A comet is a lump of rock and ice. Spacecraft have flown by comets. A comet only has a tail when it is near the sun. Most comets come from the Kuiper belt. A comet has actually been witnessed hitting a planet. Most comets have short orbital periods.
A comet is a tiny, frozen entity in the Solar System that heats up and starts to emit gases as it approaches the Sun. This process is known as outgassing. This results in an apparent atmosphere or coma, and occasionally a tail as well. These occurrences are caused by how the solar wind and solar radiation interact with the comet's nucleus.
The size of comet nuclei varies between a few hundred meters and tens of kilometers, and they are made up of loose clumps of ice, dust, and tiny rocky particles. A comet's orbit is typically very eccentric and elliptical, and its orbital period can range from a few years to possibly millions of years.
Learn more about Kuiper Belt here:
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<span>Scientists choose where are units of time began and ended based on major changes in life forms at certain times</span>
Answer:
the earth surface is constantly changing from force in nature the daily process of precipitation wind and land moments result in changes to landforms over a long period of time driving forces into rows and volcanoes and earthquakes people also contribute to changes in the appearance of land
