How Long for a Beam of Light to Reach Earth?

In summary, a beam of light from the Sun takes approximately 8 minutes and 20 seconds to reach Earth. This duration is the result of the vast distance between the Sun and our planet, which is about 93 million miles (150 million kilometers). Light travels at a speed of about 186,282 miles per second (299,792 kilometers per second), allowing it to cover this distance in a relatively short time compared to other celestial phenomena.
  • #1
felizgu
17
8
TL;DR Summary: This is an astronomy application.
Mentor note: Moved from a technical forum section, so the homework template is missing.
How long does it take a beam of light to reach Earth from the Sun when the Sun is 93,000,000 miles from Earth? Express your answer in seconds, using scientific notation.

Let me see.

Given information:

- The distance between the Sun and Earth is 93,000,000 miles.

- The speed of light is approximately
300,000,000 miles per second.
Mentor addition:

The above should be 300,000,000 meters per second, the value that is used below.
Convert the distance from miles to meters.
1 mile = 1.609 × 10^3 meters
93,000,000 miles = 93,000,000 × 1.609 × 10^3 meters = 1.5 × 10^11 meters

Calculate the time it takes for the beam of light to reach Earth.

Time = Distance / Speed of light

Time = (1.5 × 10^11 m) / (3 × 10^8 m/s)

Time = 5 × 10^2 seconds

I say that it takes a beam of light approximately 5 × 10^2 seconds to reach Earth from the Sun.

Is this right?
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
Sounds about right ie 8.33 minutes.

You can google check it too.
 
  • Like
Likes felizgu and FactChecker
  • #3
This appears to be homework. It should be posted in the proper homework forum.
 
  • Like
Likes FactChecker
  • #4
felizgu said:
The speed of light is approximately
300,000,000 miles per second.
Off by quite a few orders of magnitude. (If it were true, light would only take a fraction of a second to cross 93,000,000 miles!)

You have mixed up miles and meters and made several other mistakes - though at the last second you managed to somehow use the correct value in your actual calculation.

This is one of the reasons why it is important to post homework in the appropriate homework forum. They get a different kind of treatment.
 
Last edited:
  • Like
Likes FactChecker and phinds
  • #5
I think he meant to say it was 300,000,000 meters per sec as that is what he used in the actual calculation.

But in any event, a teacher would likely have taken off points for that.

Good catch @DaveC426913
 
  • Like
Likes FactChecker
  • #6
DaveC426913 said:
This appears to be homework. It should be posted in the proper homework forum.
It is not homework. I graduated in June 1994.
 
  • #7
jedishrfu said:
I think he meant to say it was 300,000,000 meters per sec as that is what he used in the actual calculation.

But in any event, a teacher would likely have taken off points for that.

Good catch @DaveC426913
Thank God I am not a classroom student.
 
  • #8
DaveC426913 said:
Off by quite a few orders of magnitude. (If it were true, light would only take a fraction of a second to cross 93,000,000 miles!)

You have mixed up miles and meters and made several other mistakes - though at the last second you managed to somehow use the correct value in your actual calculation.

This is one of the reasons why it is important to post homework in the appropriate homework forum. They get a different kind of treatment.
Moving forward my questions will be posted in the Precalculus section.
 
  • #9
jedishrfu said:
Sounds about right ie 8.33 minutes.

You can google check it too.
Good idea.
 
  • #10
DaveC426913 said:
This appears to be homework. It should be posted in the proper homework forum.
Can you move this post to the proper section? I don't know how to move a post from one section to another. I am a new member trying to learn the website rules when time allows.
 
  • #11
felizgu said:
It is not homework. I graduated in June 1994.
I graduated in June 1977. I still post questions in the homework forums, when I'm looking for hints and confirmations rather than for answers and explanations.
 
  • Like
Likes berkeman
  • #12
Hill said:
I graduated in June 1977. I still post questions in the homework forums, when I'm looking for hints and confirmations rather than for answers and explanations.
Can you please move this post to the right section?
 
  • #13
felizgu said:
Can you please move this post to the right section?
I can't. Mentors can.
 
  • Like
Likes felizgu
  • #14
Hill said:
I can't. Mentors can.
The standard way to request such is to click "Report" on the post. In the report message, explain the action that you would like taken. This avoids polluting the thread with the banter about contacting mentors.

However, given that the thread has already been moved, maybe I should just have remained quiet.
 
