- #1
sumofprimes
- 8
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Hi all,
I've been dusting off the grey matter a bit, and have a question regarding an example I found used in both high school and university physics when broaching the topic of Special Relativity.
I do tend to ramble, and so I'll point you to my blog post at sumofprimes.blogspot.com/2008/04/relativistic-mass-in-introductory.html if you care to read the whole spiel. For those that don't wish to suffer, here it is more briefly stated:
Regardless of any other reasons that may prevent an object with mass from accelerating to the speed of light, the often-used argument that an infinite amount of fuel would be required seems inherently flawed -- this argument typically presents the apparent mass increase of an object that's accelerating (as observed from a stationary frame of reference), then proceeds with the reasoning that if the apparent mass is approaching infinity, then the amount of "fuel" required to continue acceleration would approach infinity, too. The main flaw with this line of reasoning appears to be that:
a.) if we assume that the object is carrying the fuel with it for the trip, then
b.) the observed mass of the carried fuel will increase proportionately with the increase in the mass of the accelerating object (and so, too, approach infinity)
So -- the static observer would see the mass of the system as a whole increase (m[observed] = m[rest]/(1-(v^2/c^2))^0.5), whereas the "traveler" would simply see "Ah, yup, 29,875kg of fuel left now..." -- a steadily decreasing amount of fuel as it was consumed.
I think I may have expanded on this and a few other niceties more effectively in the linked blog post, if you have the time to read it.
Is my reasoning/example flawed, or is this really a poor argument when indicating why accelerating to the speed of light is problematic?
- Sum
I've been dusting off the grey matter a bit, and have a question regarding an example I found used in both high school and university physics when broaching the topic of Special Relativity.
I do tend to ramble, and so I'll point you to my blog post at sumofprimes.blogspot.com/2008/04/relativistic-mass-in-introductory.html if you care to read the whole spiel. For those that don't wish to suffer, here it is more briefly stated:
Regardless of any other reasons that may prevent an object with mass from accelerating to the speed of light, the often-used argument that an infinite amount of fuel would be required seems inherently flawed -- this argument typically presents the apparent mass increase of an object that's accelerating (as observed from a stationary frame of reference), then proceeds with the reasoning that if the apparent mass is approaching infinity, then the amount of "fuel" required to continue acceleration would approach infinity, too. The main flaw with this line of reasoning appears to be that:
a.) if we assume that the object is carrying the fuel with it for the trip, then
b.) the observed mass of the carried fuel will increase proportionately with the increase in the mass of the accelerating object (and so, too, approach infinity)
So -- the static observer would see the mass of the system as a whole increase (m[observed] = m[rest]/(1-(v^2/c^2))^0.5), whereas the "traveler" would simply see "Ah, yup, 29,875kg of fuel left now..." -- a steadily decreasing amount of fuel as it was consumed.
I think I may have expanded on this and a few other niceties more effectively in the linked blog post, if you have the time to read it.
Is my reasoning/example flawed, or is this really a poor argument when indicating why accelerating to the speed of light is problematic?
- Sum