Physics Discussion Thread

negi · Post by **negi** » 10 Oct 2013 03:57

^ Nope there are quite a few physical phenomena which exhibit elastic collisions for eg. Rutherford backscattering.

member_22872 · Post by **member_22872** » 10 Oct 2013 04:06

I see, but firstly atomic configuration is but a spherical approximation no?...since I am not a physicist, I don't know about Rutherford back scattering.

Vayutuvan · Post by **Vayutuvan** » 10 Oct 2013 05:45

venug wrote:...in case if reactors, moderation is done to reduce the number of neutrons and/or slowing down the neutrons...in case of A-bomb no control exists once it is initiated.

I have no clue at all but from pop science books I have an impression that the Cadmium (they are Cd right? If not correct please) rods absorb neutrons. Physics - especially nuclear and quantum - is tricky

So I will stop making a fool of myself.

member_22872 · Post by **member_22872** » 10 Oct 2013 05:53

matrimc(On your insistence only, ji dropped), me too, I am not either, just remembering things as I read here and there...I think even graphite and D2O(heavy water) serve the same purpose.

Vayutuvan · Post by **Vayutuvan** » 10 Oct 2013 06:36

venu, do not think about the ji part. If we were face to face, would you start your every sentence with a "ji" or garu?

Yes, I remember Graphite (a form C). $D_2 O$ is used as shielding in reactors (to absorb harmful "radiation" - no idea what are the constituent particles in this "radiation"). Maybe tritium is a different matter? Who knows?

SriKumar · Post by **SriKumar** » 10 Oct 2013 06:43

Amber G. wrote: 1) If one sleeps under a tree, one will not get wet from morning dew. (or not as wet as if one sleeps under open sky)
Because the tree:
a) Absorbs star light
b) Keeps air from rising
c) Emits infrared radiation
d) Blocks the clouds
e) Tree is older than Chernobyl, hence it absorbed all radioactive Cs and produces heat
f) No, it is not true, you get almost as wet..

So the main kosin is ..what causes dew. Some random thoughts....If the temperature of air is below a certain value, say 'T', which results in moisture condensing out, you have dew. The temperature 'T' is called dew point. Dew is more likely to form on cooler/coldest surface around because cooler air holds lesser moisture than warmer air.

What are the surfaces in question here....ground, person and tree. At night, ground is cooler than person, who, if he is a healthy mammal, will be at 98.4 F (as opposed to a stone, which will be at same temperature as the ground). Tree should be warmer than the air around it, since it absorbed heat all day and is slowly emitting it out, at night (just like the ground). So, how does the tree affect the dynamic i.e. how is a treeless person affected vs. a fully-treed person?
(i) Air around the tree should be warmer due to the heat it gathered during day and now emits at night.
(ii) air around a tree is generally more moist than air away (because of the leaves which have some moisture in them, though one could argue that there is not much evaporation at night). If there is any truth to this, then one could argue that around a tree, more dew might form. Setting this aside for now...
(iii) while it is true that trees emit Co2 at night, ..am not sure what that would do. Co2 is being formed at night due to respiration, so it will not have absorbed any solar radiation during day, so it cannot emit any.
So, am concluding that if there is a stone below a tree, it is likely to be around slightly warmer air near the tree ('cose tree emits radiation gathered during day). Warmer air means dew is less likely. So, a stone that is tree-ed will have less dew due to (c). Follow-up kosin: would dew form on a body that is always at 100F, when cooler surfaces are present in immediate vicinity.

member_22872 · Post by **member_22872** » 10 Oct 2013 06:57

matrimC, Infact I would saar, I had tough time when I first landed in massa land, even now meeting professors and my elders, I would call them 'sir' and 'ji' if Indian.

member_22872 · Post by **member_22872** » 10 Oct 2013 07:00

SriKumar ji, I think you are forgetting relative humidity, it also plays a vital role in air conditioning. dew point is the same in same in both cases.

