Is everything we know about Space obsolete?

Question

I watched a video that said it would take 5 years traveling at the speed of light to reach the nearest star to our solar system. And 100,000 years at the speed of light to be able to see the milky way galaxy in its entirety. So does this mean that everything scientists look at in space are an image (reflection of light) from hundreds or thousands of years ago? By the way, when people say "light year" is this just a measure of the distance traveled by light in a year?

Answer 1

Everything we see is as it were in the past. This doesn't mean it's obsolete. Obsolete would mean the information we obtain by looking is no longer relevant. In general, that will not be true, and here's why: most things move much less slowly than the speed of light, so very big things like the Milky Way Galaxy do not change very much during the time it takes light to cross them. Distant light from the furthest parts of the Milky Way takes 100,000 years to reach us. But during that time, the Milky Way will only have rotated a little bit---a tiny fraction of one degree. So our picture of the Milky Way is mostly right, even though it is old.

It's actually a good thing that light takes a long time to travel, because it lets us see stars and galaxies from the distant past. We don't have to guess how they evolved over the billions of years, we can just look! If you want to know what a galaxy looked like 10 billion years ago, you can see one in a telescope. Most of the galaxies in the Hubble Deep Field are billions of years old.

Answer 2

A light year is indeed a distance; the distance you would travel in a year at a speed of 186,000 miles a second. It is almost six trillion miles.

And yes, we see the stars as they were many years ago. But since stars last for millions or billions of years, that is no big deal.

The nearest star is not in our solar system. It is far outside our solar system.

You can see the Milky Way as a whole in the night sky, but from the inside. It looks like a band of light crossing the sky, especially in summer. But you need a dark sky, far from city lights to see it because it isn't very bright. To see it from outside, you would indeed have to travel many thousands of light years away, and then look back, since we are inside it and it is 100,000 light years wide.

Answer 3

When astronomers study star systems etc they are looking in the past. Alpha Centauri, our nearest star after the Sun, is 4.3 light years away. Its distance from Earth is 4.3 x 365.25 x 186,000 = a really big number (my calculator only has 8 digits). Even the light from the Sun is 8 minutes old by the time it reaches us.

Whether all of this means our knowledge of space is obsolete, I doubt it. Our knowledge develops as our technology reaches further into space to shorten the gap of how far back we must look.

The concepts demonstrated by Star Trek and its ilk are beyond us for the moment so it is physically impossible for us to move beyond our solar system therefore studying the past in space is our only method of furthering our space knowledge.

Answer 4

Obsolete is a bit of a strange word. I'd call it more like looking into the past. The speed of light and the vast size of the universe make it more interesting. The further away something is that we can see the older it is. We can look at the very origins of this universe by studying early stars and even earlier with the background microwave radiation.

Answer 5

Yes a light year is how far light can travel in a year. And Yes when you look up at the night sky your looking at everything in it at how it existed in the past. Sirius, the closet star to Earth besides the Sun, is around 4 light years away from Earth so when you look at it you see it how it existed 4 years ago. So if something is 5,000 light years away, when you look at it you see it as it existed 5,000 years ago.

Answer 6

Yes.

The looking back time is called the lookback-time. This is how we know of the background radiation from the big bang. The Eagles Nebula is thought to be already destroyed by a stellar explosion, but we are seeing it as it was 4000 years ago.

And yes.

A light year is a unit of distance measurement, not time measurement.

Answer 7

We know very little about the space and its origins, and scientists try to make up for this by using our limited knowledge and they make theories. But it cannot be considered obsolete because no new knowledge has come in which renders what we know useless. Also a light year is a distance.

Answer 8

1, light year or an eon is the distance traveled/time taken for a photon to travel that distance!

we know nothing about space, its mostly theory and a lot of that is science fiction and not science fact, so you will form ideas and theories of your own if you can think outside the box if you can't you'll believe that E=MC2... which i believe is probably the greatest intellectual joke ever but hey don't take my word for it spend about 10 years reading,writing making assumptions rethinking your ideas and you might just get back to where you started or you may hit on something new...

Answer 9

We are not even in the bicycle stage yet. You need to build on something and granite's we got a long ways to go before we start warping across the Galaxy .

Answer 10

0. No, some of it is still very useful.
1. Yes.
2. Yes.