Dark matter

Yes, I know, probably, most of you know what dark matter and dark energy are, combined they are responsible for over 82% of the weight of the Universe, but they can't be seen. Also according to Einstein, nothing could accelerate to the speed of light or beyond, but he accepts that if something is already travelling at that speed - it can stay there unless it changes. So, mabe, actually, that dark stuff doesn't exist? Instead we have many galaxies and star clusters that are travelling away from us at the speed greater than the speed of light and thus we don't see them?

P. S. I just thought of that, if there's a theory about it - i'd like to read it.

Originally posted by Citizen John
Yes, I know, probably, most of you know what dark matter and dark energy are, ...

No, actualy, none of us knows what dark energy and dark matter really is. I don't think anyone knows it.

We have at most hypothesis but nothing else. The only thing we know is some properties, like lacking mass and a repelling gravitational-like force, but this is about it.

Originally posted by Citizen John
Yes, I know, probably, most of you know what dark matter and dark energy are, combined they are responsible for over 82% of the weight of the Universe, but they can't be seen. Also according to Einstein, nothing could accelerate to the speed of light or beyond, but he accepts that if something is already travelling at that speed - it can stay there unle ...[text shortened]... them?

P. S. I just thought of that, if there's a theory about it - i'd like to read it.

Are you trainded in physics or a similar field of knowledge?

Originally posted by adam warlock
Are you trainded in physics or a similar field of knowledge?

Can you explain your opinion?

I'm not trained in physics but I'm able to follow most explanations as I understand the concepts.

well there are black holes, we cant see them but we know that there are there, abd we cant see them becouse light cant get out of them. scientists strat to think that they are in the middle of all galaxies. every thing in the universi is expending, but not at that speed. onse i read an article in science america about expanding galaxies, they said that in 100 billion year we will not see any galaxies in the sky becouse they would be to far and light wont reach us that fast. here is the article for more info: http://www.sciam.com/article.cfm?articleID=C420F7DE-E7F2-99DF-3E47CE32FD4AD465&chanID=sa026
if your intrasted you could sign up for there newsletters they do have very interesting articles

ps. i want to take physics as a minore in collage

Originally posted by Palynka
Can you explain your opinion?

I'm not trained in physics but I'm able to follow most explanations as I understand the concepts.

If he was trained in physics I could give some good info on that. Technical info.

I don't like very much of pop-science because some times they sell you an utterly wrong information. Books like the ones Gradiva and such are very good to inform people on what's happening but that's all. Just information not knowledge. Sometimes people think that by reading that they are understanding but they are not. They are memorising. I know that by self-experience. When I was ypunger I read a lot of those popular books, and I when I entered college I thaght I was a hotshot and had a lotta knowledge. Boy I was wrong! I didn't know virtually nothing. I had some memorised facts but no understanding and that's crucial on physics. After the first shock I put some sense on my head and really started to know things. This was a gift that I had from a first teacher. He taught what I think is the most valuable thing I know now: "To know what I really know and what I don't know".

For instance FabianFnas posts a lotta things on this forum that I would describe as pop-science and sometimes he says wrong things. I'm not criticizing you so don't judge me wrong Fabian please.

Maybe you are trained on something similar to physics and that way you can understand what's going on, but you have no training on physics nor something alike you don't know really know what is dark matter.Trust me on that.

Originally posted by O Artem O
ps. i want to take physics as a minore in collage

Take it then. What are you doing now? I reccomend you to read the Feynman Lectures on Physics before you goto college. That way you'll really know something and it'll be very usefull to you. Not to mention that he was one of the best teachers out there.
And while you are at college try to read the Landau collection of theoretical physics. A little bit outdated but a tru learning experience. You don't have to read them all but please read the one on mechanics, the one on field theory and the one on statistical physics. These are a must read to any physicist diserving of that name.
Of course you'll have to read a lotta stuff reccomended by your teachers but if you have time do it.
The Greiner collection is very good too.
Let me just shut up or you'll read all of your life out. 😳

Originally posted by adam warlock
Maybe you are trained on something similar to physics and that way you can understand what's going on, but you have no training on physics nor something alike you don't know really know what is dark matter.Trust me on that.

Pretend I'm trained in physics and explain it to me. If I don't understand it, that's too bad, but at least I can try.

ow, well thanks for the tips. i have read sevral as you call them 'pop-science" books and i have all 10 volumes of Landau, i try to read the starting from the first one. well i am mostly a programmer learning emmbeded prgroming (prgrams that control the hardware it self), also reading an electronics book 'the art of electronics", like physics very much and also read some textbooks, i will have physics next year, but as i sespect we will not learn anything very interesting in there. what will you be doing when you get out of college ? reserch?

