Not 2000 Kg, we’re talking 200 THOUSAND Kg. You’re off by a factor of 1000.
To put this in perspective, an adult bull African elephant tops out at about 6000 Kg, so we’re looking at rolling around the equivalent of 36 large elephants.
He was talking about the silver sphere, which is about 2000kg, and should roll on a reasonably strong floor. Moving the copper sphere is going to take heavy lifting equipment.
Probably simpler to bring the foundry to site and cast the thing in situ.
At least he didn’t ask about aluminum - about 1/3 the price of copper, and less than 1/3 the density. 3 times the weight, around 10 times the volume, for a sphere a bit more than twice the diameter.
Good thing the guy’s rich. We’re gonna need a bigger house for that one. 25 foot ceilings are tall even for hotel lobbies.
The million is only the face value, though (not that face value means a whole lot for a non-circulating ‘because we fucking can, that’s why’ display item). The actual value of the gold in the coin (100kg of 99.9999% pure gold) is actually closer to 2.5 million (though it was probably closer to the face when it was struck a few years ago).
Judging from that coin, the 5’ (and 100lb) ball sounds about right for the gold.
Gotcha. The silver sphere is like a smallish female elephant, more plausible. 
2000kg is pretty much the weight of a big pickup truck.
On a hard floor the rolling resistance of a smooth sphere will be a lot less than the rolling resistance of 4 rubber pickup tires with brakes slightly dragging, differentials turning, etc.
Two ordinary guys can readily push a pickup. One strong guy can push it a little ways.
For that one we may have to just make an array of 8 12 foot spheres, or even 64 6 foot ones, we wouldn’t want to to be *too * ostentatious after all
That would make a damned expensive cannon ball.
@Wolfman: Here’s a picture of a large aluminum sphere in a large house: https://en.wikipedia.org/wiki/…
Looks nice to me; a bunch of smaller ones would be so low-class by comparison. 
If I did go mad and suddenly want a 200 ton copper sphere, are there many places that could make one? I know that there’s foundries that that can press iron structures of that order weight-wise, but a sphere?
Just get a lot of copper really hot and roll it around while it cools. That’s how I make a sphere from Play-Doh.
Ohh sure. The naysayers and single giant metal sphere purists will take their shots now , but the tables will turn when I realize my hour-and-a-half-long dream of making a rolling ball clock…
out of 64 6 foot solid aluminum spheres!
Would a $1million sphere of Plutonium 238 or U235 be critical? I’m too lazy to look things up and do maths.
Cursory googling suggest that the price of plutonium is in the ballpark of $4000/g, so one million dollars would get us a couple of hundred grams, I doubt [sup]235[/sup]U would be much cheaper.
According to wikipedia, critical mass of [sup]238[/sup]Pu is 9-10 kg, and 52 kg for [sup]235[/sup]U.
So $1M would get us nowhere close to critical.
In other words, mounting the silver or copper on the wall ain’t gonna happen.
I’m sure you could charge admission to let people watch it in action. I know I’d gladly pay. That’d be so cool!
Noisy too. Big meaty clunks from the 24" cross-section wooden beams and the umpteen hundred pound balls.
[ul][li]Forging temperature of copper: 900 C[]Temperature change from room temperature: ≈ 880 C[]Specific heat of copper: 385 J/kg/°C[*]Amount of energy required to get this ball up to said temperature: Q = m c ∆T = 7.34 x 10[sup]10[/sup] joules ≈ 20 mega-watt hours.[/ul][/li]For reference, this is about double the average monthly household energy usage in the US. So you’re going to have a pretty big electric bill that month.
A semi can carry about 22 tons. That copper ball is about 239 tons. What kind of heavy lifting equipment can move that?