[Tycho?]

Good question.

No, I dont know the answer. Check wikipedia of course, but you may not be in luck.

I'm quite sure the bit about orbits becoming circular is not true. Elliptic orbits are just as stable as circular ones. An elliptic orbit may be changed due to the gravitational pull from other planets' date=' but so may circular orbits too. "Tidal interactions" between the planets will only affect their rotation, not the orbit itself: Earths pull on the moon has over time slowed it down to always turn the same side towards Earth, but it hasn't changed its orbit.

[/quote']

 

Nope

 

"...some of the Earth's rotational momentum is gradually being transferred to the Moon's orbital momentum, resulting in the Moon slowly receding from Earth at the rate of approximately 38 mm per year."

 

http://en.wikipedia.org/wiki/Moon

If Triton's orbit around Neptune has become circular due to gavitational pull, then what about Mercury? The Trition/Neptune mass ratio is about 4770, while the Sun/Mercury mass ratio is almost six millions, and the gravitiational force per mass is much much larger. Then why is Mercurys orbit still eccentric? Probably because elliptic orbits are stable...

 

I'm sure it can be shown mathematically too.

 

best regards,

Michael

 

"Another unique feature of Triton's orbit, arising from tidal effects on such a large moon so close to its primary, is that it is nearly a perfect circle with an eccentricity of zero to sixteen decimal places."

 

http://en.wikipedia.org/wiki/Triton_%28moon%29

 

The eliptical orbit itself may be stable, but the orbit alone does not account for tidal interactions, which definately do affect the orbit of bodies. I'm not definately sure on this since I can't back it up mathmatically, but it seems at least half likely.

A star after supernova (after the fusion stops) is still about about 99% hydrogen. its only a very small volume of the core(relatively, for the sun its about the size of the earth i believe) has the right conditions for fusion.

Good, I wasn't just making it up.

Are you talking about my post?

 

So your saying the two particles quickly come together and turn back into energy. Thats the meaning of decay.

 

So wheres all the antimatter thats ment to exist for all the matter we see in day to day lvies. Even ourselves.

I'm not sure what you're talking about, but I think you're quite confused about the subject. Antimatter that's meant to exist? What does this mean?

When a star goes supernova it means its core has run out of fusionable elements (ie its trying to fuse iron). But that doesn't mean that all of the hydrogen in the star has been consumed, only the hydrogen near enough the core to be exposed to the high temperatures and pressures. I'm not too sure about this, but I would think most of the stars outer layers would still be lighter elements when the star goes supernova.

How the matter was moving at the star of the solar system, other planets (yes they can have a large effect), collisions... etc. But yeah, orbits are elliptical because they did not being as perfect orbits.

I think you are correct in saying the orbits will gradually become more circular due to tidal interactions with the object it is orbiting (unless the orbits are kept out of shape by a planet or something).

An interesting example is Triton, the largest moon of Neptune. It has a very close retrograde orbit around Neptune, and is under very large tidal forces. Its orbit is the most circular of any body in the solar system, its eccentricity is a zero to 16 decimal places. Which is pretty damn non-eccentric!

From what I read the researchers arn't sure how they got such a high temperature. They have ideas about it, but they certainly wern't looking to break a temperature record when they ran the experiment.

Well yeah your summary is pretty much correct. I wouldn't call it an illususion, but you can say gravity isn't so much a field that attracts stuff, but instead something that warps spacetime so that objects travel in a different path.

This really is not favorable to antigravity however. If gravity is just a field one can conjur up the idea of anti gravity, just like you can have an electric field and have charges be repelled from it. But if gravity is the result of curved spacetime.... then anti gravity is space time that is negatively curved. And how the hell do you do that? (With "exotic" matter you might say, which just a a different way of saying matter that does stuff that we dont understand).

Yeah I'm kinda drunk right now, I hope that made sense.

