Questions about Time, Distance, and Relativity

[Mudhammam]

A good read of Flatland might help. How about this: let's say you're in a car going 100 mph, driving east to west. There's someone south of you, and he sees you silhouetted on the horizon. You turn your car 45 degrees to the right, so you're now going northwest. He can only see the car's east-west movement, do to him it now looks like you're only going about 71 mph (100*sqrt(2)/2).

When we're not moving, we're going (speed of light) through time. When we move, it's like we're still going the same speed, but we've turned 45 degrees (or, in reality, like, a billionth of a degree) off of the straight past-to-future line and into the set of dimensions we see.

That's probably a really inexpert way of thinking about it, but that's how I always sort of conceptualized it. Someone please tell me if I'm way off. And I will note that the particular paragraph you quoted, for me, was the one paragraph in that book that I have always remembered and cherished.

I don't think you're off. That sounds pretty similar to an analogy Greene offers.

[Zen Badger]

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A thought experiment:

run a string from here to the Andromeda galaxy (2 million light years m/l)

put a knot in the string every mile.

fly along side the string at .999whateverC relative to us stationary along side the string. To you, on the spacecraft, counting knots as they go by for an hour, you will note relative to YOU, that you're traveling at an extremely large multiple of the speed of light, and going "WTF?, I thought faster than light was impossible !!!"


If you get to the Andromeda galaxy in 20 years (thanks to time dilation), your speed you measured was 100,000 times the speed of light. To us stuck at home, however, it really did take you 2 million years to get there.

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Le me:

It all makes sense now.

[TheRealJoeFish]

Le me:

It all makes sense now.

You... you wouldn't want to put the universe in a tube...

[Mudhammam]

Now that I'm onto A Universe From Nothing by Lawrence Krauss, two additional questions:
1. Does the following question make sense?
2. How do physicists know that the "hot" and "cold" spots in the cosmic microwave background radiation are sub-Planck length quantum fluctuations magnified by inflation if such ultra-microscopic regions of empty space are far beyond the technological limits of observation?

[Mudhammam]

Also, when they speak of the CMBR being observable in every direction that our telescopes point, I visualize it similarly to the "waves" of a smoke ring that dispense outward from the center of an explosion (as in the big bang, time, space, and matter expanding from the Singularity). Have I gotten this wrong? Is there a better way to visualize it?

[Surgenator]

Now that I'm onto A Universe From Nothing by Lawrence Krauss, two additional questions:
1. Does the following question make sense?

I'm guessing the question is "does a universe from nothing makes sense?"

I haven't read Krauss's book, so I don't know exactly his argument. However, there two observations that make me think it is possible.

The first is general relativity's basic principle that mass distorts spacetime. Is the opposite true that distorted spacetime makes mass? If it is, then fluctuations in spacetime creates mass.

Second, we know that particles and their exact opposite pop out of quantum vacuum and disappear, i.e. virtual particles. Some will argue that the quantum vacuum is something, but I don't buy their arguments. To make the quantum vacuum into something is to bring another aether theory. In my opinion, these virtual particles demonstrate the instability of nothing. So a particle and it's exact opposite can pop into existence and before the pop back into nothing one of the particles decays into 3 particles. So the original particles can't recombine back to get nothing. Tada, something from nothing.

I will admit that my ideas still have some holes in them. And the first and second reasons have some contradictory statements. I haven't yet spend too much time refining them.

2. How do physicists know that the "hot" and "cold" spots in the cosmic microwave background radiation are sub-Planck length quantum fluctuations magnified by inflation if such ultra-microscopic regions of empty space are far beyond the technological limits of observation?

First, the maximum starting size of the universe is a Planck length because the uncertainty principle (what effectly allows for the existence of virtual particles) allows gravity poping into existence.

Second, the Planck length is by no means the smallest unit of distance. The Planck length is the smallest distance that can be measured. The expansion of the universe is not a measurement.

So the starting size of the universe being a Planck length and then expanded to something much bigger is just magnifing what was going on inside.

[Cyberman]

Also, when they speak of the CMBR being observable in every direction that our telescopes point, I visualize it similarly to the "waves" of a smoke ring that dispense outward from the center of an explosion (as in the big bang, time, space, and matter expanding from the Singularity). Have I gotten this wrong? Is there a better way to visualize it?

It might help if you think that there is no actual centre, in the sense with which we're familiar. Everywhere in the Universe is the centre. The classic balloon illustration is a pretty accurate way to visualise it.

Basically, if someone asks where the Big Bang occurred, you can point to any random spot you like and say "there" and you'd be right.

[Surgenator]

Also, when they speak of the CMBR being observable in every direction that our telescopes point, I visualize it similarly to the "waves" of a smoke ring that dispense outward from the center of an explosion (as in the big bang, time, space, and matter expanding from the Singularity). Have I gotten this wrong? Is there a better way to visualize it?

It is more like you are one of the smoke particles from the explosion.

All of space was created at the Big Bang and the space was expanded. So the big bang occured everywhere in space, not at some specific spot.

[Alex K]

Also, when they speak of the CMBR being observable in every direction that our telescopes point, I visualize it similarly to the "waves" of a smoke ring that dispense outward from the center of an explosion (as in the big bang, time, space, and matter expanding from the Singularity). Have I gotten this wrong? Is there a better way to visualize it?

I think it's not useful to think of the CMBR as coming from one point in space or time. It was produced everywhere simultaneously, going off in all directions from every point in space when the universe was 1/1100 the size it is today, hundreds if thousands of years after the (probably non existent) Singularity.

[Mudhammam]

Ok..few more...for now...
Considering the balloon analogy, how can galaxies collide if the space BETWEEN them is expanding?

Why is it that we don't actually experience the expansion of space? Is it because of the gravitational field? As in... it keep us "bounded" to this particular bodily composition, in terms of persons, planets, solar systems, galaxies, superclusters, etc.?

I understand Krauss to be arguing something to the effect that space must RESULT from fluctuations in the quantum gravitational field... but isn't this "quantum foam" itself an ultra-microscopic region of space? Doesn't he just mean that space can be inflated and produce matter from prior energy?