 # Sensei

Senior Members

5886

13

## Everything posted by Sensei

1. But free neutron is not proton+electron. Proton energy 938,272,046 eV Electron energy 510,999 eV Neutron energy 939,565,378 eV Subtract sum of energies of proton+electron from neutron energy and you will have missing 782,333 eV
2. Newtonian mechanics is limitless. It doesn't have limit of speed of objects. In it velocity of object can go up to infinity. Modern physics has limit - speed of light.
3. You should concentrate on classical physics. When it will have no mysteries to you, learn Standard Model. Then you can go to unconfirmed theories. Without extensive knowledge you can't even judge if something is correct or incorrect. Plausible or not. Otherwise you're in kinda like position of somebody who is reading about calculus without knowing what is multiplication..
4. I remember other thread on SFN where person interested in string theory asked what are all these 11 dimensions. And nobody, literally nobody, could answer... I don't think so he asked for precise math. Just simple explanation.
5. But first you need to verify that water has 1 g/cm^3 Take f.e. glassware with volume scale, put it on Weighing scale, reset settings, fill with water, read volume and mass. Calculate density of substance in g/cm^3. Some scientists did it with the all chemical elements, the all chemical substances ever produced. It was repeated over and over again during the last couple hundred years with better scales to receive more precise results. You can take a bit of substance, let's say 100 grams, measure it's volume, and then extrapolate to higher mass, higher volume. That's how you can calculate mass of Earth. Average density of Earth multiplied by volume = mass. Volume of Earth = 4/3*PI*radius of Earth^3
6. That was quote on top of some Renaissance school if I recall correctly. Don't trust anybody words. Verify them all by yourself.
7. If some scientists is publishing his/her discovery, other people (not just scientists) can check it and verify and confirm or contradict (perhaps showing where has been made mistakes). Trust is necessary only if somebody doesn't want to learn. If I say you 1 m^3 volume of water has mass 1 ton. You Nicholas, can believe me on word, or check it by yourself. Tell me how you would do such experiment.. ?
10. If you will make f.e. 1 undividable length unit 1 femtometre (10^-15 m) everything what we know (especially macro scale & cosmic scale) will appear really big. Atom of gold has diameter ~288 pm = 288*10^-12 m. So 288*10^-12 / 10^-15 = 288000 base units. Visible violet photon has wavelength 400 nm. From perspective of 1 femtometre, it's 400,000,000..
11. http://en.wikipedia.org/wiki/Bit
12. No, you cannot have mili bits. You can't even have half of bit. However you can have integer multiply of bits. You can have Mega bit for instance (typically used in network transmission speed Mbps = Mega bits per second). If you have 1 GB of memory stick, it's 8 * 1024 * 1024 * 1024 = 8589934592 bits. It's similar case, from other discipline, as in physics quantity of electrons, protons or neutrons that must be integer number. You can't have half of electron, half of proton, half of neutron. That's assertion. Quarks could be theoretically made of something smaller, but not necessarily strings. String theory is just one of many theories. Difference is that it has many (theoretician) scientists on its side. That does necessarily make it more plausible/probable. Simply it's well known by public (from just name mostly). Ask people for string theory math.. It always looks impossible, until somebody invent a way to do it. And then get Nobel prize.. BTW, look at neutral pion particle decay mode. http://en.wikipedia.org/wiki/Pion
13. What is composition of bit? (in computer sense) We know that it can have value 0 or 1 (kinda like property of bit), and we know its address (kinda like position of bit). We can read bit, write bit, compare two bits, store it on disk, restore, group them to byte (8 bits), short (16 bits), long (32 bits) etc.etc. I am not saying that Universe is some kind of database or so. Universe is "alive". Particles interact constantly. But as you can see in above example, not everything has to be made of infinitely smaller things. Bit is unbreakable. It's fundamental.
14. A. Erwin Schrödinger B. Marie Skłodowska-Curie
15. The best is to see it on your own eyes. If you will place magnet/electromagnet in Cloud Chamber and send beam of particles, or from radioactive decay, you will see how they behave in magnetic field based on their charge, mass, and momentum. Building your own Cloud Chamber costs \$20. Just find steady source of dry ice in your area.
16. No,no,no... In Coulombs Law you don't have flowing charged particles (so you can't say "charges per second"). They are stationary. Motionless. At least during verification of law we're not using moving charges. When Coulomb created his theory, batteries didn't exist yet. http://en.wikipedia.org/wiki/Charles-Augustin_de_Coulomb http://en.wikipedia.org/wiki/Alessandro_Volta Distance between leafs in electroscope device is changing the more it's "charged". Leafs are further each other the more electrons gathered on them. Distance between leafs = r in equation. Q symbol is used to denote charge not C. C is unit. http://en.wikipedia.org/wiki/Electric_charge Are you reading the all articles that are posted here? "charges per second" has sense in electrical circuits, when electrons from one side (negative - electrode) of battery flows to other side (positive + electrode).
