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Because if the Sun expands to 1 AU or very close to it, its density and hold on outer layers will be much weaker so a dense object like the Earth can slowly absorb material because Earth would be much denser than the outermost regions and would the Earth become a gas giant from it?Would there be some iron in the outermost regions of the expanded sun which when falling onto Earth make the inner core bigger?

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    $\begingroup$ The Sun will not become a red giant for more than 7 billion years. $\endgroup$
    – ProfRob
    Commented Mar 30 at 0:57

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The opposite. The Earth orbits at 30 km/s. The Sun's material would not have comparable net rotation, so the Earth would be subjected to a 30 km/s wind. This wind would easily strip off the Earth's atmosphere, and it would continue to strip any of the Sun's gas that got temporarily captured by the Earth.

Even without the wind, the temperature would likely be far too high for any gas to remain bound to the Earth, because the thermal velocities would exceed the Earth's escape velocity.

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    $\begingroup$ Would a solar expansion to 1AU put enough resistance on earth that it would start to slow down and spiral into the sun? $\endgroup$
    – Questor
    Commented Mar 30 at 0:07
  • $\begingroup$ Wouldn't the Earth's magnetic field cause the solar wind to strike the Earth directly causing Northern Lights instead of strip away the Earth's atmosphere? $\endgroup$ Commented Mar 30 at 11:23
  • $\begingroup$ @RussellHankins It depends on how much wind there is. Particles trapped in a magnetic field exert their own magnetic field in the opposite direction. With enough charged particles, the Earth's magnetic field would be completely counteracted. $\endgroup$
    – Sten
    Commented Mar 30 at 16:25
  • $\begingroup$ @Questor Indeed, the earth would slow down gradually and, given enough time, sink into the sun. Not my field but, last I heard, this is the expected outcome. $\endgroup$
    – Sten
    Commented Mar 30 at 16:27
  • $\begingroup$ The speed of the wind is not the crucial issue here. The present solar wind speed is a lot higher (several hundred km/sec). It is its density that would make all the difference (not to mention the vastly increased radiation intensity) $\endgroup$
    – Thomas
    Commented Apr 7 at 17:37
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Funny you say that. Basically, No. Actually the literal opposite will happen.

As others have said, the wind caused by the expansion of the sun will be so incredibly fast (30 kilometers per second) that all gasses will be stripped away from our planet. The heat will also strip all of the gasses because of the thermal velocity being higher than earth's escape velocity. After that all happens, the sun will slowly slow it down before the planet corkscrews into the sun.

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  • $\begingroup$ Wouldn't a significant portion of the mass be in mars's orbit and jupiter's orbit?So the Earth once it expands back into a bigger orbit can absorb some of the mass. So maybe 3 Earths worth of hydrogen. So it will still gain mass right? $\endgroup$ Commented Apr 4 at 1:17
  • $\begingroup$ @MiltonTheMeme That'd be a good thing to do more research on. I didn't think of that, nice thought. :-) $\endgroup$ Commented Apr 4 at 16:48
  • $\begingroup$ The speed of the wind is not the crucial issue here. The present solar wind speed is a lot higher (several hundred km/sec). It is its density that would make all the difference (not to mention the vastly increased radiation intensity). $\endgroup$
    – Thomas
    Commented Apr 7 at 17:38

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