# csmyth3025

Senior Members

306

1. ## Proton Propulsion

If you're still thinking in terms of the electrons of an ionized gas separating from the plasma and "leaking out" through the walls while leaving the nuclei (protons) still contained, you're wrong. This simply will not happen. Chris
2. ## CMBR isotropy, then --> space isotropy, today ?

Perhaps my math is too simple for this calculation, but if one projects a one degree segment on a circle with a radius of 45 Gly, it seems to me that it would represent: [LaTeX]\left(\frac{2\times pi\times45\,Gly}{360} \right)=\,\sim758.4\,Mly[/LaTeX] -and- [LaTeX]758.4\,Mly\times\left(\frac{1\,Mpc}{3.262\,Mly}\right)=\,\sim240.77\,Mpc[/LaTeX] This figure is only somewhat larger than your calculation quoted above, but I would be interested to know if there's an error in the way I calculated it. As you noted in your post #2, this is the current co-moving arc length of one degree at a distance of 45 Gly. As I understand it, the distance to the source of the CMB photons we're seeing today was originally about 42 million light years away from our spot in the universe at the time of recombination. This would make these arc segments ~224.7 Kpc in length - which is roughly the estimated distance between the Milky Way galaxy and the Leo I dwarf galaxy in our local group. Chris
3. ## Proton Propulsion

If your proposed system is "much like an ion thruster" then you may want to examine the Wikipedia article on such devices here: http://en.wikipedia....toplasma_Rocket According to the article, these devices can theoretically utilize hydrogen instead of the argon currently used in the prototypes: Chris
4. ## Energy to compress gases...

I'm no expert on refrigeration, but I think you'll find an answer to most of your questions in the Wikipedia article on refrigeration here: http://en.wikipedia....i/Refrigeration Chris
5. ## Relativity Question

I think the main point is that Special Relativity explains both why and how this happens pretty successfully and to a very high degree of predictive accuracy. Remember, when Einstein proposed his theory of special relativity no one had even imagined that such things as muons even existed. (ref. http://en.wikipedia....ki/Muon#History ) Although special relativity may seem counterintuitive to laymen like ourselves, the logical consistency and unrivaled predictive power of the theory makes it rather hard to argue that it doesn't represent the way the world actually works. Chris
6. ## Standard Model

For those who are still following this thread, please note that although a proton half-life of 1034 seconds is a very long time (~2.3 x 1016 x the present age of the universe), the lower limit given for the half-life of the proton in my previous post is ~1034 years (~7.3 x 1023 x the present age of the universe). Out of curiosity, I'm wondering: Suppose one ignores effects such as protons being splattered by cosmic rays (or particle accelerators), smashed into neutronium in neutron stars or gobbled up by black holes. If one assumes that the fate of all the protons left over after the big bang is that they will decay with a half life of ~1034 years, what percentage of those primordial protons are left today? I tried to figure this out using the Wikipedia information on exponential decay ( http://en.wikipedia....ponential_decay ), but the math is beyond my limited comprehension. My instinct is that if 1/2 of the original protons will have decayed in 1034 years, then 0.5/(7.3×1023) will have decayed by the present time and this would result in about 0.9999999999999999999999993150684 of all the original protons still being around today. Can anyone give me a correct way of calculating this? Chris
7. ## Relativity Question

(ref. http://en.wikipedia....ns#Muon_sources ) This Wikipedia passage may help in understanding why the seemingly fanciful notion of length contraction and time dilation are real effects that are observed in the real world by researchers who are very particular about being sure of the observations that they publish. Chris
8. ## What is the difference between mass and energy?

Initially I thought that quarks and leptons were two entirely separate "horses of a different color". After reading about pions and muons, though, I'm not sure: (ref. http://en.wikipedia.org/wiki/Pion ) Also, (ref. http://en.wikipedia....ns#Muon_sources ) Quarks seem to rather easily change into leptons. Chris
9. ## Standard Model

(bold added by me) I think you might mean neutrinos and anti-neutrinos. Free neutrons have a half life of about 885.7 seconds (~14.75 minutes). (ref. http://en.wikipedia....ki/Free_neutron ) As far as protons and anti-protons are concerned, there is no observational evidence that they decay as far as I know. There are experiments that indicate a lower limit on the half-life of protons of nearly 1034 years: (ref. http://en.wikipedia....mental_evidence ) Chris
10. ## Standard Model

I can see now where you draw your pool of "elementary" particles. The lists of baryons and mesons are, indeed, long lists: http://en.wikipedia....List_of_baryons http://en.wikipedia..../List_of_mesons Although these lists seemed to include hundreds of elementary particles in the 60's, they are now thought to be composite particles of more fundamental particles - quarks. Almost all of these composite particles were created briefly in high energy environments such as the particle colliders where they were first discovered: (ref. http://en.wikipedia....ki/Particle_zoo ) Chris
11. ## What is the difference between mass and energy?

