# koti

Senior Members

1252

5

1. ## Rules update: scope of the rules

Thank you for clarifying this.
2. ## Rules update: scope of the rules

I have a question regarding the messaging system. Are the moderators or admins or anyone apart from the people involved in a private message able to read that private message?
3. ## Time and speed and how speed impacts time

PI can have a different value in extreme curvature like in the case of a black hole.
4. ## Time and speed and how speed impacts time

To visualise what Strange wrote above, a black hole with a circumference of a few miles can have a radius of thousands or even millions of miles due to extreme space-time curvature.
5. ## Cannot access forum using Data connect but only on Wi-Fi

Turning an iphone off and on didnt work for me as well as doing the hard reset didnt work. I had to go into data options in settings and reset from there <— Apple support confirmed.
6. ## A question on Thermodynamics - Metal heat conductivity + convection.

I'm loosely considering different materials for flashlight building and I would like to understand more about the physics of heat conductivity and convection. Most mainstream flashlights are built from aluminium, the more expensive ones for collectors are copper, titanium and rarely some exotic alloys. Copper being the best conductor of heat (price wise) is often used as a shell of high end flashlights which produce high amounts of heat. My question is this...comparing Lead and Aluminium (for ease of discussion, I'm not actually considering building a flashlight out of lead). Lead is roughly 5 times denser than Aluminium and is also roughly 6 times less thermally conductive than Aluminum. These are not the exact numbers as you can see by the numbers in the links I provided but lets keep them like that for ease of the experiment. Say we have a plate of Lead weighing 1kg and a plate of Aluminum weighing also 1kg where both plates have the same thickness of say 1cm - lets assume they are square shaped. Aluminum plate will have roughly 5 times the surface area of the Lead plate (right?) If I solder the same LED emitter onto each plate and provide same, steady current to them: 1. Which plate will heat up quicker to its final, maxed out temperature (same?) 2. Which plate will keep the LED emitter cooler for longest? 3. Which plate will transfer more heat to the ambient air around due to convection and at which point in time for each plate?
7. ## Is space itself conductive?

No. Is that comprehensible enough for you? If you want reasons read the posts above again.
8. ## Cannot access forum using Data connect but only on Wi-Fi

Mordred, I know how this sounds but did you pay your bill? Also, I’d call your provider to ask them how to reset the network setting on your particular phone/OS and ask them to reset your settings from their side.
9. ## Hardest word for you to spell

Oh yes, these are a problem for as well, thanks.

11. ## Hardest word for you to spell

Weird, this is one of the easiest words to spell for me in English. I struggle with words with double l’s and double r’s in them for some reason but believe me, English is a joy to spell, I struggle far more with Polish, try: Dżdżownica (earthworm), Chrząszcz (beetle), rzeczywiście (really) or essencially any other word - its a nightmare.
12. ## koti

You know you’re getting old when just yesterday you got spam about dating girls in your mailbox and now it’s either toe fungus medication or viagra.

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2. Well I'm still stuck getting the hot russian wants to date you spam messages so yeah.

3. I use Gmail and never get that stuff.

4. So do I!

13. ## Time and speed and how speed impacts time

I promise I will and everyone will be more kind you (you will be surprised) when you stop posting ridiculous things like: ...in a relativity forum where people are required a certain rigour which you are as far away from as the nearest pulsar. Gravity in General Relativity is space-time curvature. Gravity does not have an „aging effect” it’s just what happens to space-time when mass/energy is in it. Time dilation is not caused by „molecular activity at light speed” Time dilation is one of the properties of space-time which we observe when mass moves at a velocity to another reference frame - it has nothing to do with „molecular activity”, this is not some mid-evil alchemist mumbo-jumbo, its a well known and tested phenomena. You were also told in that other thread which got locked that a massive object cannot achieve light speed (c) Show that at least you understand anything from what is being thrown at you. Edit: Moderator please feel free to kill my post as several previous posts got killed.
14. ## Hijack (from Time and speed and how speed impacts time)

