Light Travel Time: Seeing the Past?

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SUMMARY

The discussion centers on the concept of light travel time and its implications for observing celestial bodies. Participants confirm that when viewing Mars, the light takes approximately 12 minutes to reach Earth, meaning we see Mars as it was 12 minutes ago. This principle applies to all astronomical observations; for instance, observing the Andromeda Galaxy reveals its state over 2 million years ago. The conversation also highlights the challenges of real-time communication with Mars rovers due to light travel delays, which can range from 8 to 41 minutes.

PREREQUISITES
  • Understanding of light speed and its implications in astronomy.
  • Basic knowledge of celestial distances, particularly between Earth and Mars.
  • Familiarity with the concept of time dilation in physics.
  • Awareness of the operational constraints of Mars rovers due to communication delays.
NEXT STEPS
  • Research "Time Dilation" and its effects on perception of time in space.
  • Explore the "Einstein Clock" and its relevance to relativity.
  • Investigate the operational protocols of Mars rovers and their communication systems.
  • Learn about the varying distances between Earth and Mars and how they affect light travel time.
USEFUL FOR

Astronomy enthusiasts, physics students, and anyone interested in the implications of light travel time on space exploration and observation.

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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