SriKumar · Post by **SriKumar** » 10 Oct 2013 07:03

Amber G. wrote:
P5 Professor A J K (in the movie Ek Tha Tiger) walks a dog. The dog (weighing 52 pounds)
pulls on the leash, (pulling AJK), with a force of 200 N . According to Newton's third law, equal and opposite force of 200N is applied by the leash on the dog. In the movie we see that dog does move.This is is best explained by:

a) This is just a movie scene, in actual life dog will not be able to pull AJK as the forces cancel out.
b) The bus (shown in the background in the movie) is in contact with the road.
c) We need more than Newton's law, and have to consider odd results of Relativity, particularly, that pressure generates its own gravitation field pulling the dog in a geodesic trajectory of the curved space.
d) We have to consider Newton's first law, which is more relevant here than the third.
e) Write it in your own words.

Prafesser AJK is pulling Ekta Tiger, his pet dog, not a tiger, in the vicinity of a bus whose wheels go round and round. Newton has it that AJK pulls the dog (which may yet be a tiger) with the same force. So, how the dog is doing locomotion (never mind doing motion, which was perhaps the original purpose of walking Ekta Tiger, the dog). Well, for once, the presence of earth is a life saver. The dog push on earth and the earth push back. Free body diagram sez main players are: earth, dog,leash, AJK and earth. Dog pushes earth with a force greater than 200N, out of which 200 N is used for pulling AJK. So, the dog locomotes. AJK is being pulled by leash, but using earth to brake himself. He locomotes at the same speed as dog (which implies that he reacts out exactly 200N into earth).

SaiK · Post by **SaiK** » 10 Oct 2013 07:09

matrimc ji.. my dad was always particular to address by ji, huzoor, avare, garu, etas, and all the vanga-pongas especially against an individual of any age as long as the knowledge is shared.

brf is a place, people come with knowledge to share.. so, it is entirely fine to add that ji or garu or whatever that makes you feel good.

btw, one can't claim it.. but earn it. if someone has addressed it, means he/she has seen you hold the information knowledge model for him/her.

now my problem is the law of transformation of such information to my kids.. it is failing.. they don't fall under the indic concepts we (i hope you don't mind to include you all) all grew up with.

Vayutuvan · Post by **Vayutuvan** » 10 Oct 2013 07:25

the force due to friction is proportional to normal force. the constant of proportionality is friction constant. just a factoid which may or may not help in solving this problem. require several details - weight of the person, dog, friction coefficient between dog's (tiger?) feet and earth and likewise for the person and some more physical constants.

(may be not)

Let us say it is not a dog but an elephant called tiger and the rope is not really a rope but a steel chain. Would the man be able to pull the "tiger" or the "tiger" pull the man?

member_22872 · Post by **member_22872** » 10 Oct 2013 07:27

SaiK garu, me thinks so too...I feel small in front of many, hence, it is some what uncomfortable to address by just name basis...just an old habit.

member_22872 · Post by **member_22872** » 10 Oct 2013 07:34

I think initial velocity of the dog needs to be taken into consideration. If the dog is accelerating, then the frame of reference would be non-inertial anyway, so it is not just Newton's third law alone that governs the motion of the dog. For a second if we consider the man holding the dog stationary, then the tension in the leash would be governed by Newton's third, but if the dog-man pair already has an intial velocity, they will keep moving, unless acted on by an external force ofcourse...so 1st law needs to be applied along with 3rd.

Theo_Fidel · Post by **Theo_Fidel** » 10 Oct 2013 08:01

Reactor uranium is only 2.5%-4% U-235. This is not enough to sustain a chain reaction unless neutrons are slowed down with moderator and use control rod, etc.

I think it came as a surprise to everyone that just the hydrogen explosion could cause as much damage as it did at Fukushima.

