Light from distant star question???

Question

When Scientist describe distance of stars , they say the nearest star is 50,000 light years away. So the light we see in space as at or more 50000 years of travel time. So when they see changes in stars or explosions of these stars its a view/picture of the past 50000 years or more ago. how can we guarentee what were seeing has not been distorted by time or space? The gases and refractions of dust and particles? * plus one statement to everyone out their....-> We need to quit trying to move faster in space, were never going to reach 100,000 times (X) the speed of light , its obviuos it was meant for us to figure out how to create space distortions not speed to reach nieghboring systems.

Answer 1

Well for one, the nearest (after Sol) is a bit more than 24 trillion miles away and the parallax system of determining distance works quite well for such a 'close' celestial object. As we go farther out different means of finding distances all seem to jive, and so these distances are pretty much ---what they are!

Answer 2

The nearest star (Proxima in the Alpha Centauri system) is about 4.3 light years away.  When we view Proxima, we're seeing the star the way it appeared 4.3 years ago.

Even light from the Moon is 1.5 seconds old when we see it.

Space is not perfectly empty, but it's close enough to pretty well guarantee that the light hasn't been distorted on its way here.

Answer 3

the speed of light has been known to be finite for 350 years. so what?

uh, what is your question?

Answer 4

If it was distorted a star 10,000 light years away would have 1000 time as much distortion as one 10 light years away. But they look the same.

Answer 5

Well. I imagine you know that space/time can itself be distorted by gravity. Which in turn "appears" to distort light. I sometimes wonder what effect the theorized "dark matter" and all it's gravity would have on our perceptions also.

http://images.google.com/imgres?imgurl=h...

Answer 6

Your question?

Answer 7

The nearest star is 4.2 light years away, not 50,000. But you are right, things can happen to light as it travels through space. Most commonly, some of it is absorbed by gas and dust between here and there. But space is mostly empty, so unless there is a nebula in the way, this effect is very small in most cases. Another thing that happens to light is that light from very distant galaxies is shifted toward lower frequencies by the expansion of space. Any motion of the star towards or away from us will cause a shift in wavelengths, though for stars in our own galaxy this is much smaller than the red-shift of distant galaxies. Magnetism and gravity can also cause slight wavelength shifts.

The way we can tell what happens to the star's light is by comparing it to other stars. All stars have distinctive dark lines in their spectra at known wavelengths, so we can compare what the wavelength is to what we can calculate it should be. We can also identify the true brightness of some stars, and compare that against observed brightness to see if any light has been absorbed.

It's impossible to move at or beyond the speed of light, so you're right, we would have to do something else if we hope to reach other stars. Supposedly wormholes can connect two distant points in space, but no one has been able to figure a way they could be of any practical use. The physics of that, if it's possible, is beyond anything we currently know.

Answer 8

Yes,  you are correct that when you see light from a distant star, you are actually looking into the past (i.e. light from proxima centauri takes 4.2 light years to reach earth, so if you look at proxima centauri, you're looking 4.2 light years into the past and seeing what it looked like then).  

As for distortion, you DO get distortion, and you're supposed to.  For instance, if you look at the light from a supernova (explosion) you get specific pattern variations that one would expect to accompany an explosion.  

As for trying to move faster and reaching the speed of light, I've got a surprise for you:  

everything in the universe, including you and me, already and always travels at the speed of light.  It's not only the universal speed limit, it's the universal speed.  

The misunderstanding you have is in thinking of the speed of light as a speed only.  

Space-Time is one entity, and the speed of light is equal to your speed through space plus your speed through time.  

We here on earth move at a specific speed through time, which is equal to:  the speed of light minus our speed through space.  

By space distortions to reach neighboring systems, I think you're on the money there, and in theory it certainly seems easier than trying to move "faster through space/slower through time" to get to a neighboring star more quickly.  However, I'm wondering how much energy it would take to create such a spatial distortion?

Answer 9

To answer your question directly.  The way that we know that what we are seeing is not overly distorted is that we can cleraly image stars in the vicinity of other space obejcts.  At their distance from earth, a telescope cannot magnify the image most stars (i.e. make the star appear larger).  All that a telescope can do is to collect more light and look into a narrower region of the sky, magnifying the apparent distances between the stars.  But a good telescope will bring most stars to a point image that is limited by the optics of the telescope itself, the "diffraction limit".  So if we see stars as point obejcts in our telescope image we know that there has not been any distortion in the intervening space.  

Most of the distortion that we see comes from refraction in our atmosphere.  There are 3 solutions to this:

1- Build observatories on mountain  tops to get above most of the atmosphere - only partly effective

2- Use "adaptrive optics wavefront correction" to correct for the distorting effects of the atmosphere.  This was originally developed in secret for imaging satellites from earth and was declassified some time in the early 1990's.

3- Put the telescope up in space above the atmosphere.  For example, the Hubble Space Telescope orbits at about 350 miles above earth.  The James Webb Space Telescope, scheduled to be launched around 2015, will be in a stable position about 1 million miles from earth to be beyond earth's influence in terms of stray light and thermal radiation.

There are relativistic effects that do distort our images from deep space.  The presence of black holes, which exert a huge gravitational effect, causes "gravitational lensing" where light from more distant galaxies is actually bent (gravitationally refracted) as it passes by a black hole.  This produces clearly distorted circular images of the more distant objects.

To address your other comments:

True that the light that we are seeing from more distant stars started on its voyage to earth in the distant past.  Light from a star that is 4.3 light years from earth (the closest star) has been traveling for 4.3 years to get here. The most distant galaxies that we have seen directly are billions of light years from earth.  By imaging them we are seeing events that happened much earlier in the history of the universe.

Finally, nothing can travel faster than the speed of light in vacuum. One of the responders, "Feythe" states that everything in the universe, including us, is traveling at the speed of light - WRONG.