Question

what happen if earth's core become cold suddenly ?

Answer 1

The core and the mantle are a super heated semi liquid made of iron cobalt magnesium silicon manganese aluminum and other such heavy elements' combination.  Due to the rotation of the earth this fluid too rotates amid in a different rate . This rotation gives rise to the magnetic field which shields our earth from harmful charged radiations from sun n outer space.

Now if this core goes cold the fluid will become solid and would no longer flow. If it stops flowing the magnetic field vanishes.  And the charged radiations will

Blow away our atmosphere.

Cause devastation static discharges

Ionise our bodies and that of other life forms simply killing us.