# Observing Light Flash from 0.9999c Moving Body

• nitsuj
In summary: The yellow circles show the transformation and reflect the light pulse back to the observer (so they can measure). The green and red circles are the reflection and show the time dilation (green collapses before red).

#### nitsuj

A body moves at 0.9999 c, in my FoR i have placed two devices one light second distance apart. As the body passes right next to each device it (body or device) flashes a pulse of light. Would it look like this from my FoR?

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Yes, after about 7.5 seconds after the first flash.

I think this is what the body sees from its FoR, (not scaled with first picture, just to illustrate body is in the middle of the light rings).

With the picture in the first post, I am guessing where the line crosses the circles the distance between is 1 light second, which is the distance between the light pulse triggering devices.

This spacing gets smaller towards the area of the body where the circles pretty much are in the same spot (picture in first post).

From my FoR, is the spacing between the cirlces (picture in first post) all of the same interval (as the 0.9999c body would measure, one light second)? I read from Taylor & Wheeler that intervals are invariant.

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nitsuj said:
I think this is what the body sees from its FoR (body is in the middle of the light rings).
Your second image is what it looks like in the body's FoR, but it's not what the body can see. The only way observers can "see" traveling light is to put reflectors at equally-spaced locations with respect to themselves and then all they can tell is the round-trip speed of light measures to be the same for all of them. But they cannot conclude exclusively from any measurement or observation that the light looks like it does in the FoR. Each FoR defines the speed of light to be a constant in that frame which is the reason the two FoR's give a different image.
nitsuj said:
With the picture in the first post, I am guessing where the line crosses the circles the distance between is 1 light second, which is the distance between the light pulse triggering devices.
No, it's just under 2 light seconds. The flashes occurred 1 second apart so the radii of the circles will have a difference of 1 light second but the difference in the diameters is 2 light seconds.
nitsuj said:
This spacing gets smaller towards the area of the body where the circles pretty much are in the same spot (picture in first post).
Correct.
nitsuj said:
From my FoR, is the spacing between the cirlces (picture in first post) all of the same interval (as the 0.9999c body would measure, one light second)? I read from Taylor & Wheeler that intervals are invariant.
The difference in the center points of the two circles is 0.9999 light seconds.

Have you seen my animation that illustrates how two observers with a relative speed of 0.5c will both think they are in the center of an expanding circle of light that was emitted when they were colocated?

Thanks for the replies ghwellsjr

I see that in the first image the distance between the light pulse circles at the bottom is not 1 light second.

But I see it as the distance between the devices 1 light second + the time it takes the body to pass by each device and trigger the light pulses 1.0001 light seconds (1/.9999) so 2.0001 light seconds.

Your animation looks really cool, but I can't tell what the Green and Red circle represent. I am still trying to understand what I see in my single frame image :)

oh wait it looks like the yellow circles that follow each FoR illustrates the transformation and reflects the light pulse back to the observer (so they can measure of course :) The green and red circles are the reflection and show the time dilation (green collapses before red). Very slick

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You are right, thanks for correcting my mistake.

## What is the speed of light?

The speed of light is a fundamental constant in physics, denoted by the letter c. It is approximately 299,792,458 meters per second in a vacuum.

## What does 0.9999c mean?

This refers to a speed that is 99.99% of the speed of light. In other words, an object moving at this speed is traveling at a very high velocity, but not quite at the speed of light.

## How do scientists observe light from a moving body at this speed?

Scientists use a technique called time dilation to observe light from a moving body at this speed. This involves measuring the time it takes for light to reach an observer at rest and comparing it to the time it takes for light to reach an observer on the moving body. This allows for accurate observations of the moving body's light flash.

## What is the significance of observing light from a moving body at this speed?

This observation has important implications for the theory of relativity. It confirms that the laws of physics remain the same for all observers, regardless of their relative velocities. It also helps us better understand the behavior of light and the effects of high speeds on it.

## Can objects actually move at the speed of light?

According to the theory of relativity, objects with mass cannot reach the speed of light. As an object approaches the speed of light, its mass increases and it requires an infinite amount of energy to accelerate it further. Therefore, it is not possible for an object with mass to reach the speed of light.