Jump to content
Science Forums

Agen

Members
  • Content Count

    62
  • Joined

  • Last visited

Reputation Activity

  1. Like
    Agen got a reaction from sanctus in Is mass also relative?   
    hehe.. I love this argument.
     
    I could respond to that with this: We can never know if we can ever know exactly happens in any event... and we can never know if that is true either.
     
    Wouldn't you agree? :confused:
  2. Like
    Agen reacted to Jay-qu in Virtual reality physics.   
    Yes your right, because in VR a fake time can be dilated, but they cant dilate the time of the observer (yet :D)
  3. Like
    Agen reacted to billg in Growing nerves   
    Certainly progress is being made, but how close we are to actually being able to grow new, functional nerves is hard to say. It may well take considerably longer than ten years. I had to do an essay on a neurotrophic factor GDNF a few months ago, and one of the things I picked up from my reseach was how many molecules were initially heralded as nerve growth factors ten or even twenty years ago; and yet many have since been all but discarded as candidates for treatment, or if not, their use in treatment is still uncertain or risky, varies between studies and individuals within studies, and may grow nerves but not nerves that can actually perform the appropriate functions.
     
    On the other hand the progress made in the last ten years has been enormous. It's always difficult to make a prediction in where science or medicine will be in ten years time, almost to the point where it's not really worth bothering at all. But people do and my guess would be - maybe in twenty years.
  4. Downvote
    Agen reacted to CraigD in Time dilation does not make sense to me.   
    Both observers see one another living in slow motion. It is confusing – or at least counter-intuitive. 
    There are many ways to clear up the confusion, which results, I believe, from a failure to appreciate that, when dealing with fast moving objects, they not only move fast, but go far, and when dealing with far distances, intuitive ideas like “at the same time” become more complicated.
     
    Rather than learning to perceive the situation in terms a space-time coordinate transforms – a good approach, but not a quick nor easy one - you might try coming up with a simple model of how the 2 observers can “see” one another, then write everything of relevance about it in a table. For example:
     
    Assume things work like this: The person on the rock and the person on the ship both have a simple stop-watches that read-out in seconds, and gadgets similar to a camera flash, but powerful enough to be seen at interplanetary distances. They also have notepads and pencils (or good memories) to note when they see each others flashes. The ship has a super-engine that accelerates it to 60% the speed of light in a fraction of a second. Each person agrees that he will trigger his flash every 60 seconds after the ship is launched, and recording the time on his watch when he sees the other’s flash. This gives them each a picture of how fast the other is living. When they’ve each sent and received four flashes, they’ll somehow compare results (how isn’t important – any sort of radio would work).
     
    All we need know how to simulate this experiment is how to calculate the time dilation factor for a speed of .6 c, [math]\sqrt{1 - .6^2} = .8 \, \mbox{c}[/math], using the Lorentz formula. The rest is just arithmetic, and gives a table like this:
    Signal locations Base- Ship- Base- Ship- Base- Ship- Base- Ship- Base Ship Ship Ship Base Ship Base Ship Base Ship Base time Time Loc. #1 #1 #2 #2 #3 #3 #4 #4 (s) (s) (ls) (ls) (ls) (ls) (ls) (ls) (ls) (ls) (ls) 0 0 0 60 48 36 0 75 60 45 15 45 120* 96 72 60 0 0 150 120* 90 90 30 90 180 144 108 60 60 0 225 180 135 105 15 45 135 240* 192 144 120 0 60 120 0 300 240* 180 180 120 60 60 180 360* 288 216 180 0 120 120 450 360* 270 270 210 30 480* 384 288 240 0 600 480* 360 360Note that, to keep things simple, units of light-seconds (ls) are used for location measurements. A light-second is about 300,000,000 meters. An “*” next to the clock reading indicates when each flash signal is received.
     
    Note that the table shows each observer sees the other living at exactly 50% normal speed. If they do the math to compensate for the time required for each signal flash to reach them, they’ll adjust that rate to 80%, but both will still see the other living in slow motion.
     
    We left the 2 observers drifting apart at .6 c, never to be reunited. To really make sense of what’s going on, we need to extend the experiment a bit, and bring them back together. They’ll be able to compare clocks up close and personal, where we no longer need to pay attention to how they do it by tracking each signal passed between them. Depending on how they get back together, they’ll find that less time has passed on one watch than on the other, without any paradoxical difficulty deciding which one.
     
    Expanding the table is left as an exercise to the reader. I recommend using the ship’s miracle motor reverse its velocity to .6 c in the opposite direction, then using it one more time to bring it to a dead halt back on the base rock (the calculations work out in nice whole numbers using a speed of .6 c).
  5. Downvote
    Agen reacted to Janus in Time dilation does not make sense to me.   
    Here's the thing: You also have to take length contraction into account. The distance between A and B will depend on whether it is measured from the rock or the ship. From your description I'll assume that A nd B are at rest with respect to the rock. (assume that there are two other rocks at rest with respect to the frst rock sitting at those two points.) Thus these two points are moving when measured from the ships perspective, and undergo length contraction, A and B will be closer together then as measured from the rock. While you are on the ship it will take less time from the instant that A passes till B passes because of the shorter distance between the two, and you will only be on page two when you pass point B.
     
    Now comes the part that a lot of people have trouble wrapping their mind around, it is called the "Simultaneity of Relativity"
     
     
    It turns out that two people traveling at relative speed to each other will not always agree as to which events happen at the same time.
     
    To illustrate, Let's put two more people into the situation, one each sitting at A and B. They also have books. By arrangement, they both start reading the instant the person on the first rock does. (as determined by them and the person on the first rock. )
     
    Therefore, according to them, the ship passes point A, and everyone starts reading. It passes point B and everyone stops reading. So when the ship passes point B the reader at point B has reached page 15.
     
    Now from the ship's point of view: the man at point A starts reading as point A passes, But The man at point B had started reading already and by this time is quite a ways into page 14. In the time that take for point B to pass( and for the person in the ship to read 2 pages), the man at point B finishes page fourteen and starts page fifteen.
     
    While the three readers on the rocks all agree that they started reading at the same moment, the reader in the ship will not agree, but will say that reader B started reading before reader A.
     
    The upshot is that everyone agrees the reader on the Ship starts reading as he passes A and that the reader at A starts reading at the same moment. They will also agree the the reader at B will be on page 15 when the ship passes A, and that the reader on the ship will be on page 2.
     
     
    This goes back to what I said about having to lose preconceptions on the behavior of time. The fact the "at the same time" depends on relative motion is not an easy idea to digest.
  6. Downvote
    Agen reacted to Boerseun in Should the moon have a name?   
    The sun's name is Sol, as far as I know, and we've been referring to the moon as 'Luna' for a while now. "Solar" and "Lunar" exploration, etc.
     
    But I prefer George.
  7. Like
    Agen got a reaction from Michaelangelica in What happen to the mater who go through black hole   
    Well thats what I mean. We have an infinity amount of time to think of something that would bypass these time dilation events or be fast enough to get the subject back.
×
×
  • Create New...