Anyway this is NOT nuclear thread but physics thread.
End of OT from me.
-----------------------------------

That said WRT the dog problem, in a perfect controlled environment I would look at the forces applied as vectors, they have magnitude & direction. Due to curvature of the earth the angle of leash 200N is slightly oblique to the angle of the dogs 200N. -> 200 Cos Theta x angle subtended. Hence the restraining force will be less than acting force. Ergo Dog moves forward. Also a byproduct is that A.B cos theta would make the dog & human weigh fractionally more.

In real life engineering you never try to perfectly balance forces precisely because of such unknown unknowns. Always use a factor of safety. In this case I suggest to the professor that he apply a restraining force of 400N with his feet. If he is unable to supply a 400N restraining force I suggest that this is animal cruelty and a disaster waiting to happen. The police should tazer him immediately and take away the dog for further 'processing'. All names have been suitably changed and in no way reflect real people.
-------------------------

OTOH I would go for option

x. My best guess is Project Orion was letting of 800 atomic bombs in the atmosphere in the near vicinity. The good professor got startled, "hai! Whyfor this phattaka! and irrational fear of radiation. Don't run away people Don't run away. Its just an atomic explosion. Don't follow the clout people I say."

The dog took advantage of the moment and moved forward. Bad dog.

Amber G. · Post by **Amber G.** » 10 Oct 2013 21:09

venug wrote:AmberG ji, one question, in the case of long ranges like that of sniper rifle bullets, won't aerodyanmic design also have a say on the range? some bullets might even enter supersonic speeds and shocks can dampen the speed hence the range of the bullet? and angular velocity imparted to some bullets might increase the heat dissipation as well.

Of course what you say is correct and aerodynamic design, muzzle velocity etc are critical part for sniper rifles (wrt bullet range, and accuracy).

But here is slightly less known part about Newton's brilliance. When all is said and done, for example, taking this (link link ( from google ) the range here depends mainly on the "length". It talks about " source: Journee's formula" which is nothing but saying that range is 2200 times the "length" of the bullet!

(The factor 2200 is for spherical slugs and "length" here is diameter, but this kind of relationship is similar for cylindrical bullet too)

The formula can be derived directly from Newton... that is the (maximum) range is about (about 2-3 times) the length of the bullet times the (ratio of bullet's density /air density).

(And one can sort of ignore the muzzle velocity and other factors to get this calculation)

****
This is why gun battles are rare under water. (One sees long spears and spear-guns). Water is about 1000 times dense than air, and the range of bullet will thus be reduced by similar ratio.

****
One famous story is about Jules Verne, in which a gun (cannon) is fired giving the rocket escape velocity and send a capsule to the moon. The dimension and material of the capsule, is described in the book and Verne knew that physics wise it was not possible. This detail bothered him because he paid attention to many other laws of physics but could not think of how to take care of this. (He did not think of three stage rockets)

(You need self-propelled, and multistage rockets to overcome the air resistance - No gun can shoot a projectile (made of known materials and reasonable shape) into the space.

Amber G. · Post by **Amber G.** » 10 Oct 2013 21:21

venug wrote:In fact no collision is elastic ever. There is always energy and momentum loss.

Depends on what one calls "loss"..
In practical terms when you study things like collision of tennis balls, (or automobile accident)..
- Momentum is strictly conserved.
- Energy is "lost" in a non-elastic collision if one considers KE only, as some kinetic energy is "lost" and converts into, say, heat.

