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Everything posted by pzkpfw

  1. I just remembered a detergent-only method described in a Kurt Vonnegut book (for common house flies): You fill a bowl with soap bubbles. Raise the bowl up towards a fly sitting on the ceiling. The fly drops a little before trying to fly away - and falls into and is caught by the bubbles. (Amusing in the book, no idea if anyone ever tries that.)
  2. I just did a quick google, and all the first hits suggest apple cider vinegar. Easily bought in any relevant shop. Maybe the "fruitiness" is what attracts the flies? Having said that, they are fruit flies, not common house flies. (I agree with iNow.)
  3. https://edition.cnn.com/2023/02/28/us/crying-indian-ad-campaign-cec/index.html#:~:text=Born Espera Oscar de Corti,campaigns is pictured in 1986. I learned about this from an episode of "American Pickers" where they happened on an old tent of his. On the OP: birth rates in the "more developed" countries falls. Look at the population crisis in many places like Japan. It gets expensive to raise kids, you don't need them to (directly) look after you when you are old, and people simply have other things to do. Equal rights and opportunities for women helps. i.e. given the choice to have kids. The idea in the OP that women need to be lectured on birth control is a very colonial view. So the real trick, will be to develop all nations (so birth rates look after themselves) - but somehow without everyone consuming all resources and polluting like it's 19xx all over again.
  4. Nice points. Probably also means on a tandem bike, both people can pedal to their ability, and are not locked by a chain into needing the same RPM.
  5. Point 10 seems silly to me. (Well, all the points.) For a start it wasn't a total war against China, for example the UN/US where not bombing Chinese territory. And the casualty counts for the Battle of Chosin Reservoir are the definition of cherry picking. https://www.statista.com/statistics/1131592/korean-war-military-casualties/
  6. Once you stick a battery in, then regenerative braking starts having value, so no more of your energy goes to making brake pads get hot. Maybe then it's seen more as a battery driven bike, where your pedaling is a range extender? I like the idea that (at the cost of more weight) this would make it possible to stick another motor in the front wheel - a 2 wheel drive bike? Maybe good in mud? I don't have the skills to calculate which is best.
  7. Makes me wonder if no true Scotsman would have a civil war?
  8. According to relativity, if you and I are in relative motion, we both consider our clocks normal (ticking one second per second) and we both consider each others clocks to be slow. How does the above work with that?
  9. I read the OP as two parts: (paraphrased) A=heard that cosmic rays includes neutrons, B=stuff about neutrons that makes that hard to believe. While B included correct information about neutrons, it seemed possible the whole question might be a red herring if A was just that simple mix up. But I will back away slowly now.
  10. Is the OP simply a mix-up of Neutron and Neutrino?
  11. Radio works at the speed of light. Lasers are also already used for some communication. No time travel involved. Edit: my comment above was posted before the message above was seen. What do you mean by "binary light frequency"? And, it's still not clear why you think/thought information would be received before it is sent.
  12. Just to link it up for Moontanman, the bits I bolded above are worked examples (reverse order) of what I described in the 3rd post:
  13. It's always about who is measuring what relative to what.
  14. For Moontanman: in the above, that 0.5c is as measured by the space station, and each rocket to the station; and the 0.8c is as measured by each rocket to the other rocket. For the space station, the closing speed of the rockets (which is not the speed of either rocket) is c.
  15. I think you really need to get clear on the difference between measuring closing speed (which is the speed of a gap, a nothing), and the speed of a thing. And it depends a lot on who is observing. Say the fastest car in the World can do 500 km/h. Stick two of them on a track facing each other and run them, at top speed. The gap between (from the point of view of the track) them is decreasing at 1000 km/h. Hang on! That's faster than the car can go! But that 1000 km/h isn't the speed of either car according to the track. Sure, if the track considers it from the point of view of one of the cars, then the other is getting closer at 1000 km/h, but that reference point is moving according to the track. It's an illusion, if you like. Relativistic addition comes in (in this scenario) when you consider the point of view from one of the cars. Each car can consider itself as still, and the other car moving towards it. But note that the track is also moving towards it! The track is moving towards each car at 500 k/h, and the other car is moving towards it at 500 km/h relative to the track. And that's where you cannot (at relativistic speeds where it starts to matter) just add the 500 and 500. Each car will consider the other car approaching at 999.99999 km/h. The track considers the closing speed as 1000 km/h, and the cars consider the other is approaching at 999.99999 km/h. These are different numbers.
  16. You are confusing yourself by being imprecise. You cannot make your mind up on whose point of view is involved. Who is the observer, one of the rockets? Or someone else? (And: As noted before, someone else (not in the rockets) can consider the rockets as approaching each other at more than c, closing speed can be as much as 2c.)
  17. No they can measure speed relative to themselves, as in your first post. In your first post, rocket A (to give it a name) measures rocket B to be coming at 0.99999c. And vice versa.
  18. The existence of the space station doesn't affect anything. But if that's what speeds are being measured against, it changes your scenario. You started off saying each rocket measures the other as going some speed. Well then that's just what they measure. But if you change the scenario so that each rocket measures some speed from themselves to the station, and the other rocket as at some speed relative to the station, then yes, each rocket needs to use the proper formula to determine the speed of the other rocket relative to themselves.
  19. Then swansont gave you the answer.
  20. Try rephrasing the question with a little more precision on who is measuring what.
  21. Edit 2: darn, misread. I'll leave this here but as swansont points out I've misread your question. [ The formula is here: https://en.wikipedia.org/wiki/Velocity-addition_formula The "interesting" bit (to me) is the division by 1 + ( ( v x u' ) / ( c x c ) ) Where v and u' are small fractions of c, this ends up being a division by almost 1, i.e. at regular day to day speeds, it hardly makes a difference. But where v and u' are large fractions of c, that becomes close to a division by two, i.e. you can add to speeds close to c, and still get a speed close to c. As exchemist points out, you need to be careful who thinks what speed is what. edit: but don't mix this up with closing speed, that can be as much as 2c. e.g. someone considering themselves as still, who sees two rockets coming towards them from opposite directions, each at 99% of c, does see the gap between the rockets decreasing at close to 2c. But that's not the same as seeing a thing moving faster than c; neither that middle observer nor either rocket sees any rocket going over c here. ]
  22. You may be looking for: from the equivalence principle, clocks at the tip and base of an accelerating rocket will measure different times.
  23. I'd add: learning latex would be a good start. In the photo of math, it's not all oriented the same way as the forum, and being a photo is impossible to properly quote, or dissect for discussion. Nobody is being paid to review your posts, if you want feedback you need to make the interest high and the effort low. I will say your handwriting is very good.
  24. Are you claiming the acceleration is a direct cause of the differential aging in the twins' paradox?
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