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My favourite bit in the blog was "(picture not ready yet (my markers are dried up. I have to go out and buy some more - picture coming soon!)".

There certainly were times when certain things * occurred (or started, or stopped) when everything was closer together than it is now. That's a kind of "nearer". But be sure that doesn't mean nearer a central location; everything was closer to everything else (i.e. I am not contradicting imatfaal). (* e.g. inflationary period)

If your left eyeball is taken as the centre, then your right eyeball is closer to the centre than either of my eyeballs. If Alpha Centauri A is taken as the centre, then Proxima Centauri is closer to the centre than Aldebaran.

Some of that's covered in the linked Universe Today article. (I'd suggest looking into inflation also, for a period of faster expansion. https://en.wikipedia.org/wiki/Inflation_(cosmology)) The rest is perhaps a bit speculative, and maybe deserves a thread of its own.

It's a very sad "technique" to ask oversimplified questions and try to "trap" people into simple answers looking for a "gotcha". Current science is very clear. e.g. https://www.universetoday.com/122768/how-are-galaxies-moving-away-faster-than-light/ i.e. Nothing is moving through space faster than c, but, due to expansion of the Universe very distant objects are getting further away, faster than c. This answer has not changed since the first five times you asked it.

He could aim to stop by hitting the stronger central part of the building - i.e. where the lifts are. Maybe there'd be some secondary benefit or peril - damage to lifts holds off security? Or removes an escape route?

I think you're missing what "dimension" means. It doesn't mean "value". Follow that link you quoted out of wikipedia. e.g. note that the speed of a car might be measured in km/h (or mph) regardless of whether it's going away from you or coming towards you.

(edit: On second thought, best to step aside a while.)

I generally think that a kind of "entry exam" for forums is the ability to properly use them. * changing font for no good reason (sizes, colours, and type faces). * inability to figure out how to use quotes. * inability to use functions like "report". These (singly or in combination) all say something about a poster.

True. Or false. Definitely one or the other. Maybe.

It's all about proper definition. I no longer have any weeds; just an ugly garden. Science!

Very briefly (I don't want to distract from post #176; you should read the post by Janus, again and again). No, you're not getting the answer you want. Time dilation? Length contraction? Relativity of simultaneity? What absolutes? The departure speed between A and C is 1.2 c according to B; but don't (again) confuse that with anyone actually moving at 1.2 c; B sees the distance between A and C grow at 1.2 c; but since B does not consider A as stationary, B does not consider C as moving at 1.2 c (and vice versa). Sure. (But be sure that the speeds, time and distance are all as measured by B.) And time! Close enough; see above. (Not "speed", "departure speed"). Actually not quite so easy. Who is measuring the time? Is t1 according to C the same as t1 according to B? As with your insistence that there are absolutes, you're expecting some "God's eye view" where there's one "real" truth. There's no such thing. Relativity is the opposite of "absolutivity". All this time and you've never heard of length contraction? See post #172 by imatfaal. Day to day life doesn't prepare us to intuitively understand this stuff. People learning relativity often talk of "logic" or "common sense". Of course 1 + 1 = 2 ! Sorry, it's not that easy. Please read post #176 by Janus again.

It's the same thing again and again. You can't ask the same question 4 times and expect a different answer the 4th time. Once again, you're using the view from B of A and C, and applying it to the view from A of C. That can't work the way you want it to. Whether you simply look at speed, or dress it up with distance traveled, you're ignoring that thing called relativity. Speed, time and distance don't simply add the way you will think if viewed from a naive pre-relativistic way. Edit: one specific additional point raised in your post is important here ... when you write (my underline) "... That can't represent the real increased distance of ..." what makes you think any one of those distances is any more "real" than another? Why does the increase in distance between A and C as seen by B have to be "real" and why do you demand that the same thing is seen by A of C, or by C of A? This shows how you are ignoring relativity in your thinking. You are looking for absolutes.

False dichotomy.

Expansion of the Universe isn't about speed of Galaxies through space. Ants walking across the surface of a balloon that's being inflated, may appear to be moving faster than any ant can actually walk. Using the correct velocity addition formula, if A considers C moving at 0.88 c and B moving at 0.6 c, then the speed of C from B can be calculated by rearrangement ... 0.88 = (Vbc + 0.6) / (1 + (( 0.6 + Vbc ) / 1)) 0.88 = (Vbc + 0.6) / (1 + 0.6 Vbc) 0.88 ( 1 + 0.6 Vbc) = 0.6 + Vbc 0.88 + 0.528 Vbc = 0.6 + Vbc 0.28 = 0.472 Vbc Vbc = 0.59322 ... which is (given all the rounding) basically that 0.6 c we're expecting.

Edit: Janus beat me to it, but I typed all this so will post anyway ... From the point of view of B, the distance between A and C does grow at 1.2 c; but neither A nor C is actually moving faster than c, according to B. To get the speed of C, as seen by A, takes the proper velocity addition formula. It is not simply 0.6 + 0.6 - the Universe doesn't work that way. You'll see the formula here: https://en.wikipedia.org/wiki/Velocity-addition_formula#Special_relativity (edit: and above e.g. by Janus). In short (i.e. no latex): v3 = ( v1 + v2 ) / ( 1 + ( v1 x v2 ) / ( c x c ) ) As you can see, at low speeds (i.e. our day to day speeds), we get: v3 = ( v1 + v2 ) / ( 1 + ( v1 x v2 ) / ( c x c ) ) v3 = ( v1 + v2 ) / ( 1 + ( small / big ) ) v3 = ( v1 + v2 ) / ( 1 + almost 0 ) v3 ~ ( v1 + v2 ) / 1 v3 ~ ( v1 + v2 ) So sure, run at 6 km/h through a train that's going at 50 km/h, and someone on the ground watching the train (and you) go past pretty much sees you going at 50 + 6 = 56 km/h But at speeds approaching c, we get: v3 = ( v1 + v2 ) / ( 1 + ( v1 x v2 ) / ( c x c ) ) v3 = ( v1 + v2 ) / ( 1 + ( pretty big ) / ( big ) ) v3 = ( v1 + v2 ) / ( 1 + almost 1 ) v3 ~ ( v1 + v2 ) / almost 2 What you see is that as v1 and v2 approach c, they add, but are divided by two. (c + c) / 2 = c In units of c, and your 0.6 ... C seen by A (and A seen by C) = ( 0.6 + 0.6 ) / ( 1 + ( 0.6 x 0.6 ) / ( 1 x 1 ) ) = 1.2 / ( 1 + ( 0.36 / 1 ) ) = 1.2 / ( 1 + 0.36 ) = 1.2 / 1.36 = 0.88 Nobody sees anybody go faster than c.

