LIGHT SPEED

I need some help please.

Andromeda when we look up and see it i am under the impression that we are seeing it as it was 2.500.000 years ago.

So its 2.5million light years away.

What i am asking is,At this point in time NOW how many light years is it from our galaxy it cant be 2.5million light years away or is it.

It should be closer to us by whatever speed its been traveling towards us then multiplied by 2.5million or am i completely off the ball.

Any help will be greatly appreciated on helping me understand light speed.

thank you.

originally posted by: KROandSOTV


It should be closer to us by whatever speed its been traveling towards us then multiplied by 2.5million or am i completely off the ball.

Don't 'should' on yourself.

We don't even know whether the astral bodies we see still exist.

All we do know when we look to the heavens is, what we observe, is NOT what is there now.

Sorry this goes right over my head, though I would like to know the answer to this as well. I don't know why but it is very hard for my brain to process the time and speed of light stuff, my brain just isn't wired that way but I find it fascinating. What also confuses me a lot is the farther we look into the universe the further back in time they are, so if we look far enough we can see the beginnings of the universe, how is this....damn I can't even word how this confuses me, it just does.

originally posted by: KROandSOTV
I need some help please.

Andromeda when we look up and see it i am under the impression that we are seeing it as it was 2.500.000 years ago.

So its 2.5million light years away.

What i am asking is,At this point in time NOW how many light years is it from our galaxy it cant be 2.5million light years away or is it.

It should be closer to us by whatever speed its been traveling towards us then multiplied by 2.5million or am i completely off the ball.

Any help will be greatly appreciated on helping me understand light speed.

thank you.

It will be 2.5million light closer than what you see it as now.

what would happen if I instantly teleported to say Andromeda, would the earth still be in the same time period? Probably a stupid question lol

Yes, Andromeda (as long something didn't come along and wipe it out within the 2.5 million years that it took the light to reach us) is closer to us currently then we can actually see it.

originally posted by: Shepard64
what would happen if I instantly teleported to say Andromeda, would the earth still be in the same time period? Probably a stupid question lol

If you instantly teleported anywhere, the earth would always be in the same time period. It would APPEAR to be 2.5 million years older though (if you could see it).

a reply to: Psynic

So if Andomeda doesn't exist anymore what will happen when it gets closer and closer? My brain hurts

I wonder if it makes a difference if you are a Briggs and Myers type S or type P?

a reply to: Shepard64

Since Andromeda is a galaxy, anything that would destroy it, would be MASSIVE and would likely wipe us out next.

a reply to: Krazysh0t

That is insane! It really makes you wonder what the heck time is anyway.

a reply to: Krazysh0t

Since Andromeda is a galaxy, anything that would destroy it, would be MASSIVE and would likely wipe us out next.

Good point

originally posted by: Krazysh0t

originally posted by: Shepard64
what would happen if I instantly teleported to say Andromeda, would the earth still be in the same time period? Probably a stupid question lol

If you instantly teleported anywhere, the earth would always be in the same time period. It would APPEAR to be 2.5 million years older though (if you could see it).

It cant though because light would take 2.5million years to get there so you would see the earth as it was 2.5million years ago.
Thats me last brain cell gone now

Okay here is one for you. What if someone lived since the beginning of the universe and didn't move, what would the earth look like from where they are after 6 billion years...dammit I really don't know where I am going with this lmao I am at work and tired

originally posted by: Shepard64
Okay here is one for you. What if someone lived since the beginning of the universe and didn't move, what would the earth look like from where they are after 6 billion years...dammit I really don't know where I am going with this lmao I am at work and tired

dunno im trying to work out where Andromeda is ive got me own problems

originally posted by: Shepard64
Okay here is one for you. What if someone lived since the beginning of the universe and didn't move, what would the earth look like from where they are after 6 billion years...dammit I really don't know where I am going with this lmao I am at work and tired

After 6 billion years from now on, or after 6 billion years after Big Bang? That question is confusing. And it depends where the observer is located.

But anyway, if you mean 6 billion years from now one, Earth wouldn't exist. It already has been swallowed by the expanding Sun. Three innermost planets are gone, Mars is closest planet to cold Sun. You would be able to see Earth if you were located about 2 billion light years from Earth, and owned really huge telescope to actually spot Earth. You would see Sun slowly expanding and finally swallowing Earth. Earth would look very different, oceans would have vaporized million of years ago, Earth would be completely dry.

And if you mean 6 billion years after The Big Bang, Earth hasn't formed yet

a reply to: KROandSOTV

When scientists calculate distance to Andromeda I am not sure if the calculate the distance the light has traveled to get here or if the also calculate how much closer Andromeda is now since that light left Andromeda.

You would need to figure out how far away the light traveled, the speed Andromeda is moving toward us then how far Andromeda should have moved closer two us since the light left Andromeda. Then subtract the distance Andromeda moved over the time it took the light to get here from the distance the light traveled. I think!



Even after all that you have to hope the light traveled here at a constant rate and was not bent or slowed by passing gravity wells to know exactly...

If you teleported to Andromeda right now, you and I could both pick our nose at the same time, but it'd take 2.5 million years (or whatever the precise current distance is) for you to see my pick my nose with your super amazing telescope.

If Andromeda is moving closer to us, I suppose we are actually seeing Andromeda on slight fast forward.

I have heard some reports that Andromeda and our galaxy is on a collision course, but other reports that our universe is still expanding. It does raise some doubt for when these two galaxies will come together if they do, measuring for a red or blue shift in the light from Andromeda will help determine how fast it is coming closer or moving further apart.

For arguments sake lets say Andromeda is moving towards our galaxy. At the current distance it will take 2.5 Million years for Andromeda to get here if it did travel at the speed of light. While galaxies may move around quite fast, due to their mass they do move a lot slower than the speed of light. As a rough practical guide, it could take billions if not trillions of years for Andromeda to finally get here.

In a bit like looking at the headlights of a car traveling towards us on a quite, dark and long country road, the light does reach us a lot faster than what the car finally does.

It's simple really:

Light travels at 299 792 km/s.

The Andromeda Galaxy is approaching our galaxy at 110 km/s.

So the light from Andromeda is going 2725 times faster than the galaxy itself is actually moving.

We measure it's distance based upon what we see (the light). The Andromeda Galaxy is at about 2.5 million light years away, so indeed, the light we are seeing is from where it was 2.5 million years ago.

So yes, it's actually closer than what we are seeing, because it is approaching us.

But how much closer?

We can calculate that. 1 lightyear is 9,460,730,472,580 km. Multiply that by 2.5 million:

23,651,826,181,450,000,000 km.

That is how far away it was, 2.5 million years ago. But, because we know it's coming towards our galaxy at 110 km/s, we can figure that out too.

It's velocity is 3,468,960,000 km per year. Multiply that by 2.5 million:

8,672,400,000,000,000 km is how far it has traveled towards us in that 2.5 million years.

Now, subtract that number, from how many kilometers there are in 2.5 million light years:

23,651,826,181,450,000,000 - 8,672,400,000,000,000 = 23,643,153,781,450,000,000 km.

Now, divide the answer by the amount of kilometers in a light year:

23,643,153,781,450,000,000 / 9,460,730,472,580 = 2,499,083.32 lightyears.

So, even though it's had 2.5 million years to approach us, at only 110 km/s, it's still well over 2.4 million lightyears away.

It certainly would not look too much bigger to our eyes or telescopes!