NowThatWeKnow

I wouldn't want to spend that much time with my brother or sister but maybe twins would.

I think the younger twin is the one that accelerated but am confused by "The one who doesn't accelerate. Being at rest in a gravity field is an accelerated frame, which is one of the quirky concepts of GR." I posted these four twin scenarios in another thread and there were no replies. I know that 1 and 2 are true so 4 should also be true. The calculators say 3 is not true unless Jane stops separating from the Earth and waits for Dick to make a similar trip speed and acceleration wise. Since I am wrong much of the time would someone confirm that. 1. Dick takes a space trip at relativistic speeds and when he comes back to Earth he is younger the Jane. 2. Jane doesn't want to be old so she takes a similar space trip and comes back the same age as Dick. 3. Jane wants to be younger then Dick so she starts off an a space trip. Some time later Dick decides he doesn't want to be older so rather then wait for Jane to turn around and come back, he jumps in his space ship and goes to her. They are the same age? 4. They both want to be younger and take off an similar space trips but in the opposite direction. When they get back they will be the same age even though they were in different inertial frames the entire trip. Is that right? The separation and closure during the trip was equal.

Excellent! Another piece of the puzzle starts to come into focus. Could you explain the difference between 1G from the rocket engines or 1G from (the apparent) centrifugal force. Inertia could keep a rocket spinning for 1G and not use fuel. Does the 1G have to be consistent with the direction of travel? Merged post follows: Consecutive posts merged Between you and Janus I am making progress. It does seem that when things seem clear, I can view things from a slightly different angle and take them out of focus again. The first paragraph above is an example of what sinks in and should stick. The second is what makes my head hurt. I am hoping that others might benefit from my questions and your efforts.

From a layman's point of view there are good and bad episodes. Some is pure speculation but they do not misrepresent what they say. Some seems factual but I do not have your eye for it. They did peek my interest and that is why you are having to put up with me.

I was mixing frames trying to better visualize what is happening in both frames. In the end they traveled over 100,000 ly and and aged 12 years while the galaxy aged over 100,000 years but never exceeded the speed of light. I understand the definition of gravitational potential but am not getting a clear picture on how it fits in to this picture. Is the "g" in the above formula gravitational potential that should be "G" so google can work with it? Or is it # of g's acceleration. Merged post follows: Consecutive posts merged It was more like keeping up with both frames while being temporarily in one. The space travelers real world is at rest in the Milky way. (G * mass of Earth) / (radius of Earth * (c^2)) = 6.95453588 × 10^-10 But as you pointed out it does not apply here. If Gravitational time dilation is dependent on difference in gravitational potential, what influences the change in gravitational potential? Not at all clear here. But who gets old is determined by who accelerates to a different frame? The online dictionary says: "an accelerating dragster or space shuttle. Spinning objects such as merry-go-rounds and ferris wheels are subjected to gravitational time dilation as an effect of their angular spin." Is there a contradiction here? Thank you for your participation.

I have a couple of questions later for Janus and swansont but it is Saturday night and time to chase skirt.

Where Does Space End? It Must End Somewhere! http://www.scienceforums.net/forum/showthread.php?t=6390 Martin warned you and I agree with him. However, you may learn something if you can wade through the trash. I should have said if the universe is finite and flat, there may be an edge. "The universe" program on the History channel says so far the laser measurements say it is flat. Even if it is a 2d spherical surface it could be getting larger like the Hubble balloon. It is expanding into... Merged post follows: Consecutive posts merged I am glad that I am not the only one. Merged post follows: Consecutive posts merged reality=????

So you are saying that charged particles from the solar wind would have no influance on the atmosphere of a planet if they got through the magnetic field? Just a question, I do not know the answer.

Maybe the question should be is the universe infinite or finite and if it is finite, what is past the edge. Seems like there is a long thread about that.

http://en.wikipedia.org/wiki/Earth's_magnetic_field "The magnetosphere shields the surface of the Earth from the charged particles of the solar wind and is generated by electric currents located in many different parts of the Earth. It is compressed on the day (Sun) side due to the force of the arriving particles, and extended on the night side."