(Of course, to a physicist, strictly speaking, both energy and momentum is always conserved

)

Amber G. · Post by **Amber G.** » 10 Oct 2013 22:18

venug wrote:..., very interesting, but in the case of the plate, assuming a sound speed of 330m/s, it is clearly in hypersonic regime. I am not sure why they even assumed that the plate would survive a 200 mach flow where high surface temperatures would dominate once it hits the atmosphere. This is also the reason as you might already know for heat shield on the shuttle and reentry vehicles which are subjected to 20-25 mach flows(approx). But in case of the bullet even though it might not experience such high temperatures, drag could play a role...me thinks.

hmm... energy needed to propel a 900 Kg plate with 66Km/sec is about 2TJ (or about 0.5 KT.. that is 500 tons of TNT), less likely to come from Pasclal-B test, whose TOTAL yield was about 300 Tons of TNT
(Link: http://nuclearweaponarchive.org/Usa/Tes ... ml#PascalB

SaiK · Post by **SaiK** » 10 Oct 2013 22:46

This has happened to me in desh streets when I was a kid.. lot of street dogs used to chase me.. some are mad! So, normally I have a certain amount of energy to expend - but when these dogs chase me, I get the extra energy coming from no where! where is that conserved? Is it that we can produce more than we can consume?

member_22872 · Post by **member_22872** » 10 Oct 2013 23:53

AmberG Ji, you are right, the velocity of the plate couldnt have been 66km/s, from the link you provided, the velocity of the plate ~56km/s seems closer, that would give the energy to be 330 T TNT....closer to 300 T TNT yield, may be the plate velocity measured is bit off to the higher side.

member_22872 · Post by **member_22872** » 10 Oct 2013 23:54

SaiK ji

you are funny sir, I can imagine bunch of dogs running after you.

Theo_Fidel · Post by **Theo_Fidel** » 11 Oct 2013 00:08

66km/sec or 41 miles/sec is the lower bound of the velocity from photographic evidence and specifically calculated by Dr. Brownlee, the scientist in charge. Take your arguments up with him. I tend to believe him.

It is very much possible to explosively fire shells into space. Artillery has routinely done that since the 1940's. Getting into orbit is a whole different thing. Project Harp fired a shell to 180 km altitude, not that far below the ISS today. Higher altitudes are possible with better guns. The Bull guy tried to sell some designs to Saddam as I recall.

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

Amber G. · Post by **Amber G.** » 11 Oct 2013 00:19

venug wrote:AmberG Ji, you are right, the velocity of the plate couldnt have been 66km/s, from the link you provided, the velocity of the plate ~56km/s seems closer, that would give the energy to be 330 T TNT....closer to 300 T TNT yield, may be the plate velocity measured is bit off to the higher side.

The ~56km/s velocity you see (or what I think you are seeing) is velocity of gas particles (or vaporized concrete) hitting the plate which was about 150 m above the nuclear device placed on a collimator.

You get 56 km/sec for the expanding gas (assuming 100 Tons of TNT or 1/3 of 300 Tons were used to vaporize and push the plate)... It is NOT going to propel a 900Kg plate anywhere near that speed.

Also, as said before, fairly simple (back of an envelop type) calculation can show that any steel plate of reasonable shape
can not be shot in the space from earth's surface (due to atmospheric drag) by shooting it off with an initial high velocity alone...

One interesting aspect to keep in mind for rough calculations ... even a 10 ton meteorite will keep only about 5-6% of its cosmic speed (and most of the speed is lost in last 10 km of atmosphere) when it hits earth.

Amber G. · Post by **Amber G.** » 11 Oct 2013 01:02

venug wrote:I see, but firstly atomic configuration is but a spherical approximation no?...since I am not a physicist, I don't know about Rutherford back scattering.

Venug - A very good source, for those who are scientifically inclined, as I suggested previously, is "Los Alamos Primer" by Robert Serber.

member_22872 · Post by **member_22872** » 11 Oct 2013 01:31

AmberG ji, thank you, is it just 26 pages? : http://www.fas.org/sgp/othergov/doe/lan ... 349710.pdf

member_22872 · Post by **member_22872** » 11 Oct 2013 01:36

I see it's partial book which I linked...anyway, I will get the book.

