Questions about Big Bang Theory

[Ariphaos]

He means the size of mercury's orbit, not physically near the path of mercury. It takes increasingly large particle accelerators to achieve the kinds of event power to peer back into the kind of fine mish-mash of energy at those times.

Yar. Eventually, superconducting coils reach a feasible limit in their strength - currently about 30 Tesla but I've seen papers about various materials being in the ~140 Tesla range. Past that the needed length goes up linearly with relativistic momentum, which at the insane velocities we are speaking of, is nearly linear with energy.

So we could build a Pevatron on Earth, and an Evatron in the Clark orbit, but a zevatron would be required for probing the low end of where the inflaton is expected to appear (10^12 GeV) by some papers. I put it at the orbit of Mercury (in the latest revision of my sci-fi setting) because you can use photon pressure at that distance to stabilize it.

I don't quite understand this. How can a point object like a singularity be everywhere? Did it stop being a singularity the moment space became greater than zero size, or was it "smeared-out" in some fashion by quantum effects? Or something else?

A singularity is not necessarily point-like. In rotating black holes (ie, all of them), the singularity is a ring. The singularity refers to the mathematical singularity - a point or region where a number gets listed as 'infinity'. It does not need to be a single point in hyperspace or whatever existed during the planck epoch.

Kuroneko's point was that the Universe is expanding, but not into pre-existing space, the way a time-reversed black hole would describe it. Whereas for our purposes, the Big Bang occurred and is occurring everywhere.

[Surlethe]

Xeriar is right in that one can think of Big Bang expansion as qualitatively similar to a time-reversed black hole, although there are differences, one of which is that the Big Bang singularity occurs everywhere.

I don't quite understand this. How can a point object like a singularity be everywhere? Did it stop being a singularity the moment space became greater than zero size, or was it "smeared-out" in some fashion by quantum effects? Or something else?

I suppose you could put it like this: if you can find a point in space where the Big Bang didn't occur, then the singularity wouldn't be everywhere.

[Broomstick]

It is an interesting fact that you can actually observe evidence of the Big Bang with common household appliances. It's easiest to find with older, analog tuners, but some of the static in between stations on radio and TV is actually of Big Bang origin. In fact, it was a couple of guys trying to get to adjust an antenna for radio astronomy and satellite communication experiments who came up with the first proof of the ubiquitous background radiation that is yet another piece of direct evidence of the Big Bang (Penzias and Wilson at Bell Telephone Labs in New Jersey, 1965, for which they receive the 1978 Nobel Prize). Of course, the Big Bang static is mixed in with a lot of static of other origin as well, but I still find it a neat concept.

[Surlethe]

Speaking of the cosmic microwave background radiation, can you model it as the inside of a blackbody? That is, standing waves of constant energy whose energy density gets "smeared out" as the universe expands, so the wavelength increases?

[Ariphaos]

Speaking of the cosmic microwave background radiation, can you model it as the inside of a blackbody? That is, standing waves of constant energy whose energy density gets "smeared out" as the universe expands, so the wavelength increases?

I'm not sure what you mean, AFAIK the cmb is the most perfect blackbody known, to an absolutely insane precision.

[Twoyboy]

Please correct me if I'm wrong but does big bang theory not require the existance of so called "dark matter", followed by "dark energy" and now "dark flows".

This appeared to get lost in the confusion. I'd just like to point out that these things are NOT required by Big Bang theory, they are required to explain current observations. Even if we dumped Big Bang theory, these are our best explanation to what we are now observing in the universe. So it's a bit of a red herring.

Penzias and Wilson at Bell Telephone Labs in New Jersey, 1965, for which they receive the 1978 Nobel Prize

Completely off topic, this is a funny story because apparently they were told the erratic signal was coming from pigeon crap on the satellite dish. The cleaned it off, and the background radiation was still there. The in-joke was they got a Nobel prize for discerning the difference between pigeon shit and the start of the universe.

[Kanastrous]

The in-joke was they got a Nobel prize for discerning the difference between pigeon shit and the start of the universe.

They deserved it.

Consider the billions of people who demonstrate every weekend, that they can't distinguish between pigeon shit, and the actual start of the universe...

[Surlethe]

Speaking of the cosmic microwave background radiation, can you model it as the inside of a blackbody? That is, standing waves of constant energy whose energy density gets "smeared out" as the universe expands, so the wavelength increases?

I'm not sure what you mean, AFAIK the cmb is the most perfect blackbody known, to an absolutely insane precision.

Yes, the CMBR is a perfect blackbody. I meant, can you predict experiment by modeling the CMBR as standing waves of radiation the length of the universe?

[JGregory32]

Followup question, if space time can expand as it did in the big bang event that could it also not contract? Would this contraction then establish conditions much like they were before the expansion? Could we be looking at a constant process of expansion and contraction?

[Surlethe]

Followup question, if space time can expand as it did in the big bang event that could it also not contract? Would this contraction then establish conditions much like they were before the expansion? Could we be looking at a constant process of expansion and contraction?

That's a model that's generally not accepted. Whether space begins to contract depends on the average energy density of the universe; if it is above a certain parameter, it will eventually contract into another singularity (and explode again?); if it is below the parameter, it will continue to accelerate its expansion. And if it is equal to the parameter, it will be pretty much flat forever. Current observations indicate that the energy density is significantly below the parameter: the universe's expansion is accelerating even as we speak.

[starslayer]

Surlethe is correct except for one small nitpick; a flat universe (Ω=1) still expands forever, but the rate of expansion asymptotically goes to zero.