Originally posted by Palynka
Pretend I'm trained in physics and explain it to me. If I don't understand it, that's too bad, but at least I can try.

Ok. During the 20th century Astronomers made some kind of survey of the Universe and measured the velocity of the outer stars of galaxies and realised that they were bigger than it was supposed to be given the assumed masses of the galaxies. At first it was assumed that this was due to the astronomical amount of stuff that's out there and we can't se. Small planets, comets, asteroids, some feeble stars. But even with the wildest assumptions they could'nt come up with the given mass. So the conclusion was that there was something out there that only interacted gravitually with the resting matter. And why just gravitually. Because if there was some other kind of interaction we certainly see the results. Either x-ray radiation or any other kind of radiation. And massive amounts of that. Because the invisible stuff had to be something like 90% of the Universe. So if 90% of the Universe was interacting and we could only see the gravitational effects than or telescopes would bee really lousy.
But now the Dark Matter research has evolved a lot and I'm simply not up to date with it.It's notm my field of research, not one of my main interests, not what is given during undergraduations in Portugal and just too esoteric if you ask me. There are a lot of candidates to what the dark matter may be. Neutrinos, tachyons, supersymmetric particles and a whole lotta fauna if you ask me.
Besides that we have another field with much less proponents. That's MOND.Moddified Newtonian Dynamics. Nad their thesis is that F=ma is not always valid. Instead we have F=f(x)ma. The down points of this is that f(x) is not known and probaly won't ever be knowed. Ony it's assymptotic form can be given. For very small x, and here small is really big for us humans, f(x) is very near to 1. And for large x f(x) has the right value so has to see the dynamics we see. Not very smart I know but that's how things go on on physics. Very rarely a problem has neat solution right away.

http://www.math.ucr.edu/home/baez/physics/General/open_questions.html Scroll down a bit and you will find out what the experts say on that. Cause my explanation was very much pop-science. The main reasons to that is my lack of real, concrete knowledge on this stuff and the other is lack of time. I could give you a much better explanation if I wanted to, still very incomplete, but I have work to do.

Originally posted by O Artem O
ow, well thanks for the tips. i have read sevral as you call them 'pop-science" books and i have all 10 volumes of Landau, i try to read the starting from the first one. well i am mostly a programmer learning emmbeded prgroming (prgrams that control the hardware it self), also reading an electronics book 'the art of electronics", like physics very much and ...[text shortened]... ing very interesting in there. what will you be doing when you get out of college ? reserch?

All the 10 volumes of Landau!!! Wow! Treasure those books then. But don't be too disappointed if you find them too hard at first. Landau was the head of physics institute for over 20 years and for you to get admitted you had to pass his minimal theoretical exam. Well, only 40 some people ever got i. So you can see that he wasn't fooling around.

I'm already out of college and doing research. Here in Portugal it's a little bit different. You have a licenciatura, equivalent to an undergraduation, and after that you either do a Master degree and then a phd. But if you have an high enough average you can skip the Master and go directly to a phd. Now I'm waiting for some paper work to be done and I'll do a phd on boson fermion-mixtures under the influence of random potentials. A hot topic even thought the strange name.

You'll have physics for a whole year? If so you can learn some stuff even though just skin-deep at most of the subjects I think.

yea, how much physics did you have in high school?

Originally posted by adam warlock
Ok. During the 20th century Astronomers made some kind of survey of the Universe and measured the velocity of the outer stars of galaxies and realised that they were bigger than it was supposed to be given the assumed masses of the galaxies. At first it was assumed that this was due to the astronomical amount of stuff that's out there and we can't se. S ...[text shortened]... a much better explanation if I wanted to, still very incomplete, but I have work to do.

Thanks.

Originally posted by O Artem O
yea, how much physics did you have in high school?

In Portugal first we have 12 years of education and the we go to college. The first time I had physics at high school was on my 8th year. But it was simultaneousn with chemistry. It was like this till my 11th year. Finally on my 12th I just got physics and got rid of the chemistry. I'm not a big fan of chemistry as you can see.

I've just noticed your flag. You must know a lot of Landau and how good hisbooks are. Are you studying in russian now? If so I think that there are good chances for you to learn some good physics.

Originally posted by Palynka
Thanks.

It was a crappy explanation. But if you check the link you'll really learn something.