# Gold price at near speed of light

Hi, (theoretically or otherwise and aside from the cost to get it up to that speed) if here on earth you accelerate a quantity of gold to near light speeds, the mass increases, so the weight would increase relative to earth gravity, would you then have more weight in gold and be richer, and could you cash in?
Then if you decelerated it back to nil, would it be a crime to keep the money?
virtually yours
Virtually Yours

I assume that this is a whoosh and not a serious question.

If you can figure out how to accelerate to close to the speed of light cheaper than gold, than, go for it!

The mass does not increase in any sense relevant to selling and buying the gold.

you can look at it how you want, but isn’t the dollar is based on gold locked away in fort Knox etc, no, probably never to be used? what is the difference if you hitch a bar of gold on a space ship going very fast, or centrifugal or other accelerator built for experiment purposes?
vy VY

So the extra weight is just ignored?
On the moon the gold does not weigh much, does it still have the same value?
If gold was found on the moon, would they have to bring it back to earth gravity to weigh it to price it or base the value on the weight on the moons gravity?
vy VY

1. Gold is not the basis of US currency value
2. Weight is not mass.
3. For those moving with the gold, the mass is at rest relative to them, so there is no additional “mass” to worry about.
1. ok.
2. I thought that the reason one can never reach the speed of light is because the mass increases which makes or at the same time the object becomes heavier and harder to accelerate to get to the speed of light.
3. ok
vy VY

There is no extra weight. If you put the gold on a scale it will weigh the same. Mass and weight are not the same thing. And observed mass is relative. If you and your buyer are traveling along with the gold, you will not notice any difference in mass.

Number 3 is the key.
If you are sitting there with a mass of gold, it “weighs” the same (by whatever means you choose to determine its mass) whether you are sitting on earth, the moon, or a spaceship doing 0.9c compared to the earth.

What relativity is saying is that as a mass whooshes by you at 0.9c you will see its effect on other masses (i.e. gravitational effect) as being much larger that it would be if the same mass at rest were nearby. Similarly, a person on a spaceship doing 0.9c would as they zip past the earth feel the gravitational effect of the earth (how it deflect the path) as if the earth were much more massive… which makes sense, time is slowed down from POV of , so the deflection of the ship’s trajectory appears much stronger in (apparent) slo-mo than in Newtonian time. The apparent increase in mass, decrease in length, and slowdown in time are a result of altered points of view.

“Relativistic Mass” as used in the OP is an artifact of a thought experiment and not a real effect.

The gamma factor changes but the intrinsic mass does not. Under GR inertial mass and gravitational mass are equivalent and in fact the entire theory depends on it so it is easy to get stuck in the traditional mass/weight confusion and this is why the whole concept of “relativistic mass” has been dropped in the field for a very long time.

From Einstein’s paper, showing it is a base assumption

Source: Relativity: The Special and General Theory © 1920

The idea that mass increases with speed is a analogy for thinking about relativity that tries to use our intuition about mass in every day life to help gain an understanding of how the equations of relativity work. Like all analogies it is imperfect. I believe that the concept of relativistic mass is falling out of favor because people feel it creates more confusion than understanding.

On a side note about where relativity does apply to gold.

Due to the specific type of orbitals, which allow the electron clouds do be tighter than in other substances, those electrons actually travel a significantly faster speed and undergo relativistic effects which result in the color of the material itself.

Gold would be silver in color if it wasn’t for the effects of relativity and it would also “weigh” less for a similar volume too.

I for one would pay money to buy a huge amount of gold moving at a speed that I cannot possibly possess it, or even perceive it. But it would not be very much money.

I think your best bet may be to weigh the gold while travelling in an elevator between the ground floor and top floor in a tall building. Do it in an Up elevator if you’re selling the gold; Down elevator if you’re buying. (This won’t work with ordinary balance scales.)

Interesting. Thanks.

Here is an other quote from Einstein against using “relativistic mass”, from Wikipedia’s bit about relativistic mass:

Mass is easier to grasp for many than momentum and energy, which is why relativistic mass still makes it into high school lessons, pop-sci and badly researched thought experiments.

‘Yes, hi, I got about half a kilo of gold, what’s it worth? Wanna buy it?”
“Depends. Is it coins, bar, jewellery?”
“It’s a Krugerrand!”
“yeah, they don’t come over 34 grams - not sure what you got th-“
“But mine’s on a spaceship! Going really realy quickly!”
“Well, bring it in, we’ll take a look at it”
“Zounds! Foiled again!”

With the problems of relativistic mass and not using the Lorentz factor it should also be noted that the SI system is also expressly defined now to indicate that these are only apply to local experiments.

https://www.bipm.org/en/publications/si-brochure/section1-5.html

(emphasis mine)

It is very problematic and complex to try and move these units past their useful domain.

If mass doesn’t increase, what is it that prevents one from approaching the speed of light then?