Lamborghini Aventador 349 km/h SR72: 6,400 km/h Apollo 10: 39,897 km/h Speed of light: 1,079,000,000 km/h

This comes to mind: https://en.wikipedia.org/wiki/Telomere (Is this homework?)

A little more time, so ... A greedy algorithm is one that at each step chooses the immediately (local) "best" looking choice, with the hope that overall it leads to something close to the best overall (global) solution. https://en.wikipedia.org/wiki/Greedy_algorithm They can work well, but are not guaranteed to always give the best solution. Take a simplified knapsack problem; you have a knapsack that can hold N kg of rocks and some rocks of equal value per kg, but of different sizes. You want as much of the rocks in the sack as possible, i.e. as little space un-filled as possible. A simple greedy algorithm is to always pick the smallest rock to put in the sack, to leave as much space as possible for more rocks. That may work well in many cases, especially where there are lots of small rocks, but can go wrong. Say you can fit 10 kg in the sack, and have 10 x 1 kg rocks, and 1 x 5 kg rock. The simple greedy algorithm would put all 10 of the 1 kg rocks in the sack - no space wasted. Perfect. (Actually equal to the 5 kg rock plus 5 of the 1 kg rocks). If there were 9 x 1 kg rocks, and 1 x 5 kg rock; the greedy algorithm would put 9 x 1 kg rocks in the sack and have 1 kg space left over as the 5 kg rock can't fit. That's not as good as sticking the 5 kg rock in first, followed by 5 of the 1 kg rocks - but still not a bad result. If there were 1 x 1 kg rock and 2 x 5 kg rocks, then you get 6 kg of rocks in the sack, with 4 kg of space wasted, a much worse result than if the two 5 kg rocks went in. https://en.wikipedia.org/wiki/Knapsack_problem I thought the usual huffman coding method was greedy, but anyway, this article covers it: http://www.geeksforgeeks.org/greedy-algorithms-set-3-huffman-coding/ (Seems a bit detailed for homework help, but it's there on the internet anyway. Also, note that some of the comments on that item miss the point.)

So what did you mean by:

fiveworlds, can you give an example where a properly written bubble sort doesn't sort correctly?

You're wanting a simple intuitive understanding to be handed to you on a platter. With relativity that's pretty hard to do. Please, just do the little exercise in post #18.

Try one small step at a time: see Post #5 ... (Ignore the yellow lines for this, don't worry about when they see each others clocks.) A: As seen in pic 1, according to the stay at home twin (blue) what does their (blue) clock read when the travelling twin (green) reaches the halfway point (meets red), and what does the travelling twin clock (green) read? B: As seen in pic 3, according to the travelling twin (green) what does their (green) clock read when they reach the halfway point (meet red), and what does the stay at home (blue) clock read? C: As seen in pic 2, according to the travelling twin (red) what does their (red) clock read * when they reach the halfway point (meet green), and what does the stay at home (blue) clock read? * remember that red got their reading from green here. Something important happens when you compare B: with C: - take note of that (especially the blue clock as seen by green and red) then read the "Relativity of simultaneity" section here: https://en.wikipedia.org/wiki/Twin_paradox#Relativity_of_simultaneity

That's not quite right, but it'd derail this thread to get into it. Take a step back and look at post #5 again. In picture 1, the journey of the "travelling twin" is shown by the green line 'till half way, then the red line. Janus does it this way to show that it's not specifically the acceleration that directly causes the asymmetry, but the multiple inertial frames *. (Instead of one clock that accelerates at half way to go back to blue, green passes their clock reading to red at 3.46). Note that in all of the pictures, i.e. from blue's rest frame, green's rest frame and red's rest frame, there's a single line for blue - they stay in one rest frame. This is different than the travelling twin, their journey is made up of green and red - two rest frames. Also, at all times, each observer (blue, red, and green) considers the other two observers to have slow clocks. But when red gets back to blue, red's clock actually does read less than blues. That first picture shows why. The situation is not symmetrical. * of course, for the travelling twin in the usual thought experiment, it is acceleration that causes them to have been in those multiple rest frames. But that's not the point in post #5. It may be worth pointing out that acceleration is absolute. Imagine stay at home twin and travelling twin both holding very full cups of coffee. Travelling twins' rocket blasts off, travels for a while, then turns and blasts again to go back home. Which twin spilled their coffee? Which twin didn't? This just illustrates that the situation isn't symmetrical, and the stay-at-home twin has stayed in a single rest frame the whole time.

It's not "defending science" when you claim to base your idea on current science but then extend it in ways that are utterly different to current science. If, instead of feigning asking a question in the relativity section, you had started your thread in the speculations section, and if you had properly defended your claims, then your thread might well still be open. (Did you ever have a thread in speculations that got closed? I didn't find any.)