# Dark Matter and Atoms

1. May 12, 2008

### Jøhn

I recently had some thoughts about the big "space" between electrons and the nuclei and how weird it would be if that space were truly "empty". This led me to try to understand exactly what was empty space and the more I thought about it, the more I began to think about dark matter. I know empty space and dark matter are very different especially in the sense that dark matter has gravitational properties and empty space does not. However, since I do not believe we can say for certain the size of dark matter, it would seem that the gravitational oddities in atoms may be a result of dark matter. I would love any feedback on this, especially those who can say, "Your wrong!" Haha.

2. May 12, 2008

### MeJennifer

What "gravitational oddities" are you refering to?

3. May 12, 2008

### Jøhn

I mean in the sense that we cannot seem to combine gravity within quantum mechanics because at the level of atoms, gravity breaks down.

4. May 13, 2008

### Wallace

Our gravity theory works fine on the scale of atoms most of the time. The problem is when you get an enormous amount of mass ( ~ the mass of a star) compressed to the scale of an atom that problem emerge. There is no major problem in gravity on small scales that would lead to an explanation of dark matter in the way you propose.

5. May 13, 2008

### Jøhn

I see, I will have to look further into the ideas of gravity and atoms before opening my mouth again, though I do find it hard do really understand with out the math in front of me. Sadly, most of my knowledge comes from speculation and books because I have never really been able to look deeply into the math. If anyone has any suggestions on how to obtain that knowledge, I would be grateful, however I just started calculus :/

6. May 13, 2008

### Wallace

Apologies if my statement came across as harsh, obviously you can't know everything and it's okay to try and link together whatever you do know to try and explain the unknown.

As for getting more knowledge, it is really important to get a firm base in maths if you want to go into any physics areas later on. If you want to get some basic knowledge of the science before you learn it formally in all the gory mathematical details try some good pop sci. Scientific America is usually pretty good, New Scientist is okay but tends to sensationalise things too much and presents new speculation as if it was far more certain than is warranted, but none the less isn't the worst science journalism you can find.

There are also plenty of good books, for instance if you want to know about modern cosmology I would recommend "the Big Bang" by Simon Singh.

7. May 13, 2008

### Jøhn

I do not believe your statement came off harsh at all, remember I did say if anyone can tell me wrong I am more than happy to learn from it. Thanks a lot for the suggestions I will be sure to try them out!

Also, most people tell me college will be the answer to most questions, anyone want to vouch for that? I am only a junior in highschool.

8. May 13, 2008

### malawi_glenn

John, just give it time. Enjoy the ride to become a scientist :)

9. May 13, 2008

### Wallace

The good (although it may seem bad?) thing about a lot of modern physics, particularly cosmology and high energy (particle) physics, is that college won't tell you a lot of the answers, mainly because nobody knows! We will probably know more by the time you are in college, but there will still be plenty of mysteries for you to solve that you can't simply learn from a book or a lecture by a professor.

I think we will see the next major revolution in physics sometime in the next decade, although such things are of course very difficult to predict.

Last edited: May 13, 2008
10. May 13, 2008

### Nabeshin

QFT!

11. May 13, 2008

### Jøhn

Thanks a lot guys! Though, I am still very impatient when it comes to my questions and answers haha. I just become very frustrated in the sense I do not really have anyone to talk to about many of the concepts I learn, mainly due to the fact that I will read books or watch shows in which no one else seems to do... Sigh, college can never come quickly enough!

12. May 14, 2008

### malawi_glenn

what? elaborate
i know QFT is quantum field theory, but what do you mean by that?

13. May 14, 2008

### Nabeshin

Oh wow I didn't even realize that posting that on physics boards is a surefire misinterpretation. Alternate definition of QFT: Quoted For Truth. So in 15 years when someone writes a book about physics they can quote your prediction XD

14. May 15, 2008

### malawi_glenn

haha, here - abbreviations for physics are prioritized

Remember when Feynman introduced Quantum Electrodynamics (QED), which has the same abbreviation as http://en.wikipedia.org/wiki/Q.E.D. which you often writes after you have prooven something;)

15. May 19, 2008

### LongOne

I want to chirp in on the math/understanding issue. Advanced math is necessary to understand the exact operation of many physics processes, but I believe too many people seem to say that advanced math is NECESSARY to understand advanced physics concepts, which I believe is wrong. It is true that most physicists are comfortable with advanced math and readily use that as a tool to explain their meaning; and math makes the meaning unambiguous. But folks miss the point in saying that math is necessary. Mathematics reflects an exact understanding of how nature behaves; it doesn't explain the concepts of how nature works. A good example is Faraday and what's-his-face ( a sure sign I'm getting old, as I know his name as well as my own!). Faraday was a research physicist and had many insights into how electromagnetic properties worked; he developed the concepts. But it was what's-his-face that took Faraday's concepts and turned them into mathematical rules. The mathematics was not the starting point; the concepts were. I defy anyone with no knowledge of Faraday's experiments (or equivalent) to come up with the laws of electromagnetism.

