- #1
b_dobro
- 9
- 0
Wouldn't the Doppler effect stop us from seeing the beginning of the universe unless it starts approaching us? (or unless the universe stops expanding and begins retracting?)
b_dobro said:Wouldn't the Doppler effect stop us from seeing the beginning of the universe unless it starts approaching us? (or unless the universe stops expanding and begins retracting?)
Fredrik said:Since that's the oldest light around, there's no light that's redshifted more. So light from e.g. the oldest stars must be redshifted by a factor that's less than 1100. (Probably much less, but I don't know how much).
b_dobro said:I see...that is some mind-boggling stuff.
What makes something opaque?
In this case, the answer is "charged particles", and in particular "electrons". The universe was so hot and dense back then that atoms couldn't exist for very long. If an electron and a proton combined to form a hydrogen atom, it was very likely that a collision with something else would smash the atom to pieces very soon. Because of that, there were plenty of free electrons flying around, and photons (light) interacts with electrons. The free electrons absorbed most of the photons, but the universe kept expanding and cooling, and after a while it was cold enough for atoms to stay intact much longer. That made the universe transparent because atoms are electrically neutral and therefore much less likely to absorb low-energy photons. High-energy photons would still interact with the component particles of the atom, but the photons with lower energy would just see the atoms as neutral particles with irrelevant internal structure and therefore not interact too much with them.b_dobro said:What makes something opaque?
The sun is mostly just hydrogen gas. Hydrogen is normally transparent. The reason we cannot see into the inner bowells of the sun is because the outer layer is hot, like 6000 kelvin, and partly ionized. So it scatters visible wavelength light like crazy and any light that did get thru would have been scattered so many times on the way that it would be totally randomized.
About sixty-five (65) nuclear physicists at Brookhaven National Laboratory, the Thomas Jefferson National Accelerator Facility and several other leading research facilities and universities around the world, including MIT, have cautiously confirmed strongly repulsive forces between neutrons.
This probably marks the end of the standard model of Hydrogen-filled stars.
In the spring semester of 2000 five graduate students (Cynthia Bolon, Shelonda Finch, Daniel Ragland, Matthew Seelke and Bing Zhang) and I made this three-dimensional (3-D) plot of the rest masses of the 3,000 different types of atoms that constitute all visible matter in the universe:
http://www.omatumr.com/Data/2000Data.htm
This "Cradle of the Nuclides" showed that neutron-proton interactions are attractive, unlike proton-proton and neutron-neutron interactions [1], and exposed repulsive forces between neutrons as the energy source that powers the Sun, ordinary stars, neutron stars, and the cosmos [2-10].
In this new report from Brookhaven National Laboratory [11] on collisions between two heavy nuclei, four nuclear physicists report that:
A. Nucleons "repel each other strongly" at close distances.
B. "In nature there exists another way to create dense nuclear matter by using another force to overcome the strong inter-nucleon repulsion at short distances. Neutron stars . . . . . This dense nuclear matter is created by the large gravitational force, which adds the necessary compression."
C. "The difference between neutron-proton and neutron-neutron or proton-proton pairs is due to the nature of the nucleon-nucleon interaction. The tensor force in the neutron-proton interaction, which is missing in the neutron-neutron or proton-proton interaction, is probably what creates the difference between cold dense matter of nucleons of the same kind, and cold dense matter of mixed nucleons."
D. "These surprising new results were confirmed in a higher-precision experiment completed recently at Jefferson Laboratory in Virginia."
The results of measurements at Jefferson Laboratory involving collisions between electrons and the Carbon-12 nucleus were recently published in the 13 June 2008 issue of Science magazine [12].
This paper stresses the high number of neutron-proton pairs in Carbon-12 from attractive neutron-proton interactions.
The importance of these results for astrophysics is stated in the last sentence of the abstract: "This difference between the types of pairs is due to the nature of the strong force and has implications for understanding cold dense nuclear systems such as neutron stars."
Fredrik said:Edit: Man I'm slow...I started writing this before Marcus posted his answer (but I also left the computer for a while during that time).
b_dobro said:Alright it's official; I'm in way over my head.
I think I'll focus on the basics before trying to understand the news from deep space. I should mention I've only done 2 university level physics courses, but it can't hurt to explore the leading edge of physics. Thanks again for the answers & links, they've been very useful. I'll try not to jump to conclusions in the future.
The Big Bang theory is a scientific model that explains the origin of the universe. It states that the universe began as a hot, dense singularity and has been expanding and cooling over billions of years.
The exact cause of the Big Bang is still unknown, but it is believed to have been triggered by a rapid expansion of space and time, known as inflation. This led to the formation of subatomic particles, which eventually evolved into atoms and molecules.
Scientists use various techniques, such as the Doppler effect, to observe the beginning of the universe. The Doppler effect is the change in frequency of light or sound waves as an object moves towards or away from an observer. By studying the light emitted from distant galaxies, scientists can determine the speed at which they are moving away from us, which provides evidence for the expansion of the universe and the Big Bang.
Some of the key pieces of evidence that support the Big Bang theory include the cosmic microwave background radiation, the abundance of light elements, and the expanding universe. These observations are consistent with the predictions of the Big Bang model and provide strong evidence for its validity.
The Doppler effect is an important tool for understanding the expansion of the universe and the Big Bang theory. By measuring the redshift of light from distant galaxies, we can determine the speed at which they are moving away from us and how the universe has been expanding over time. This supports the idea that the universe originated from a single point and has been expanding ever since.