Originally Posted by EvoN1020v

Regardless' date=' I found this interesting information on antimatter particles:

 

The world's largest scientific research facility --- Switzerland's Conseil Europeen pour la Recherche Nucleaire (CERN) -- recently succeeded in producing the first particles of antimatter. Antimatter is identical to physical matter except that it is composed of particles whose electric charges are opposite to those found in normal matter.

 

Antimatter is the most powerful energy source known to man. It releases energy with 100 percent efficiency (nuclear fission is 1.5 percent efficient). Antimatter creates no pollution or radiation, and a droplet could power New York City for a full day.

 

There is, however, one catch...

 

Antimatter is highly unstable. It ignites when it comes in contact with absolutely anything... even air. A single gram of antimatter contains the energy of a 20-kiloton nuclear bomb --- the size of the bomb dropped on Hiroshima.

 

Until recently antimatter has been created only in very small amounts (a few atoms at a time). But CERN has now broken ground in its new Antiproton Decelerator --- an advanced antimatter production facility that promises to create antimatter in much larger quantities.

 

One question looms: Will this highly volatile substance save the world, or will it be used to create the most deadly weapon ever made?

 

[stored from Angels & Demons by Dan Brown']

 

-------------------------------------------------------------------------------------

 

I wont comment on that post, since this is supposed to be a thread about black holes. I'll point out the things wrong with this article if you make a thread about it. Quoted by [Tycho?].

 

 

 

Ok, I have made a new thread only for antimatter particles. What is wrong with the article?

Well creation of antimatter isn't exactly recent. It is created natrually from certain types of radioactive decay. Even if they were talking about actual atoms of anti-matter thats still something that was done several years ago.

Anti-matter is not created atoms at a time for the most part. Most anitmatter is just positrons, since they are the easiest to get. Next would be anti-protons I would guess. Making them into actual atoms is very difficult and inneficient, so when someone says "antimatter" they virtually never mean atoms of antimatter.

And I doubt antimatter will be saving or dooming the world anytime soon. The huge difficulties and inneficiencies in creating it make it nonsense for a source of energy (since it isn't a source of energy, at best its just a horrible way of storing energy). And it would make a hugely expensive weapon, even though we have nukes that can do the job anyway for a tiny fraction of the price.

Regardless' date=' I found this interesting information on antimatter particles:

 

[math']\rightarrow[/math] The world's largest scientific research facility --- Switzerland's Conseil Europeen pour la Recherche Nucleaire (CERN) -- recently succeeded in producing the first particles of antimatter. Antimatter is identical to physical matter except that it is composed of particles whose electric charges are opposite to those found in normal matter.

 

Antimatter is the most powerful energy source known to man. It releases energy with 100 percent efficiency (nuclear fission is 1.5 percent efficient). Antimatter creates no pollution or radiation, and a droplet could power New York City for a full day.

 

There is, however, one catch...

 

Antimatter is highly unstable. It ignites when it comes in contact with absolutely anything... even air. A single gram of antimatter contains the energy of a 20-kiloton nuclear bomb --- the size of the bomb dropped on Hiroshima.

 

Until recently antimatter has been created only in very small amounts (a few atoms at a time). But CERN has now broken ground in its new Antiproton Decelerator --- an advanced antimatter production facility that promises to create antimatter in much larger quantities.

 

One question looms: Will this highly volatile substance save the world, or will it be used to create the most deadly weapon ever made?

 

[stored from Angels & Demons by Dan Brown]

I wont comment on that post, since this is supposed to be a thread about black holes. I'll point out the things wrong with this article if you make a thread about it.

3) It would be expected that one of the polar pulse/jets would be largely anti-matter and the other largely matter.

I've read this before, or something like it, on these very forums. It must have been like a year ago now, but was it you the first time around?

I think the main force resisting a complete gravitational collapse is due to the fact that neutrons are fermions - but I have to say that this is just a guess the name "Neutron star" suggests to me.

Being fermions they must occupy a seperate state' date=' each. As a good approx, this will be all of the lowest states. With decreasing volume, the energies of the states grow, so the total energy of the neutrons must grow. Because of that, it takes energy F*dr to compress a sphere of fermionic gas by dr (r is radius, here). You can associate this with a force F resisting compression.

