1)
Message boards :
SETI@home Science :
Black Holes and quasars
(Message 249552)
Posted 17 Feb 2006 by Jason Post:
The energy of the mass of the black hole is still in its mass. Black holes can be fully described by two properties: mass and angular momentum. I know it's not very intuitive to think about infinite densities, but unless there's some fundamental physical force we haven't discovered, a point mass with infinite density is the only explanation to what happens to an object so massive that its gravity overcomes all other forces.
Let me preface my response by saying there is just as much (or more) confusion in the field about this subject. There is at least one nobel prize for the first person (or people) to discover the true nature of dark matter. I believe it's much more than 73% (more like 95%), and it would take a fundamental revision to our theory of gravity to explain the observations away without it. But as Solomon has hinted at, the current theory is that dark matter is contained in "Dark Matter Halos" around galaxies; since it does not interact with baryons except through gravity, it does not follow the small scale structure of the galaxy (ie our solar system). |
2)
Message boards :
SETI@home Science :
Black Holes and quasars
(Message 248322)
Posted 15 Feb 2006 by Jason Post:
Nothing can escape a black hole once its past the event horizon, the radius at which the escape velocity is equal to the speed of light. Outside of that, light and extremely fast matter can and does escape. That extremely fast matter is what you're actually seeing when you see a quasar. [edit] I think you may be confusing "sound" with the radio waves that are emittied from Quasi Stellar Radio Sources (quasars). While Sleestak is correct in saying sound is nothing more than the propagation of density waves, I'm not aware of any observations of such a thing around black holes. Radio waves are just another wavelength of light that we happen to use to encode signals for your radio; they are not sound waves. [/edit] A black hole is simply the extreme case of physics. Its existence does not overcome the physics of the four forces; it is a direct consequence of the interplay between them. Black holes occur when there is so much mass that force of gravity becomes stronger than the other three fundamental forces. This is possible because gravity, unlike the other forces, is only an attractive force and it can act over an infinite range.
A quasar is a baby galaxy, the first stage in its evolution. We know this because when we scan the sky, we only see them at high redshift, which means they're very far away and when they emitted their light, the universe was just a fraction of its current age. As we look at various red shifts (various epochs of the universe), we can see a gradual decline of quasars and a gradual increase of galaxies. Black holes are still at the center of most galaxies, but since they've run out of matter to accrete, you don't see them. There's a common misconception that black holes suck in everything. This is not the case. If the sun were replaced by a black hole of equal mass, the orbits of the planets wouldn't change at all. Black holes can "evaporate," which is a consequence of the uncertainty principle and vacuum energy, but the timescales on which they do so are much greater than the current age of the universe. |
3)
Message boards :
Cafe SETI :
signature testing
(Message 247130)
Posted 13 Feb 2006 by Jason Post: Hi!Hi, Lilia! You have to use BBC code, not html. So to insert and image, it's like this: [img]image_url[/img with another "]" at the end. If you click to reply to my post, you can see the exact syntax I used with your url. |
4)
Message boards :
Cafe SETI :
Stupid or Funny Signs [CLOSED]
(Message 246435)
Posted 11 Feb 2006 by Jason Post: My personal favorite: |
5)
Message boards :
SETI@home Science :
Big Bang Theory and Time...
(Message 237405)
Posted 25 Jan 2006 by Jason Post:
My problem is the arrogance with which you cast aside 400 years of work, claiming you know better even though you have obviously had very little training. I'm done too, I waste too much time here anyway. |
6)
Message boards :
SETI@home Science :
Big Bang Theory and Time...
(Message 237395)
Posted 25 Jan 2006 by Jason Post:
There are two types of people in the world, those who think they are the next Einstein, and those who know they're not (I'm leaving out the "those who actually are" because it's so neglibily small). People think that because Einstein was a patent clerk when he came up with his theory of relativity that anyone could do it, but those people forget he had (or was getting, I'm not exactly sure) his PhD in mathematics and physics at the time. To date, I can't think of anyone who made a useful contribution to physics in its 400 year history without being an expert in the field. I can, however, think of countless examples of people who think they're going to revolutionize the field with their ill informed theories. If you want to make a contribution, great, question what you're taught... but first truly understand what you're taught. Get a PhD. |
7)
Message boards :
SETI@home Science :
Big Bang Theory and Time...
