
What's Wrong with E=MC^2? - xparadigm
https://www.science20.com/hammock_physicist/whats_wrong_emc2
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blamestross
I like that somebody called out that there is a lot of misinformation/crap
around relativity and the speed of light.

The article points out that mass doesn't increase with velocity.

The next big lie is that nothing can go faster than the speed of light. One
thing can: Me (or you from your point of view). The whole time dilation thing
only happens to other things/people. I can accelerate to any velocity. The
universe just won't let me observe anybody else going faster than the speed of
light. It doesn't change the fact that I can accelerate well past c and get to
alpha centauri as soon as I am willing to expell propellant for. It's only
everybody else time will do wonky things for.

~~~
jjtheblunt
I'm curious why you write what you wrote: at Fermilab, where some high school
students took physics including from a Nobel laureate, I remember (as a high
school student) that the problem with exceeding the speed of light, from the
point of view of a reference frame, is that, if

e = mass * celeritas^2 / Sqrt( 1 - velocity^2/celeritas^2 )

describes relativistic mass and energy conversion, where i spelled out c as
celeritas as the speed of light, at least in the reference frame, something
implausible is implied.

Looking at that equation, as an object's velocity approaches the speed of
light, the denominator approaches zero, and the equivalent energy of the
moving mass goes towards infinity.

That led to the quandary : can you really get something to go that fast?

(I'm on a keyboard with no paper to fiddle with, or I'd further monkey with
the equations.)

~~~
blamestross
From the outside perspective that is mostly true.

The flaw is that you don't gain mass as you go faster. You gain momentum. That
momentum energy even causes gravity in a way[1].

The reason it seems to take infinite energy to go faster than light is that
the rate of time for the traveler changes as they go faster. From your
observer's perspective, whenever they accelerate the speed increase is exactly
cancelled out by the change in relative time rates. The more energy they spend
the faster they go, but never quite fast enough to go at C.

From the traveler's perspective it is a totally different adventure. When they
add energy they accelerate. Period. They don't notice the time dilation
outside of observations of their origin and destination. If they have enough
fuel, they can accelerate smoothly to 2 times the speed of light and travel a
light year in 6 months. The problem is that more than a year will have gone by
in the origin and destination on the way and they were never observed going
faster than C.

If we had a way around the rocket equation we could easily cross the Galaxy
within a human lifetime. It would just be Earth would be gone by the time we
got there.

[1][https://physics.stackexchange.com/questions/63961/does-
relat...](https://physics.stackexchange.com/questions/63961/does-relativistic-
mass-have-weight)

~~~
mikewarot
In fact, if you see light from 10 billion light years away, as far as the
photon is concerned, it just left, traveled for zero time, and hit your
eyeball.

