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Messages - distimpson
1
« on: 03/05/2013 21:27:31 »
A very deep question, lot of great answers here. I've done a few simulations using computer generated “pseudo-random” numbers and the Monte Carlo method at Los Alamos many years ago. We needed a random number with a Gaussian distribution and we had a uniform random number generator over the region 0 to 1. So we added 6 of these together to get an approximation to a Gaussian distribution by way of the central limit theorem. The ends of the distribution are cut off at 0 and 6 but for many purposes it worked just fine. It was easy enough to test the numbers for mean, standard deviation, correlation or whatever parameters might be important in the simulation and insure they were “random enough” for the problem at hand. Of course there are built in functions in many math packages that do this now, yes I am that old, started out using punch cards. Thought this might be of interest here, my rather old 2 cents worth!
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« on: 02/05/2013 21:47:25 »
You raise very good points menageriemanor, I assumed the discussion was "is it possible" not "lets do it". But please note CliffordK last comment, I agree that brains would age regardless of what body they are in, brains become senile, living tissue but not cognizant, hence no renewing Dick Cheney indefinitely, at least not in a form that would take over the world. If you doubt this just visit any nursing home, it is a real eye opener. I’d be more worried about cloning to provide replacement organs; somewhere I think a fellow traded his kidney for an ipad or something. As long as a society deifies wealth I’d say anything can happen.
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« on: 02/05/2013 19:46:14 »
If I may expand the discussion to include dreams or rem sleep. Does anyone know if dreams are necessary?
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« on: 02/05/2013 19:43:33 »
Be sure the dentist gets all the "roots" in the first pass. Maybe the procedure is different now, in my case they numbed, opened the tooth and removed a nerve and then I had to wait a week for the next step. At this point the tooth should feel no pain as there are no nerves present. However, the dentist had taken only one x-ray from the side and missed a second nerve in the tooth. In addition to being in pain for a week (which he said was not possible) I nearly punched the dentist when he inserted a probe to clean out the canal as he was digging into a live nerve. I'm not a violent fellow, it was a reflex to the pain. I'm guessing this is a rare event but one I'll never forget, might be worth a mention to the dentist before he starts. If all goes well there should be very little pain involved.
5
« on: 01/05/2013 21:08:28 »
Very far out of my area of understanding, I was OK with the idea of some sort of decompression of the dense matter, unless there is some other force to keep it together, some conditions where the strong force would hold the material together like a macroscopic radioactive super nucleus. That is what you are saying with beta decay to get some protons in the mix? Sorry if this is really out there, I don't even know what questions to ask.
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« on: 01/05/2013 17:54:32 »
"Neutron stars have overall densities predicted by the APR EOS of 3.7×10 17 to 5.9×10 17 kg/m 3 ... which compares with the approximate density of an atomic nucleus of 3×10 17 kg/m 3. The neutron star's density varies from below 1×10 9 kg/m 3 in the crust, increasing with depth to above 6×10 17 or 8×10 17 kg/m 3 deeper inside (denser than an atomic nucleus). This density is approximately equivalent to the mass of a Boeing 747 compressed to the size of a small grain of sand." this information from http://en.wikipedia.org/wiki/Neutron_starSeveral years ago I asked an astrophysicist (can not remember name) "if somehow a spoonful of this dense matter could be removed from the star, would it expand into a large volume of ordinary matter?". Her answer was yes it would, any thoughts here?
9
« on: 01/05/2013 14:04:51 »
Jack Stott asked the Naked Scientists:
Dear Dr Chris.
I have plucked up the courage to write to you with a question from a colleague of mine which I can't answer.
I have no idea why he wants to know this ( I think he reads too many science fiction comics or watches too much 'Star Treck' ) but here goes :-
If an object of negligible size & mass is launched from a standing start in a vacuum, and is subjected to an acceleration force of 1 G - how long will it take to reach the speed of light.
Hope you are able to provide an answer, or even a formula to calculate an approximate result when and if you have the time.
Best Regards
Jack Stott BSc(Hon) Elec Eng Science
What do you think?
Wonderful question, the answer depends on the details, if "negligible" mass means zero then the particle is already moving at c and can not be at a standing start in any (inertial) reference frame. If not, then the velocity can be computed from the equations of Einstein's special theory of relativity, rather than repeat, please refer to this link for the details: http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.htmlSince we are assuming an acceleration of 1g, the size and mass does not enter into the velocity calculation, it will matter in terms of the energy required to accelerate the particle. So, after 1 year at 1g, 0.77 of the speed of light, 2 years, 0.97c, 12 years to get to 0.99999999996, pretty close to c but not close enough for a physicist :-) Hope this helps, a simplified answer to a sophisticated question. Science fiction sometimes becomes science fact, keep the wonder!
