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Old 06-11-2015, 08:45 PM
 
Location: Pacific 🌉 °N, 🌄°W
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Hello everyone

I have a question about the speed of light after reading this.

What Travels Faster Than the Speed of Light? | Big Think

What I don’t understand is what prevents us from traveling faster than the speed of light? If I was alone in empty space and started accelerating (due to some undefined force) then what stops me from accelerating? Supposedly, my mass would increase to the point that it would take infinite force to accelerate any more as I approached the speed of light. But, how would I know I was at the speed of light if I had no reference point in empty space? Speed only makes sense in reference to something. Doesn’t that imply there’s something out there that we don’t know about, some medium that establishes the reference and hence the limitation on velocity?
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Old 06-12-2015, 03:07 AM
 
Location: Auckland, New Zealand
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From the link above;
Quote:
1. The Big Bang itself expanded much faster than the speed of light. But this only means that "nothing can go faster than light." Since nothing is just empty space or vacuum, it can expand faster than light speed since no material object is breaking the light barrier. Therefore, empty space can certainly expand faster than light.
There is a rather obvious contradiction here. The universe can hardly be considered 'nothing'.
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Old 06-12-2015, 03:35 AM
 
Location: Pacific 🌉 °N, 🌄°W
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Quote:
Originally Posted by 303Guy View Post
From the link above;There is a rather obvious contradiction here. The universe can hardly be considered 'nothing'.
This is what they meant.

Since nothing is just empty space. Therefore, empty space can certainly expand faster than light.
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Old 06-12-2015, 09:18 AM
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n/a posts
Wikipedia has a decent explanation if you want science: https://en.wikipedia.org/wiki/Faster...rsal_expansion

Cornell has the classic dough with raisins in it explanation: Is the universe expanding faster than the speed of light? (Intermediate) - Curious About Astronomy? Ask an Astronomer

Basically the speed of universal expansion is not trivially related to local velocity.
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Old 06-13-2015, 12:59 AM
 
Location: Heart of Dixie
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Electric cars and four-cylinder engines?
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Old 06-13-2015, 12:09 PM
 
Location: Westwood, MA
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You're right. Velocity only makes sense in reference to something else. There's no experiment you can do that will give you an absolute velocity. Without any reference one typically takes the velocity to be zero (it makes all the other problems easier), but you could assign yourself any velocity and the physics would all still work out.
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Old 06-13-2015, 10:05 PM
 
Location: Heart of Dixie
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Quote:
Originally Posted by jayrandom View Post
...There's no experiment you can do that will give you an absolute velocity...
Measuring the speed of unmodified light through a vacuum.
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Old 06-13-2015, 10:27 PM
 
Location: Pacific 🌉 °N, 🌄°W
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Maybe it will help if I ask the question a different way….

Here’s what I know the theory says:
1. Nothing goes faster than the speed of light (except in very specific circumstances that don’t apply to my question).
2. As mass approaches the speed of light the relativistic mass increases and approaches infinity. Because of this the force required to accelerate the mass to the speed of light becomes infinite and it’s impossible to apply infinite force so it’s impossible to exceed the speed of light.
3. We can’t directly observe anything going faster than the speed of light.
4. “c” doesn’t change no matter how fast you’re traveling or how strong the gravitational field you’re in is.
Conditions for this thought experiment:
1. There is one electron in empty space in an empty universe being acted upon by a constant force that’s accelerating it.
2. There is no gravity except that generated by the relativistic mass of the electron.
Questions:
1. Is the cause-effect chain something like this? Achieving 99.99999999….% the speed of light:
a. the mass of the electron increases towards infinity
b. then since the relativistic mass of the electron becomes almost infinite the gravity of the electron becomes almost infinite
c. and as gravity becomes almost infinite time slows to almost zero
d. and as time slows to almost zero further increase in velocity is impossible

2. This is really what I was trying to ask previously… Why is the speed of light a constant even in the void of deep space or on the surface of a neutron star (assuming it’s a vacuum)? It seems strange – space warps, time warps, gravity changes, mass changes, but the speed of light stays the same. Why is this one constant unchanging?
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Old 06-14-2015, 03:17 AM
 
Location: Auckland, New Zealand
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Quote:
Originally Posted by Matadora View Post
This is what they meant.

Since nothing is just empty space. Therefore, empty space can certainly expand faster than light.
Why would empty space expand? If empty space were nothing then nothing would be expanding. Anyway, it's all just a play on words.

This is the real question;
Quote:
Why is the speed of light a constant even in the void of deep space or on the surface of a neutron star (assuming it’s a vacuum)? It seems strange – space warps, time warps, gravity changes, mass changes, but the speed of light stays the same. Why is this one constant unchanging?
The way I see it, the C does not change relative to the spacetime it propagates through.
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Old 06-15-2015, 02:54 PM
 
Location: Pacific 🌉 °N, 🌄°W
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Quote:
Originally Posted by 303Guy View Post
Why would empty space expand? If empty space were nothing then nothing would be expanding. Anyway, it's all just a play on words.
Yes it's a play on words.
Quote:
Originally Posted by 303Guy View Post
This is the real question;
The way I see it, the C does not change relative to the spacetime it propagates through.
We are saying the same thing.
Quote:
4. “c” doesn’t change no matter how fast you’re traveling or how strong the gravitational field you’re in is.
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