madscience

In the big bang model, our current universe started with a big explosion from a small object with extremely high density, the debris of this explosion re-grouped and evolved into stars and galaxies. The debris carried initial momentum of the explosion which makes the universe keeping expansion, the proposed dark energy causes the expansion even faster. We do not have any reason to think that such explosion was not uniform in three dimension space. So if the big bang was uniform in 3 dimension space, then, we should be able to find the center of the explosion (or the center of the universe) because the density of the galaxies/stars in the center direction should be higher than the opposite direction, also, the universe should have more or less the spherical shape. However, the various simulated models about the shape of the universe indicate that the universe is like a flat disk shape with thicker in the center. I am puzzled. Thank you for your help.

Hi; Folks, Thank you all for your nice replies to my thread. I got more clear picture about the "volume" of photons. Sisyphus indicated that "AFAIK, the short answer is "no." That's why you can't hit a photon with a photon. However, the wave function does mean there is a finite (though not rigidly bounded) region where the wave's magnitude is non-negligible. So in a certain sense it does have a volume, but not in the way we're used to thinking about it." The wave is in a "finite" region, such region is the "volmue", we should say that it is a "soft" volume or "transparant" volume, I mean that other objects can occupy this region also. So if you hit a photon with a photon, the two photons will occupy the same region when they meet and then pass through each other.

Hi; Guys, A college student asked the question if a photon has physical volume or geometrical size. Does anyone have a good answer? From the particle point of view, it should have volume/size; from wave point of view, it should not have volume/size. A photon travels from a remote star to the earth (Billion years), does not fall apart during the long journey, it should have certain volume/size.

That is what the paper claims that the tidal friction can not be the primary contribution to the recession of the Moon.

The fact is that the Moon was closer and the Earth's rotation was faster in the past, the gravity of the moon pulling the water had to be stronger, the earth's rotation is always ahead of Moon's orbital motion, the ocean tidal current had to be higher than present value, the friction at the ocean bed should be no less than present value, even there was no land to get in the way as assumed in Pangea-like arrangement. The tidal friction theory used "the paleontological evidence shows a much slower lunar acceleration in the past" to construct its model, therefore, it is guaranteed that the result of the model is compatible with the evidence. The new model does not depend on the past evidence and any assumed continental conditions, but it gives a reasonable description of the past evolution which is compatible with the paleontological evidence. This is what I think making more sense. I believe in the "KISS" Rule (Keep It Stupid Simple), that is the nature should be. Or I could be wrong. Nice discussion.

Hi Guys, I recently read a very interesting article about a new model of the evolution of the earth moon system, which is based on non-Newtonian physics approach. To me, this model makes a lot more sense than the tidal friction theory. Here is the link http://arxiv.org/ftp/arxiv/papers/0704/0704.0003.pdf Any comments?