Nicholas Kang

I suppose OP simply means radiation that travels at c in vacuum, which is EM radiation. Why are you unsure about his statement? Do you imply that they are other types of radiation? What are they? In Malaysia, we, secondary students study 3 types of heat transfer-conduction,convection and radiation. Teacher simply teaches us radiation and its properties, of course, excluding quantum properties since this is classical physics, but not explaining types of radiation. Do you mean the radiations in different wavelength/frequency in the EM spectrum? I once posted a question: are they any other ways of heat transfer apart from the 3 listed above in speculations. An answer was advection-heat transfer by bulk motion of liquid, iirc. http://www.scienceforums.net/topic/83692-heat-transmission-apart-from-conduction-convection-and-radiation/?hl=advection#entry810529

What are your 2 previous science forums?

You have to understand astrophysics in this context. When stars that are 3 times more massive than the sun i.e. more than 3 solar masses collapse, their immense gravity will overcome the strong nuclear force acting in the core and gravity wins, engulfing the star until supernova. The remnants of the star will be expelled forming supernova remnants and the remaning core will be black hole. Why rip space and time, this has something to deal with Einstein`s Theory of Relativity. Gravity, as according to Einstein`s General Relativity, in fact occurs when a massive body with mass-energy acts upon space-time, causing it to bend the trajectory of other projectiles like satellites, light, or any massive bodies in its pathway passing through the collpasing star. The light for instance will travel in a slightly curve path due to the wrap of space-time. Light itself does not has mass but according to E=mc2, anything has mass has energy and vice versa. So, you can consider light, if viewed as a photon, can bend through space-time. Now, if the object is massive, it will cause so strong a gravitational field that the mass-energy wraps the whole space-time, ripping it from its surrounding space-time and a singularity is achieved. Usually, scientists suspect that such violent and cataclysmic event will emit gravitational wave, ripples in space-time.

I think most of you are supporting positivism approach, as stated in Hawking`s The Universe In a Nutshell. I agree with all of you. Thanks, in particular to Dr. Andrew for answering my question in clear and comprehensive way and your examples are clear. I roughly know what 'shut up' means. it means don`t ask things that are untestable by QM, am I right? I give everyone a +1 for appreciating their efforts to help me in understanding what 'shut up' really means. Thanks.

I agree that we mustn`t research on one source but many sources can help to verify the previous one to chech and see if any of them have a problem. Daily experience isn`t bad but thay are restricted by parameters like air resistance, gravitational force or even weight/mass etc. In laboratories, scientists are good at controlling those parameters to ensure nearly accurate results and they published their papers. Thay are highly technical but very accurate. You cannot assume daily practices are accurate becuase parameter controls are out of your hand. You don`t expect to check every corner of your tools or hardware to ensure no rust, no dirt or any variables that might alter your results whenever you use them, do you?

Knowledge is power, but you need enthusiasm to learn. The keypoint here is the passion to learn. You must be enthusiastic in math and physics. Einstein was expelled by his gymnasium headmaster before he moved to Italy. He did not complete his high school education but still succed in applying for a position in ETH. Later, he suceed in relativity. I take one and a half year to learn physics from almost nothing to everything. My teacher didn`t teach me physics because it is not my level but I still involve in extensive self-study. I borrowed science magazines, books and bought encyclopedias from bookstores and study by my own. it is good to hear that getting academic books in Netherlands is easy. You should appreciate such a good opportunity and grab it. I don`t stand a chance because science education in Malaysia isn`t very welcomed and lack of infrastructures and supports from community.

