I How do forces change with speed?

AI Thread Summary
Forces such as gravitation and magnetism behave consistently across different frames of reference, according to the principles of relativity. While an observer perceives time dilation and length contraction for an object moving near the speed of light, the fundamental laws governing forces remain unchanged. The concept of "relativistic mass" is outdated; instead, invariant mass remains constant regardless of speed. Electric and magnetic fields transform between frames, but their underlying physics is preserved. Understanding these transformations requires a mathematical approach, as the behavior of gravitational fields is more complex than that of electromagnetic fields.
Hyperspaced
Messages
1
Reaction score
0
TL;DR Summary
What happens to magnetism and gravitation when materia hits near lightspeed?
Hey dear physics community :)

I ask myself what exactly happens to forces between materia when the materia hits near lightspeed.

I know, that for an objective bystander watching let's say elon in his rocket with 99,99999% the speed of light, that the time goes slower, the mass of the rocket goes up and the length of the rocket decreases.

What i ask myself now is what happens to all the forces like gravitation and magnetism. Gravitation and magnetism don't change for elon on the spaceship, so the other way around it means they have to decrease for the objective bystander aren't they?

Thanks a lot for your time and knowledge :)
 
Physics news on Phys.org
Answer it yourself. Right now, you are going 99,99999% the speed of light relative to something else. In the reference frame of the other something, you are the one traveling fast.

How does it feel?

p.s. All linear speeds are relative. No speed is absolute.
 
  • Like
Likes russ_watters
Hyperspaced said:
objective bystander
No such thing. But for any observer who sees the rocket move, some of the things you wrote are true.
Hyperspaced said:
the time goes slower
The rockets tick slower as measured by clocks that see it as moving, yes.
Hyperspaced said:
the mass of the rocket goes up
No - "mass" means the invariant mass which does not change. Relativistic mass does increase with speed, but is a long deprecated concept that causes more confusion than it's worth.
Hyperspaced said:
the length of the rocket decreases.
Again, as measured by anyone who sees the rocket moving, yes.
Hyperspaced said:
What i ask myself now is what happens to all the forces like gravitation and magnetism.
What do you mean? A key point of relativity is that all laws of physics are the same in all frames of reference, so all forces work the same way at all speeds. Electric and magnetic fields do transform - a field that is a pure electric or pure magnetic field will be seen by observers in other frames as electromagnetic fields.

Gravitational fields are more complicated. They are not forces, but are rather spacetime curvature. Again, the laws are the same at all speeds, but the fields transform. There are loose analogies with electromagnetic fields in the way the transformed fields behave, but really you need to do the maths for that - I'm not sure there's a non-technical description of it.
 
Consider an extremely long and perfectly calibrated scale. A car with a mass of 1000 kg is placed on it, and the scale registers this weight accurately. Now, suppose the car begins to move, reaching very high speeds. Neglecting air resistance and rolling friction, if the car attains, for example, a velocity of 500 km/h, will the scale still indicate a weight corresponding to 1000 kg, or will the measured value decrease as a result of the motion? In a second scenario, imagine a person with a...
Dear all, in an encounter of an infamous claim by Gerlich and Tscheuschner that the Greenhouse effect is inconsistent with the 2nd law of thermodynamics I came to a simple thought experiment which I wanted to share with you to check my understanding and brush up my knowledge. The thought experiment I tried to calculate through is as follows. I have a sphere (1) with radius ##r##, acting like a black body at a temperature of exactly ##T_1 = 500 K##. With Stefan-Boltzmann you can calculate...
Thread 'Griffith, Electrodynamics, 4th Edition, Example 4.8. (First part)'
I am reading the Griffith, Electrodynamics book, 4th edition, Example 4.8 and stuck at some statements. It's little bit confused. > Example 4.8. Suppose the entire region below the plane ##z=0## in Fig. 4.28 is filled with uniform linear dielectric material of susceptibility ##\chi_e##. Calculate the force on a point charge ##q## situated a distance ##d## above the origin. Solution : The surface bound charge on the ##xy## plane is of opposite sign to ##q##, so the force will be...
Back
Top