ABandOn
.:The Final Frontier:.
According to this lecture about the expansion of the universe after the Big Bang:
"Light from the Big Bang was seen in Holmdel New Jersey in 1968.
Arno Penzias and Bob Wilson were using a microwave antenna in a telecommunications experiment. They noticed a noise in their system. The noise came from radio waves sent out by the big bang. The radio waves had been traveling through space and time for 14 billion years.
The big bang started out very hot and very dense. It has been expanding and cooling ever since. 300,000 years after the big bang (one source says 500,000 years) the Universe cooled to 4000 kelvins. This is a very important temperature. Hydrogen atoms hotter than 4000 K collide with enough energy to ionize each other creating an opaque plasma. Below 4000 K the hydrogen can exist as neutral atoms a transparent gas. So, at the time when the plasma went away, the universe became clear, and the last photons emitted by the plasma could travel through space and time to reach us today.
The light emitted by a 4000 K plasma is orange. And yet when we look out into the vacuum of space between the stars we do not see orange light. As the orange light was traveling through the vacuum of space, the space itself was expanding and the wavelength of the light was stretching.
Since the time when the light was emitted, 300,000 years after the big bang, to now, 14 billion years later, the universe has expanded 1300 times in size, so the wavelength has stretched 1300 times. This stretches the wavelength of the orange light until it is in the microwave part of the electromagnetic spectrum. Human eyes cannot see microwaves, thus the sky looks black."
So, could it be 300,000 years after the Big Bang? This is called the "recombination era" and it seems that we couldn't have any instrumental proof of what happened before that date.
"Light from the Big Bang was seen in Holmdel New Jersey in 1968.
Arno Penzias and Bob Wilson were using a microwave antenna in a telecommunications experiment. They noticed a noise in their system. The noise came from radio waves sent out by the big bang. The radio waves had been traveling through space and time for 14 billion years.
The big bang started out very hot and very dense. It has been expanding and cooling ever since. 300,000 years after the big bang (one source says 500,000 years) the Universe cooled to 4000 kelvins. This is a very important temperature. Hydrogen atoms hotter than 4000 K collide with enough energy to ionize each other creating an opaque plasma. Below 4000 K the hydrogen can exist as neutral atoms a transparent gas. So, at the time when the plasma went away, the universe became clear, and the last photons emitted by the plasma could travel through space and time to reach us today.
The light emitted by a 4000 K plasma is orange. And yet when we look out into the vacuum of space between the stars we do not see orange light. As the orange light was traveling through the vacuum of space, the space itself was expanding and the wavelength of the light was stretching.
Since the time when the light was emitted, 300,000 years after the big bang, to now, 14 billion years later, the universe has expanded 1300 times in size, so the wavelength has stretched 1300 times. This stretches the wavelength of the orange light until it is in the microwave part of the electromagnetic spectrum. Human eyes cannot see microwaves, thus the sky looks black."
So, could it be 300,000 years after the Big Bang? This is called the "recombination era" and it seems that we couldn't have any instrumental proof of what happened before that date.