Science brought me here. I am young. I don`t very agree with my current knowledge in school. They teach classical physics that doesn`t make sense when things approach the speed of light or in microscopic scale. I used to argue with my teachers. So, I am here to expand my knowledge. I consider it to be fortunate to learn modern physics from members here, to name a few, they are Dr. Andrew (ajb), Dr. Tom Swanson(swansont), Studiot, Strange and Mordred. They are experts in their own science disciplines but they provide very useful information about astronomy and physics. Enthusiasm keeps me involved. The passion to learn science has strucked my mind and etched deeply in it. I feel happy to gain and attain knowledge whenever I flip through science articles, magazines or reading materials. I never thought a 15-year-old can master relativity until I read Egdall`s Einstein`s Relatively Simple. I never thought of how a brand new symmetry in particle physics can solve the problem of uniting QM with EM science until I studied Stephen Hawking`s The Universe In a Nutshell (that was an old book published in 2001, but I only get to read it in high school now). Here are some contribution from some members. Dr. Andrew taught me some principles of physics and shared quite a number of PDF files in arvix.org with me. Strange taught me some basic facts of science starting from classical physics to modern astrophysics. He helped cementing my fundamental knoledge of science and change some basic science that I thought correct since I was in primary school. Studiot, a student from top university in the UK(I have forgetten whether it is cambridge or oxford) helped answering some questions of mine in physics. He is keen to use diagrams when explaining. They are comprehensive and make sense much quicker compared to words, so as Strange. Their diagrams are equally important and infomative as those you might have seen in science books, except that they are not in digital form. Dr. Tom Swanson, a moderator in this forum, has been doing his job well all the time. He never forgets to contribute some of his science knowledge apart from banning "useless" members and locking "useless" threads or spliting threads to avoid hijacking. He is quite friendly. Ophiolite is a nominee for the most humorous member in this forum. He answers your question in a very humorous way, yet they are compelling. He is an expert in geology and petroleum-related industry, I supposed. Enjoy!

I don`t really get your meaning, because I am stupid. Why you assume our universe is a virtual particle in your statement? You seemed to treat it as QM.

1. A comma missed in between? 2. typing error?

I learn astronomy by reading encyclopedias, published papers on arxiv.org, scientific books like The Universe In A Nutshell by Stephen W. Hawking etc. , discussion with members in the SFN, posts from cosmo basics in the astronomy&cosmology section in the SFN, and some from NASA official website. I will suggest 2 useful source of learnings. There are: 1. Basics of Space Flight by NASA JPL http://www2.jpl.nasa.gov/basics/index.php 2. Orbiter Space Flight Simulator http://orbit.medphys.ucl.ac.uk/ Enjoy astronomy!

Well, doctor, I am checkmated. Please explain in detail in your post next time so that I don`t have to ask for further explanation many times in the future. Anyway, can you explain 'lots of things could be used as example'? And please relate your explanation with this topic- you are a moderator, so I suppose you know well. Please, doctor, no one/two sentences reply, if possible. Maybe I am stupid, doctor, I supposed.

Sorry, doctor, I don`t really get what you mean. I read about Copenhagen Interpretation before. My mind relates it with Schrodinger`s Cat problem. They said there are 3 ways to solve this problem. One is to open the box and check whether the cat has dead or still alive, this action will make either one of the probability wave of the cat`s condition to be clear, but Einstein hate it-he asked would the moon disappear becuase a mouse eat it. This approach to the cat`s problem is made/came from the Copenhagen Interpretion. The second approach is the many-worlds interpretation. A scientist(I am lazy flip my book to check his name) proposed that the cat may die in one world but still alive in another world. This means the second world requires a new set of physics laws. The third approach is to believe in god. Since you need infinite observer to collapse the previous`s probability waves, there must be a universal cosmic consciousness, and that is god. You say it has nothing to do with Schrodinger cat`s problem but your answer seems to indirectly link back to my question, in another words, answering my question.

In this topic? You mean Rix`s post? I just see Schrodinger`s Cat in Rix`s post. Is it untestable?

I will stay with you and continue to discuss this topic. It is good to be skeptical, studiot. I like the words 'citations and references needed'. Can you describe it in detail but not just animation in words like BANG! and done? I mean more strict, formal and quite professional with scientific jargons way of saying. I am interested in modern physics. I would like to know how elementary particles will affect the frictional force. Anyway, i don`t get the idea from the 'animation in words' posted by you in the previous post. Please explain in detail, thanks.

Examples of untestable claims?

Agree and sorry. How is shut up used in regimes of QM? I mean shut up for what? Not asking probabilities of particles? This sounds like contradicting Doctor Tom Swanson`s Statement, provided that QM is not physics.

