B Space, Reflection: See Earth's Past in Mirror?

Click For Summary
The discussion explores the theoretical possibility of using a mirror in space to capture images of Earth and its past. It highlights that light takes time to travel, meaning any image captured would inherently reflect a moment in the past, albeit a very short one. While mirrors could introduce slight delays, the practical limitations of setting up such a system mean that significant historical moments cannot be observed. The time required to position a mirror in space would negate any substantial advantage in viewing the past. Ultimately, the concept remains largely impractical for capturing meaningful historical imagery.
atarah
Messages
1
Reaction score
0
TL;DR
can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?
can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?
 
Physics news on Phys.org
We don’t even need a mirror to produce that effect. When I see a fly land on a table 3 meters away…. The fly actually landed about 10 nanoseconds before I saw it land, because that’s how long it took the light to travel the 3 meters between the table and my eye. The same thing would happen if we were using a camera instead of a human eye to form the image.

And yes, sending the light on a circuitous path with one or more mirrors allows us to introduce yet more lag between event and eye. In practice however, we’re not going to be able to get more than a tiny fraction of a second of additional delay that way.
 
Last edited by a moderator:
atarah said:
Summary: can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?
Unless the mirror is already there, getting it set up will require so much time that you'll not see any farther into the past than when you launched it.

So if you are planning on getting some long distance images of the grassy knoll at a particular historically relevant moment, you are out of luck.
 
Reply
  • Haha
  • Like
Likes Herman Trivilino and phinds
How about this view? It looked back 3 seconds in history.

1654605141806.png
 
atarah said:
Summary: can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?

can you theoretically put a mirror in space, take a photo of earth/dirts reflection and see it in the past?
Your bathroom mirror will give you a delay of ten nanoseconds or so. that would be a start!
 

Thread 'Gravitational effects of a small black hole passing your body'

Abstract The gravitational effects of a Primordial Black Hole (PBH) passing through the human body are examined, with the goal of determining the minimum mass necessary to produce significant injury or death. Two effects are examined: The damage caused by a shock wave propagating outward from the black hole trajectory, and the dissociation of brain cells from tidal forces produced by the black hole on its passage through the human body. It is found that the former is the dominant effect...
View full post »

Similar threads

B How would light work on a mirror very far away?
  • · Replies 11 ·
Replies
11
Views
2K
B What If We Could See the Past by Placing a Mirror on the Sun?
  • · Replies 13 ·
Replies
13
Views
3K
I Fabry-Perot Interferometer mirrors
  • · Replies 7 ·
Replies
7
Views
4K
B What Color Do Mirrors on Earth Appear from Space?
  • · Replies 35 ·
2
Replies
35
Views
4K
B Could you use the Moon to reflect sunlight onto a solar sail?
  • · Replies 21 ·
Replies
21
Views
4K
I Infrared Photovoltaics: Powering Ham Radios & Cooling Earth?
  • · Replies 16 ·
Replies
16
Views
3K
I Two mirrors to focus sunrays into a tiny spot -- possible?
  • · Replies 6 ·
Replies
6
Views
4K
Mirror system in geometrical optics
  • · Replies 9 ·
Replies
9
Views
2K
I Understanding magnification of concave mirrors for near-eye situation?
  • · Replies 11 ·
Replies
11
Views
2K
I Do my parabolic mirrors need to be really shiny to reflect infrared?
  • · Replies 3 ·
Replies
3
Views
2K