  • Informative
Likes Hill
  • #15
jbriggs444 said:
The standard way to request such is to click "Report" on the post. In the report message, explain the action that you would like taken. This avoids polluting the thread with the banter about contacting mentors.

However, given that the thread has already been moved, maybe I should just have remained quiet.
Yes, the thread has already been moved. It looks like I started WW3 here over something silly.
 
  • Like
Likes jbriggs444
  • #16
felizgu said:
It is not homework. I graduated in June 1994.
To be clear, it does not matter if it is actually homework for you. If anyone has a question that is of the form "here are some givens; find the formula and get the answer", it still should be posted in the homework section with the homework template. :wink:
 
  • Like
Likes Bystander
  • #17
DaveC426913 said:
To be clear, it does not matter if it is actually homework for you. If anyone has a question that is of the form "here are some givens; find the formula and get the answer", it still should be posted in the homework section with the homework template. :wink:
Like I said a few times already, my college algebra textbook questions will be posted in the Precalculus Homework Section moving forward. I don't want to turn this into an online war. It was a simple mistake on my part. Can we move on?
 
  • #18
felizgu said:
I don't want to turn this into an online war. It was a simple mistake on my part. Can we move on?
Of course. I was not trying to admonish.
A bunch of similar responses all came close together. But it was all one wave, not repeated waves. Wasn't trying to beat a dead horse. :wink:
 
  • Like
Likes felizgu
  • #19
DaveC426913 said:
Of course. I was not trying to admonish.
A bunch of similar responses all came close together. But it was all one wave, not repeated waves. Wasn't trying to beat a dead horse. :wink:
Very good. Wait for my next set of questions.
 
  • #20
felizgu said:
Very good. Wait for my next set of questions.
I don't think so. Thread is paused for Moderation... :wink:
 
  • #21
berkeman said:
I don't think so. Thread is paused for Moderation... :wink:
I am not talking about this thread.
 
  • #22
Thread will remain closed. Turns out the OP is the latest sockpuppet of a previously banned problematic member.
 

FAQ: How Long for a Beam of Light to Reach Earth?

1. How long does it take for light from the Sun to reach Earth?

Light from the Sun takes approximately 8 minutes and 20 seconds to reach Earth. This is because the average distance from the Sun to Earth is about 93 million miles (150 million kilometers), and light travels at a speed of about 186,282 miles per second (299,792 kilometers per second).

2. What factors affect the time it takes for light to travel to Earth?

The primary factor affecting the time it takes for light to travel to Earth is the distance from the light source to Earth. Additionally, the medium through which light travels can affect its speed, but since light travels through the vacuum of space to reach Earth, this factor is negligible in this context.

3. How fast does light travel?

Light travels at a speed of approximately 186,282 miles per second (299,792 kilometers per second) in a vacuum. This speed is considered a fundamental constant of nature and is denoted by the symbol "c."

4. Does the distance from Earth to other celestial bodies affect light travel time?

Yes, the distance from Earth to other celestial bodies significantly affects the time it takes for light to travel from those bodies to Earth. For example, light from the nearest star, Proxima Centauri, takes about 4.24 years to reach Earth, while light from distant galaxies can take millions or even billions of years to arrive.

5. Can we see light from stars that no longer exist?

Yes, we can see light from stars that no longer exist if the light emitted by those stars has not yet reached Earth. Since light takes time to travel across vast distances, we may be observing stars as they were in the past, sometimes millions of years ago, even if they have since burned out or exploded.

Similar threads

Deflection of light passing the Sun
Replies
3
Views
1K
(Introductory SR) Light sent from a spaceship received by Earth
Replies
6
Views
1K
How Far Has Earth Traveled Since Its Birth?
Replies
5
Views
3K
How does relativity affect the detection of atmospheric muons?
Replies
11
Views
1K
Length contraction and Time dilation for LIGHT?
Replies
8
Views
2K
What is the distance between the Sun and the Earth?
Replies
18
Views
2K
Gravitational potential energy traveling from earth to mars
Replies
7
Views
2K
Calculating attenuation necessary to reduce number of photons
Replies
8
Views
2K
Light Signal Travels Between Earth and a Spaceship
Replies
19
Views
2K
Speed of a star in Special Relativity
Replies
6
Views
955

Hot Threads

Recent Insights

Back
Top