Speed can only be zero, not negative.

 

Speed is the measure of how much an object is moving - it's the same with heat, you can only go down to 0K, you can't have "negative" temperature because the atoms are either moving or they're not.

 

Photons are the fastest things that can move.

 

Everything else is dragged slower by the Higgs field, which gives it the property of "mass".

 

Photons are not affected by the Higgs field, which is why they can move so fast. Everything else is subject to the influence of the Higgs field.

Oops! Double post by mistake.

Speed is the measure of how much an object is moving - it's the same with heat' date=' you can only go down to 0K, you can't have "negative" temperature because the atoms are either moving or they're not.

[/quote']

 

 

Negative temperature does have meaning in atomic electron-state descriptions, though it is not an equilibrium condition.

Really? Ah, it would seem my knowledge is a little out-of-date...

 

I hate that.

Really? Ah' date=' it would seem my knowledge is a little out-of-date...

 

I hate that. [/quote']

 

 

Population inversions, for example. You naturally get some atoms in excited states depending on their temperature. Something like [math]N_2/N_1 = e^{-(E_2-E_1)/kT}[/math] (for a two-state system)

 

But if you invert the populations by some means, T must be negative. As I said, it's a non-equilibrium condition, but it does have meaning in the right context.

"negative" velocity would just be travelling in the opposite direction of whatever you consider "positive" velocity.

"negative" velocity would just be travelling in the opposite direction of whatever you consider "positive" velocity.

Speed, however, will not be negative since it has no direction.