Speed of light and small distances

Click For Summary

Discussion Overview

The discussion revolves around the implications of the speed of light on perception and observation, particularly regarding delayed visual information due to light travel time. Participants explore this concept in both terrestrial and astronomical contexts, examining how distances affect the timing of visual experiences.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that light's travel time creates a delayed perception of objects, both on Earth and in space.
  • Another participant agrees that while the delay is negligible at human scales, it is still present and consistent with measurements, citing GPS as an example.
  • A humorous remark is made about looking in a mirror to see oneself in the past, with a follow-up comment noting the delay is about two nanoseconds.
  • A participant introduces a speculative idea that traveling faster than light could imply time travel, discussing the analogy of sound and how it relates to events occurring before their light reaches an observer.
  • There is a recognition that while the concept of faster-than-light travel leading to time travel is intriguing, it diverges from the original topic of small distances.

Areas of Agreement / Disagreement

Participants generally agree on the existence of light travel time affecting perception, but the discussion includes speculative and humorous elements that introduce varying interpretations and ideas about time and speed.

Contextual Notes

The discussion includes assumptions about human perception and the practical implications of light travel time, which may not be fully explored or defined. The speculative nature of faster-than-light travel and its consequences on time is also acknowledged but remains unresolved.

masteri
Messages
3
Reaction score
0
Hi,
i have tought of a something that i don't know if is it true. As far as i know speed of ligh is 300,000 km/s and it is about 8 minutes to reach the earth. Now when we look ate the other planets we are looking at sort of a delayed picture because of the time light needes to travel from that planet to earth. Am i right about this? If i am does this also means that we on Earth alos have a dlayed picture becouse of time light needs to travel from object that we are looking at(on earth) to us. So for example, let's say that i am in a hugh room and it is total dark. 100 metes from me is another man that i can't see. So someone comses along and turns on a light. Light travels form source of light to that men, bounces back to me and i can see the guy. Am i right about this too? Does this mean that there is also a small delay of picture because of the distance? So when ever a guy moves i see it delayed becaous of a distance?

Thank you
 
Science news on Phys.org
You are 100% correct. For distances on Earth the delay is so small that isn't even close to noticeable for people.
 
If you want to look at yourself in the past, look in a mirror. =)
 
Human perception is too slow to notice the effect but it is in total agreement with the best measurements so far. GPS for instance relies on it.

If you want to bring the huge number (3x108ms-1) down to human scales then think of a modern cpu, operating at 3GHz light travels only 10cm in the time it takes for said cpu to complete one cycle.
 
Bloodthunder said:
If you want to look at yourself in the past, look in a mirror. =)

Indeed, about two nanoseconds in the past!
 
ryan_m_b said:
Indeed, about two nanoseconds in the past!

Wow that's kind of neat. Never thought about it that way but your right.
 
Curses! This thread has caused my mind to ponder the speed of light and time and everything! I realized that to exceed the speed of light actually would be time travel!

"What?" you might say? Well, if you can travel faster than light you can see go someplace where what has happened in the past hasn't "happened" yet, because the information usually is limited by the speed of light, but if you can travel faster than light (which is illegal of course) you could know about something before it happened. You would actually be able to see yourself doing something that happened in the past, but as it happens, because you are now in the future.

OH sure you probably think that is crazy talk, and it is, because you can't travel faster than light. But the analogy of the speed of sound will serve. And since a bullet can travel faster than sound, the bullet does indeed outrun the event of it's source.

You can shout, then race faster than your own voice, so that the event hasn't happened yet, meaning you went backwards in time. Now you are someplace waiting for an event that already happened to happen. If you could do the same thing with the speed of light, you could outrace the light of an event, and be back in time before it actually "happened" yet.

You see why I started with "Curses!". Faster than light travel would be time travel. Not very practical, you might think. But in our fantasy world of of faster than light travel you could outrace light and "go back" in time and watch the creation of the Universe, because somewhere far far away it hasn't happened yet.

OK that is stretching things a lot. Especially since the topic is about "small distances", not really big ones. But it's the same principle.

I think. OK ignore all that. I just had to get it out of my head. And it really was all this thread's fault.
 

Similar threads

High School Can Light Speed Be Increased by Straightening Its Wave Path?
  • · Replies 11 ·
Replies
11
Views
1K
High School Speed of light versus wavelength
  • · Replies 14 ·
Replies
14
Views
2K
High School Is light breaking its own speed limit when cornering?
  • · Replies 25 ·
Replies
25
Views
2K
Graduate Speed of Light when not in a vacuum?
  • · Replies 5 ·
Replies
5
Views
6K
Graduate Interferometer delay & line light spreading
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad Achieving the speed of light at the end of a whip
  • · Replies 15 ·
Replies
15
Views
6K
High School Does light ever go from the eye to the image?
  • · Replies 17 ·
Replies
17
Views
3K
High School Is Infrared Light Invisible to Humans Due to Eye Limitations?
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Speed of Light Thought Experiment
  • · Replies 4 ·
Replies
4
Views
2K
High School How would light work on a mirror very far away?
  • · Replies 11 ·
Replies
11
Views
2K