(Message 237256)
Posted 25 Jan 2006 by Jason Post:
No, I cannot prove to you that time exists, no more than you can prove to me length exists. It's a philosophical question that cannot be addressed scientifically. However, the entirety of physics is based upon the assumption that space and time exist and are measureable quantities... and based upon the sucess of physics, I say it's a pretty good assumption. I asked you for an example, you gave me one. I showed you why it was wrong. You ignored that and just insisted that I give you an example. Yes, people should question what they are taught, but to think that you can undermine nearly 400 years of some of the brightest minds' work in 10 minutes is arrogance, plain and simple. |
8)
Message boards :
SETI@home Science :
Big Bang Theory and Time...
(Message 237234)
Posted 25 Jan 2006 by Jason Post:
You are the one making the extraordinary claim that you can describe the universe without one of its fundamental dimensions. Extraordinary claims require extraordinary proof. Other than poorly supported hand waving arguments, I've seen nothing. What makes time any different than length? Can you prove to me that length exists? |
9)
Message boards :
SETI@home Science :
Big Bang Theory and Time...
(Message 237205)
Posted 25 Jan 2006 by Jason Post: Ok, let's do a 10 minute critical analysis of your 10 minute, off the top of your head revolution of the entire field of physics...
Ok, v has units of m/s, c has units of m/s. Divide the two, you have no units. Ok, so the units of "velocity" are gone... by definition, it's not a velocity anymore, but we'll go with it.
Your "light meter" is nothing more than a renamed meter. The number 5e6 "light meters," was not derived in any fashion, but simply chosen to get you the right answer when multiplied by 0.1. (3e7 m/s)/(3e8 m/s)*(5e6 m) = 5e5 meters. You haven't gotten rid of time in these equations, you never used it.
Dimensions are not conventions, they are physical properties of the universe. The only potentially valid point would be if you said everything was a human construct, because one of the fundamental assumptions of science states that there is a physical, rational reality. However, this is a matter of philosophy, and science cannot, and makes no attempt to answer this question. |
10)
Message boards :
SETI@home Science :
Big Bang Theory and Time...
(Message 236760)
Posted 24 Jan 2006 by Jason Post:
There's a very fundamental difference between time and a second. Time is a dimension, a property of the universe. A second is a unit by which humans measure this property. A second is exactly 9,192,631,770 cycles of microwave light absorbed or emitted by the hyperfine transition of cesium-133 atoms in their ground state undisturbed by external fields. You can certainly say that a second is a construct of man (which it is), but time is most certainly not.
Force, velocity, acceleration, energy, etc cannot be ratios. They wouldn't have the correct units. I can travel .1c (3e7 m/s), but I can't travel .1. How far is San Francisco? Oh, it's 6. You might be interested in the units of measurement where all the physical constants equal 1. This seems to be the most "natural" system of units, and it's called Planck Units. |
11)
Message boards :
SETI@home Science :
Black holes 'do not exist'
(Message 232063)
Posted 16 Jan 2006 by Jason Post:
The theory of black holes. The force of gravity has long surpased the force that repels protons and electrons, compressing each pair into a neutron (like a neutron star). |
12)
Message boards :
SETI@home Science :
Black holes 'do not exist'
(Message 232052)
Posted 16 Jan 2006 by Jason Post:
But black holes are electrically nuetral. That equation doesn't apply here. |
13)
Message boards :
SETI@home Science :
Black holes 'do not exist'
(Message 232014)
Posted 16 Jan 2006 by Jason Post:
What's A in your equation? Something with the units kg*m^3/s^2... I've never seen an equation for energy like that before... |
14)
Message boards :
SETI@home Science :
Black holes 'do not exist'
(Message 231990)
Posted 16 Jan 2006 by Jason Post:
Why would it take an infinite amount of energy? I've explained below why that's not true.
