What Happened Before the Big Bang?

The Bad Astronomer writes to tell us that a recent advance in Loop Quantum Gravity theory appears to allow the mathematics of cosmology to be extended to the time before the Universe underwent the Big Bang. Bad Astronomer also attempts to simplify things a bit with his own explanation of the new discovery.

Comments

There is no before the Big Bang.

[Ckwop]

I've always held that asking what came before the Big Bang is like asking what is North of the North Pole? It's a grammatically correct question but we can't expect it to mean anything.

While we don't have a working theory of quantum gravitation, we do have some strong hints that time and and space themselves were forged in the Big Bang. If you look at a Universe a Planck Length is size, the error in the time of any event observed would be longer than the time the Universe has existed for, to this point, and any error is position would be large than the current Universe at that size.

In short, time and space are useless measurements of a Universe this small.

In a very real sense, the Universe has always existed but has a finite age. I think once I came to understand what this really meant, it's very a beautiful truth about the world. I am sceptical of any theory that talks about a "before" the Big Bang - I think it misses one of the most important truths there is to know!

Simon

Re:There is no before the Big Bang.

[xPsi]

You are basically right on (IAAP). Here's my two cents into the thread:

There are are lots of different ways to understand the Heisenberg Uncertainty Principle physically -- most of them not very satisfying without acclimating to the lingo and concepts of quantum theory. Nevertheless, I think one can gain an intellectual foothold into the idea, before even digging into the quantum theory, by realizing that ALL wave behavior (sound, water, radio, light, etc.) obeys something akin to a HUP. If you can get the basic idea down for sound or water waves, then you can start to build a conceptual bridge to matter waves. Since you are an EE, the conceptual underpinnings will probably look quite familiar.

Lots of mathematical qualifications aside, basically ALL waveforms can be represented by a sum of harmonic waves (pure sine and cosine functions). A single pure sine or cosine has a well defined frequency, wavelength, and wave velocity. However, in contrast, an arbitrary waveform does NOT have a single wavelength or frequency -- it has many, given by the distribution of sines and cosines that were used to construct it. A handy variable to use is called the wavenumber, which is basically the number of cycles per meter (proportional to 1/wavelength) of a harmonic wave. An interesting thing to do is plot a particular waveform, say a snapshot of a water wave shaped like a lump at a moment in time, and then also plot the distribution of wavenumbers from all the sines and cosines making up that lump. They are two representations of the same object. One looks like a water lump in space, and the other will look like another lump telling you the distribution of sines and cosines in "wavenumber space." What you find is that if your water lump in space is narrow, then it takes many sines and cosines of many wavenumbers to make that happen. If the water lump is very spread out, you only need a narrow range of wavenumbers of harmonic waves to make this happen. Many engineers are very familiar with this bandwidth effect in the context of transmission theory, but the same will be true for ANY waveform. It is a byproduct of wave theory: the width of the spatial distribution of an arbitrary wave is inversely related to the width of its wavenumber distribution. If you allow the wave to change in time, you get a similar inverse relation for the distribution of the wave in time and the distribution of frequencies in the wave. You are probably familiar with all that in the context of Fourier analysis etc. One says that wavenumber and position are "complimentary" (so are frequency and time).

The big leap in quantum mechanics is that the momentum of a particle is inversely related to the wavelength of some harmonic wave "associated with" the particle. The larger the momentum, the shorter the wavelength of the matter wave and vice versa. That is, momentum and position are complimentary variables. Keep in mind, the wave isn't the particle itself but rather tells you where the particle is likely to be. Once you accept the rather odd idea that momentum and wavelength are inversely related, *wave theory alone* tells you that the more likely a particle is to be at a particular location in space, the wider its distribution of wavenumbers is -- and thus the wider range of momenta it can have. Similarly, if you have a very narrow range of wavenumbers, the wider the spatial extent of the matter wave -- thus for a well defined momentum the particle has a wider range of spatial positions available to it. This is basically the heart of the Heisenberg Uncertainty Principle.

Since this matter wave tells you about probabilities, you need to prepare an ensemble of identical objects and do a statistical analysis of their positions and momenta to see the effect of the HUP. For example, lets say you prepare 100 particles each with a well defined position. Now you perform a position measurement followed by a momentum measurement for each particle. Taking your raw data, you made a plot of the number

Well, the last thing said before was...

[Critical Facilities]

"Hey guys, watch this"

You mean...

[grub]

"What Happened 6001 Years Ago?"
Fixed that for you.

Re:North of the North pole

[peragrin]

says the man who failed to understand the analogy.

you can not go north of the North Pole. Once you get to the north pole everything is quite literally south of you, no matter which way you go. If you leave the sphere in question(ie head into space) you no longer have a compass as the magentic field that the north pole is based on no longer exerts it's force on you.

What you think Astral(space) Navagation uses compasses for heading and bearing? That we can use the sun's magentic field t find our way across this planetary system?

Re:Easy

[elrous0]

Before the big bang? That was back when God was in college. He totally meant to create the universe--but he was having problems with his girlfriend, his parents were giving him all kinds of shit, his weed connection got busted by the cops, and his humanities professor was riding his ass about that late paper. He finally did get his shit together and did the whole "let there be light" thing, though. Hey, we've all been young, right?

Re:The punchline

[mhall119]

Just because something is testable means that God could not have played a role? No, being testable means that it doesn't matter whether or not God played a role.