Can We Really See the Past Through Science?

  • Context: High School 
  • Thread starter Thread starter terencesiu
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around the concept of perceiving the past through scientific means, particularly focusing on the speed of light and sound. Participants explore whether it is possible to see or hear the past by manipulating the speed of these signals, and they question the implications of such manipulation in the context of astronomical observations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the possibility of seeing the past by suggesting that light from distant planets takes time to reach us, implying that we are observing their past.
  • Another participant asserts that there is no way to decrease the speed of light, challenging the feasibility of seeing the past through light manipulation.
  • A participant proposes decreasing the speed of sound by creating a vacuum, questioning if this would allow them to hear voices from the past.
  • It is noted that while rarefying the medium can slow sound, it does not do so appreciably, and that slowing signals would not enable observation of the past.
  • Participants discuss the academic nature of comparing present points in time between Earth and distant planets, emphasizing the speed of light as a limiting factor.
  • Questions arise about how observations of planets are made, including whether images are received instantly or after a delay, and if a hypothetical speed-slowing device could allow for past observations.
  • Clarifications are made that current observational devices, like telescopes, are limited by the speed of light and do not allow for instantaneous images of distant planets.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of seeing or hearing the past through manipulation of signal speeds. There is no consensus on the possibility of such observations, and the discussion remains unresolved regarding the implications of speed limits on perception of time.

Contextual Notes

Participants highlight limitations in understanding the nature of light and sound propagation, as well as the implications of manipulating these speeds. The discussion does not resolve the complexities involved in observing distant astronomical objects.

terencesiu
Messages
4
Reaction score
0
I am watching a movie about a person who can see the future. I have thought a lot of time and I think it is impossible, but how if we see the past? In fact, we can see the relative past of a planet which is far far away, since time is needed for light to pass to our eyes. But can we do that on a very short distance, by decreasing the speed of light/sound/etc? Does it possible? And are there any research about it? thank you.

My English is poor, hope you understand it.
 
Physics news on Phys.org
There is no way to decrease the speed of light.
 
then, how about decrease the speed of sound, by making the medium tends to be vacuum? Can we hear the voice from the past?
 
terencesiu said:
then, how about decrease the speed of sound, by making the medium tends to be vacuum? Can we hear the voice from the past?

Rarefying the medium slows the sound down but not appreciably, not practically.

Note that, even if you could find a way of making a light or sound signal travel slower, it would not allow you to see or listen to the past. It would simply mean any signal you sent after the device was in place would travel slower - which is pretty useless.

For example: email takes a few seconds to get from point to point around the Earth. If you slowed this transit time down to a year, you would not start getting emails from last year. No, it would simply mean that, when people started sending emails today, they would now take a month to arrive.
 
DaveC426913 said:
Rarefying the medium slows the sound down but not appreciably, not practically.

Note that, even if you could find a way of making a light or sound signal travel slower, it would not allow you to see or listen to the past. It would simply mean any signal you sent after the device was in place would travel slower - which is pretty useless.

For example: email takes a few seconds to get from point to point around the Earth. If you slowed this transit time down to a year, you would not start getting emails from last year. No, it would simply mean that, when people started sending emails today, they would now take a month to arrive.

I can mostly understand,
does it means that we can see the past of planets is because the medium "space" is already exists?
but, really thank you!:smile:
 
terencesiu said:
I can mostly understand,
does it means that we can see the past of planets is because the medium "space" is already exists?
but, really thank you!:smile:

No. Light does not need a medium to travel through.

It is kind of academic to talk about seeing the past of a distant planet. Since c is the speed limit on any connection between distant points, it is kind of meaningless to compare a point at our "present" with some point at a distant planet's "present".
 
DaveC426913 said:
No. Light does not need a medium to travel through.

It is kind of academic to talk about seeing the past of a distant planet. Since c is the speed limit on any connection between distant points, it is kind of meaningless to compare a point at our "present" with some point at a distant planet's "present".
:confused: I think I have more and more questions. How does the people can observe the planet? Do they get the picture of the planet instantly, or just get the picture after the device have been set up for a long period? If they can get the message instantly, does it means that we can see the past after the speed slowing device have been operated for a long period? I think it will be funny if it can be made.
 
terencesiu said:
:confused: I think I have more and more questions. How does the people can observe the planet? Do they get the picture of the planet instantly, or just get the picture after the device have been set up for a long period? If they can get the message instantly, does it means that we can see the past after the speed slowing device have been operated for a long period? I think it will be funny if it can be made.

What device? We don't have a device.

Our devices for observing planets are telescopes, which of course are limited to the speed of light.
 

Similar threads

High School Do all events in my past lightcone have fewer past events in theirs?
  • · Replies 14 ·
Replies
14
Views
1K
High School New Paradox Discovered, I Think
  • · Replies 98 ·
4
Replies
98
Views
9K
High School Would We See the Same Light After Traveling Back to Earth Faster Than Light?
  • · Replies 2 ·
Replies
2
Views
2K
High School Can We Use Space/Time Fabric to See the Past?
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Does the past of an observer still actually exist in their "now"?
  • · Replies 58 ·
2
Replies
58
Views
6K
High School Time traveling in the future and in the past
  • · Replies 23 ·
Replies
23
Views
3K
High School What If We Could See the Past by Placing a Mirror on the Sun?
  • · Replies 13 ·
Replies
13
Views
3K
High School Can we see 2 black holes orbiting each other?
  • · Replies 57 ·
2
Replies
57
Views
4K
Undergrad Spacetime expansion - time dimension expansion
  • · Replies 48 ·
2
Replies
48
Views
4K
Undergrad Is there a theorem that we can't see objects getting behind EHs?
  • · Replies 5 ·
Replies
5
Views
1K