Speed of Light & Space: Exceeding the "Universal Speed Limit

Click For Summary

Discussion Overview

The discussion revolves around the concept of the speed of light as a universal limit and the implications of the expansion of space in relation to this limit. Participants explore the mathematical and conceptual aspects of how space can appear to exceed the speed of light, particularly in the context of cosmological expansion.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that while nothing can be accelerated to the speed of light, the expansion of space can exceed this limit, suggesting that light cannot keep pace with the expanding universe.
  • Others clarify that the expansion of space does not represent an actual velocity, as it does not involve the motion of objects, and instead is described in different units (1/time).
  • One participant questions the mathematical aspects that allow for space to exceed the speed of light, emphasizing that space itself is not a material entity and does not possess a velocity in the traditional sense.
  • There is a reiteration that the speed of light remains a limit for the motion of objects, distinguishing it from the expansion of space.

Areas of Agreement / Disagreement

Participants express differing views on the nature of space expansion and its relationship to the speed of light. While there is some agreement on the distinction between the motion of objects and the expansion of space, the discussion remains unresolved regarding the implications and interpretations of these concepts.

Contextual Notes

Participants highlight limitations in comparing the expansion of space to the speed of light due to differences in units and definitions. The discussion does not resolve the mathematical or conceptual nuances involved.

Sullivan Stockwell
Messages
8
Reaction score
0
It's generally understood that nothing can be accelerated up to the speed of light, and that nothing can surpass it. That being said, the expansion of space itself can exceed this "universal speed limit," as the Universe is expanding so fast that light can't catch up to it. Regarding the properties of light and Einstein's works on relativity, what mathematical aspects permit space to exceed the speed of light? What makes it seemingly exempt from the restriction of not being able to travel past the speed of light?
 
Physics news on Phys.org
Sullivan Stockwell said:
That being said, the expansion of space itself can exceed this "universal speed limit,"
The distance to objects far away can increase faster than the speed of light. This is not an actual velocity, as it does not involve the motion of objects.

The speed of light is a limit for the motion of objects.
 
Sullivan Stockwell said:
what mathematical aspects permit space to exceed the speed of light?
Space isn't a material. It doesn't have a velocity. Velocity has units of length/time, but the expansion of the universe is in units of 1/time, so it is not a quantity that can be sensibly compared to the speed of light.
 
Last edited:
mfb said:
The distance to objects far away can increase faster than the speed of light. This is not an actual velocity, as it does not involve the motion of objects.

The speed of light is a limit for the motion of objects.
Indeed. I wasn't sure what was meant by
mfb said:
The distance to objects far away can increase faster than the speed of light. This is not an actual velocity, as it does not involve the motion of objects.

The speed of light is a limit for the motion of objects.
mfb said:
The distance to objects far away can increase faster than the speed of light. This is not an actual velocity, as it does not involve the motion of objects.

The speed of light is a limit for the motion of objects.
This makes sense. I wasn't sure what was meant by space expanding faster than light. From our perspective, at a set velocity i.e.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 25 ·
Replies
25
Views
2K
Replies
60
Views
5K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 21 ·
Replies
21
Views
5K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K