The curse of Elon Musk

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  • #51
But even if you manage to fulfil this requirement, there's still the small issue of getting it off the ground :smile:
Lead is dense not massive. So it won't be hard.
 
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  • #52
etotheipi
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Lead is dense not massive. So it won't be hard.
but lensing is proportional to mass... it might take up less volume, but you must still do the same amount of work (and in the case of lead - an awful lot!) to bring it away from Earth! I dare say there's a reason that no one has ever tried to build a rocket out of lead...
 
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but lensing is proportional to mass... it might take up less volume, but you must still do essentially the same amount of work to bring it away from Earth! I dare say there's a reason that no one has ever tried to build a rocket out of lead...
Lensing is not just proportial to mass it is proportional to the object's density as well.
If that was the case then gravitational lensing of a neutron star could be the same with the gravitational lensing of the sun.

But yes a rocket made of lead will be more massive and we would need extra energy to lift it up.
 
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  • #54
etotheipi
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Lensing is not just proportial to mass it is proportional to the object's density as well.
Well, mass is proportional to density, at constant volume, though Wikipedia states the dependency of the deflection angle ##\theta## explicitly with mass, as ##\theta = \frac{4GM}{rc^2}## if ##r## is the distance from the mass to the light.

But this is besides the point...
 
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  • #55
Ibix
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Lead has a density 1k times less than a neutron star so the effects are not neglible.
As I say, you need to run the numbers.

The angle of deflection for light passing a distance ##r## from an object of mass ##M## is ##\theta=\frac{4GM}{rc^2}##. The Hubble space telescope has a mass of around 11,000kg and an angular resolution of 1/20 arcsecond. Using Hubble's mass as a guide to what we can put into orbit and its angular resolution as a guide to the deflection we can detect, you would need all of that mass inside a radius of around 10-26m. Note that the Schwarzschild radius associated with 11,000kg is approximately three orders of magnitude greater than this.

A lump of lead isn't even close to producing detectable deflection of light.
 
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  • #56
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Lead has a density 1k times less than a neutron star so the effects are not neglible.
Wait, what? Did you confuse 1k (1000) with 10trillion (10000000000000)?
 
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  • #57
No I am pretty sure it is 1k.
 
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  • #58
Ibix
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No I am pretty sure it is 1k.
Please cite your sources for this claim.

Edit: While I'm waiting, nuclear diameters are of order 10-14m and atomic diameters of order 10-10m. Neutronium will, therefore, be around (104)3 times denser than ordinary matter.
 
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Please cite your sources for this claim.

Edit: While I'm waiting, nuclear diameters are of order 10-14m and atomic diameters of order 10-10. Neutronium will, therefore, be around (104)3 times denser than ordinary matter.
Ah yes it says white dwarfs not lead! Oups.
 
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Please cite your sources for this claim.

Edit: While I'm waiting, nuclear diameters are of order 10-14m and atomic diameters of order 10-10m. Neutronium will, therefore, be around (104)3 times denser than ordinary matter.
Well blame Leonard for this.Always blame Leonard.
 
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