 

@[Thyco?']: I didn´t say there is no evidence for black holes. And perhaps saying there is no real experimental proof was not a good idea, too. It´s a bit up to debate where the lines between "real experimental proof", "strong evidence", "evidence" and "indirect evidence" lie.´I just wanted to say that E.g. atoms are on a more solid ground than black holes.

Oh, yeah my post wasn't a resonse to yours or anything, I posted before I read the rest of the responses. But your point is taken, black holes are not on as strong a ground as other many other things in physics (like atoms).

If there was a black hole with the size of the Sun' date=' how big would the Event Horizon be?

 

I thought I heard that the diameter of a Black Hole of Solar mass would be the same as the diameter of Earth... is this true?[/quote']

 

Look up the schwarzchild radius and you can calculate it. I'll do it just to get a number, but the forumla is a simple one.

 

edit: so the equation is r=2Gm/c^2

where G is newtons gravitational constant = 6.67e-11

m is mass of the sun = 2e30 kg

c is the speed of light = 3e8 m/s

 

so I get just shy of 3km for the radius.

There is quite a lot of evidence that suggests they do indeed exist. If they dont, then some other super dense must exist which we dont know about.

Look it up on wikipedia, they have info on the evidence to support and go against black holes.

It should be noted though that the vast majority of the scientific community consideres them to exist.

You obviously don't spend enough time reading the chemistry and biology forums then...

 

Or maybe it's more of a result of people being able to much better spot rediculous theories in the field that they are the most familiar with...

Yeah, I do spend most of my time on the physics boards and know the most about it. Point taken.

Why dont people post this kind of garbage in the other forums? Nobody seems to make up stupid theories for chemistry or biology, its always us physics guys that get to deal with idiocy like this.

If any of you guys have heard of the Canadian show "Trailer Park Boys" I know two of the actors in it. But I'm not sure how popular the show is even in Canada, I'm not sure if its broadcast in the US.

Remember that headlights always coming from same light source how can it be incoherent?

Two different filaments, two different panes of glass, different amounts of dirt and stuff on them. They may be in phase, then again they may not be. Your getting a ton of different wavelenths moving in all kinds of different directions be reflected and refracted all over the place. As was pointed out, interference will occur, but I dont think there would be much of an interteresting pattern coming out of it.

So is acceptable that ribs act as a diffraction grating for the X–rays

Technically it is acceptable, but the effect is so small to be undetectable.

They do cause some diffraction although it will be insignificant at the distances encountered in a hospital. you could maybe measure it ove a light year.

Good luck detecting a chest x-ray a light year away.

Just look up fission and fusion on wikipedia. After you've done that, then you can ask questions.

Why is sunspot still allowed to post in the real physics forums? Put him in speculations, or better yet, pseudoscience.

it is possible to slow light down so it does not travel at C .. some danish sciencist did it..

This is somewhat true. When light is traveling through a medium "like air" it is constantly being absorbed and emitted by the atoms and molecules that make up the medium. Once is has been absorbed, for a short while it is not a photon, it is energy in an electron that is around the atom. This is why it can seem like light slows down. Its not the photons themselves slowing down, its just the light is spending more time being absorbed and emitted, or is taking a longer path.

But an individual photon not interacting with matter travels at c, always. This is why c is usually stated "at vacuum" because the speed that light rays move in air or water or whatever is slower.

Ecoli made a point about friction within our upper atmosphere causing space junk to lower its velocity causing it to fall to the earth. That seems reasonable. But it rasies another question; isn't the earth in the sun's atmosphere. We call it the solar wind. Where does the earth get the energy to overcome this friction and not end up with a decaying orbit?

The effect is super super super tiny. And besides, the Earth's orbit is decaying, just by a very small amount.

First year university physics so most of my knowledge is fairly elementry and generalized. Although I know a disproportionate amount about space related topics.