Is there the reference frame of the universe?

The Newtonian mechanics, the beginning of physics, is based on Galilean relativity: every inertial frame has the same laws of physics and there is no reference frame. But, is it?

Development of electromagnetism in 19th century discovered that the speed of light is universally constant in our universe. This implies that the Galilean relativity does not work anymore: 100 mph ball thrown on a truck running 100 mph is no longer 200 mph! Instead, there is special way of adding speeds to preserve the speed of light, which is the special relativity.

All these theories are developed in belief of relativity i.e. no reference frame, and Einstein's relativity shows time dilation, length contraction, and blue/red-shift: if we are getting closer to the light source, it seems more bluer than its original light, and if we are getting farther, it seems more red-er. We call it relativistic Doppler effect. This is the natural consequence of the relativity.

If it is the natural consequence of the relativity, and if there is no reference frame, then the universe must be isotropic just as we see on the earth even if we are speeding relativistically away from our home. Is it?

We are having detected cosmic background radiation, the remnant heat from the big bang, which is uniform in any corner of the sky. If we are moving at speed of 99.5% of the speed of light away from our home, our clock is 10 times slower than our home, and we can detect 10 times stronger the radiation in the moving direction, and 10 times weaker in the opposite direction. So, if we have enough fuel to accelerate to that speed, we can definitely take advantage of the 10-time time dilation, but we may not survive from the star radiation coming toward our windshield.

This phenomenon gives the exact reference frame: if we move away from that frame, the universe may not look isotropic anymore. This makes us ask a question: where did the relativity come from?

Theoretically, of course, we can make a theory, a set of laws of physics, which guarantees the relativity, but the solution of the equation being not. But the relativistic principle itself came from the empirical conclusion. Galileo might experiment many times about motion, momentum, inertia, and relativity. It is believed so strongly because it has never been disproved, but we cannot prove that it is right assumption. A postulate can never be proved.

So far, every modern experiments prove the Einstein's relativity to be right. However, we are already facing a contradiction: black hole problem in General relativity. Science is waiting for another big wave following Newton, and Einstein.