Would there still be light if its source was gone?

[unknownspiritx]

What i mean is that...say a massive star is emitting light for billions of years and then it explodes into a supernova. There would still be light from the supernova that would travel out into space, but eventually the supernova will go away, but then will the light that once came from the supernova go away too? Or will it keep traveling in space in our ever expanding universe?

[Astrowannabe]

Yes, once light is emitted, it will continue to travel regardless of what happens to the object that emitted it. The object may not emit any more light, but the light that has already been emitted will continue on it's merry way. So if we see a star go supernova 100 million light years away, the star that emitted the light would have long since become a neutron star or a black hole, yet the light continues to travel to us regardless.

Kind of like if you throw a snowball at someone really far away and then run off before the snowball hits the person, the snowball will still travel through the air even though you aren't there anymore.

[Fortis]

You could also think of the two photons emitted when a positron and electron annihilate each other. :)

[jamesabrown]

It's a common story line in movies about submarines. Two subs are circling each other, launching torpedoes, etc. The enemy sub will finally be struck and destroyed, but during the good guys' cheering the sonar tech will start screaming that one more torpedo was launched just before the enemy was defeated. Then the sub (often damaged, to boot, to ramp up the tension) will have to scramble frantically to avoid the last torpedo.

Same thing. When a star goes out, it's last few photons may travel for billions of years before being absorbed by something (dust, a rock, the back of your eyeball, etc.)

[crosscountry]

can we say CMBR or Cosmic Microwave Background Radiation?

[EvilEye]

This is an easy one.

Propagation is the word.

If I give birth to a son, does the son die when I do? Or does he go on?

My DNA will continue to propagate until it is totally mutated into something else.

Light is the same way.

[unknownspiritx]

This is an easy one.

Propagation is the word.

If I give birth to a son, does the son die when I do? Or does he go on?

My DNA will continue to propagate until it is totally mutated into something else.

Light is the same way.

Wow that really hits it.

But yeah, thanks everyone else for your answers too. They def. helped.

[zebo-the-fat]

The light will continue to travel outwards, but it will spread out as it travels so becoming fainter as it goes. (The same "amount" of light but spread over a greater area)