So I encourage everyone to understand, and pursue rigorously to understand, the concepts of physics. The math is just a way of unambigiously explaining the detail operation. Those that say that you can't understand advanced physics without math are hiding behind mathematics due to their inability to explain the concepts.

16. May 19, 2008

### Wallace

I think your what's-his-face is Maxwell. Interestingly though, Maxwell didn't actually come up with what we call Maxwell's equations, at least not in the simplified 4 equation form we learn.

You are right that physical concepts are very important to learn and understand, there are many great mathematicians who struggle with physics precisely because physics is more than just a branch of maths. Have you ever seen the play 'Copenhagen'? It is a three character play with Niels Bohr, his wife and Heisenberg. Most of the scenes are Bohr and Heisenberg chatting about quantum mechanics and Bohr constantly says words to the effect of 'but we don't understand it unless we can explain it to my wife' which, although somewhat patronising(!) effectively is what you are saying I think, that is we have the maths (in this case of QM) but unless the concepts can be explained to a non-expert that doesn't know the maths then we don't understand it.

For the most part this is reasonable, the only note of caution I would make is that occasionally some folk who have tried to understand physics by learning the concepts alone feel they can either find flaws in the theory or extend the theory purely in 'words'. This is where the maths really does become absolutely essential. You cannot properly determine the worth of a theory or make a new theory without being conversant with how the theory is defined, which is always (in physics at least) done in the language of maths. Of course you really do need to fully understand the concepts as well, not just the maths, to do this but you really do need both. You often find people saying 'my theory works, I just need someone to work out the maths' which is a nonsense statement.

17. May 20, 2008

### ZapperZ

Staff Emeritus
OK. Would you care to try and "explain" the "concept" of Gauss's Law, for example, without invoking any mathematics?

This is not a trick question. In fact, I will immediately qualify that to say

"The divergence of the electric field is proportional to the charge density"

is nothing more than an English language version of the mathematical statement

$$\nabla \cdot E = \rho$$,

meaning that it is still a mathematical statement, just less precise. So use this to illustrate how you are able to explain a concept in physics without it being nothing more than a "human" language statement of a mathematical formalism.

Zz.

18. May 21, 2008

### g33kski11z

:rofl: .. I'm sorry, but that is the funniest thing I've seen all day.

.. and just my 2 cents on the side "math" conversation.
I'm happy to hear this. I suck at math, but I love reading any and all cosmology/astrophysics books, articles, etc.. Unfortunately, a lot of the concepts that I read about I "take for granted" that they are right because I can't do the math. I've also been interested in topics but unable to find a "layman’s terms" write up of it and thus unable to pursue it.

Last edited: May 21, 2008
19. May 26, 2008

### LongOne

I read a book recently, titled "The Mystery of Missing AntiMatter" by Quinn & Nir. Excellent book, covering many areas of cosmology, including baryogenesis and other things, yet never invoking any math more difficult than E=mcc. Interestingly, in this one example, I learned more about the concepts of Cosmology, Astrophysics, Big Bang & Quantum Mechanics than I did from several more (unreadably) math-flavored expositions (no, it doesn't cover everything to a fully expressive depth, but I'm talking about learning the concepts, not being able to calculate, say, a field strength).

20. May 26, 2008

### LongOne

Your example is an excellent one. Although I've had advanced math training during my electrical engineering courses, that was forty years ago and I don't immediately recall the mechanics of much of the more advanced topics. When I read "The divergence of the electric field ...", I know exactly what it means. When I see the equation, it causes me to have to dig up math I haven't used in decades, which just slows down my reading and understanding. The "... divergence ..." sentence is all I need; the other is a bother (for my purposes). As an example, I didn't recall offhand the meaning of E and rho, so the equation alone is not enough, by itself, to tell me anything useful. Also, there are many things that cannot be expressed in math; take the Big Bang, for instance (t=0). Or the singularity.

Perhaps the best notion is that working physics folks need the math; understanding doesn't. I think it's only natural that physicists try to explain everything in math, as it's the tool of their trade, but by attempting to do so, they leave a wide gap in understanding between themselves and the general public, including policymakers. And perhaps this gap is why we don't have a CERN here in the US, or why China may beat us back to the moon, etc.