Amber G. · Post by **Amber G.** » 11 Oct 2013 01:44

matrimc wrote:
venug wrote:...in case if reactors, moderation is done to reduce the number of neutrons and/or slowing down the neutrons...in case of A-bomb no control exists once it is initiated.
I have no clue at all but from pop science books I have an impression that the Cadmium (they are Cd right? If not correct please) rods absorb neutrons. Physics - especially nuclear and quantum - is tricky So I will stop making a fool of myself.

FWIW- People may already know this, but it seems to me that there may be some confusion between moderator and absorber.

Moderator - Slows down the neutrons. (Basically neutrons collide with these lighter nuclei and slow down - they loose energy and hence the speed). Example: Water, Heavy Water, and Graphite. These basically allow nuclear fission (in U-235) proceed even if the concentration of (U-235) is fairly low. (About 3% or even less eg natural Uranium for (0.7% U235) for Candu types)

Neutron Absorbers: - Absorbs neutrons, and control (or even shuts down) the chain reaction. Example: Cd, Boron (one of the most common - B4C in control rods, or boric acid as in a coolant water), Hf, Zr molybdenum etc.. (Actually U238 is a nice absorber too!).

Amber G. · Post by **Amber G.** » 11 Oct 2013 02:49

Looks like most say here that a nuclear reactor can not explode like a atom bomb.

Is this true for all kinds of reactors?

What about fast breeder reactors?
What about older Candu type?

***

Also looks like there is an agreement while discussing dew under a tree. But I did not see any post here about experimental results. What do people really see? Is there less dew or not ? Have you noticed any difference?

***
Did any one see the movie Gravity? What do people think?

Vayutuvan · Post by **Vayutuvan** » 11 Oct 2013 05:29

Amber G. wrote:(Of course, to a physicist, strictly speaking, both energy and momentum is always conserved )

Is that a "central dogma" of physics? Especially conservation of energy? Can it be empirically proved/proven? or is it an axiom (if you are offended by the word "dogma" though looks like there is such a central dogma in Biology according to a biochem and computational chem friend of mine).

SaiK · Post by **SaiK** » 11 Oct 2013 05:36

there was some program in sci ch that talked about black hole weapons.. or was it i was reading some articles.

can someone say more on this? is it like something the energy out of the black hole, that it had consumed in an earlier process? primary question would be does black holes conserve energy?

Amber G. · Post by **Amber G.** » 11 Oct 2013 05:50

^^^ I don't think there is any "dogma". Conservation of momentum (or energy) is an experimental fact.

Vayutuvan · Post by **Vayutuvan** » 11 Oct 2013 07:50

AmberG ji, could you please point me to some source for conservation of energy as an experimental fact? Please note I am not asking for conservation of momentum. I am not challenging your claim but have read somewhere (but forgot the source) that "conservation of Energy" is taken to be an axiom of Physics. On a side note, I think {you,Bade} and moi seem to have the same tension which Feynman and his math peers had when he was a UG at your alma mater (I presume and also possibly brihaspsti's lair).

nachiket · Post by **nachiket** » 11 Oct 2013 11:27

^^There can be no better teacher than Feynman. Here is the link to his lecture on Conservation of Energy: http://www.feynmanlectures.info/docroot/I_04.html

negi · Post by **negi** » 11 Oct 2013 14:01

Amber G. wrote:Looks like most say here that a nuclear reactor can not explode like a atom bomb.
Is this true for all kinds of reactors?
What about fast breeder reactors?
What about older Candu type?

All kinds of reactors on purpose via design make a point to not allow for

1. Confinement or dense packing of fissile material (fuel and control rods are spread around in a grid like fashion)
2. Deflect the neutrons and confine them in the fissile core so that they do not miss a U235 atom.

So in a hypothetical scenario if one were to withdraw all the control rods from a reactor core and allow the chain reaction to proceed unabated the core will meltdown but it will not explode like an atom bomb because the fissile material will expand and melt away and such a mass will become subcritical.

