poker

But how to define the speed of light experimentally? And how to make sure that this method will lead to high precision result?

In the gauge field theory photon is represented by a gauge vector field which is massless. But how can we measure the mass of the photon to very small value to convince ourselves that photon is definitely massless? Somebody say that as the universe is just about 13.7 billion years old from the big bang to now, so if we measure the mass of photon through any quantum effects, we will ultimately arrive at a threshold under which we can not push on. In other words, we have no method to measure the absolute zero mass of photon. What are your opinions?

I'm always confused reading literatures by the notions: electroweak scale, GUT scale and Planck scale. Where do they come from and what do they exactly mean?

I'm a senior student majoring in physics. I was asked to take a five-week seminar this summer holiday. Can anybody provide some interesting subjects of theoretical physics? Maybe after the holiday you will find a good cooperator to discuss and work with.