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If it is true that the light we are seeing from other galaxies is light that began traveling our direction long long ago, is it possible to see the earth at some distant historical time and place through a satellite?
Am I overthinking it, or should the location of the earth (or sun) a million years ago be viewable since our solar system has been drifting through the universe?
Maybe it's not possible, since we are not moving as fast as the speed of light?
Any thoughts?
We see the sun as it was 8 minutes ago, because it's 8 light minutes away. A star a million light years away we see it 1 million years in the past. However we cannot do anything to see it in the present.
I'm not sure what you are asking.
I'd like to know about seeing the earth a million years ago. Where it was in space...
Or some other distant time... if it is possible?
Unfortunately lightspeed is the maximum speed possible in nature.Quote:
Originally Posted by oneguyinohio
Light from previous locations must have spread faster than the earth could move, and has to be beyond our reach, now and forever.
The only possibility to still see it could be once that light has gone around the entire universe to return here.
At that moment "we" will see it again - if at that time it is still visible, and if anyone will be around to see it , in many billions of years from now (minus that 1 million years) :rolleyes:
I suggest we all wait for that moment then...
:D
That brings me a couple more questions.
If light particles are given off during lights travels, does that mean there is a point when the light would stop because all of the particles have been given off.
Is it possible to follow the path of particles given off?
With the Hubble telescope viewing images closely connected with the Big Bang, why is that evidence still visible? Shouldn't that light also be invisible to us since it would have been traveling faster than we moved?
I don't follow.. light doesn't give off light, unless it's through some sort of interationQuote:
Originally Posted by oneguyinohio
The big bang happened everywhere in the universe, then the universe expanded at every point, cooling as it went. The cosmic microwave background radiation is the remnant of the big bang, the photons reaching us from about 400,000 years after the big bang happened.Quote:
Originally Posted by oneguyinohio
You'd have to be observing it at a point a million light years away from Earth.Quote:
Originally Posted by oneguyinohio
If we put a mirror out into space 500,000 light years away, and look in the mirror, you would be able to see the Earth a million years ago. But you'd need to wait more than 500,000 years to get your mirror in place (and there are other obvious technical problems.. )
Thanks for your answers. It helped me understand better.
Please don't hesitate to ask more :)Quote:
Originally Posted by oneguyinohio
Is the location of that background radiation then believed to be in the center of the universe?
There is no "center" in the universe.Quote:
Originally Posted by oneguyinohio
There is no inside nor outside of the universe.
Everything in the universe happens on some sort of expanding spacetime "skin".
See "String" and "Brane" theories for that.
:rolleyes:
No, it's coming from a sphere that is about 13 billion light years around us. The big bang happened everywhere in space, so these are the photons from the big bang that are just reaching us.Quote:
Originally Posted by oneguyinohio
The Big Bang happened when spacetime was only a fraction of what it is today. Actually there never was a 'bang'. Just a superfast growth of spacetime. Note that we and everything else in the universe are part of that same expanding "sphere" that you mentioned. A four dimensional universe with width, length, height, and time. Einsteins acclaimed "expanding balloon" suggestion is a good three dimensional representation of that. (All other claimed dimensions still have to be proved to exist)...Quote:
Originally Posted by Capuchin
.
:rolleyes:
No, the CMBR sphere I'm referring to is due to the expanding light cone that grows at 1 light year per year (actually slightly more due to the expansion of spacetime).Quote:
Originally Posted by Credendovidis
I stand corrected!Quote:
Originally Posted by Capuchin
:D
How is this shape known?Quote:
Originally Posted by Capuchin
The cone is just the shape on a 2Dspace-1Dtime graph, "light cone" is a term we use a lot. The actual shape in 3D space is a sphere (or pretty close to one) due to the uniform speed of light.Quote:
Originally Posted by firmbeliever
It's my understanding that light travels at speed of light, based on measurable perspective. Meaning that if your on a spaceship traveling at the speed of light. The lights in the spaceship work fine because from your perspective the lights aren't traveling faster than the speed light. So your flashlight would also work just fine from your ship but if I was trying to see the flashlight from a point outside your ship I would not see the light from the flashlight or the flashlight for that matter until it either past me or hit me because you can't see an object going the speed of light because your vision is based on the light bouncing off the object so if the object is going the speed of light the light that bounces off can't be seen until the object would have already gotten there in the first place.Quote:
Originally Posted by oneguyinohio
The mirror experiment would be interesting. I'd be interested in trying that, 500,000 light-years away might be tough but 16 minutes away might be doable.
They have mirrors on the moon for precise range-finding, I wonder if they're big/useful enough to see a reflection of the earth. You'd be able to see ~2 seconds into the past ;)Quote:
Originally Posted by michealb
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