How Long for a Beam of Light to Reach Earth?

• felizgu
felizgu
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.

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:
Sounds about right ie 8.33 minutes.

You can google check it too.

felizgu and FactChecker
This appears to be homework. It should be posted in the proper homework forum.

FactChecker
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:
FactChecker and phinds
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

FactChecker
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.

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.

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.

jedishrfu said:
Sounds about right ie 8.33 minutes.

You can google check it too.
Good idea.

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.

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.

berkeman
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?

felizgu said:
Can you please move this post to the right section?
I can't. Mentors can.

felizgu
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.

Hill
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.

jbriggs444
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.

Bystander
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.
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?

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.

felizgu
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.
Very good. Wait for my next set of questions.

felizgu said:
Very good. Wait for my next set of questions.
I don't think so. Thread is paused for Moderation...

berkeman said:
I don't think so. Thread is paused for Moderation...

Thread will remain closed. Turns out the OP is the latest sockpuppet of a previously banned problematic member.

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