See MigL up there and the two sentences he wrote? Now take a few minutes or few hours or few days to understand what he wrote - spacetime is a coordinate system and space is a volume. Come back when you are capable of asking a legitimate question and I’m sure everybody will be happy to answer. And stop posting unsupported nonsense as many people come to this subforum to learn (like me) and I certainly dont want to read cardinal crap like what you are posting here.
15. ## Hijack (from Time and speed and how speed impacts time)

Do you have anything to support the above nonsense? This is a science forum and you’re posting in the relativity subforum, my eyes are hurting from the nonsense I just read.
16. ## How gravity works

The „word salad” as you are refering to it, is posted by physicists with degrees and years of practical experience in the field of relativity. If you want to stay around and learn something I suggest you lower your ignorance level and start trying to understand what is being thrown at you, GR is far from an easy concept to grasp fully. You can start by spelling „you’re” instead of „your”
17. ## koti

I have a serious dilemma tonight, please help. Is the spider „incy wincy” or „itsy bitsy” ?

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2. Is there a reason for it besides the obvious UK/US thing?

3. 'incy wincy' is the beginning of a child's poem.  I notice, on searching, there's 'eensy weensy' and 'itsy bitsy' spider poems as well.

Probably just because of particular poems where they originated.

4. Confirms my initial predictions. The reason I ask is that I watch a lot of toddler movies on youtube lately...in some versions they sing "incy wincy" with UK accents and "itsy bitsy" with US accents.

18. ## How gravity works

Awesome analogy to explain relativity to a layman. I’m stealing this.
19. ## Today I Learned

It depends on your keyboard language preference. The English correct quotation marks are ”text” whereas my device is set to a different language where „text” is the correct quotation. I hope thats ok.
20. ## What are your regrets?

My marriage. I regret being blind for years and letting her play the victim to a point where I really believed I’m the opressor which opened a door for her to destroy my life and everyone elses around me. It’s not all regrets though, its been almost 8 years since my divorce and I learned a lot, I’m a different person now.
21. ## Today I Learned

I wrote „m/s” instead of „km/s” - it is a big difference and I stand corrected. I’m going to blame the „.” instead of „,” on typing from my phone but it is also a horrible error and I stand corrected here as well. Thank you for your usual accurate assistance John.
22. ## Today I Learned

Sound waves are really slow compared to electromagnetic waves (343 m/s) Electromagnetic waves (radio, microwave, visible light, UV, etc) all have the same speed which is refered to as the speed of light (300.000 m/s)
23. ## Today I Learned

Today I learned that you can measure the speed of light with a microwave oven and some chocolate. You put some previously molten chocolate evenly spread out across a plate and place the plate in an oven with the integral plate of the oven upside down to prevent the chocolate from spinning while heating up. Put it on low for about 40 seconds and take the plate out. Since a microwave oven creates a standing wave which heats the chocolate unevenly, you get „hotspots” of molten chocolate on the plate. You take a toothpick and poke the chocolate to find the hotspots and leave the toothpics there - you just found the peaks of your wave. You now measure the distance between the toothpics sticking out of the chocolate with a ruler and multiply it by the frequency of the oven. Pretty awesome experiment especially for kids. A guy on youtube got an 0.3% error margin result which is very impressive considering the crude methodology of this measurement. Theres a youtube film explainig the whole thing, its in Polish but I’ll post it anyway for reference if anybody wants to see that the numbers really add up surprsingly accurately: Edit: This is such a simple and cool experiment which you can perform in any kitchen without any lab gear and yields a wonderfuly accurate result. I wonder if any physics teachers are using this in class @swansont
24. ## new alloy?

I don’t know about other uses but amongst knife makers, titanium is unacceptable as a high end knife material. It doesn’t come close to s35vn, s30v or m390 steel alloys as hardness/chipping/holding an edge is concerned. All of the mentioned steel alloys are carbon/vanadium/nickel alloys and do not contain any titanium. I don’t know much about aviation/aerospace materials but I would presume that since ceramics and carbon is used in high end cars it is also used in aero technology?
25. ## new alloy?

Titanium is not that hard compared to steel, there are much harder alloys, cheap 440c steel is way harder than titanium. The „magic” of titanium is that its ridiciulously light.