Recent content by ta66505477

Thank you! I am going to find this electroscope.

I am really confused that the whole process of the method of image. Suppose I have the + q near the infinite conducting plane which is grounded. My first question is: Is the conducting plane grounded before putting the +q or after putting the +q then grounded? The first question would lead to...

I understood now. What I have overlooked is the wire Your graph makes perfect to me. I can think it intuitively by your graph. Like Path A takes less time but the light has to use more time to chase back in Path B. Path C initially takes more time to detector but quickly goes back to...

Suppose all the things are on the train including devices, time detector and the explosion system. So all device should "agree" the light came from same time because all the devices follow S' coordinate. Space and time we cannot touch. We cannot hold it on hand so we can easily accept...

I have a little bit confuse on the Simultaneity I know if there are 2 coordinates. One coordinate S' is moving V relative to S. We all in inertial reference frame. like the following graph...

Thx a lot. I understood something in here. And thanks all of you. I will keep on trying to learn more from the textbooks and go back here to check my understanding. All of the textbooks using Tensor from the beginning and tell you that Tensor is a wonderful tool in general relativity...

I think that is a fundamental question of why we need Tensor when dealing with GR? Quoting from the textbook (Relativity, Gravitation and Cosmology: A Basic Introduction) Tensors are mathematical object having definite transformation properties under coordinate transformations. The simplest...

it helps me a lot! thx everyone. and one more question. I am reading the cosmological constant that is different between the observation and theory. By theory, they use something called vacuum energy which came from quantum mechanics. I cannot understand why vacuum energy can be a result of...

How can people measure the Hubble's constant using WMAP? I found a journal named First-Year Wilkinson Microwave Anisotropy Probe (WMAP)* Observations: Determination of Cosmological Parameters http://iopscience.iop.org/0067-0049/148/1/175 In 4.1 said [SIZE="5"]CMB observations do not...