From: bobonthejob 8/04/00 13:58:54 Subject: Mass and velocity post id: 54743 From what I understand, the faster something travels, the heavier it gets. Right? Why exactly does this occur? Does the rearrangement of the equation E=MC^2 to M=E/C^2 support this? From: B.C. 8/04/00 14:07:32 Subject: re: Mass and velocity post id: 54744 As something moves it gains energy- therefore it gets heavier as per the equation E=Mc2,it also gets shorter in the direction of travel and time dilates.All this happens in the view of someone in an outside reference frame.As for a person or person moving at x velocity everything is as normal,in his own reference frame. From: bobonthejob 8/04/00 14:16:23 Subject: re: Mass and velocity post id: 54745 From the point of view, of something travelling very fast, they are not moving but everything else is. Does that mean everything else gets heavier? From: Robert 8/04/00 15:02:31 Subject: re: Mass and velocity post id: 54748 It's all relative - it depends on the frame of the measurer. So, to answer this question, From the point of view, of something travelling very fast, they are not moving but everything else is. Does that mean everything else gets heavier? The 'something' will measure most things to be heavier than they would if their velocities were equal. I believe this is called relativistic mass, and that it is this which gets heavier with speed. I think that's right.... From: bobonthejob 8/04/00 15:44:40 Subject: re: Mass and velocity post id: 54752 If I were in a spaceship and I was moving away from the earth close to the speed of light. It is said that time would move slower for me than a person on earth. Hence the "Planet of the apes" scenario. But how could this be true? Since relative to the space ship it is the earth that is moving and consequently the earth that would experience slower time. From: Grant¹ 8/04/00 19:06:29 Subject: re: Mass and velocity post id: 54800 Check the FAQ on the twins paradox & FTL travel. From: B.C. 8/04/00 23:31:43 Subject: re: Mass and velocity post id: 55017 Yes thats the best advice,check under F.T.L.Heres my down to earthexplanation anyway.If you are in the space ship travelling at a good percentage of the speed of light,nothing would change for you and your environments in the space ship.If you looked back at your good mate back on earth,you would notice that time has speeded up,and everthing is moving faster.Your friend on earth would not perceive any difference or anything strange,withregards to his time keeping,but if he looked up at you travelling at a good percentage of the speed of light,he would notice that he would perceive everthing to be slowing down.This is what is meant by relativity.The differences each perceived in the others time rate would be bought to tthe fore when the traveller returned to whence he came.To give an example if the traveller travelled at 99.9999% the speed of light and returned,witha time frame according to his clock of 12mths,the friend back on earth would be well and truelly dead and buried with the earth based clock showing 250yrs down the track! From: Chris (Avatar) 10/04/00 12:03:39 Subject: re: Mass and velocity post id: 55419 Hi Bob. To understand relativity, you need first to completely understand the concept of Frames of Reference (FoR). In relativity frames of reference are distinguished by velocity. For example, suppose I am sitting in a car travelling constantly at 60km/hr (so as to avoid Daryn's evildoer tax) north and I throw a tennis ball out the passenger window at 50km/hr in the direction I'm travelling (north). There are three frames of reference here. In the frame of the road, the car is moving north at 60km/hr and the ball north at 110km/hr. In the frame of the car, the car is still, the road is moving south at 60km/hr and the ball is moving north at 50km/hr. In the frame of the ball, the car is moving south at 50km/hr and the road is moving south at 110km/hr. Relativity tells us that provided all of these frames are inertial, they're all equivalent. ie none is more "right" than the other. What is important is that the way you observe and measure the universe depends on your relative frame of reference. In the example above, the answer to the simple question "How fast is the car going?" depends on the FoR of the answerer: either 60km/hrnorth, 0km/hr, or 50km/hr south. It turns out that our measurements of relative velocity, distance and time intervals, energy and relativistic mass, momentum, and other quantities depend on the frame in which we make them. So let's look at mass/energy. In order to make sense of mass, we define the quantity "rest mass" to be the mass you measure in your own frame of reference. This rest mass figure is the most useful, and so we make the quantity invariant (by definition). But our measurments of mass are frame dependant. If I rush past you at a speed which is a decent fraction of the speed of light, you will measure my mass to be more than I measure it to be. We call any mass measurement which is made from outside the mass' rest frame the relativistic mass to distinguish from the rest mass we defined above. The two are related in the following way: mr = mo / Ö (1 - v2/c2 ) ...where mr is relativistic mass mo is rest mass v is the velocity of the observer in frame r with respect to the mass and c is the speed of light. Notice that the factor Ö (1 - v2/c2 ) is called the Lorentz transform and is a special rule for transforming from one frame to another moving frame. You will find it pops up in the time dilation and length contraction relations as well. In the mass relation, notice that when v=0 (ie in the rest frame), mr = mo (as we would expect). However as v ® c, mr gets progressively larger. This is the commonly understood result that relativistic mass tends to infinity as velocity increases. However rest mass does not change, meaning that a quickly travelling mass does not get "heavier" or eventually turn into a black hole. Hope this helps! Chris This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.