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Member of Michio Kakus's organisation

  1. Feb 21, 2004 #1
    I am a member of Michio Kakus's organisation.Some days later i have ask this organisation a question about astrophysics and in reply they have told me to send this question in Michio Kaku's forum. As a member of the organisation i would like to ask you a question about astrophysics.If you give me a reply i will be very much obliged.In a serial of NATIONAL GEOGRAPHY they say that, after about 3 billion years the sun will expand and covers almost all the distance between the earth and sun.As a reult the earth will turn to magma due to excesive closelyness to sun.Now it is also said that this will happend due to the hydrogen of the sun will turn to helium.Here i found some problem,if the hydrogen of the sun will turn to helium then certainly there is some loss of mass in the sun,because some mass will turn to energy.Now if there is a reduction of mass then the attraction power of the sun will decrease.So the attraction to the earth will also decrease.So the earth will be situated in a bigger distance than the preasent and this will happen in same ratio of the reduction of mass.So if the sun covers the distance between sun and earth,then at that time the earth will be situated in much further distance,and the distance remain almost same and the radiomagnetic wave have to coverthe same distance.So how can they say that the earth will turn to magma after 3 billion years due to the reduction of distance.It may happen that the earth will be cooler than the preasent,because the power of the sun will decrease.
    Please give the answer of my question.
    Yours faithfully
  2. jcsd
  3. Feb 21, 2004 #2


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    what if the sun gets to be only a little bit
    less massive, while it becomes much bigger?

    The sun operates by converting hydrogen to helium (thermonuclear fusion deep inside it where the temperature and pressure are high enough). But when hydrogen fuses to form helium the decrease in mass is less than one percent

    So the sun, in several billion years, will be nearly the same mass,
    and have nearly the same gravity as it does today. It will be reduced in mass by less than one percent.
    This will not allow the size of the earth's orbit to change very much.

    The big change will be in the temperature and size of the sun, because of running out of the customary hydrogen fuel.
    We have seen this happening with other stars that have run out of their hydrogen. They swell up!

    What happens is, when there is no more hydrogen in the core of the star for it to fuse, the core contracts until the pressure and temperature conditions are so extreme that it it is able to fuse helium and convert it to carbon

    unfortunately once this helium-fusion begins, it happens at a somewhat faster rate than the star can normally accomodate (perhaps this resembles an
    attack of indigestion or fit of cholic in one of us) and the star swells up to an abnormal size

    Because we have seen the results of this bloating in other stars (like the one in the shoulder of the constellation Orion) we can reasonably expect it to happen to the sun.

    But it will not happen until the sun has finished consuming the hydrogen in its core and coverting that hydrogen to helium. Therefore we can expect several billion years of good behavior before this happens.

    best wishes

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