scratch Definition and 73 Threads

I have a bk7 prism (borosilicate...) and I'd like to polish it to a 4020 scratch surface rating. How would I go about doing this?

just a (random) thought problem I've been trying to get my mind around... :p lets say we wish to grow a field of crops from scratch 'x' number of new baby crops 'appear' (or begin to visibly exist) on this field per time unit (Eg. days). hence in 't' time, we will have a total of tx baby...

A study conducted in San Antonio indicates that there could be a linkage. Could the cure for MS be as simple as a round of antibiotics? http://www.ksat.com/health/18915077/detail.html

I'd like to take a poll to see how inclined to hands-on calculation we are, collectively, at cosmo forum. Generally speaking what I mean from scratch is from basic numbers most of us know like 71 and 0.73 (estimated current Hubble rate H = 71 km/s per megaparsec and current dark energy density...

***Building a pump from scratch, engineering competition*** Hello everyone. I have been entered into a competition. The spec is to build a pump that can pump 30 litres of water a minuet for 30 minuet to a height of 4 meters. The pump has to be built over 3 days (18hours) but i have...

Here is a fun thing to try The Google calculator knows the values of pi, the speed of light c, Newton's G and stuff like that. So you can easily make it calculate the cosmological constant from a few familiar facts. You have to know that the usual estimate of the Hubble parameter is 71...

I am an EE student and I feel a bit confused right now, thus far I've only taken circuit analysis (nodal/mesh/thevenin/transformers/phasors etc) and one semester of E&M. I was taking a look at this http://www.ledsales.com.au/kits/nixie_supply.pdf and I know that is explains the function of the...

Hey guys, I just recently started lurking these forums and I need some help. I have decided to start from scratch in my math/physics and chemistry studies. Throughout my school career I have been a slacker in doing my homework and paying attention in class and that has cost me to have a horrible...

A friend of mine is really pulling my chain. He said the answer to this was right in front of me. I doubt that! Does anyone have an idea on this? "I have a bar of chocolate 6 blocks wide by 9 blocks long and I want to split it into its individual blocks making the smallest number of breaks...

I've been studying and thinking about statistical physics for a couple days now... and what bothers me is the grand canonical partition function. Namely that for a system with fixed chemical potential and energy \epsilon_i the probability of having N_i particle in that state is proportional to...

Hello, I'd like to learn about tensors so i can start learning about special relativity. I understand nothing right now about tensors, except that they mean different things to mathematicians and to physicists, which is where my confusion begins! Should i learn about the modern way of...

I wish to design (if not actually build) an ultra-simple "computer" from scratch, just for fun and profit. I'm looking at only a fundamental level of computing power, with only one instruction, such as: "Given two single-digit numbers, output the product." I need three to design 3 things...

Hi y'll. I am majoring in Electrical Engineering and I am currently in the 2nd year. I love to build things out of scratch (and unfortunately break precious electronic gizmos to see how they work). But I also love mathematics and physics. So I was wondering, which of these following areas should...

A buddy from work and I have been debating an article we read the other day stating that it is a bad investment to play scratch lottery ticket games that have been on the market for an extended period of time (ex: hypothetical 2004 Christmas Game Scratcher). The article stated that this is due...

For those of you who don't chat with me outside PF, I'm interminably buried in mountains of work. I tend to bite off more than I can chew, mainly because I like being busy. Only problem with that is that I'm definitely in the running for least productive human being alive (ok, so I'm...

See http://www.msnbc.msn.com/id/7279844/did/9598565/. The virus that caused the deadly "Spanish" flu epidemic of 1918-1919 has been reconstructed using a sample of its DNA. The object is to study how flu viruses mutate and attack.

"The Universe from Scratch" (new AJL paper) http://www.arxiv.org/abs/hep-th/0509010 The Universe from Scratch R. Loll, J. Ambjorn, J. Jurkiewicz 30 pages, 5 figures; review paper commissioned by Contemporary Physics and aimed at a wider physics audience Report-no: SPIN-05/28...

I am a new member on these forums and my first post here concerns resources for reaccquainting myself with the wonderful world of physics. After an extended absence from this field, I am looking to re-immerse myself in all the subjects it has to offer, starting from the beginning. I am currently...

Ok, I failed the first semester of my physics class, but my teacher says that if we take the AP Physics B exam and get a 3 or better, he'll give us an A. Anyone suggest any books, or any tips on how to start? I'm starting from scrap, because I really don't know anything.

Hey everyone, I'm building a rocket with my friend from scratch. I have calculated the specific impulse of the rocket engine that we have designed and it turned out to be around 235 Newton-seconds. I was wondering what the maximum weight of rocket this engine would get off the ground, and...

Hello there, Not that I actually want to do this but theoretically I would like to know how I could prove to myself avogardro's number using only the most primative knowledge of math, physics and chemistry as possible. It all makes sense in whatever text you are reading, but it never gets...

http://rn01.rednova.com/news/stories/2/2003/11/13/story007.html

Did any of you ever try to program his own operating system ? I have been trying to do so for some weeks now, i made some little stuff (a loading message, showing a picture on screen ...), but this is far from doing a real OS ! (all was did in assembly) Anyone here has experience in that ?