I realize that this is an old thread, but it's the first one I could find that fits the subject of my question. Basically, I'm wondering if quarks are ever destroyed. In this sense I'm thinking of the gamma rays produced by the mutual annihilation of an electron-positron pair. (ref. http://en.wikipedia....on_annihilation ) This passage from the cited Wikipedia article seems to indicate that quarks can be directly or indirectly converted into energy (photons), but that such events are rare. Conversely, the Wikipedia article on color confinement seems to be saying that separating quarks is pretty much impossible: (ref. http://en.wikipedia....lor_confinement ) What I'm having trouble with is, if quarks can't be separated without spontaneously creating a new quark-antiquark pair, how do they manage to decay to (ultimately) leptons and/or photons? Chris
12. ## Standard Model

In view of the ensuing discussion I'm guessing that you just pulled the "99.9%" figure out of your ear. That said, you've sparked a question in my mind - which is: How many of the known elementary particles are considered stable? As far as I know, protons and electrons are thought to be stable. Are all three types of neutrinos stable (in aggregate)? Free neutrons are not stable but are neutrons combined with protons (as in deuterium or helium) stable? NOTE: From my reading of the Wikipedia article on Stable Isotopes, I'm thinking that neutrons are as stable as protons in at least 90 nuclides. (ref. http://en.wikipedia..../Stable_nuclide ) And then, of course, there is also the question of whether quarks are stable. In short, are there always going to be about the same number of protons, electrons and neutrinos as there were just after the big bang? Chris Edited to add NOTE and reference.
13. ## Theory for universal expansion...

As far as I know, any part of the universe that is causally connected to our universe is considered part of our universe. I'm not sure what definition you're using for universe when you speculate about "two or more universes", but if they are causally connected to each other then they're all part of the same universe. Chris
14. ## Gravitational waves ?

http://upload.wikime...olarization.gif The above link is an animation of how a gravitational wave would effect a ring of particles. The animation is taken from the Wikipedia article on Gravitational Waves here: http://en.wikipedia....vitational_wave Chris
15. ## Gravity as a repulsive force

You're probably thinking of an inflaton rather than a graviton: (ref. http://en.wikipedia.org/wiki/Inflaton ) Chris
16. ## sun poles reverse

You might want to check out the Wikipedia article on "Pole Shift Hypothesis": (ref. http://en.wikipedia....hift_hypothesis ) If, on the other hand, you're referring to a magnetic pole reversal, Wikipedia also has an article on this phenomenon: (ref. http://en.wikipedia....gnetic_reversal ) In both cases no scientific consensus exists that they cause significant climate disruption. Chris Edited to add portion on magnetic pole reversal.
17. ## Black holes and the scarcity of anti-matter

Is this the basic idea (absolute difference)? http://demonstration...teFrequencyOfC/ Chris
18. ## cosmos

Imatfaal is correct that Special and General Relativity place no limits on the rate at which space itself expands. Your calculation of the average rate of expansion is somewhat off the mark: $\frac{4.2\times10^7\,LY}{3.8\times10^5\,yr}=110.526\,LY/yr$ This doesn't really change the validity of the point you're making, though - as long as you realize that the rate of expansion was much greater than this average value at times very close to the big bang and much less than this average value at the time of recombination (~380,000 years after the big bang). Chris Edited to correct spelling erreor
19. ## Black holes and the scarcity of anti-matter

"...However, the odds of parity diminish with an increased number of interactions even as the the average converges towards it..." Is this part of the theory of large numbers? Can you provide a proof for this statement - or a link that contains such a proof? Chris
20. ## Maintaining the appearance of fixed distance in spite of length contraction?

The thought experiment you propose sounds like "Bell's Spaceship Paradox": http://en.wikipedia....aceship_paradox Is this the situation you're thinking about? Chris
21. ## Black holes and the scarcity of anti-matter

(bold added by me) I'm no expert on probability theory. I'm relying on the following passage to predict that a large number of interactions will show virtually no preference toward one interaction over another: (ref. http://en.wikipedia....f_large_numbers ) You're proposing a precondition (the preferential absorption of anti-matter by primordial black holes) that is just as speculative as any other explanation that might result in the observed disparity between matter (which is ubiquitous) and anti-matter (which is almost non-existent). As far as I know there is no evidence to support this speculative assumption. Chris
22. ## Gravity and Light

The relationship between special relativity and electromagnetism is that an observer will always see light traveling at ~300,000 km/s in a vacuum regardless of his own motion or the motion of the emitting source. Is this the relationship to which you're referring? Chris
23. ## Time as a Distance Vs Biological Clock

You'll have to explain what your topic is. The subject header makes no sense. Chris
24. ## Relativity Question

(Bold added by me) You seem to think that somewhere in the universe there is an object that has zero velocity relative to the universe. As far as I know, the whole point of special relativity is that every object in the universe is moving relative to some other object. The equations of special relativity simply provide the means for transforming measurements taken in one inertial frame of reference into the equivalent measurements taken in another inertial frame of reference that's moving relative to the first. Special relativity doesn't claim that the measurements taken on object A are right or wrong or that the reflect anything other that what the observer on A measures. It only says that if measurements are taken on object A they can be mathematically adjusted according to a very specific set of equations to produce the measurements that an observer on object B that is moving relative to A will obtain. What part of this doesn't seem real to you? Chris
25. ## Can virtual particles come from nothing?

Do you mean virtual particles? If so, what theory pertaining to virtual particles do you have in mind? Chris
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