What The Entire Universe Is Made Of, Thanks to Planck!

[T]his picture is far more exquisite than any that came before. In the early 1990s, the COBE satellite gave us the first precision, all-sky map of the cosmic microwave background, down to a resolution of about 7 degrees. About a decade ago, WMAP managed to get that down to about half-a-degree resolution.

But Planck? Planck is so sensitive that the limits to what it can see aren’t set by instruments, but by the fundamental astrophysics of the Universe itself! In other words, it will be impossible to ever take better pictures of this stage of the Universe than Planck has already taken.

Planck being an ESA satellite mission to measure the cosmic microwave background differences down to a resolution of a few parts per million.

POW! Teaching Physics with Batman

A more interesting version of the ballistic pendulum experiment.

Neil deGrasse Tyson explains the timelessness of photons

Caveat emptor: he’s doing a radio show, so there’s a necessary downconversion of the depth of the discussion. He does err when he implies that massive objects traveling at c is a technological/engineering barrier, and we just haven’t figured it out (like breaking the sound barrier), rather than a physics barrier that would demand that current theory be wrong or incomplete, with some new physics necessary to explain what’s going on.

In general the “photons don’t experience time” is a bit of a tiptoe in the mine field, because we can’t definitively say what things look like from a photon’s perspective — relativity doesn’t afford us a description of what things look like to a photon. The Lorentz transforms — what we use to see what things are like for massive objects — “blow up” when v=c, which means that the photon is not in an inertial frame, and all that physics we do is for objects in inertial frames. The reason I hesitate is that an equation diverging from some infinity showing up means that the equation has failed, so the fact that a term is tending toward infinity (or zero) as it fails isn’t a guarantee that infinity (or zero) is the right answer when the equation no longer applies.

The idea does paint a nice picture, though, and seems consistent with the QED path-integral idea that photons sample all paths and most of them destructively interfere, and what we see is the result, but I think it’s easy to take the idea too far and imply things that don’t have any experimental backing to assure us they are true.