Let me rephrase #1: Speed as observed by the crew and shown by the ships clocks well exceeds the speed of light relative to the Milky Way when star map time and distance measurements are taken. This would be an observation from math measurements and not a visual view distorted by length contraction. We know that star A and star B on our map are x ly apart when at rest in the Milky Way frame. 2. I was afraid you were going to say that. Help me out here. I view the 1G force as a byproduct of acceleration. My calculations show 1 G vs way out in space as .22 seconds per year. Nothing to get excited about. Using the calculators on http://www.cthreepo.com/cp_html/math1.htm shows a non accelerating frame speed of .97c having a time dilation of 4.11 Consider my chart. After 2 years accelerating you reach a speed of 0.97c with a time dilation of 3.99 Is the small difference because of 1G gravity? By looking at this it seems that speed, and not gravity, is responsible for most of the time dilation. Also as the speed increases and gravity remains constant, the time dilation and length contraction increases.

We leave tomorrow if the two questions are answered. You don't have any thought on that?

We are going to travel 113,242 light years across the Milky Way starting at rest in our galaxy's inertial frame near an outer edge. We will use a continuous 1G of acceleration the entire distance. The table below is from http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html T= time in rockets inertial frame t= time in earths inertial frame d= distance in light years v= light speed Y= time dilation T --------- t ----------- d ----------- v -------------- γ 1 year --- 1.19 yrs ----- 0.56 lyrs --- 0.77c ----------- 1.58 2 ------- 3.75 -------- 2.90 -------- 0.97 ----------- 3.99 5 ------- 83.7 -------- 82.7 -------- 0.99993 --------- 86.2 8 ------- 1,840 ------ 1,839 -------- 0.9999998 ------ 1,895 12 ------ 113,243 ---- 113,242 ------ 0.99999999996 -- 116,641 Relative to the clocks in the space ship and as observed by the crew, they will travel well over 100,000 light years in just 12 years. Their speed increases during the trip, as the distance covered according to their galaxy map shows. True or False: 1. Due to time dilation, the ship's inertia frame as observed by the crew and shown by the ships clocks well exceeds the speed of light relative to the Milky Way. Especially during the last half of the trip. 2. 99%+ of the the time dilation is caused by SR with only a small part of the time dilation caused by GR because of the 1G from acceleration.

It seems I would have easily seen a decimal point out of place. Not sure what I did at this point.

That was my first thought but... radius of Earth = 6,378.1 kilometers (G * mass of Earth) / (radius of Earth * (c^2)) = 6.95453588 × 10^-10 Of course. If I use meters instead of kilometers. (G * mass of Earth) / ((6 378.1 * (10^3)) * (c^2)) = 0.695453588 nanometers. Can I blame it on being old? Thanks moth, Thanks for the link. I understand what is happening but like you, I have a little trouble with the math. Even with the simple math sometimes as you see above.

I agree. If matter and antimatter can not coexist, where in the universe would you find antimatter and what produced it? Welcome.

It seems our local gravity does not have a large influence on our clocks -------- (G * mass of Earth) / (radius of Earth * (c^2)) = 6.95453588 × 10^-10 Because of our Earth's mass and radius, clocks are slower by about 0.7 parts per billion. 60.5 microseconds per day. .022 seconds year compared to way out in space. (G * mass of the Sun) / (radius of the Sun * (c^2)) = 2.12324397 × 10-6 Because of our Sun's mass and radius, Clocks on the surface would be slower by about 2.1 parts per million. .1728 seconds day. 63 seconds year compared to clocks way out in space. (GPS satellite - Altitude 12,000 miles) Our Earth clocks are slower by 45 microseconds per day. --- I was trying to figure out how to use these formulas to calculate the 45 microseconds difference in time between the GPS satellite and the Earth surface. I can not even tell what unit of measurements are being used for "radius of Earth" or "mass of Earth". I would also like to know the time difference between the Sun's surface and the Earths surface. Can anyone help?

Yes! Time is the power to produce an outcome or achieve a result. When I look in the mirror I can see that time does exist. However, with out consciousness it may not exist.

Martin has a sticky on "Cosmo Basics" with several good links in it. I liked this one and it answers many questions and is a fun read. http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf Local gravity keeps the galaxies and even galaxy clusters from expanding but the space in between expands. As Baby Astronaut pointed out.

Not at all. You pointed to the answer. Why struggle with words when someone already did it for you? Good post. I'm on you side here.

There you go. A word invented by man and defined by man. I like Bookshelf's definition: "A nonspatial continuum in which events occur in apparently irreversible succession from the past through the present to the future."

Exactly! Not that they expected life on the moon but the astronauts were quarantined after the first moon trip. Who were we protecting? Us or them?

Hi "12 year old boy with a 1200 IQ". Could you use some punctuation so us folks with a lower IQ don't have to work so hard?

In another thread there were several that agreed that it was.