Thread: Question about light-years

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That's right.
If something is at a distance of X light years then we can only see it as it appeared X number of years ago, not as it is "now".

Thank you!

Originally Posted by xcasper

This question is going to make me sound like an idiot, but it's fine. I'm trying to clear something up that I just can't wrap my head around for some reason. It's like how everyone has that one word that they can never remember how to spell.
If light-years is a measure of the distance that light can travel in one year, does that mean if something is 40,000 light years from Earth... then it takes 14,600,000 days for light to travel from here to that location? It takes 40,000 Earth years? So if something is 800 light years away, light traveling from here to there will take 800 years?

Just one little comment. it would take 14,610,000 days for light to travel 40,000 light years as the "year" used for a light year is the Julian year of 365.25 days. So technically, it would take light 800 calendar years plus a bit over 6 days to travel 800 light years( as the mean tropical year is 365.24217 days long).

Speaking of distances, and this may be more of a philosophic question, but is it even worthwhile to pursue inter galactic travel? For one thing, aren't there enough stars to occupy us within the confines of our own Milky Way Galaxy? The nearest star in the galaxy is about 4.3 ly away and the farthest approximately 775000 to 900000 ly away with a billion or so stars in between. Is it really necessary to go inter galactic?

I'm not sure what reason we would have to go intergalactic unless it's because we can. Can't see any trip of a vast distance even worth being a two way voyage. So many things to consider like there not being enough resources for us to plunder from billions of planets, moons, etc......highly unlikely IMHO. Spread the seed? Rule the Heavens? What are good reasons for leaving the Milky Way?

Larry Niven came up with a good reason: a mega super nova at the centre of the galaxy that, due to the close proximity of stars closer in toward the centre, caused a "chain reaction of supernovas" - which resulted in a spherical front of hard radiation moving outwards at light speed.
That's why the Puppeteers left (taking all their planets with them) and that's how they discovered Ringworld.

Originally Posted by Dywyddyr

Larry Niven came up with a good reason: a mega super nova at the centre of the galaxy that, due to the close proximity of stars closer in toward the centre, caused a "chain reaction of supernovas" - which resulted in a spherical front of hard radiation moving outwards at light speed.
That's why the Puppeteers left (taking all their planets with them) and that's how they discovered Ringworld.

Should we be looking for it? How much time would we have? What would happen if an entire galaxy all of a sudden just blew up, a universe buster chain reaction?

Originally Posted by zinjanthropos

Originally Posted by Dywyddyr

Larry Niven came up with a good reason: a mega super nova at the centre of the galaxy that, due to the close proximity of stars closer in toward the centre, caused a "chain reaction of supernovas" - which resulted in a spherical front of hard radiation moving outwards at light speed.
That's why the Puppeteers left (taking all their planets with them) and that's how they discovered Ringworld.

Should we be looking for it? How much time would we have?

By the time see saw it, it would be too late . The only reason the Puppeteers new about it was because they had sent a prototype hyperdrive ship(with a human pilot) to the core. They themselves didn't use hyperdrive as they felt it was too risky, which is why they decided to flee at sub-light speed (Beside they were only heading for the Magellanic clouds

What would happen if an entire galaxy all of a sudden just blew up, a universe buster chain reaction?

Probably not, galaxies are pretty far apart, and the intergalactic medium is thinner and even less conducive to transmitting a shock wave.

If by the time we see it being too late then does it matter if we can travel inter galactic? Just out of curiosity, now that we can observe a vast number of galaxies, is there someone looking for a galaxy destroying event or has evidence of one been spotted?

Originally Posted by Dywyddyr

Larry Niven came up with a good reason: a mega super nova at the centre of the galaxy that, due to the close proximity of stars closer in toward the centre, caused a "chain reaction of supernovas" - which resulted in a spherical front of hard radiation moving outwards at light speed.
That's why the Puppeteers left (taking all their planets with them) and that's how they discovered Ringworld.

Looking at people like Trump: http://ih0.redbubble.net/image.18103...x800,075,f.jpg
Putin and Boris Johnson, I sometimes think we live in Ring World.