Signal

[john e. holliday]

I have a question for our guy in the know.  If a planet is 40 light years away, how long would a signal of any kind take to get to us?   Same with exploding stars or planets would any thing be left where the explsion took place for anybody to see?  I know there is a delay between the signals we use and the astronauts that traveled to the moon and and back had a delay.

[Brett Buck]

I have a question for our guy in the know.  If a planet is 40 light years away, how long would a signal of any kind take to get to us?   Same with exploding stars or planets would any thing be left where the explsion took place for anybody to see?  I know there is a delay between the signals we use and the astronauts that traveled to the moon and and back had a delay.

40 years - that is the definition of a light-year, how far light travels in a year. Same with the astronauts on the moon (about a second and a half) one way, or even talking via a communications satellite (1/8 of a second up and 1/8 second back down).

    That's why very powerful telescopes also allow us to see things far back in time, if you can see the faint (and red-shifted) light from, say,  13 billion light-years away, it is 13 billion years old, from the universe as it was shortly after formation.

     Brett

[Ted Fancher]

My God!  Don't you just love to have this guy on our forum!?

[Ken Culbertson]

I have a question for our guy in the know.  If a planet is 40 light years away, how long would a signal of any kind take to get to us?   Same with exploding stars or planets would any thing be left where the explosion took place for anybody to see?  I know there is a delay between the signals we use and the astronauts that traveled to the moon and and back had a delay.

Just to put it in perspective, the closest sun to ours is about 25 trillion miles away. The fastest space "ship" we have now goes about 300,000mph.  So to go and actually see if that sun is still there will take 18,950 years at our present state of technology.  Pack a lunch?   Somebody fact check me.  I get all twisted up with numbers that approach the national debt.

I wonder if you get a refund from the Star Registry if yours actually disappeared a couple of million years ago?

Ken

[Roy DeCamara]

So you send a signal asking Is anybody there??  Eighty years later you hear Huh??

[Brett Buck]

So you send a signal asking Is anybody there??  Eighty years later you hear Huh??

  That's about right. Those guys are just getting the first season of "The A-Team"!

     Brett

[Mike Griffin]

The Earth and the Moon captured from Saturn by NASA's Cassini spacecraft, over 900 million miles away.  Cassini was launched on October 15, 1997, 26 years ago and it took it almost seven years to reach Saturn.

Mike

[john e. holliday]

id I read that right?  Someone on the internet stated a light year is 300,000 kilometers a second.   So the signal that started from its location 70 light years away probably not in existance any more.   Just like this piece of space object will cease to exist once the Sun has exploded and how long will the blast take to reach Mother Earth?    Of course I hope I'm not around when it happens.

[Mike Griffin]

id I read that right?  Someone on the internet stated a light year is 300,000 kilometers a second.   So the signal that started from its location 70 light years away probably not in existance any more.   Just like this piece of space object will cease to exist once the Sun has exploded and how long will the blast take to reach Mother Earth?    Of course I hope I'm not around when it happens.

The sun is 93 million miles away.  It will not take long.  Somewhere between 5-8 billion years from now, our sun with become a red giant and vaporize the Earth but I would not worry about it. 

Mike

[Brett Buck]

id I read that right?  Someone on the internet stated a light year is 300,000 kilometers a second.   So the signal that started from its location 70 light years away probably not in existance any more.

    Every signal ever sent is still in existence - just depends on how far it has fallen into the noise.



 

Just like this piece of space object will cease to exist once the Sun has exploded and how long will the blast take to reach Mother Earth?    Of course I hope I'm not around when it happens.

     If it just suddenly exploded, it's about 8 minutes for the radiation, and much longer for the particles. But as noted, the sun is not going to explode in any normal scenario, it will grow into a red giant (and engulf the earth) then end up as a white dwarf. That will take at least hundreds of thousands of years, if not billion or so, so the light travel time will not be relevant.

    Interestingly, the sun used to be less powerful/luminous, maybe 90% of the current brightness at the time of the Cambrian explosion, and maybe 95% when the first dinosaurs evolved. It is still getting brighter.

     Brett

[Ken Culbertson]

 It is still getting brighter.

Especially in the morning when it is always down wind!

Ken