Amber G. · Post by **Amber G.** » 14 Oct 2013 01:19

matrimc wrote:AmberG ji, could you please point me to some source for conservation of energy as an experimental fact? ....but have read somewhere (but forgot the source) that "conservation of Energy" is taken to be an axiom of Physics. On a side note,.....

Nachiket gave a good resource, to add, let me make a few comments.
To me, beautiful part of physics is that no matter how beautiful a mathematical model is, if it does not fit the experimental results, it has to be discarded. The fun part of physics, to me, is NOT to use big words, but explain even the complex issues in simpler terms so that they are logical. (And not worry too much about philosophical part.... if you can't observe it, why worry about it)..Also rather than just talking about abstract theories, I enjoy the practical part to use this in everyday problems.

For example, basic idea of conservation of Energy, can easily debunk the flying manhole cover urban legend, which claims that a 900 Kg flying disk achieved 66Km/Sec (or more) speed by a 300Tons of yield of a nuclear bomb.

BTW, it seems that the this urban legend was some one's idea to claim Sputnik was not the first object in space.. (See for example this link: http://www.skepticblog.org/2011/12/15/u ... t-sputnik/. (Of course, there will always be a few people who will be ready to believe any thing ).To me the laughable part was some one to believe a claim that 66Km/sec was the "lower bound" because a high speed camera just had only one image in the frame or the "expert" said he saw the disk "flying as a bat"

. (Other references talk about this). All this without giving any details about how, where, and what type of camera in 1950's could photograph, in a reliable way, something which will move more than 66 meter in a millisecond!, or where the expert was (near this nuke device) to see it as "flying as a bat"... or how did it was determined that it remained in one piece and not vaporized..etc..etc..

Sure there are people who will believe in Jinn Thermodynamics but for logical people, a simple calculation (KE= mv^2/2) can debunk urban legends like this.

Theo_Fidel · Post by **Theo_Fidel** » 14 Oct 2013 05:35

BTW the reason Dr Brownlee is confident in his calculation is not due to Djinn power (First time I'm seeing this argument in Sy-kicks thread)
but due to the fact that the power of the Pascal explosion was not pinned down.

It was originally meant to be a 3 lbs TNT type explosion, yes there are no missing zeros.
But obviously the actual yield was wildly above this.
Dr Brownlee believes it was far above the number reported but can't prove it, all he has is lower bound on yield as well.
The collimator was vaporized and so the actual yield is indeterminate.

It hard to believe people resort to djinn power without reading the notes of the scientists in charge.
--------------------------

Newtons Approximation is an approximation. Never intended as a hard rule. Even under that rule a steel object 1.3 meters in length can easily make it through the atmosphere. The plate was 4 feet in diameter BTW.
Again no Djinn power needed either for the math or for knocking some sense into P-cysts.

Here is Dr Brownlee's full verbal account. Fascinating. Certainly more fascinating than the Djinn power.

http://www.radiochemistry.org/history/n ... ownlee.htm

"June 2002"

Sometime in 1956 Dr. Alvin Graves, Division Leader of the Test Division at Los Alamos told me that we were going to have to test underground in order to reduce fallout as much as possible. He asked me to see what I could learn about it by making what calculations I could.

The temperatures and pressures generated by a nuclear explosion are such that there was considerable doubt that any underground test buried at a "reasonable" depth could be contained.

In 1956 we were severely limited in computing capabilities-compared to nowadays they were laughable, and miniscule, and arguably nonexistent. I had the equations of state of four materials. They were air and water, aluminum and uranium. As it happens, there is a lot of aluminum in NTS soil, so I called that "earth". I called that of uranium "fire", and the others were air and water, so with earth, air, fire and water, how could I fail?