You may want to try Orbiter 2010 for a simulation that really makes sense and free but it is something like 2GB. You might like Basics of Space Flight by JPL NASA for a quite complelling explanation and fact-filled. Last but not least, you get a certificate for your tutorial http://www2.jpl.nasa.gov/basics/index.php http://orbit.medphys.ucl.ac.uk/ In my opinion, the spacecraft retains its momentum and velocity in outer space. Since there is no air drag/resistance, to slow down the spacecraft in space would require retro thrust. Or simply rotate your spacecraft and engage thrust. You didn`t mention slowing down of spacecraft in the OP. So, I think here is the point. To stay together with earth above it isn`t possible but not effective, usually, we fly spacecraft at the same speed as earth rotation, this is applied in GTO and GEO(geostationary/geosynchorous orbit/transfer orbit) In this way, the spacecraft/satellite would travel at the same speed and remains the same position above the sky. You can always find it and it is above your head. All in all, geosynchrous/geostationary orbit would be more efficient and it does not require much fuel. Satellites launched backed in 1960s still orbit Earth today without fuel but they keep moving. Of course, to change direction or raise apoapsis/periapsis would require minor burn of fuel.

A slightly cooler region in the south of CMB Map by WMAP might be the clue showing that multiverse exist. Our universe is expanding into space-time, since it is made up of space-time. (That`s why we used to say spacetime continuum) This means there is no space and time outside our universe. So, we need new physics in this case.

No, not so. If you include life chemistry, you fail. What differs life or scientifically organic life from non-living things? Organic life forms are capable of processing lots of life process-respiration, reproduction, growth, metabolism etc. But not for inorganic non-living things. I think the OP is thinking too much. This is more of literature than science. It is true that the early universe was in fact too small and expanded after time. But you have forgetten progress through time. Progress here means evolution of life that is described scientifically, not through quasiscientific imagination(s). You may relate live emotions with natural phenomena but you may never explain them with emotions. 'We are star dust from all corners of the universe' From scientific perspective, I think you mean observable universe with event horizon something like 47 billion light years away(proper distance) Well, your statement as in the title of this thread couldn`t be true. We are made from stellar remnants created in supernova nucleosynthesis around 5 billion years ago after a supernova. The main evidence came from heavy elements exist on earth-Uranium, Plutonium, etc. By the way, what do you mean by 'star dust'? Stellar wind? Or comet meteorites? Can you clarify? All in all, you are quite imaginative, but in the wrong aspect, I supposed. You can be a good poet, but maybe not a good scientist. You must relate your imagination scientifically, not simply come out with unsupported speculations based on words. Sometimes, it is best to provide objective answers, the best is mathematical description(s), because numbers are always objective.

It depends on the source of motion. The rear wheel is powered by the force transmitted from the pedal to the rear wheel, so the rear wheel travels in a clockwise motion when touching the ground, resulting in an opposite direction(forward) motion of friction. From the front wheel perspective, nothing propels the front wheel, it moves forward (not any clockwise/anticlockwise/angular movement) but net movement is forward. So, the friction is acted backwardly. Combining both explanation, the rear wheel`s friction motion is forward while the front wheel`s friction is backward, thus opposite. Refer: http://www.quora.com/When-a-bicycle-is-not-in-motion-the-force-of-friction-exerted-by-the-ground-on-the-two-wheels-acts

I would like to express my deep apology to Dr. Tom Swanson for not respecting him when calling him. I would like to thank Mr. StringJunky for advising me Dr. Tom Swanson`s real name. Sorry, Dr. I should have researched deeply about your name before postring this topic. it was my fault for not respecting you, Dr. Learning is part of a teenager`s life. Thank you Mr. StringJunky. Sorry, Dr. Tom Sawnson.

Do you mean 1. there are many bumps 2. One point touches and deform 3. Second point touches and deform and so on 4. until TSA of bumps defom to a point where the deformation can support the block`s weight?

