Symmetry he invented.
So let's say the 3-D space can tear and heal, and black holes drop themselves out of our universe (in terms of both space and time), but their gravity persist, and that is conceivable if what string theory says is true -- that graviton is a ring/loop-shaped string with no ends, thus can't stick itself onto any brane. Some even conjectured that gravity is "shared" among branes. I won't get into that but here's what I imagined:
If heavy/high density objects such as black holes leave our spacetime/universe, they aren't really that "far away" but sort of gather near our brane (spacetime) and linger. Gradually more and more joined and they form a gravity halo like morning fog above a flat plain.
If graviton (like the string theory describes) are truly shared and spread among all branes (spacetimes) and are free to move around (some even suggest that is why gravity is so weak), can't we imagine that it is precisely these halos plus their gravity that render the phenomenon of dark matter, your favorite subject?
After all the only thing we know about dark matter is its gravity, and absolutely nothing else, isn't it?
To me this line of thought seems reasonable and logical, do you see any loopholes? Are there any research in this direction? Is the above even a viable conjecture? That, is my question.
In the show you mentioned how you use your time smartly and efficiently. I won't take up too much of your time, my question is long enough. Any answer from you will be greatly appreciated, it doesn't have to be technical. I just want to know how experts think, to what extent, and how they plan to attack the problem.
Have a wonderful Chinese New Year and best wishes for a brightest future in your career. I hope I can get a chance to read your book in short order.
暗物質臆想
