# losfomot

Senior Members

323

1. ## Special relativity: Can you explain the paradox?

I don't think that is possible no matter how fast they were going. edit - <scratch that There was no quantity for v given, so I don't think you can work out how much the clocks will differ, only who's clock will be ahead or behind.
2. ## Special relativity: Can you explain the paradox?

Although I think you may be right about both of those situations (not positive about the first one), neither applies in this instance. There was never any mention of B 'catching up to' A... They start in the same rest frame and end in the same rest frame, they undergo the same acceleration (apparently instant) just at different times.
3. ## Special relativity: Can you explain the paradox?

So if A and B synchronized their clocks in the starting rest frame (before anyone took off anywhere, say at time = -1), then A 'takes off', accelerating instantly to some velocity (the final rest frame)... and then sometime later (in your diagram it appears to be 1 second later?) B takes off, accelerating instantly to A's frame (the final rest frame)... they compare clocks in the final rest frame and B's is behind A's? This doesn't make a lot of sense to me.
4. ## You have received $100,000,000,000. Don't judge me! There's a million things I would do with that money, I only mentioned a few things that particularly interest me, individually. Believe me, the world would benefit if I had that kind of money. Philanthropy is kind of an obvious answer. Do you want everyone to spout off about how many hospitals and schools they would build? That wouldn't make for a very interesting thread. Besides, I think taking the first steps toward leaving this planet would be a great benefit for humanity. I think its in our best interest to spread ourselves out a bit... the sooner the better. 5. ## Should We Prevent Suicide? You don't at all entertain the idea that they were trading certain death for the (extremely) slim possibility that they, miraculously, survive the jump? 6. ## You have received$100,000,000,000.

Hotel orbiting Earth. School... lots of school. Obviously friends and family would be taken care of. Lot of travel. Some new shoes. Cancer research. Cryonics research. Hotel on the Moon. That will be the second in a future chain of hotels. The third will obviously be on Mars... of course the venture will have to prove itself profitable by this time as 100 billion only goes so far.
7. ## Special relativity: Can you explain the paradox?

I am not a physicist, but I don't think anyone has answered clearly enough for you, so I will point out a couple of things i think you don't get yet: Actually no, your assuming that half the speed of light = time dilation of 2... this isn't how it works. At 1/2 c the time dilation factor is about 1.15 So if Brian's clock read 100 days at the end of his journey, Andy's clock would read about 115 days. If you change Andy's clock to 115 days, then yes. You've got it completely wrong here. Lets assume that Brian does travel for 50 days out before turning around as you say and coming back. Brian would look back at Andy and see Andy's clock going slower on the outbound journey. On the inbound journey, Brian would see Andy's clock going faster. Brian would receive more pips from Andy on his journey back to Earth than he did on his journey away from Earth. But, in total, Brian would receive 115 pips from Andy, while only 100 pips on his own clock. Andy would receive 100 pips from Brian, while seeing 115 pips go by on his own clock. Brian and Andy would see the same thing, there is no paradox there. When they are back together, comparing clocks, Brians clock will say 100 days, and Andy's clock will say 115 days... which is exactly the number of pips they will both count during the journey.
8. ## question about mass-energy equivalence

If you are doing these types of equations frequently, then you will probably have a good calculator. Good calculators have letters that you can assign value to. I imagine most physicists have the value of c assigned to the letter c on their calculator. It is much easier to punch c^2 into your calculator than to figure it all out ahead of time and punch the actual long number in.
9. ## Was there ever a Nothing?

Your question is worded as though it were clear cut... but it isn't. I have no idea what you are looking for. In your original post, you are asking where everything (the big bang) came from. This is a question to which we currently have no answer. You seem to be aware of this, and yet you want 'some common sense that I can understand' what does this mean? There is no 'common sense' answer to the question. There is only speculation. I am guessing that you are looking for more speculation. My opinion is that it didn't come from 'nothing'. But that doesn't mean I'm right, and it really doesn't tell you anything about where it came from. Some people would say that 'nothing' could never have existed, because it isn't anything to exist. 'Nothing' is the absence of 'things', so there could never be 'a nothing'. The word 'Nothing' is not a noun.
10. ## Was there ever a Nothing?

I, also, am not a physicist... however, I believe the most correct answer would be that we do not know yet. If you already know this, then you are just looking for possibilities. There are many to choose from. If you have an imagination, you could make one up... it might be right! There are many universes. In one of them, there was an enormous black hole. The local intelligence there were trying out a new type of cosmic weapon near their black hole, when suddenly BLAM! the black hole disappeared. The locals were stumped because they knew about conservation of energy... a black hole can't simply disappear. The truth is, it burst into another universe... ours. Actually, The universe has always existed, it just has cycles of expansion and contraction... we just happen to be in the expansion phase currently. No, but seriously... it was God, silly. But if you question where he came from, well then you're lost because its all about faith my friend. Could be we will never know.
11. ## What Good has come from the forum?

Touche, my friend.
12. ## What Good has come from the forum?

