jee_c Creative Commons License 2007.09.15 0 0 3

"It has been estimated that 100,000 tonnes of extraterrestrial material reach the Earth's surface every year. It can be anything from fine dust to metallic masses weighing many tonnes."

Ennyi potyog le.


A veszteségekről: alapvetően az, hogy milyen gázokból áll a légkör azon is múlik, hogy mit tud a Föld az adott hőmérsékleten (molekula- sebesség!) megtartani.

Amit nem tud, a könnyű molekulákat, azok már megszöktek (lásd pl. H2, He2, ...). Ami megmaradt, biztos abból is van valami "kopás", de ez nagyon kis mértékű lehet. Ehh, megnézem ezt is.. :)

Na it ta pontos válasz a kérdésedre:


" Subject: Re: Gaining or Loosing
Answered By: willie-ga on 05 Nov 2002 05:25 PST
  Hello, and thanks for the question. According to Jeff Brown at Washington State University, several hundred tons of meteorites enter the Earth's atmosphere every day. The total amount per year can range from 10 million to 1 billion kilograms. A lot of this is just dust or micrometeorites, but it adds up. For example, let's say an average of 500 million kilograms a year has landed on Earth over the past 10,000 years. That's 5 trillion kilograms. Or 5 billion metric tons. That might seem like a lot, but the total mass of the Earth is over 5 x 1021 metric tons! (That's a 5 with 21 zeroes.) The Earth also loses mass in several ways. All the time, we're losing light elements, mostly hydrogen, from the atmosphere. In a study "PLANETARY SCIENCE:ON THE SOLAR WIND AND ATMOSPHERE EROSION" ( ) The author points out that " present the Earth loses matter at a rate of 1 to 3 kilograms per second, the rate and composition varying with solar cycle (sunspot cycle). Recent measurements (K. Seki et al, Science 291:1939 2001) suggest the rate is lower than this, but even with a net loss of 3 kilograms per second, it would take 50 billion years to deplete the Earth's atmosphere and at least another 15 trillion years to evacuate the oceans. For comparison, the total lifetime of the Sun is only approximately 10 billion years." Assuming the worst case from this study, say we lose 3kg/second. That works out at: 3*60secs*60mins*24hours*365.25days or 94,672,800 Kg/year So to answer your question, over long periods of time we gain more from "space dust" and asteroids than we lose from the escape of gases, but in some years it may be a net loss. But gas escape is not the only way we lose mass. Another way the Earth loses mass is through radioactive decay. The Earth's interior is peppered with radioactive elements such as uranium, thorium and potassium 40. These radioactive elements are mixed in with other rock. Granite, for example, can contain as much as four grams per ton of uranium and 13 grams per ton of thorium. As these radioactive elements decay, they give off heat and in the process of releasing this energy, the elements also lose mass. Gary Collins, who is a physicist at WSU, says …"it should be possible to figure out approximately how much mass is lost, but it would be a difficult calculation" Taken from: "Ask Dr Universe: The Big Questions" at ( ) And "space dust" and meteorites are not the only ways we gain mass. For one, Earth gains a tiny amount of mass from the "solar wind," the stream of charged particles from the Sun's corona. This varies wildly, as you’ll find from the NASA site on the solar wind here: "The Solar Wind" ( ) Hope that answers your question, but if you need clarification, just ask. willie-ga Google search used earth mass gain loss"


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