Recent content by Mike_bb

Spacetime curvature is geometric property.

If we consider free falling frame then we can state that gravity dissappear because in inertial frame the inertial force dissappear. Is this true?

Ibix, Ok. Inertial force arises in non-inertial frame not in inertial. But elevator on the surface of the Earth is inertial frame. From this point of view how is it possible that gravity is inertial force?

Dale, We can measure gravity with an accelerometer if we stay in elevator on the surface of the Earth.

Ibix, Could you explain how does thought experiment with elevator lead us to the fact that gravity is geometric property (not the force)? Thx.

FactChecker, In Russian sources I read another explanations. It confuse me.

From ##M_i=M_g## we can conclude that gravity is fictitious force. Right?

Ok. If gravity was force then mass of object (gravity mass) in elevator on the surface of the Earth differs from inertia mass of object in elevator in the space. Is this statement true? Could anyone provide easy explanation ? Thx.

I read about equivalence principle. I tried to understand Einstein's thought experiment with elevator and I can't understand why we compare elevator in the space and elevator on the surface of the Earth and conclude that gravity is fictitious force. Why? Thanks!

Hello! When I was proving that coefficient ##a## ##(s'=as)## is equal to ##1##, I noticed that ##(t_1' - t_2')^2## should be constant then the proof works but otherwise it doesn't. ##c^2(t_1'-t_2')^2 - (x_1'-x_2')^2 - (y_1'-y_2')^2 - (z_1'-z_2')^2=a(c^2(t_1-t_2)^2 - (x_1-x_2)^2 - (y_1-y_2)^2 -...

At first, I consider two frames: Frame 1: 1m/s Frame 2: 5m/s; (1-5)m/s and (5-1)m/s => absolute value of relative velocity is 4m/s Then, I consider another two frames: Frame 3: 2m/s Frame 4: 6m/s; (2-6)m/s and (6-2)m/s =>absolute value of relative velocity is 4m/s What's wrong?

martinbn wrote: I wrote in more details as martinbn said above:

##ds_1^2## - interval between two events in frame 1. ##ds_2^2## - interval between the same two events in frame 2. ##ds_3^2## - interval between another two events in frame 3. ##ds_4^2## - interval between the same two events in frame 4.

No. Different pair of events. For two events in the frame 1 and the frame 2: ##ds_1^2## - interval in the frame 1 ##ds_2^2## - interval in the frame 2 For another two events in the frame 3 and the frame 4: ##ds_3^2## - interval in the frame 3 ##ds_4^2## - interval in the frame 4

##ds_1^2## - interval in the frame 1 ##ds_2^2## - interval in the frame 2 ##ds_3^2## - interval in the frame 3 ##ds_4^2## - interval in the frame 4