In attempting to mock up the earth, I had some information about NTS soil densities and water content. I used a cylindrical pipe filled with air of several densities, depending upon the possible use of vacuums. I was allowed considerable freedom to choose other parameters as I wished. For example, what might the efficacy of plugs of various masses be, and where might they be placed for optimum results. I worked regularly with Bill Ogle, the deputy division leader, and we decided to have a first test in an "empty" pipe (cables were present), open at the top. Then we would do a test with a cap, and then do tests with plugs, the first one used to be in the middle of the hole, and the second one at the bottom. Thus we hoped to learn from test to test, acquiring data and information incrementally. Incidentally, the Pascal B test, and those immediately following, had a 4-foot diameter pipe. The cap welded to the top of Pascal B was four inches thick, so was of appreciable mass from a "man-handling" point of view.

The first test of our "series" was Pascal A, with results as documented.

For Pascal B, my calculations were designed to calculate the time and specifics of the shock wave as it reached the cap. I used yields both expected and exaggerated in my calculations, but significant ones. When I described my results to Bill Ogle, the conversation went something like this.

Ogle: "What time does the shock arrive at the top of the pipe?"
RRB: "Thirty one milliseconds."
Ogle: "And what happens?"
RRB: "The shock reflects back down the hole, but the pressures and temperatures are such that the welded cap is bound to come off the hole."
Ogle: "How fast does it go?"
RRB: "My calculations are irrelevant on this point. They are only valid in speaking of the shock reflection."
Ogle: "How fast did it go?"
RRB: "Those numbers are meaningless. I have only a vacuum above the cap. No air, no gravity, no real material strengths in the iron cap. Effectively the cap is just loose, traveling through meaningless space."
Ogle: And how fast is it going?"

This last question was more of a shout. Bill liked to have a direct answer to each one of his questions.
RRB: "Six times the escape velocity from the earth."

Bill was quite delighted with the answer, for he had never before heard a velocity given in terms of the escape velocity from the earth! There was much laughter, and the legend was now born, for Bill loved to report to anybody who cared to listen about Brownlee's units of velocity. He says the cap would escape the earth. (But of course we did not believe that would ever happen.)

The next obvious decision was made. We'll put a high-speed movie camera looking at the cap, and see if we can measure the departure velocity.

In the event, the cap appeared above the hole in one frame only, so there was no direct velocity measurement. A lower limit could be calculated by considering the time between frames (and I don't remember what that was), but my summary of the situation was that when last seen, it was "going like a bat!!"

As usual, the facts never can catch up with the legend, so I am occasionally credited with launching a "man-hole cover" into space, and I am also vilified for being so stupid as not to understand masses and aerodynamics, etc, etc, and border on being a criminal for making such a claim.

I'll add that we learned a lot with our series of low-yield tests. Plugs helped, but the closer to the nuclear device, the better. "Tamping" the device is better yet, and there are some ways to do that which are more clever than others. Mostly we learned that even an empty hole could cause a reduction to the atmosphere of as much as 90 percent, depending on specific design parameters. Later we were to see that if the hole is deep enough and the yield is high enough, an empty hole will close completely, allowing nothing whatsoever out except the initial light, which is not radioactive of course. In time, the tests became very sophisticated-and expensive, but we were able to achieve complete containment for almost every test, and for all but a handful of those that had containment "failures", nothing was detected off site. So I would judge our containment efforts to be quite successful. The case for these views are pretty well laid out in the book Caging the Dragon, by Carothers.

But it took time and money!

SaiK · Post by **SaiK** » 14 Oct 2013 06:27

when it comes to releasing human energies, i always think men can only do fission. without wimmen, there is no fusion.

Vayutuvan · Post by **Vayutuvan** » 14 Oct 2013 10:37

Amberg ok so I take it that you are not sure about general theory of relativity? What do you think of quantization of time? Sri ECG Sudarshan had conjectured that time is quantized. I would like to know whether this can be proved or disproved experimentally. Honest question, I promise.

SaiK · Post by **SaiK** » 15 Oct 2013 03:46

http://www.thehindu.com/sci-tech/scienc ... epage=true Together, Higgs and Englert described a mechanism, since called the Higgs mechanism, to explain the process of mass-‘formation’ as it could have happened a billionth of a second after the Big Bang 13.82 billion years ago

q: how did they get the 13.82 billion years ago?

