Good astrophysics book? Also - what's past particle horizon?

[wired]

So, I've been reading a little bit about event horizons this morning. (I watched a video of the known universe and it got me thinking about things.) I have VERY little background in physics. Think high school and Physical Science 100 from BYU. Relativity played with my mind a little bit, but I think I got the basic idea of it.

Does anyone have recommendations on learning about the beginning of the universe and the current theory of the universe that is on a somewhat comprehensible level?

On a related note, anyone who knows about this stuff.... If I understand the theory correctly, the big bang set off a burst of energy and matter that has been creating our universe ever since. The bounds of the universe is the particle horizon which is where light from the big bang has reached. If I understand correctly, if I were somehow able to technically move faster than the speed of light, catch up to the particle horizon, then move past it, there would be absolutely nothing there - is that right? If I were to stay static in space, eventually the light from the big bang would catch up with me and the universe would expand past me. Correct?

Assuming I could move faster than the speed of light, is it even theoretically possible to move past the particle horizon? (I know that removing one assumption is kind of cheap - speed of light is a cosmic speed limit - to ask about another is a little whacky, but I was just thinking about it.)

I might actually submit this to the board if any of the writers want to write a comprehensive answer. If so, just say so in this post and I'll submit it.

[Digit]

You should email Dr. Michio Kaku at mkaku (at) aol.com and see if you just happen to be lucky enough to get a response. Proof that's really his email address
Here's Stephen Hawking's contact information, too, as long as I'm talking about extreme long shots, as I think he's more of a universe guy than Kaku.
Finally, maybe this is the best of the long shots. Dr. Neil deGrasse Tyson says on his contact page that he will answer one science question per month. Well, after that service is no longer backlogged.

[Katya]

This isn't exactly what you were looking for, but Blind Watchers of the Sky by Rocky Kolb is a really good (and really funny) book on the history of astronomy. (I can't resist recommending it, even with only a marginal excuse to do so.)

[NerdGirl]

I'm on my way out the door, but I can come back later and write you a very detailed answer. Also I would recommend Stephen Hawking's "A Brief History of Time" and "Black Holes and Baby Universes" and Terence Dickinson's "The Universe and Beyond". I first read those Stephen Hawking books when I was 13, and I did not have a PhD back then, so I don't think they're super technical. Also you might be interested in watching "The Elegant Universe". It's about 6 hours long to watch all of it (I think), and Netflix probably has it, but if you go digging around on the PBS website there's a place to watch it for free. I'll find the link and post it when I get back.

One thing I will say before I go: think of the Big Bang as more like an expansion. Everything (all the matter/energy) in the universe was at a single spot, then the Big Bang happened and it started expanding, and as it expanded, structure (galaxies, stars, etc) started to form.

[NerdGirl]

Okay, my mom's not ready yet, so I found the Elegant Universe. Start here: http://www.pbs.org/wgbh/nova/physics/el ... stein.html. And maybe it's only 3 hours long. It's kind of more about string theory and particle physics, but there's definitely some cosmology in it.

And the particle horizon is actually the boundary of the observable universe. If we could get beyond it, there would be stuff there (who knows what kind of stuff), but because of the way the universe expanded (inflation), there are parts of it that we can't see. The particle horizon is the maximum distance that light could have traveled to reach us in the age of the universe (age of the universe x the speed of light). When inflation was happening, the universe expanded at a rate that was much faster than the speed of light, so there are parts of the universe we can't see because the light can't get to us. They will always be too far away because the universe keeps expanding. More about inflation here: http://map.gsfc.nasa.gov/universe/bb_cosmo_infl.html, but I'll try to have some better stuff later! I love talking about this stuff, so if you think of more questions, post them.

[wired]

NerdGirl:

Thanks for the answer! Hopefully you can be patient with me as I ask some understanding questions.

You said, "Because of the way the universe expanded (inflation), there are parts of it that we can't see... If we could get beyond it, there would be stuff there..."

Now, when I conceptualize the Big Bang in my mind, I imagine a dot that exists at the center of nothing (space that isn't filled with any element, particle, or atomic particle... etc. to the infinitesimal degree). Then, when the Big Bang occurred, that single dot started pushing outward. (I previously thought of it as an explosion, but it seems you seem to say its better imagine it as an expansion.) Our universe is that dot as it expands. We can't see anything beyond the dot because light doesn't reflect back from it.

As a thought experiment, I'd like to imagine going outside of the dot. You are saying that there would be stuff there, though we have no idea what kind of stuff. So is my conceptualization of the Big Bang as a dot in the middle of absolutely nothing a poor one since for there to be something outside of our known universe, it would have had to existed outside of that single dot?

Further, has anyone hypothesized about other "dots" existing? So, there's two dots that exist, both expanding toward each other and eventually light from the other dot will begin to transverse our space and we'll see that other dot?

[wired]

Also, I watched The Elegant Universe about five or six years ago - I think I'll give it another watch. Thanks for the link!

[NerdGirl]

Ok, this will be kind of weird to imagine, but hopefully it will help. The dot analogy is good, but instead of the dot expanding into space, think of the dot containing everything, including space. So as the dot expands, space expands. Anything outside the dot we can't see, but because the dot expanded faster than the speed of light for a while, there are also regions inside the dot that will always be too far away for us to see. They are too far away for the light to get to us and they always will be because space keeps getting bigger and the light will never catch up to us. There is not a finite, fixed amount of space. We keep getting more of it. And because we keep getting more space, if there are other dots, we won't ever run into them. The dot or dots are space, time, energy, and matter. When they expand, space expands. Does that make sense? Does it raise more questions?