It is obvious that it is a great help to the layman... or to a student. And perhaps that helps, indirectly, in the long run, to advance science for mankind. Perhaps this is simply the wrong forum for that type of thing. Do you think that NLab has succeeded, in a more direct way, to advance science? It seems to me that there are probably a lot of things stopping scientists from doing any real, effective, collaborative thinking/sharing/discussion/dissemination... Fear that they might make a silly mistake. Fear that they give too much away, and someone else patents the idea they came up with or publishes the paper before them. I am not trying to take away the value of this forum and others like it. It's just that, almost 20 years ago, I discovered a forum called ask Dr. Neutrino, and I remember thinking that the internet was going to advance science like nothing else ever did... a new scientific revolution. Today there are many such forums, but I have not seen the dramatic effect I was expecting. Perhaps it is my point of view. Someone else might say science (and technology) has moved very fast in the last 30 years. Someone else might say 'look at all the different things and ideas forums like this have helped to create'
13. ## What Good has come from the forum?

Put another way: Have there been any clear advances or benefits to science as a direct result of this forum? Scienceforums.net has been around for many years now, and I love it. I know it has helped me, and it is an invaluable resource for a layman to be able to ask professional scientists questions. Or for scientists to ask themselves questions. Think about the state of communication 30 years ago compared to today. You would think that a forum (like this one) that offers virtually instant communication between scientists around the world, giving them the ability to share and compare ideas, theories, and thoughts, would be a huge boost to technological/scientific advance. Has it been?
14. ## Prostate cancer cured the easy way

I'd call that a side effect.
15. ## Should We Allow a Kidney Market?

First 500k gets my left hand.
16. ## surviving free fall into the water from high altitude

Just a comment... The diver jumped from 172 feet (or 52 meters). If you work it out, he should be going about 115km/hr by the time he hits the water. Wikipedia gives the Terminal Velocity of a skydiver belly down as 195km/hr. So, our world record diver was going almost 60% of terminal velocity when he hit.
17. ## Mirror making w Aluminum

I am considering building an 'aluminizer'... but I can't find a lot of detail in how they work. I know that they use a vacuum chamber, and then elements heat up and evaporate aluminum which then deposits on the glass surface. But how hot do the elements have to be? and can it be any old piece of aluminum, or does it have to be a certain thickness/size/shape? Are the aluminum and hot elements above the glass and the Al travels down to deposit on the glass, or its it the other way around?
18. ## Online Lectures

Physics for future presidents is an award winning class that focuses on the conceptual end of physics rather than the math. I'm working my way through it for a 2nd time. Here is a link to the relativity portion of the lectures, but I started at Lecture 1 and worked my way through... it is all excellent.
19. ## What the heck is that thing next to the Moon???

stationary with respect to the moon or the Earth? The moon would have moved noticeably after an hour.. did this object move with it? If so, not a geostationary satellite. I would guess that it was a star or planet. HERE is a picture of the sky in the direction of the moon from Las Vegas at 2:25am on the 27th... and HERE is one from the 26th (I'm not sure what day you are talking about) I don't see anything that sticks out at the position you are talking about... so maybe it WAS aliens.
20. ## Question Relativity and the past and future

The space traveller is not IN the year 2000. There is no such thing as a universal 'year 2000'. If the space traveller leaves Earth in 1999, travels in space for a year, and comes back to Earth in the year 2050... Then the space traveller is on Earth in the year 2050, he is not in the year 2000. The space traveller will NEVER experience the 'year 2000' because he was not in Earth's frame of reference that year. He will never experience 2001, 2002, 2003... or 2049, because he was not in Earth's frame of reference during those years, and he cannot go back in time to get them back... the past is past.
21. ## The Big Bang is Wrong!

The "right people" do not hand out "unsupported statements" in the first place. I have to agree with iNow when he asks 'what's your point?' You are against the current model (which has evidence supporting it) in favour of... what? You ask some interesting questions, and you have some powerful resources here to help answer those questions... but your methods are far from desirable. Instead of rejecting the science that exists outright, why not just ask the questions that bother you. Martin is probably one of the most knowledgable people you will ever have the good fortune of discussing this stuff with. You should take advantage of that fact, and not spit in the face of it. I know you are a persistent bloke, but 'SFN' is a little different from what you're used to.... if you keep on the way you're going, you won't last long here.
22. ## Expanding space needs surroundings to expand into. T or F.

There is no 'outside' in that sense either. You can choose any point in the entire universe, and it should look (on average) just like right here... with galaxies all around, in the same numbers and density that we see from here.
23. ## Gravity and the Expanding Universe

I would say 'description' gives you a 'picture or idea' of what is happening. While 'explanation' implies a 'mechanism' for what is happening... which GR does not supply. That's just how I saw the words... it is silly and I should have just kept my fingers still.
24. ## Gravity and the Expanding Universe

I would replace the word 'explanation' with the word 'description'
25. ## What is a good pictorial representation of an atom?

How about this artist conception of one proton surrounded by one electron: (I am guessing the proton in the center is not to scale (should be smaller?))
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