This post is dedicated to Mr.Egdall and Dr. Tom Swanson but others can post or reply too. Mr.Egdall I bought your book Einstein`s Relatively Simple a few months ago. I enjoy reading your book at first. It is quite humorous and the examples given are quite compelling, rigid and vivid. My knowledge have increased much ever since I started to read your book. But soon it start to fall out of stage. The book is still very new. The datas are updated but the mathematics, to me are too simple. And the mathematics are not stated clearly in the end-the appendix section. Here is an example: In appendix A, your time dilation and length contraction formulae derived from Lorentz Transform are delta x prime= delta x/F(simplified) delta t prime= delta t/F(simplified) The formulae relates reference frame S and S prime. However, I soon found out that if I rearrange the formulae (I will not write delta anymore) x` = x/F If F=0.5 ,then x=x` times 0.5 if x is 3 cm, then x` is 6cm. You are 6 cm and the observer in S` frame observe you as 3 cm. (For length contraction, for example) But what if I observe the second observer? Should I still use your(the above) formula? If I do, then it won`t work because in the end, I express x as the subject but not x` I checked wikipedia then only I know I must use positive rather than negetive for the not yet simplified formula. The actual formula is (for length contraction and x as the spatial dimension) Lorentz Transform first formula x prime = (x-v delta t)/F, where F is Lorentz Factor square root 1-(v/c)2 t=0 x prime =x/F to find the opposite, x=(x prime + v delta t)/F Change the negative sign to positive and the formula works for the opposite. However, it is not mentioned in the book. I desperately tried working the formula for months yet I only get to know it from wikipedia. (I am not blaming Mr.Egdall but advising him to do better in the future) Please don`t feel angry or irritated. I apologised if I hurted you. Also, in most technical papers, gamma factor or the reciprocal form of Lorentz factor is used. In the beginning of the book, I used to see the word the reciprocal in tables describing examples of the speed of rockets for Crash and his partner. Initially, I have no idea of why reciprocal because there is no sign of reciprocal used in the mathematics described in the appendix. Only later when I checked wikipedia, it comes to me. The book is good and examples are very humorous. But there are still lots of works to be done. The backcover of the book states that "If you only read one book on special and general relativity, this is the one to read." This can be quite misleading because it is very useful to first-time-learners but soon you find the mathematics very incomplete and it can`t really be the only book. Further reading must be done. Dr. Tom Swanson And also congratulations Dr. Tom Swanson because your name appear on one of Egdall`s Notes with Sources Section. Your replies in SFN has been adopted and acknowledged by Mr. Egdall. I am supporting you, Mr. Egdall. I like your humourous way of describing relativity. I hope you can do even better in your upcoming book. Maybe Quantum Mechanics? Finally, can your book be cheaper next time, it costs something like 62 ringgit 50 cent in Malaysia. 1 USD is equivalent to around 3 ringgit. Thanks.

Sorry studiot, I don`t understand what does "not all the block is in contact" means. Shouldn`t the face of the block facing the contact surface will all experience friction once the block is placed on it? And what do you really mean by "all the block"? Can you clarify it? I am 15 years old and still in secondary school.

This doesn`t actually sounds like a news but I still post it here because I get to know it from a newspaper. I think most of the members might have known this project. You can sign up for a boarding pass to get your name on a trip on the Orion testing module on-board the Delta IV Heavy rocket. After the landing scheduled at The pacific ocean transfer near California, your journey haven`t ended. Your name will continue to fly on subsequent Orion spacecraft in the future which is going to on-board the Space Launch System(SLS) by NASA. You collect points along the journey. For the Orion Flight Test, the point is 60000 miles. The website is go.usa.gov/vcpz The closing date is Oct. 31, 2014 The rocket is scheduled to launch by Dec 4-6(which is the launch window) 2014 from Cape Canaveral Launch Pad, Florida To prevent this topic to be graded as off-topic, here is a related news. http://www.universetoday.com/115123/nasa-invites-public-to-send-your-name-to-mars-starting-on-orions-first-flight/ I have found the official press release by NASA. Here is it: http://www.nasa.gov/press/2014/october/send-your-name-on-nasa-s-journey-to-mars-starting-with-orion-s-first-flight/#.VDkjifmSyA8