[wired]

Makes more sense and raises more questions.

As a preliminary understanding statement: there's the known universe (regions of the dot that light can return from), the unknown universe (regions of the dot that light won't be able to return to) and OTHER (regions outside the dot).

You say the dot contains space. That makes sense to me, kind of. When the dot existed as a single point, was there anything external to the dot? Is it accurate to call everything external to the dot, space as well?

[Digit]

As you can see at about 3:30 of this, beyond the edge of the universe, it is just pure white. You can create space by penciling in your starmap.

[NerdGirl]

Your preliminary statement is right. It's not accurate to call anything outside the dot (or outside another dot) space because if it's space, it's inside the dot. Or inside another dot. There might be an infinite number of dots, but outside the dots there is just nothing. Not even space. At some level this is just a definition thing, because if there's a region of space then we call it part of a universe. There could be parallel universes that are just empty space and have no matter or energy in them, but empty space is different than nothing. When the dot was a single point there may have been other universes external to it, but it probably wasn't sitting in empty space. Although we don't actually know that for sure, and science can't actually answer that question. Our universe could be embedded in some other universe, but we have no way of knowing that. There could be some superuniverse that contains our universe and infinite others all expanding. They could all be touching as they expand or they could be really far apart. Or they could all exist in the middle of nothing, in which case it doesn't make sense to even give them a location relative to each other. Or we could be the only dot and outside there is just nothing. I don't think we are the only universe, but I don't have any scientific reason for thinking that. It just fits in with my own ideas about theology to believe that there are an infinite number of universes since I believe that God started our entire universe but that he came from somewhere else.

[wired]

I love science. I love religion. They're both awesome.

I really wonder if we will ever know the beginning of everything. It seems to me that no theology or theory of science can explain the beginning of anything other than the tautology that something has always existed.

[wired]

Now, another question.

You mentioned that during inflation (which I took to meant during the early stages of the Big Bang, since we're technically still in inflation) things moved faster than the speed of light. I know faster than the speed of light is a common sci-fi theme; is there any theory that actually endorses moving faster than the speed of light? If we could, and we moved past the known universe into the unknown universe, I get that it would be unobservable. What if we continued to move past unknown space to the edge of the dot? Is there any theory on whether it's physically possible to exist external to the universe?

[NerdGirl]

I really wonder if we will ever know the beginning of everything. It seems to me that no theology or theory of science can explain the beginning of anything other than the tautology that something has always existed.

I agree. Any attempt to explain how things started using either theology or science seems to just push the beginning back in time, because if God started something, well then you still haven't explained how God got there. Any time you come up with a cause, you still have to come up with a cause for the cause.

You mentioned that during inflation (which I took to meant during the early stages of the Big Bang, since we're technically still in inflation) things moved faster than the speed of light. I know faster than the speed of light is a common sci-fi theme; is there any theory that actually endorses moving faster than the speed of light? If we could, and we moved past the known universe into the unknown universe, I get that it would be unobservable. What if we continued to move past unknown space to the edge of the dot? Is there any theory on whether it's physically possible to exist external to the universe?

Well, there is a difference between something expanding faster than light and having information travel faster than light. The laws of physics as far as we understand them prevent information from traveling faster than light. But space could expand faster than light because because there isn't any faster than light communication occurring. This probably explains it better than I'm explaining it: http://curious.astro.cornell.edu/questi ... number=387. But if somehow we did invent faster than light travel, then if we got into the unknown universe we could observe what was there. It's theoretically possible that there could be a wormhole connecting a part of the universe that we can observe with a part that we can't observe, but whether or not we could actually get through a wormhole is a whole separate issue. This is a good little thing about faster than light travel: http://curious.astro.cornell.edu/questi ... number=592. That whole site has a lot of good astronomy questions and answers on it. There is no scientific theory on whether anything could exist exist external to the universe because the laws of physics break down at that point. We probably couldn't ever get to the edge of the dot, because it's a bit of a moving target. It just keeps expanding. And the universe may actually be infinite in size (infinite and getting bigger constantly!), so there may not be an edge, which makes the whole thing even weirder. These are really interesting questions you're coming up with, by the way.

You might also like this book: http://www.amazon.com/Time-Travelers-Gu ... 47&sr=8-10 if you can find it somewhere. It's about time travel, but it's also about faster than light travel and relativity and traveling through the universe things like that. It does have some calculus in it, so if you don't know calculus there will be parts that you'll probably just skip over, but they are not essential to the main ideas. I read it for the first time before I had ever taken calculus and it's written for a general enough audience that I understood most of it. It's written as part story, part science, so each chapter begins with part of an ongoing narrative about some people trying to figure out time travel, and then the second half of the chapter goes into the science in more detail.

[wired]

NerdGirl: Thank you! You have been fantastic for this! I think I got the curiosity bug out of me for the moment. I'll probably pick up the Hawking book and the Time Traveler's Guide and try to read them before school starts back up.

[NerdGirl]

You are very welcome!