Hypothetical situation, what is seen before light arrives?

In summary, the conversation discusses a hypothetical situation where a barrier is placed between the Earth and the Sun, blocking the view and light of the Sun for an hour before being removed. The conversation delves into the concept of light particles called photons and how they travel at the speed of light. It is explained that the observer on Earth would still see the Sun's light for a few minutes after the barrier is removed, as the remaining light particles finish their journey to the observer's eye. The analogy of a tap with water is used to explain this concept.
  • #1
zanthal
2
0
Before I get pounced on by academics from near and far, I just want to mention that I'm no longer a college student and never took a course in physics. All of my knowledge on the subject is practical and thus the answer to this eludes me. So in advance please forgive me if the answer to this seems elementary and/or a waste of time.

Hypothetical situation:

One day, an gigantic opaque barrier of some kind is placed between the Earth and the sun, completely blocking the view and the light of the sun visible from Earth for an entire hour.

In a period of a few seconds, that barrier is removed.

What would this situation look like from the perspective of an observer on earth? What does the sun look like before it's light has arrived on earth, can it be seen at all?

Would the observer still see the sun's light for minutes after the barrier had been put in place, as the remaining light particles finished their journey to the eye of the observer on earth?
 
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  • #2
The light from the Sun takes about 8 minutes 19 seconds to travel to Earth.

You can think of light as particles - much like marbles - but much smaller. Particles of light are called photons and they travel in straight lines at the Speed Of Light, which is the speed limit for everything in the universe.

Photons travel out in all directions from the sun, but the light we see from the sun is only the photons that travel straight towards Earth.

Let's say you stick a giant barrier directly between the Sun and the Earth at time t=0.

Then at time t=0 the photons between the barrier and the Sun will hit the barrier and either get absorbed, reflected or whatever else, but for the sake of argument, let's assume they don't get passed the barrier, and so they don't reach Earth. These photons are normal photons traveling at light speed.

The photons in between the barrier and the Earth will continue towards Earth at Light Speed. However, there are only 4 minutes 9.5 seconds before the photons that were passed the barrier at t=0 run out, and so you will get 4 minutes 9.5 seconds of light, and then sudden darkness.

If you are still confused, think about a tap with water running out of it, and then suddenly you place a card in between the tap and the bottom of the sink.
 
  • #3
No that makes sense to me actually, it's just such an unthinkable situation that it's hard to imagine what would really happen in real time.

Thanks for the reply :biggrin:
 

1. What is a hypothetical situation in relation to light?

A hypothetical situation is a theoretical scenario that is not based on actual events but is used to explore and understand the potential outcomes or consequences of a particular phenomenon, in this case, the arrival of light.

2. What is meant by "before light arrives"?

This phrase refers to the time period before light waves reach a particular location or observer. It is a hypothetical situation because it is not possible to observe or experience this moment in time.

3. Can anything be seen before light arrives?

No, it is not possible to see anything before light arrives. Without the presence of light, there are no visible objects or images. However, other forms of radiation, such as infrared or ultraviolet, may be present and could potentially be detected by specialized equipment.

4. How does this hypothetical situation relate to the study of light?

The hypothetical situation of what is seen before light arrives is often used in thought experiments and theoretical discussions to help scientists better understand the properties and behavior of light. It allows for the exploration of concepts such as the speed of light, the nature of electromagnetic radiation, and the relationship between light and time.

5. Is this a realistic scenario or purely theoretical?

This is a purely theoretical scenario. While it is based on scientific principles and can help expand our understanding of light, it is not possible to observe or experience what is seen before light arrives in reality.

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