Video Experimental Relacionado
Updated: Aug 10, 2026
07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
La nucleosíntesis del Big Bang y la densidad bariónica del universo
C J Copi1, D N Schramm, M S Turner
1Department of Physics, University of Chicago, IL 60637-1433.
Science (New York, N.Y.)
|January 13, 1995
Resumen
Las predicciones de la nucleosíntesis del Big Bang confirman el modelo de cosmología estándar al hacer coincidir las abundancias observadas de elementos ligeros. Esto determina con precisión la densidad bariónica, destacando el rompecabezas de la materia oscura.
Área de la Ciencia:
- Cosmología Cosmología.
- La astrofísica nuclear es una astrofísica nuclear.
- Física de las partículas Física de las partículas
Sus antecedentes:
- El modelo del Big Bang es el marco cosmológico predominante.
- La nucleosíntesis del Big Bang (BBN) describe la formación de elementos ligeros en el universo temprano.
- Probar las predicciones de BBN con las abundancias observadas valida los modelos cosmológicos.
Objetivo del estudio:
- Para probar el modelo estándar del Big Bang utilizando predicciones BBN.
- Para determinar con precisión la densidad bariónica del universo.
- Para investigar las implicaciones para la materia oscura.
Principales métodos:
- Comparación de las abundancias pronosticadas de los elementos ligeros (Deuterio, Helio-3, Helio-4, Litio-7) con los datos de observación.
- Utilizando la teoría BBN para restringir los parámetros cosmológicos.
Principales resultados:
- Fuerte acuerdo entre las abundancias de elementos ligeros predichas y observadas.
- Determinación precisa de la densidad bariónica: de 1,7 x 10^-31 a 4,1 x 10^-31 g/cm^3 (1-15% de la densidad crítica).
Conclusiones:
- El modelo cosmológico estándar es confirmado por las observaciones de BBN.
- La mayoría de los bariones parecen ser oscuros.
- Si la densidad de masa total excede el 15% de la densidad crítica, se indica la materia oscura no bariónica.
Más Videos Relacionados
14:11Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis
Published on: March 29, 2016
10:57Mapping Absolute DNA Density in Cell Nuclei using Single-molecule Localization Microscopy
Published on: November 11, 2025
Videos de Conceptos Relacionados
01:52Atomic Mass
Atoms — and the protons, neutrons, and electrons that compose them — are extremely small. For example, a carbon atom weighs less than 2 × 10−23 g. When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the atomic mass unit (amu). The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which are...
03:18Radioactivity and Nuclear Equations
Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for hydrogen, neutrons. The number of protons in the nucleus is called the atomic number (Z) of the element, and the sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are isotopes of the same element.
A nuclide of an element has a specific number of protons and...
A nuclide of an element has a specific number of protons and...
03:18Nuclear Stability
Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together in the...
To hold positively charged protons together in the...
02:13Nuclear Binding Energy
The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect indicates a “loss” in mass of 4.0331 amu – 4.0026 amu = 0.0305 amu. The loss in mass accompanying the formation of an atom from protons, neutrons, and electrons is due to the conversion of that mass into energy that is evolved as the atom forms. The nuclear binding energy is the energy produced when the atoms’ nucleons are bound together;...
01:10Detection of Black Holes
Although black holes were theoretically postulated in the 1920s, they remained outside the domain of observational astronomy until the 1970s.
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.