17. ?? If you have number f.e. 1000 you can write it also using scientific notation 1e+3 or 1e3 (+ is default) Other example: 1.23e-2 = 0.0123 = 1.23*10^-2 After exponent symbol you don't/shouldn't have power ^ symbol. Read this http://en.wikipedia.org/wiki/Scientific_notation In many physical equations f.e. radioactive decay with mean-life instead of half-life there is used e mathematical constant http://en.wikipedia.org/wiki/E_%28mathematical_constant%29 Don't confuse these two things! When I have to quickly enter very small number to calculator often I am dividing by large positive number, f.e. I want to enter 1.602e-19. I am entering 1.602, hitting divide, and entering 1e19, and calculator is showing 1.602e-19. You can also enter 1.602, press EXP, then +/-, then 19, and calculator will show 1.602e-19. But much easier is doing calculations in f.e. OpenOffice SpreadSheet or Excel.
18. You're mixing everything.. Electron has charge -1.602*10^-19 C (Coulombs) It's elementary charge http://en.wikipedia.org/wiki/Elementary_charge If we have 6.24*10^18 electrons, we have: Q=-1.602*10^-19 C * 6.24*10^18 = -1 C (1 Coulomb charge) I=Q/t Current in Amperes is Charge divided by time. For t=1 second I=1 C/1s=1 A If ampere meter is connected to circuit and is showing 1 A, you know that it's 6.24*10^18 electrons flowing through wire per 1 second. Battery that has 1400 mAh (typical NiMH AA for digital camera) has 1.4 * 3600 = 5040 C. So it's 5040 * 6.24*10^18 = 3.14496*10^22 electrons total. Knowing how many electrons has battery, and knowing how many electrons is used per second, you can calculate time battery will be working in seconds. With I=1 A, such battery will be working for 5040 seconds. With I=0.5 A, such battery will be working for 10080 seconds. etc. etc. How charge -+1.602*10^-19 C has been calculated? In oil drop experiment. http://en.wikipedia.org/wiki/Oil_drop_experiment Coulomb's Law is for stationary charges that gathered on body like previously mentioned by me electroscope leafs. It costs 20-30 usd. On ebay there is a few. Anybody can build it in a few minutes using jar and aluminum foil. Buy it or build it, and you will see how it works in practice and about what we're talking.
19. Suppose so you have array of strings, and have to find string with exact name. The basic logical way of solving it is to go through all entries of array and compare. Working but slow. const char *string; // argument const char *entries[]; // array int length; for( int i = 0; i < length; i++ ) { if( !strcmp( entries[ i ], string ) return( i ); // string found, return index } return( -1 ); // string not found, return invalid index -1 For 1000 entries, it will have to compare 1000 strings (at worse case). For 1 mln entries, it will have to compare 1 mln strings (at worse case). There are algorithms that can speed up this process. For instance, you can sort array in alphabetical order. Then compare middle entry with what we are searching for. int tmp = strcmp( entries[ length / 2 ], string ); if( tmp == 0 ) // string found, else if( tmp > 0 ) // string must be in one part of array else if( tmp < 0 ) // string must be in other part of array Now you see, one compare function used, and we have just reduced quantity of entries to compare to half of initial. If initial length of array is 1000 and we will be using such algorithm recursively we will have quantity of elements to check: 1000 500 250 125 62 31 15 7 3 1 Just 10 compare functions to find string in 1000 elements array, instead of 1000 in previous brute force algorithm. Where would you learn about such algorithm if not on lesson about algorithms?
20. No. That depends on whether it would help to survive. In hot environment & food shortage environment it's favorable to be small. In cold environment & food shortage environment it's favorable to have a lot of fat and fur. etc. etc. Adaptation depends on environment.
21. If we have molecule of water H2O at altitude 0, sea level, we need to give it energy to rise it to 1m, and even more energy to turn it to vapor and reach cloud altitude. If this molecule lose its kinetic energy (f.e. give it to N2 or O2), it will turn back to fluid state and will have to fall down to the ground of Earth. Airplane, satellite, rocket or anything flying must to not lose its kinetic energy to not fall down. In high energy physics, in particle accelerators, kinetic energy of particles accelerated to nearly speed of light are turned in collision to another proton and antiproton pair I don't know about you, but for me it's enough proof that it's real thing. Is kinetic energy the real thing? For somebody touching water with 0 C, and later water with 100 C, or touching metal at 0 C then 100 C, he can really see & fell difference. N2 molecule has 4.65*10^-26 kg, so kinetic energy with v=340 m/s is just 2.69*10^-21 J (predicted change in mass of molecule 2.99*10^-38 kg) O2 molecule has 5.3137*10^-26 kg, so kinetic energy with v=340 m/s is just 3.07*10^-21 J (predicted change in mass of molecule 3.417*10^-38 kg)
22. There is physical limit how tall can be grass. That depends on internal structure of vegetable (or animal) and environment they live in. During evolution organism tries to adopt and overcome limit (if it's a way to survive). Growing quickly tall means receiving more light from the Sun *) There was time in Paleozoic when air had a lot of oxygen (~double current value), and organisms that were absorbing oxygen whole skin area were much much bigger than now. After decrease of oxygen percentage, invertebrate can't grow too big. *) in mine neighborhood last year there was cut two trees (they had 20+ meters and 50+ years old) There was leaved roots in the ground. A week later from roots grow up couple new trees and reached nearly 2 meters. In just a week.
23. Maize corn, wheat, barley, rice, rye are all examples of grasses.
24. Deep sea microorganisms never saw Sun or light. They are utilizing heat coming from Volcano, and natural heat of Earth.
25. Image is named "SlowWormSkin_DominicGreves.jpg"
×