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KatieFreese203 karma

I just did a BBC radio interview on exactly that question last Sunday! Here is the podcast link. http://www.thenakedscientists.com/HTML/podcasts/naked-scientists/show/20150823/

To a physicist, the "theory of everything" is the unification of the four forces I described a minute ago. We know the Universe is expanding from a very hot early Big Bang. So, if we look backwards in time, it's like going to hotter temperatures. The forces start to unify. First electromagnetism and weak interactions unify to electroweak (this is tested up the wazoo in particle accelerators and lots of people got Nobel Prizes for this one). Then as you look farther back in time to hotter temperatures, we are pretty sure there is a Grand Unified Theory (takes GUTs) that brings in the third force, strong interactions.

OK but what about gravity? That is the tough one. In fact that is what defines the Big Bang... the limitations of science as we know it. We don't know how to unify gravity along with all the other three. Sure, we will get it someday -- the unification of all four forces. Right now String Theory is the best bet (but it would be nice if there were one single prediction). Anyhow there will definitely be a "Theory of Everything" as defined in this physicsy ways someday. I wish my computer would stop trying to fix my typing. Yes I do mean Physicsy.

Next question: what is it good for? WE SHALL SEE. It will change your life. That's why we are paid to think. Because somebody will definitely find some application that will blow your mind. I can give plenty of examples of serendipitous discoveries, like Bell Labs funded fundamental science that had nothing to do with telephones and what came out of that? the transistor. Imagine life without the toy you are on right now (the computer). OK 'nough said. BTW on the subject of getting paid: "I think, therefore I am paid." Did you catch the reference to Descartes?

KatieFreese196 karma

There are four forces that describe everything in nature: electromagnetism (the most important one in our daily lives); strong interactions that keep our nuclei from falling apart; weak interactions that are responsible for some types of radioactivity; and gravity which makes you fall off cliffs. We understand all of them except gravity. That is why black holes and cosmology are such important testing grounds to learn from... gravity entirely dominates there! There is a good classical theory of general relativity describing gravity but we don't know how to merge it with quantum mechanics. Quantum gravity is the big unsolved problem of theoretical physics. If Einstein couldn't get it, then ... can we?

KatieFreese112 karma

An interesting question. It made me think, and in the end I decided I like the name "black hole." It really does capture the immense gravitational pull of these objects, that on the whole prevents things from escaping.

It is true that Stephen Hawking showed that "black holes aren't black." What is meant by that: Before the 1970s, it was thought that anything entering the black hole would be lost forever. More accurately, anything getting closer than the "Event horizon" would never be able to get back out, even if it were moving with light speed. The event horizon is the point of no return. However, then Stephen discovered Hawking radiation. At the event horizon of the black hole, pairs of particles and antiparticles are created. One of them falls back into the black hole but the other emerges. Because of this radiation coming out of the black hole, black holes eventually evaporate. It takes some time for this to happen: a black hole weighing as much as our Sun takes 1075 years to evaporate.

"Black" usually means nothing can get back out, yet because of Hawking radiation, it does. So in that sense "black holes aren't completely black." But I still like the name.

KatieFreese93 karma

I'm a gorgeous babe myself, dude.

KatieFreese56 karma

The Universe is full of supermassive black holes, and we are not sure how they form. This is known as "The Big Black Hole Problem." Every galaxy has one at its center; for example there is a black hole weighing four million Suns at the center of our Galaxy (the Milky Way). More surprising is the fact that there are even more enormous BH (weighing ten billion Suns) soon after the beginning of the Universe.

So how do these form? There are competing theories. The first stars may be responsible for the progenitors of these big beasts. Once these early stars die, they collapse into black holes; then these black holes could merge together to make ever bigger ones. In the standard picture of first star formation, however, the stars are just too small to get this to work. It's hopeless to try to get them to merge quickly enough to explain the very early supermassive BH.

So my collaborators and I had a new idea: Dark Stars. In fact, one of my collaborators is sitting in this room at Nordita right now also answering questions. Dark stars are stars that are made up almost entirely of ordinary hydrogen, but the power source is dark matter annihilation instead of the usual hydrogen burning fusion.

That leads me to the dark matter problem. Most of the mass in the Universe is NOT ordinary atoms. Instead, it is something not yet identified. We have known of the existence of dark matter for 80 years (from the way it pulls gravitationally on other objects) but we don't know what is. I don't want to go too far afield in this answer, but it is this dark matter that could power the first stars, instead of fusion. These Dark Stars can grow to be supermassive themselves, up to ten billion Suns, so that they will eventually collapse to supermassive black holes.

Right now the idea of Dark Stars is still speculation, but I'm excited to say that the James Webb Space Telescope (JWST), which is NASA's $10 billion dollar sequel to Hubble Space Telescope, will launch in 2018 and I'm hoping they find these early Dark Stars.