Science Forums

# Time,Light, and appearance

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Hello,

I am a new member and my question has to do with observations

using the SLOOH online telescope.

One of the galaxy's I captured the other night was 40,000,000 Lt yrs away.

I have been trying to figure (using standard speed of light and the distance it travels)

how 'old' the image was that I was viewing.

Could someone help me calculate the age of the image on the telescope mirror.

I arrived at 231,232 yrs old

( I feel I am incorrect)

Thanks for any input.. :circle:

In other words 'timewise' how far backwards am I looking?

There is no way the image is seen in real time due to its sheer distance.

Maybe I am getting our chronological time confused with light speed and space/time.

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Hello,

I am a new member and my question has to do with observations

using the SLOOH online telescope.

One of the galaxy's I captured the other night was 40,000,000 Lt yrs away.

I have been trying to figure (using standard speed of light and the distance it travels)

how 'old' the image was that I was viewing.

Could someone help me calculate the age of the image on the telescope mirror.

I arrived at 231,232 yrs old

( I feel I am incorrect)

Thanks for any input.. :rant:

First you have to be initiated into the forum, which means that Tormod must first scold you for asking a question even remotely similar to anything that's been asked before, and then we can get on with the discussion. Welcome to the site

:circle:

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...thanks very much :circle:

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Opps, I should probably include somewhat of an answer too, or Tormod might give me negative feedback again (if they can do that twice). However, you are way off in your calculation. You can't see light before the time it was given off... and your estimating that the light is younger than the distance it had to travel AT light speed.

I assume, since you don't know how to calculate this, that anyone can use this telescope? Or is it part of an introductory astronomy course you're taking at a university?

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...thanks very much :circle:

Careful, the great moderators might look down strongly for that one and give you negative reputation marks... (seems to be a Greek thing?) :rant:

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I am looking back in time 40 million years ?

Maybe my brain is stuck in Timex Time...I am new to these things...bare with me.

I just recieved 'The Fabric of the Cosmos' by Brian Greene

Also been reading 'The Holographic Universe'

I'll get it figured out sooner or later

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If I look at the Sun (not in real life,just as an example)

am I not looking backwards 8.13 mins ? :circle:

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If I look at the Sun (not in real life,just as an example)

am I not looking backwards 8.13 mins ? :hihi:

LOL... No, you're not exactly looking back 8.3 minutes. I mean, you're not looking 'back in time' and seeing the sun in its position 8.3 minutes in the past. The light has come to you after being given off that many minutes ago. Thus you ARE seeing the sun as it WAS at that time. The information has just taken that length of time to reach you.

Yes, generally speaking the galaxy you refer to gave that light off 40 million years ago. I say generally, because technically you have to also consider the expansion of the physical space in between, which can make it a bit trickier to nail down exactly.

Try asking the folks here if considering the expansion of space, the galaxy you refer to gave it's light off 40 million years ago... or whether it's 40 million light years away right now. They can not be the same answer and no one seems to want to address it (I asked a similar question and never got my answer).

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quote:"Thus you ARE seeing the sun as it WAS at that time. The information has just taken that length of time to reach you"

Exactly what I am getting at :hihi:

...my idea is that the universe is 'late' in appearance

there could be a 'new' nebula exploding right now,

but due to the distance of the light reaching us,

the nebula may have happened centuries ago.

like lightening...it takes a while for the thunder to reach our ears depending on the distance of the storm.

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quote:"Thus you ARE seeing the sun as it WAS at that time. The information has just taken that length of time to reach you"

Exactly what I am getting at :hihi:

...my idea is that the universe is 'late' in appearance

there could be a 'new' nebula exploding right now,

but due to the distance of the light reaching us,

the nebula may have happened centuries ago.

like lightening...it takes a while for the thunder to reach our ears depending on the distance of the storm.

You are precisely correct in your understanding. You can also apply your lightning/thunder example to fireworks. If you're far enough away from them you'll see the fireworks before you hear the boom.

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One of the galaxy's I captured the other night was 40,000,000 Lt yrs away.

I have been trying to figure (using standard speed of light and the distance it travels)

how 'old' the image was that I was viewing.

You saw it as it was 40 million years ago in your frame of reference. Large red shifts need a relativistic correction. 40 million lightyears is adequately Newtonian.

Did they anticipatorily wave "hello"? "8^>)

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