How do forces change with speed?

Click For Summary

Discussion Overview

The discussion revolves around the behavior of forces, such as gravitation and magnetism, as objects approach relativistic speeds, specifically near the speed of light. Participants explore the implications of special relativity on these forces and the perceptions of different observers.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how forces behave when an object approaches light speed, noting that time dilation, increased mass, and length contraction occur from the perspective of an outside observer.
  • Another participant emphasizes that all speeds are relative and challenges the notion of an "objective bystander," suggesting that the experience of speed is frame-dependent.
  • A third participant clarifies that while time dilation and length contraction are observable, the concept of mass is more complex, arguing that invariant mass does not change and that relativistic mass is a deprecated concept.
  • This participant also states that the laws of physics, including forces, remain consistent across different reference frames, although electric and magnetic fields transform between frames, and gravitational fields are described as spacetime curvature.
  • A later post provides a link to an external resource discussing the transformation of forces in relativity, suggesting further exploration of the topic.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of mass and the concept of an objective observer. There is no consensus on how to best describe the behavior of forces at relativistic speeds, and the discussion remains unresolved.

Contextual Notes

Participants acknowledge the complexity of gravitational fields and the need for mathematical descriptions to fully understand their behavior under relativistic conditions. The discussion highlights the ambiguity surrounding the terms used, such as "mass" and "forces," which may depend on definitions and context.

Hyperspaced
Messages
1
Reaction score
0
TL;DR
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.
 
Reply
  • Like
Likes   Reactions: 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.
 
Reply
  • Like
Likes   Reactions: vanhees71

Similar threads

High School Problem about postulate of the invariance of the speed of light
  • · Replies 33 ·
2
Replies
33
Views
4K
Undergrad Why do we still say “the speed of light” instead of “c”?
  • · Replies 12 ·
Replies
12
Views
2K
Undergrad Speed of light one more time
  • · Replies 5 ·
Replies
5
Views
1K
High School Do Gravitational Forces Increase for Objects Moving at Light Speed?
  • · Replies 16 ·
Replies
16
Views
4K
Undergrad A problem with how the speed of light connects to special relativity
  • · Replies 12 ·
Replies
12
Views
2K
High School Special Relativity Calc: Half Speed of Light - Jose
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Why is the speed of light the same everywhere in the Universe?
  • · Replies 64 ·
3
Replies
64
Views
11K
High School Can an Object Exceed the Speed of Light?
  • · Replies 12 ·
Replies
12
Views
2K
Undergrad Questions regarding traveling speed in time and gravity as a force
  • · Replies 95 ·
4
Replies
95
Views
7K
High School How fast do space-time changes propagate?
  • · Replies 4 ·
Replies
4
Views
2K