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Saturday, August 9, 2014

Levitating Hot Body

Is it possible that a hot body levitate,  since the gravity it produces is opposite to that of Earth's.

For this construct to lift,

MgT(M+m)g>0

We assume a linear temperature profile,

T=Tmax(1xd)

and a log squared space density profile,

ds(T)=(dTmaxdn)ln(1T2max)ln(1T2(x))+dn

ds(T)=(dTmaxdn)ln(1T2max)ln(1T2max(1xd)2)+dn

ds(T)=(dTmaxdn)ln(T2max)ln(T2max(1xd)2)+dn

ds(T)=(dTmaxdn)ln(T2max)(ln(T2max)+ln((1xd)2))+dn}

d(ds(T))dx=(dTmaxdn)ln(T2max)(1(1xd)22d(1xd))

d(ds(T))dx=(dTmaxdn)ln(T2max)(2(dx))

And we have,

gT=GTxo(dndTmax)(dTmaxdn)ln(T2max)(2(dx))

gT=2GTxoln(T2max)1(dx)

Therefore,  at  x=0,

M2GTxoln(T2max)1d(M+m)g>0

From this equation we see that small  xo  (radius of body)  and small  d  provide for greater lift.  We shall now optimize  Tmax  for greater lift.

It seem odd that  gT  should be inversely proportional to  Tmax.  In free space where  Tmax  is allowed to fall over a  distance  x=L  to reach  T=0  increasing  Tmax  increases  L  but  ds  cannot fall below zero.  Δds=dn  remains fixed,  as such,

d(ds(x))dx=dnL    when we use a linear approximation, decreases with increasing  Tmax.  And so,  gT  decreases.

We can fix  L  by placing a cold body at distance  d  but still  Δds=dn  remains the same.

So in practice  Tmax  should be increased until  gT  and so lift is at a maximum and then no further.  At this point  Δds=dn  and cannot be increased further.