Hey OP,

cool job! I love astronomy/cosmology but I was reading Stephen Hawkings' book Grand Design and I have a lot of trouble understanding some of the stuff he talks about, care to take a shot at explaining some concepts?

Feynman's Delayed-Choice experiment - I guess somehow by observing the experiment, you affect the past for whatever particles you're observing?

The Universe coming from nothing - I still don't understand it : /



have you watched this video? Richard Lawrence says the math proves the universe is flat and that it is composed of roughly 33% matter and 66% antimatter/darkmatter (I forget)

http://www.youtube.com/watch?v=7ImvlS8PLIo

What do you think..

If in the beginning, there was only a singularity, do you think it was surrounded by space, or do you think it "contained" space?

My theory is that mass creates space and space only exists where there is matter (imo, the singularity existed by itself).

Do you think of the universe as more like a bubble (with everything contained therein) or do you imagine it being more like a cloud (suspended in infinite nothingness) ?

I tend to think of the universe as a bubble filled with gas - like water - where everything is floating rather than suspended).

I might not be making much sense, sorry. I can elaborate if it'll help.

Is there anything you believe in your area of study that most of your colleagues would think is crazy?

what do you think of the idea that life is a way for the universe to experience itself

is planet earth a living being ? like.. is it a sentient (able to perceive/feel).. kinda like a super organism which does everything a human body does but on its own scale;

Guth was making a very explicate point, that it appears some laws of physics are not just descriptive but prescriptive.

So do you believe that guth is being deceitful (which seems odd as he has nothing to gain)? Or that he is ignorant(which seems odd as he is a world renowned cosmologist)? Or is it possible that you are just wrong in your assessment?

The fermi paradox is undoubtedly a strong argument for anti-ET, saying, basically, if there are so many alien civilizations, where are they? I like to believe that there are many many many intelligent beings out there, however, that doesn't mean that we're not alone in this galaxy. I suspect that even if there are millions of civilizations in the Universe, we could be the most evolved (if not the only) forms of life in this galaxy. That being said, even at speeds comparable to c, ET civilizations would have to spend millions of years in inter-stellar travel to even come across us - and even if they have, if they've been able to, I'm sure they could have come up with some sort of cloaking device

Who does? what was there before the Universe? Nothing - and we're not even talking about 'empty space' nothing - there was absolutely nothing. Therefore, I have no answer for you :P

Yes I've read grand design but I can't recall the experiment you're talking about. If you elaborate, I may be able to give you an answer

I think the Universe started as a singularity of an infinitesimally small size, but infinite density. It's almost easier to think of it as absolutely nothing, as discussed above.

I think of the Universe more like a cloud, in your example. The bubble analogy would demand an edge of the Universe, which I've mentioned somewhere is impossible imo.

Colleagues at school and work usually understand what I study. They know all the terminology and are usually understanding when explained concepts that are new to them. Friends, family, and others, however, get confused when I even mention that I studied Astrophysics, so naturally, everything is crazy to them

This makes my mind hurt. We're getting too philosophical here. I'm a scientist, so I believe the Universe doesn't experience - I believe it just is; a happenance of circumstance.

no, it's a giant rock.

can a rock feel?

What are the odds that dna originated in outer space?
Do you think it's possible that life exists in dimensions orthogonal to the ones we are aware of?

Yeah, sorry, what I was really getting at is whether you have any beliefs that your professional academic peers in your own field would think are wacky. Anything that is on the wild side in the world of cosmology.

Do you then see yourself as something seperate and distinct from the universe?

Explain this to me.

The radius of the universe is like 46 billion light-years, but the universe is only 13 billion years old. Doesn't this suggest that something has been moving faster than the speed of light?

Likewise, the things that we see 13 billion light-years away now were presumably much closer to us when they emitted the light that we're now seeing. Doesn't that also imply that we're moving away from the other object at some velocity which is large compared to c?

That's a good q^

O wait, if two objects moving away from each other at 100mph each that doesn't mean something is travelling at 200mph

That's where inflation comes in. The amount of space between the objects is expanding (don't ask me why). Two ants on a large balloon run away from each other at speed of light. But the balloon itself is also expanding.

Here's what I don't understand: if the universe is expanding like a bubble, why can't we locate a region that is the center of the universe? The spot would be dynamic, of course, because of inflation. But if there is a horizon to this expanding universe, isn't there a place midway to the other horizon?

What you're (callypigian) describing is inflation. The Universe expanded to an incredible size in a very short time very early on in its formation - suggesting faster than light travel, however special relativity was not violated. It was an expansion of space, not matter. In other words, no matter was carried between two points faster than c

@ Gullanian, It's all an issue of relativity. If two objects are moving away from each other at, say 0.99c, they're not traveling at 1.98c. Some Galaxies are receding faster than the speed of light away from us because the space in between us is expanding faster than the speed of light.

When dealing with relativistic speeds, velocities do not stack classically like they do here on earth (i.e. seeing a car move away from you at 240km/hr because you're both heading 120km/hr in opposite directions).

remember - the speed of light is the same in all reference frames! Two photons of light traveling in opposite directions would observe each other traveling at....c!

When a ballon or bubble is used the represent the expanding univerese only surface expansion(and not the interior volume expansion) makes up the analogy.

Also there is a physical limit on how fast light can travel thru space, but there is no physical limit on how fast space can expand. You can have two galaxies "moving" away from each other faster than the speed of light not because of their own momentum but rather becuase the space between them is expanding.

Astronomers use words like 'infinite' and 'nothing' concerning certain subjects. Do you agree that these words are more indictive of the gaps in our knowledge than absolutes? I.e. nothing is something you can't see yet and infinite is something you can't measure yet.

Why introduce these mind bottling concepts instead of saying 'we just don't know'?

1. If space is expanding faster than the speed of light, does that mean that at some point light emitted couldn't move from one place to another because space was expanding too fast?

2. If that is the case, as the expansion of the universe slows, will these old photons ever "catch up" and arrive in a rush?

3. If the expansion of the universe has been non-constant, doesn't that mean that our redshift-distance correlation breaks down at some point?

I'm a noob but I saw a doc on BBC afaik that said that there are parts expanding so fast we will never be able to observe them

got to intensive purposes and stopped reading but hey i'm a layman

I'll admit that as astronomers, and as scientists - all academics should be able to concede that there are things we don't know. That's why creationists may piss the hell out of evolutionists, but they can't prove evolution 100%. This is also why scientific theories, like the Big Bang theory, are just that....theories. That being said, I don't use the terms infinite and nothing to express what I don't know.

Quite simply, if the BB theory is correct (which it may not be, I'll admit), then there was nothing before the BB - and space and time extend to infinity. Nuff said

1. This is why we can't see past 14 Glyr away in every direction - its our horizon - light hasn't had enough time to reach us yet.

2. Who's to say? Will the Universe expansion ever slow down? It depends on the density of matter within it. We could be heading for a big chill, or a big crunch - or even go on expanding constantly forever.

3. Can't give you a definite answer at this point. I'm tempted in saying in the very early Universe during inflation Hubble's law breaks down

Makes sense to me