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01:50Global Climate Change
Throughout its ~4.5 billion year history, the Earth has experienced periods of warming and cooling. However, the current drastic increase in global temperatures is well outside of the Earth’s cyclic norms, and evidence for human-caused global climate change is compelling. Paleoclimatology, the study of ancient climate conditions, provides ample evidence for human-caused global climate change by comparing recent conditions with those in the past.
02:06Conditions on Early Earth
Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.
02:06Conditions on Early Earth
Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.
01:06Tidal Forces
The origin of Earth's ocean tides has been a subject of continuous investigation for over 2000 years. However, the work of Newton is considered to be the beginning of the proper understanding of the phenomenon. Ocean tides are the result of gravitational tidal forces. These same tidal forces are present in any astronomical body; they are responsible for the internal heat that creates the volcanic activity on Io, one of Jupiter's moons, and the breakup of stars that get too close to black holes.
02:45Biological Clocks and Seasonal Responses
The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. The period of light-exposure is called the photoperiod.
02:56The Fossil Record
The fossil record documents only a small fraction of all organisms that have ever inhabited Earth. Fossilization is a rare process, and most organisms never become fossils. Moreover, the fossil record only exhibits fossils that have been discovered. Nevertheless, sedimentary rock fossils of long-lived, abundant, hard-bodied organisms dominate the fossil record. These fossils offer valuable information, such as an organism's physical form, behavior, and age. Studying the fossil record helps...
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Updated: Jul 12, 2026
11:34
Scattering And Absorption of Light in Planetary Regoliths
Published on: July 1, 2019
Ritmos geológicos y impactos cometarios.
Science (New York, N.Y.)
|December 21, 1984
Resumen
Los impactos periódicos de cometas, que ocurren cada 33 y 260 millones de años, se correlacionan con trastornos geológicos y biológicos. Estos ciclos sugieren influencias extraterrestres en la evolución de la Tierra y el tectonismo.
Área de la Ciencia:
- Geología Geología Geología.
- Paleontología Paleontología.
- La astronomía es la astronomía.
Sus antecedentes:
- El Eón Fanerozoico está marcado por importantes eventos geológicos y biológicos.
- Comprender los ciclos a largo plazo en la historia de la Tierra es crucial para los estudios evolutivos y geológicos.
Objetivo del estudio:
- Identificar y analizar las periodicidades en los trastornos geológicos y biológicos durante el Eón Fanerozoico.
- Para investigar el vínculo potencial entre estas periodicidades y los fenómenos extraterrestres, específicamente los impactos de cometas.
Principales métodos:
- Análisis de series temporales de datos de trastornos geológicos y biológicos del Eón Fanerozoico.
- Comparación de las periodicidades identificadas con los ciclos de cráteres de impacto en la Tierra.
Principales resultados:
- Se identificaron dos periodicidades dominantes y estables a largo plazo: aproximadamente 33 +/- 3 millones de años y 260 +/- 25 millones de años.
- Estos ciclos coinciden estrechamente con los períodos y fases del registro de cráteres de impacto de la Tierra.
- Los hallazgos sugieren una fuerte correlación entre los impactos periódicos de cometas y el tectonismo global y la evolución biológica.
Conclusiones:
- Los impactos periódicos de cometas son un factor significativo que influye en la historia geológica y biológica de la Tierra.
- Los ciclos observados de 33 y 260 millones de años pueden originarse de las interacciones del sistema solar con las nubes interestelares durante su órbita galáctica.