The BICEP2 paper has officially been accepted in Physical Review Letters. Having survived peer review, does that mean we can now declare that inflation has now been officially observed? Not necessarily.
Closer Than They Appear
Yesterday I talked about apparent sizes, and how Pluto can appear larger than a distant galaxy, even though the galaxy is much farther away. It turns out, however, that on really cosmic scales apparent size is only part of the story. That’s because the universe is expanding.
The Universe In Your Hands
Have you ever thought about where your hands came from? Naturally, you got your hands from your parents. They gave you the DNA which determined the size and shape of your hands. All the muscles, bones and tendons in your hands were honed by natural selection to the form you have today. Your DNA traces its lineage through the entire history of life on earth from its early beginnings more than 3.5 billion years ago to the present day. It is a profound concept when you think about it, but that is just part of the story.
Dark of Night
When you look up in the night sky, there are areas of the sky that appear dark. That’s because there is nothing in that region bright enough for us to see with the naked eye. If you looked upon this region with a telescope, you would find dim stars and galaxies, but you would still see areas that appeared dark to you. How far could you take this? If you kept looking at smaller and smaller dark regions with ever more powerful telescopes, what would you see?
Boltzmann’s Brain
Ludwig Boltzmann was a physicist who developed statistical mechanics, which connects Newtonian physics of particles to thermodynamics. Boltzmann’s kinetic theory not only explained how heat, work and energy are connected, it also gave a clear definition of entropy. While this revolutionized our understanding of everything from heat to the universe, it also led Boltzmann to a rather puzzling idea known as a Boltzmann brain.
Selection Bias
There’s a new paper in the International Journal of Modern Physics which presents evidence that the universe is not expanding. You heard that right. If true it would overturn decades of cosmological theory. It’s the kind of revolutionary find that wins Nobel prizes. It’s gotten a bit of attention in the popular press, but don’t throw your old astronomy books out just yet.
Dirty Laundry
Recently rumors have been flying that the BICEP2 results regarding the cosmic inflationary period may be invalid. It makes for great headline press, but the reality is not quite so sensational. There may be some issues with the BICEP2 results, but that isn’t what the press is excited about. What they are really excited about is how science groups are airing their dirty laundry, publicly. So what’s really going on?
Reboot
One of the challenges faced by astrophysicists is that you can’t repeat your experiments. With cosmology, that poses a particular challenge because we only have one observable universe. Not only can’t we repeat the experiment, we only have one experiment to observe. What we can do, however, is simulate the universe and see how it compares to the real one.
Twist and Shout
Measuring the magnetic fields of our galaxy poses an interesting challenge. The galactic magnetic field doesn’t emit or absorb light, and of course we can’t directly measure it at various places like we can for Earth’s magnetic field. The galactic magnetic field does, however, interact strongly with things such as ionized gas and electrically charged dust, so we can indirectly measure the field by the way it affects these things.