Something I was taught in High School Driver Education class.

[alexi_drago]

Your mass doesn't change when you go into space. Your weight on earth is the gravitational force acting on your mass.

 

[Uncayimmy]

Your mass doesn't change when you go into space. Your weight on earth is the gravitational force acting on your mass.

I know that, but that wasn't my question. You said that the "change in velocity can be measured without using any external reference." In order to do that I need to measure the force, which I believe you said I could do with an accelerometer. But you implied that I need to know my mass. So, without any external reference, how can I know my mass? Sure, I could already know it, but I consider assuming facts not in evidence to be an external reference.

So, if I don't already know my mass, how do I figure it out while in my space vehicle? It's not a trick question. I don't know if you can or cannot.

 

[alexi_drago]

sorry, mis read that again. using your own mass isn't really practical anyway and you'd use some device with a known mass. There might even be some accelerometers that use lasers instead of a mass.

 

[alexi_drago]

for that last question, the only reply I can think of is - how do you know how long a second is or how long a metre is?

 

[Uncayimmy]

for that last question, the only reply I can think of is - how do you know how long a second is or how long a metre is?

I could bring a watch and a ruler with me just like I brought the accelerometer. For some reason the idea of being sealed in a spaceship is suddenly interesting. I'm wondering what I could figure out about my world.