Something that I find pretty mind-boggling is the idea of Dark Matter. What is it? How does it work? etc. etc. Well, to start off, I did what every good Physics student would do, and did plenty of research (all of ten minutes on Wikipedia. Man I'm hardcore). It turns out that "dark matter" for better or worse, is basically unexplained, unobservable stuff that's believed to comprise the majority of the matter in the universe. Because it doesn't interact with any form of electromagnetic radiation in any way (i.e. doesn't scatter, reflect, or emit any light), it isn't possible with current telescope technology to observe it, and therefore, we don't even know whether it exists. The existence of dark matter was first proposed by Jan Oort, in order to explain the missing mass that should have been there when observing the orbital and rotational speeds of galaxies, as well as a few other weird thingies like strong gravitational lensing:

Because of the particular complexities of dark matter, I'd rather not get ahead of myself by trying to explain too much detail, since, to be honest, I'm still trying to wrap my mind around some of this stuff myself. But dark matter can be broken into cold, warm, and hot dark matter. Cold dark matter is basically dark matter moving at classical velocities, while warm is any relativistic dark matter, and hot is "ultrarelativistic", or speeds extremely close to the speed of light. Much of the evidence for dark matter comes from observation of the movement of galaxies, and dark matter detection experiments are still being run today. Of course, because of the theoretical nature of dark matter, there are alternative theories such as modifying the laws of gravity, etc. Who knows? I'm sure the astrophysicists working on this stuff are pretty smart people, and we'll see (hopefully before we die) what "dark matter" really is

Another pretty picture from the internet to distract people... it's a 3D map of the distribution of dark matter, from Hubble's measurements of weak gravitational lensing.

Just a quick thought about something that I find particularly interesting - Quasars. First, I'm obviously not an authority on these things, nor am I exactly the best person to come to regarding astrophysics knowledge, but let's face it, space stuff is pretty awesome. So, first, to my understanding, Quasars are basically highly energetic, nuclei of very distant galaxies which are some of the most luminous objects in the universe, and consequently, were some of the earliest examples of redshift. It's believed that quasars are formed by accretion of material in supermassive black holes, or in other words, stuff getting pulled by the very powerful gravitational field around supermassive black holes, and the very bright light is what energy is immediately outside the event horizon (as anything past the event horizon is impossible to see - hence, black holes). Now, one may ask "what the is redshift, and why is it important? Before getting into that, I'd like to quickly highlight some of the more interesting bits of history about quasars. Early on, quasars were first "seen" in the 1950's with radio telescopes as radio sources, but without a visible image attached to them. It wasn't until a decade later that, with really big telescopes (like the Hale Telescope at Palomar) that redshifted spectral lines were observed. Fastforward a few years, allow for some of us to be born, and now, over 200,000 quasars have been observed, no just as spectral lines, but as actual, resolved objects, thanks to the construction of a lot of really big telescopes. So now, redshift - Why's it important, what the is it, and what significance does it hold? Redshift is, essentially, the Doppler effect happening with light, rather than sound. In a nutshell, the Doppler effect is observed when a wave-emitting source is moving either towards or away from a (relatively) stationary object, and because of the motion either shortens or lengthens the frequency (and consequently, the wavelength) of the wave, whether it be sound or light. Now, in the case of quasars, the redshift implies that the quasars, being extremely luminous and very very far away, emit electromagnetic waves which are detected by whatever instruments we use here on earth. The spectral lines detected by us turn out to be shifted further into the red region that they should be, hence the term redshift. The significance of this lies in the fact that the shift towards red implies a Doppler effect, and by extension, that the quasars are in fact moving further and further away from us over time. This would then imply that the universe is not stationary, but is in fact expanding. This further holds some implications related to special relativity, which coincidentally, falls into quantum mechanics and I feel a little lazy about trying to talk about in this post. Maybe next time? Yeah probably. But anyways, pretty neat stuff. Here's a cool picture to distract whoever is reading this (artist rendering of what a quasar might look like):

OOOOH PRETTY PICTURE

So, I know I haven't been posting much lately, but I stumbled across this, and felt compelled to share this with everyone. It's mind-boggling to think about the scale of all the things in the universe... how big things can be, and how imperceptibly small... and this provides some pretty cool perspective


http://onemorelevel.com/game/scale_of_the_universe_2012