10
« on: 21/04/2013 15:31:00 »
Interesting subject, all the talk of 3D printing/scanning lately has brought to mind an old scifi theme involved with teleportation, yes I'm talking beam me up Scotty. One scifi show that always comes to mind is “Think like a Dinosaur”, synopsis here: http://en.wikipedia.org/wiki/Think_Like_a_Dinosaur_(The_Outer_Limits)The idea is that you scan a human, apparently a painful but non-destructive process and then “3D print” a copy of the human elsewhere. The equation is “balanced” by destroying the original. It would seem if such a system was possible you could print anytime or anywhere in the future, great for those 100,000 year long journeys to other star systems, assuming the printer and spacecraft would last that long. Other than incredible technical difficulties given our current stage of technological development, I do not see any fundamental physical laws to prevent this from happening-any thoughts on this statement? If Moore's law doesn't curve over soon it may not be long before we are working at atomic scales. The idea of destroying the original seemed to be introduced to explore various ethical questions as scifi often does. From a practical point, I wouldn't want 10 copies of myself fighting over the checkbook but if they are stored information on the way to various star systems, bon voyage. It would be a funny type of immortality as each copy would be a distinct individual from the moment of printing. I can see an old version of myself trying to tell a younger version what to do but it wouldn't listen. I'm guessing the printed copies would not care if the original was destroyed, can always print another. Might even be able to repair some defects the way we currently fix a scratch in an old photo. Wonder if HP will be making printers 10,000 years from now :-)
11
« on: 16/03/2013 01:17:13 »
good subject and discussion homertyson. "what is energy?" is one of those simple yet profound questions, like "what is time, space?".
have to agree with Minerva on consciousness. as we define and know it, consciousness requires a physical matrix like a brain or possibly an electronic matrix (the droids are coming). If energy associated with consciousness persisted after life it would be difficult (for me) to see it as anything like a consciousness, it would be like saying the universe is conscious.
also like cheryl j dead star "afterlife" of atoms, got me thinking. not so much an energy signature after life but an entropy signature, i.e., history. everything we do perturbs a tiny part of the universe which then persists for some period of time, also after life. Not a consciousness, just a perturbation.
anyhoo, hope you don't mind me jumping in, interesting stuff. for the record, I am not a believer in ghosts, spirits, magic, ..., or supernatural forces in this universe. no answers, just interested.
13
« on: 08/03/2013 03:23:42 »
I've been kind of obsessed (in thought) with sky diving from the space shuttle since the Star Trek Voyager B'Elanna Torres Extreme Risk episode. If you had a retro-rocket to slow the orbital velocity substantially to zero could you simply drop a couple hundred miles and parachute to the ground? The data from the IRVE-3 experiment gives a pretty good idea of the conditions involved in such a jump. The IRVE-3 was an inflatable mushroom shaped heat shield about 3m in diameter, A=7m 2,m=309kg, C d=0.42. Surprise (to me), C dA/m for IRVE-3 is equal to that of the skydiver in the first air drag calculation above. Highest point for IRVE-3 was about 450km (280 miles), for the first part of the fall the velocity is pretty much v=t*9.8m/s 2 and d=1/2 vt, so falling from 450km to 100km takes about 270 seconds and the speed at 100km is about 2.6km/s. At 100km you can switch to the free fall with air drag equation, speed increases a little then a rapid deceleration with a max of about 20 times g at a height of 31km, this agrees with the NASA press release data. NASA reported a max temperature of 540 oC (1000 oF), I do not know how to calculate surface temperatures yet. The IRVE-3 was constructed from “Nextel Ceramic fabric” and “pyrogel insulation”. 6 minutes up, 14 minutes down. Anyhoo, I think you could make a spacesuit from such materials and survive the short duration temperatures involved, but the 20g force seems to be a real stopper (no pun intended). Maybe if you started with a cannonball posture then stretch out to the sky dive posture you could reduce the g forces a bit. Extreme, maybe a few 1000 years from now, RedBull X15. Fun stuff anyway. Refs. http://www.nasa.gov/offices/oct/home/feature_irve3.htmlhttp://www.nasa.gov/centers/wallops/home/irve3launch.htmlhttp://www.nasa.gov/centers/goddard/news/features/2012/IRVE3.html
14
« on: 02/03/2013 05:11:00 »
plunger is rammed to rapidly compress the air, temperature increase is sufficient to ignite the cotton. http://vimeo.com/60880888didn't know about vimeo, thank you!
15
« on: 24/02/2013 19:59:38 »
Yes, the pv=nrt thing. When explaining the meteor/fireball glow, we do a demo at the museum to illustrate heating of air by adiabatic compression. I've got a little movie of this, do not know how to up load here??? Here are few still shots of the compression sequence. The kids love the fire piston demo.