To unravel the Higgs mechanism: During the Big Bang, a sea of energy was unleashed into the universe by the explosion. It was probably symmetrical, which means one part of the ‘sea’ was indistinguishable from every other part across some time period. Just 10 seconds later, however, the symmetry was violated and broken because of some fluctuations in the field of energy, giving rise to new laws of physics.

can someone explain this better? i can only visualize that symmetry in terms of two hemisphere within the blast sphere, doing synchronous events at every quantum levels. but how come, 10 seconds comes a flux of energy? was that part of the same big bang source, that event happened 10 seconds later to hit (meaning second event produced something that travelled faster than the first event, with a 10 second gap to disturbance?). conpooshan!

Amber G. · Post by **Amber G.** » 16 Oct 2013 05:29

matrimc wrote:Amberg ok so I take it that you are not sure about general theory of relativity? What do you think of quantization of time? Sri ECG Sudarshan had conjectured that time is quantized. I would like to know whether this can be proved or disproved experimentally. Honest question, I promise.

Assuming "Honest questions"..
I really do not know what you mean, when you say you "take it" that I am "not sure about about general theory of relativity"??

I can say that I have taken regular graduate level courses both in classical as well as quantum mechanics). I was also fortunate enough to taken one advance course taught by Yang (Nobel Laureate- Parity guy). I am as sure about this (or not sure about this) as any such theory which has stood the test of time to be consistent with all experimental results.

In any case it is somewhat silly, if I understand you correctly, to philosophize about sureness (or unsureness)..without defining what you mean by being "sure"?

What I think of quantization of time? What one should say? (specially to the audience

of this forum - remember, one reputable physicist, who was chased away from this forum, cynically said something like "the audience is more interested in throwing insult to anyone who tries to educate " ..Okay I will try to answer you by saying what most people will say,
something like:

The brief answer 'Nobody knows.' (No experimental evidence in favor, OTOH no evidence against it, (Not yet found). There are no well-worked-out physics theories, IMO, incorporating quantization of time, and there are substantial obstacles to doing so in a way that is compatible with the principles of General Relativity. (Some recent work talk about theory of "loops" in space suggests that there might be a way to do something roughly along these lines--not involving a minimum unit of time but rather a minimum amount of area for any two-dimensional surface, or a minimum 'hypervolume' for any four-dimensional region of space-time.

I have known EGC Sudarshan for many decades ( a family friend) and learned a lot from him (Like quantization in coherence optics) but I really do not know much about this. You may find more information at:
http://wildcard.ph.utexas.edu/~sudarsha ... ations.htm
(You may find quite a few interesting names (:) ) in coauthors for some of the papers)

Vayutuvan · Post by **Vayutuvan** » 16 Oct 2013 06:03

AmberG, thanks. My questions are honest in areas of science. Sometimes I kid around to illustrate a point in a light-hearted manner.

Now that is out of the way, I asked that question because I remember your mentioning before that you knew Prof. EGC Sudarshan coupled with the fact that EGCS and a colleague proposed quantization of time. If this is experimentally proved to be true, what are the implications? Would it give clues to solving any long standing puzzles in Physics and mathematical logic (and even classical logic)?

As for the Conservation of Energy, I have some questions regarding whether the universe can be considered a closed system. I understand if you consider these to be more philosophical than scientific in nature. One of my side interests is Mechanical (almost) Theorem Proving where application of physics like empiricism might be helpful.

There is a gap between the rigidity imposed by Mathematics in what is considered a proof and the leniency that is afforded in physics.

Is it possible to tighten empirical methods of physics a little so that they can be converted to slightly relaxed methods of mathematics for mechanical theorem proving and solving "soft" problems that are dealt with in say journals published by SIAM?