No one is saying you can reverse time... where did that come from? |
15)
Message boards :
SETI@home Science :
RAC?
(Message 231969)
Posted 16 Jan 2006 by Jason Post: Thanks :) No Problem |
16)
Message boards :
SETI@home Science :
RAC?
(Message 231960)
Posted 16 Jan 2006 by Jason Post: Recent Average Credit |
17)
Message boards :
SETI@home Science :
Stardust mission returns to earth in 4 days
(Message 231679)
Posted 15 Jan 2006 by Jason Post: "If humans can be trained, software can be too"...... I stand by my statement. I didn't say it would be easy, but there's no reason it's fundamentally impossible, and I don't think it's that impracticle given their budget and the time they had to do it.
But the problem is humans will probably miss a lot too, and determining the systematics of what kinds of things get missed will be next to impossible. With computers, you can do monte carlo simulations on fake data and determine precisely what kinds of things you would miss. With humans, you might insert a few fake ones to see if they get found, but other than moderate completeness statistics, you wouldn't know much about selection effects. And while I agree the idea has potential to get your average Joe directly involved in science, I think there's better ways to do it... this just seems like exploitation to me. As for being published in a scientific journal... well, I've found more reliable ways of assuring that. |
18)
Message boards :
SETI@home Science :
Black holes 'do not exist'
(Message 231650)
Posted 15 Jan 2006 by Jason Post:
Although you're right, gravity is orders of magnitude weaker than all the other forces, it has the unique power to act over large (infinite) distances (though it gets weaker at larger distances, it's much much stronger than any other force at comparably large distances), and so it can add up, and there are several different regimes that are interesting. I'll make the following definitions: F_g = Force of gravity F_em = Electromagnetic Force F_w = Weak Nuclear Force F_s = Strong Nuclear Force F_g < F_em: You get a normal star where the force of gravity is balanced by pressure, as in the Sun. F_em < F_g < F_w: Neutron stars happen when there's so much mass that the force of gravity overcomes the electromagnetic force, the force that repels electrons and protons. However, the weak force is still stronger than gravity, so the gravity and the weak force are in equilibrium and the star is stable. F_w < F_g < F_s: Quark stars happen when there's so much mass that gravity is stronger than the weak nuclear force. However, the strong nuclear force is still stronger, so gravity and the strong force are in equilibruim an the star is stable. F_s < F_g: Now what if there's so much mass that gravity is stronger than the strong nuclear force? It becomes the strongest force in nature, and since there's nothing stopping it, it compresses until you get a singularity, or a black hole. |
19)
Message boards :
SETI@home Science :
Stardust mission returns to earth in 4 days
(Message 231586)
Posted 15 Jan 2006 by Jason Post:
I already read it and don't buy it. Users will be trained with particle hits in astrogel from particle accelators. If humans can be trained, software can be too. |
20)
Message boards :
SETI@home Science :
Stardust mission returns to earth in 4 days
(Message 231502)
Posted 15 Jan 2006 by Jason Post:
But now ask humans to solve 3 million of those anti-spammer things. It would take far fewer man hours to write a program to do it. Sure, it would take some sophistication, but for a 200 million project, I think they'll selling themselves short. There's no telling what kinds of biases will be introduced by doing it this way... and I think they'll have to search everything more than 4 times to be sure no one missed it. Do you really think the amount of processing time/code writing time would be less than 30,000 hours? They could have been writing the code during the 7 years it was in space... ample time to develop better pattern recognition software technologies. Then they'd spend a month taking all the necessary images and another month running and tweaking the program. Now they're counting on volunteers to do it in 6 months... your guess is as good as mine as to how reasonable that is. Well have fun... wanna find the redshifts of my 650 galaxies while you're at it? I could have a program do it, but I'm just too lazy to write the software... [edit] Oh, and what happens next time when this project works so well that they want to make it 10 times bigger... do you think this kind of effort is easily scalable? Computers and software get faster and cheaper, humans don't. [/edit] |
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