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« on: 01/02/2013 01:40:03 »
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« on: 24/01/2013 16:43:33 »
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« on: 19/01/2013 15:24:34 »
yep, me too. how the universe came to be and what is its fate are questions that will haunt humans as long as they exist. do such questions even make sense? every fractional increase in knowledge is a huge treasure, what a wonderful puzzle.
19
« on: 14/01/2013 19:45:12 »
thank you, definitely outside my area of expertise. interested to hear what comes from the specialists in this area. it is always amazing (to me) when the very large and very small realms of physics converge on the same subject.
21
« on: 07/11/2012 21:22:54 »
it's pretty cold up there, maybe with an extra pair of long johns. was the capsule heated? also, did he have a relief tube or mag pants? haven't seen any details.
22
« on: 24/10/2012 16:16:44 »
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« on: 24/10/2012 03:52:30 »
Hello Thuggery, I finally got a chance to watch the video you wrote about, I believe this is the link http://www.youtube.com/watch?v=YezKsgsPM24. Good presentation, thank you, wouldn't have know about it otherwise. I'll take a crack at your question too. Dr. Alexie Leauthaud was speaking to a question from the audience, is dark matter anti-matter? Her answer was "no" because we would see some interaction between anti-matter and normal matter (in addition to gravitational effects). Her example of the bullet cluster described the interaction between the colliding galaxy clusters, in the picture below one is moving to the left, the other to the right. It appears the two groups of galaxies passed right through each other (substantially) and left their associated hot gas clouds behind in the center of the collision (colored red). In addition, gravitational lensing suggests there is a lot more mass than we can see and it is located in two lobes in the same regions as the galaxy groups (colored blue). So, if the gravitational lensing is due to dark matter and the dm regions traveled along with the two galaxy groups then they too appear to have passed right through each other and the hot gas clouds with no noticeable effect. Speculation or hypothesis, some physicists think there are yet-to-be discovered dm particles lurking about. Since detectors are typically made of normal matter, detection may be challenging. My best effort to understand this. 
24
« on: 20/10/2012 21:12:42 »
Used a finite difference method to solve:  with these values: Air density = 1.2kg/m 3e -0.14 h(km) (approx. fit, h is height in km) C D = 1.2 (drag coefficient for sky jumper) A = 1.1 m 2 (cross section area, a guess) m = 136kg (mass, a guess, man plus suit) g = 9.8m/s 2 (assume independent of height) The orange points are taken from the estimated speed in Mr. Baumgartner’s jump video (the agreement is so good my wife suggested this is how they came by the estimated speed):  Need a little more velocity to reach the reported max speed of 1342km/h at 42 seconds, so tuck your arms (reduce area to 0.94m 2) and be more like a cylinder (C D = 0.9):  Max speed in this calculation is about 10 seconds later than the measured value. So, how high, how fast? How about 80km starting height:  Top speed in this freefall calculation is about 3000km/hour (1875mph), max deceleration is about 2 times g. Heat, I do not know how to calculate this, a few web sites report the SR71 went this fast through similar density air and max temp at the tip was about 340 o C, polyimide (Kapton) can survive this. So, a pressure suit like Baumgartner’s with an additional layer of insulation and an outer layer of polyimide fabric (or whatever the IRVE-3 is made of). Keep in mind we are talking 10’s of seconds. Balloons won’t reach this altitude so you need to use a modified sounding rocket as the 10-16 g’s of typical sounding rockets is a bit much. Or maybe skydiving from SpaceShipTwo will become a rich person’s hobby? Another concern would be stability as both Baumgartner and Kittinger experienced spin control issues but somehow figured out how to stabilize the fall. Pretty amazing. Is it possible? Enjoy, I had a lot of fun playing with these numbers. (As always, this material is provided for entertainment purposes only. Not checked for errors or omissions. Godspeed!). references: http://en.wikipedia.org/wiki/Free_fallhttp://en.wikipedia.org/wiki/Drag_coefficient
25
« on: 16/10/2012 03:26:30 »
Back of the envelope calculation, took some of the estimated data from the Baumgartner jump video (second column) from 39km height. No air resistance column is just acceleration due to gravity (9.8m/s 2 = 35km/h/s). Last column uses a constant air density and terminal velocity of 1173km/h (just a guess from the video data). I've seen a few reports his fastest velocity was 1342km/h at 42 seconds, so I'm assuming the data in the video is off a bit. t (seconds) Est. Speed km/hour No air resistance Constant air density 0 0 0 0 21 697 735 651 30 945 1050 837 40 1137 1400 975 50 1173 1750 1060 Jumping from higher would result in some high velocity. Neglecting air drag, free fall jump from 80km would result about 3000km/hour at Baumgartner's starting height of 39km after 90 seconds. I think that's getting close to the SR71 speed. I worked this out pretty quick, check my math, didn't spend time to put it in the table format, couldn't figure out how to paste it here. Used equations from here http://en.wikipedia.org/wiki/Free_fall. Glad Baumgartner is safe and sound on the ground!
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