# Gold price at near speed of light **URL:** \ **Category:** Factual Questions\ **Created:** [November 14, 2018, 2:32pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502 "2018-11-14T14:32:09Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![virtually\_yours](https://avatars.discourse-cdn.com/v4/letter/v/a587f6/32.png) [@virtually\_yours](https://boards.straightdope.com/u/virtually_yours)\ **Post date:** [November 14, 2018, 2:32pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/1 "2018-11-14T14:32:09Z")
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 ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [November 14, 2018, 2:33pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/2 "2018-11-14T14:33:55Z")
I assume that this is a whoosh and not a serious question. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [November 14, 2018, 2:34pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/3 "2018-11-14T14:34:43Z")
If you can figure out how to accelerate to close to the speed of light cheaper than gold, than, go for it! ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [November 14, 2018, 2:37pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/4 "2018-11-14T14:37:05Z")
The mass does not increase in any sense relevant to selling and buying the gold. ---
**Author:** ![virtually\_yours](https://avatars.discourse-cdn.com/v4/letter/v/a587f6/32.png) [@virtually\_yours](https://boards.straightdope.com/u/virtually_yours)\ **Post date:** [November 14, 2018, 2:41pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/5 "2018-11-14T14:41:40Z")
> [@bob\_2](#): > > I assume that this is a whoosh and not a serious question. 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 ---
**Author:** ![virtually\_yours](https://avatars.discourse-cdn.com/v4/letter/v/a587f6/32.png) [@virtually\_yours](https://boards.straightdope.com/u/virtually_yours)\ **Post date:** [November 14, 2018, 2:45pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/6 "2018-11-14T14:45:34Z")
> [@naita](#): > > The mass does not increase in any sense relevant to selling and buying the gold. 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 ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [November 14, 2018, 2:49pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/7 "2018-11-14T14:49:43Z")
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. ---
**Author:** ![virtually\_yours](https://avatars.discourse-cdn.com/v4/letter/v/a587f6/32.png) [@virtually\_yours](https://boards.straightdope.com/u/virtually_yours)\ **Post date:** [November 14, 2018, 2:54pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/8 "2018-11-14T14:54:33Z")
> [@Grey](#): > > 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 ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [November 14, 2018, 2:54pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/9 "2018-11-14T14:54:54Z")
> [@virtually\_yours](#): > > So the extra weight is just ignored? 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. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [November 14, 2018, 3:29pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/10 "2018-11-14T15:29:13Z")
> [@Grey](#): > > 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. 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. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [November 14, 2018, 3:40pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/11 "2018-11-14T15:40:30Z")
“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. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [November 14, 2018, 3:45pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/12 "2018-11-14T15:45:16Z")
From Einstein’s paper, showing it is a base assumption Source: Relativity: The Special and General Theory © 1920 > [@](#): > > A satisfactory interpretation can be obtained only if we recognise the following fact : The same quality of a body manifests itself according to circumstances as " inertia " or as " weight " (lit. " heaviness '). ---
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [November 14, 2018, 3:47pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/13 "2018-11-14T15:47:52Z")
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. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [November 14, 2018, 3:49pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/14 "2018-11-14T15:49:09Z")
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. ---
**Author:** ![Ravenman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ravenman/32/2929_2.png) [@Ravenman](https://boards.straightdope.com/u/Ravenman)\ **Post date:** [November 14, 2018, 3:50pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/15 "2018-11-14T15:50:40Z")
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. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [November 14, 2018, 3:57pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/16 "2018-11-14T15:57:04Z")
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.) > [@rat\_avatar](#): > > 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. Interesting. Thanks. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [November 14, 2018, 3:59pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/17 "2018-11-14T15:59:49Z")
> [@rat\_avatar](#): > > “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. Here is an other quote from Einstein against using “relativistic mass”, from Wikipedia’s bit about relativistic mass: > [@](#): > > Einstein never derived an equation for “relativistic mass”, and in later years he expressed his dislike of the idea: > > _It is not good to introduce the concept of the mass [relativistic mass formula] of a moving body for which no clear definition can be given. It is better to introduce no other mass concept than the ’rest mass’ m. Instead of introducing M it is better to mention the expression for the momentum and energy of a body in motion._ 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. ---
**Author:** ![Isosleepy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/isosleepy/32/479_2.png) [@Isosleepy](https://boards.straightdope.com/u/Isosleepy)\ **Post date:** [November 14, 2018, 4:20pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/18 "2018-11-14T16:20:02Z")
“Larry’s we-buy-gold, good morning” ‘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!” ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [November 14, 2018, 4:27pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/19 "2018-11-14T16:27:31Z")
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. > [@](#): > > The definitions of the base units of the SI were adopted in a context that takes no account of relativistic effects. When such account is taken, **it is clear that the definitions apply only in a small spatial domain sharing the motion of the standards that realize them**. These units are known as proper units; they are realized from local experiments in which the relativistic effects that need to be taken into account are those of special relativity. The constants of physics are local quantities with their values expressed in proper units. [https://www.bipm.org/en/publications/si-brochure/section1-5.html](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. ---
**Author:** ![Slash1972](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slash1972/32/6461_2.png) [@Slash1972](https://boards.straightdope.com/u/Slash1972)\ **Post date:** [November 14, 2018, 4:39pm UTC](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502/20 "2018-11-14T16:39:28Z")
If mass doesn’t increase, what is it that prevents one from approaching the speed of light then? [Next page](https://boards.straightdope.com/t/gold-price-at-near-speed-of-light/824502.md?page=2)