Light Travel Time: Seeing the Past?

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    Light Time Travel
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Discussion Overview

The discussion revolves around the concept of light travel time and its implications for observing celestial objects, specifically whether viewing these objects allows us to see past events. Participants explore the relationship between distance, light speed, and the perception of time in astronomical observations.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant notes that observing Mars through a telescope means seeing it as it was 12 minutes ago, suggesting that this implies looking back in time.
  • Another participant confirms that viewing celestial bodies always involves seeing them as they were in the past, providing examples such as the Moon and the Sun.
  • A participant mentions the significant time delay for distant galaxies, which can be billions of years, reinforcing the idea of seeing the past.
  • There are suggestions to explore concepts related to time, such as "Time Dilation" and the "Einstein Clock," to understand the complexities of time in relation to light speed.
  • One participant elaborates on the variability of light travel time to Mars due to orbital changes, explaining that it can range from over 4 minutes to almost 21 minutes.
  • Another participant discusses the implications of light travel time on communication with Mars rovers, highlighting the delay in receiving commands and responses during operations.

Areas of Agreement / Disagreement

Participants generally agree that observing distant objects allows one to see them as they were in the past. However, there are nuances regarding the implications of light travel time and its effects on real-time communication with spacecraft, which are discussed but not resolved.

Contextual Notes

The discussion includes varying distances and light travel times to Mars, which depend on orbital positions. There are also unresolved aspects regarding the complexities of time perception in relation to light speed.

Bammitzcam
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Hey guy,
I was browsing YouTube and watched a speed comparison video and it was just different races timed. I noticed that light speed took 12 minutes to reach Mars from earth. So I thought this

If we look at Mars through a telescope or what ever, Does that mean we are actually looking back in time? We are not actually there but does it mean we are seeing past events (assuming there was an event lmao)
Excited to see the responses. This is my first ever science post because I'm 14
 
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Yes indeed, we are always looking at how things were in the past. When you look at the moon you are seeing it as it was 1 second ago. When you see the Sun you are seeing it as it appeared about 8 minutes ago. The nearest major galaxy (Andromeda Galaxy) to our own is over 2 million light-years away, so if you ever see it through a telescope you are seeing it as it appeared more than 2 millions years ago.

Also, I've edited the title of this thread to something more appropriate for the topic.
 
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Hi.
Yes light travels at known speed, so when you see a distant object. what you see is what it was like in the past.
For far away galaxies it can be billions of years
 
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:welcome:
If you want to learn even more about the "oddities" of time (aka the basis of Special Relativity :oldbiggrin:), I suggest searching "Time Dilation" and the "Einstein Clock" on google.
 
Comeback City said:
:welcome:
If you want to learn even more about the "oddities" of time (aka the basis of Special Relativity :oldbiggrin:), I suggest searching "Time Dilation" and the "Einstein Clock" on google.
 
Bammitzcam said:
Hey guy,
I was browsing YouTube and watched a speed comparison video and it was just different races timed. I noticed that light speed took 12 minutes to reach Mars from earth. So I thought this

If we look at Mars through a telescope or what ever, Does that mean we are actually looking back in time? We are not actually there but does it mean we are seeing past events (assuming there was an event lmao)
Excited to see the responses. This is my first ever science post because I'm 14
That 12 min light travel time to Mars is about the average. Since the actual distance between Earth and Mars changes due to their different orbits, this time can vary from a bit over 4 min to almost 21 min.
Since this delay also applies to radio signals, this is why we can't control the rovers on Mars in "real time". If we send a command to the rover to perform an action it will take from 8 to 41 min before we will see the result of that command on the rover. The same is true during landing operations. By the time we could find out that there was a problem and tried to send a correction, the landing will have already either succeeded or not.
 
Janus said:
The same is true during landing operations. By the time we could find out that there was a problem and tried to send a correction, the landing will have already either succeeded or not.

Indeed. Also, the video of the JPL team during the landing sequence was wonderful (landing occurs about an hour into the video). For the OP, if you watch the video, you may notice that they don't send any commands to the spacecraft during the landing sequence. All of it is pre-programmed in.
 

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