Does light last forever?

[shinbits]

But that's the point, the vacuum DOESN'T weaken the intensity of a beam of light. If nothing interacts with a photon, then it will never decay.

So are you saying that light isn't inherently immune to decay, it just wont decay because of the vacuum? In other words, light is no different than say, a piece of meat left out in space, which will continue on forever unless something interacts with it?

I hope I phrased my question clearly.

 

[Cain Spencer]

But that's the point, the vacuum DOESN'T weaken the intensity of a beam of light. If nothing interacts with a photon, then it will never decay.



No, it's the opposite - it lasts forever provided it doesn't interact with something. And I agree, it's quite possible that it will (although I've no idea what supposed to happen to a photon at the edge of the universe or whether that counts as interaction), though not before travelling a staggeringly vast distance in some cases, which is why we are able to observe light from older stars with little to no loss of intensity. But photons, in and of themselves, are classified as stable, which means they don't decay into anything. In that sense, they are indefinitely existent.

Hmm... well on that note I suppose it would be good to think that while "forever" is a time measurement we need to remember that there isn't a path that will last just as long. But still, it would be small minded to assume that there is absolutely no way for light to weaken or die out. It's just thinking of what would/ could do it.

 

[Cabal]

Hmm... well on that note I suppose it would be good to think that while "forever" is a time measurement we need to remember that there isn't a path that will last just as long.

The important point is that there are two different types of lifetime here - the lifetime of its propagation before it is absorbed, and some proposed inherent decay mechanism. The fact that we can observe stars at such vast distances would imply that neither is much of an issue.

But still, it would be small minded to assume that there is absolutely no way for light to weaken or die out. It's just thinking of what would/ could do it.

I never said it couldn't - but you'll need evidence for that, and right now as far as I know, it's down on the side of stability, and I think that's unlikely to change. And you stated that light did decay out in your initial statement, that seems to have changed to a could.

 

[Cabal]

So are you saying that light isn't inherently immune to decay, it just wont decay because of the vacuum? In other words, light is no different than say, a piece of meat left out in space, which will continue on forever unless something interacts with it?

I hope I phrased my question clearly.

Like I said, there are two types of decay here. There's loss of intensity in, say, a beam, which doesn't occur in the vacuum. That's just how light interacts with the vacuum - whether you can say the vacuum is truly "nothing" or not is debatable, but it nonetheless has that property when it comes to light passing through it.

But regardless of whether light is in space or not, the photons that comprise light do not undergo some form of inherent decay as radioactive atoms or heavy quarks do, say, as they are stable particles.

 

[matthewgar]

Light doesn't decay, but what does happen is light and other waves disperse over time, so while the light from the object is still coming, for some things far away you need a gravity lense, or something that can absorb the light over a long time, like a telescope trained on a area for a period of time.

Wich I recently read may be a problem with finding radio waves from aliens, or them finding ours *if there are any out there* because radio waves don't go as far as we thought, and disperse too much to pick up any transmitted signal more then a few hundred or so light years.

 

[Chesterton]

Wich I recently read may be a problem with finding radio waves from aliens, or them finding ours *if there are any out there* because radio waves don't go as far as we thought, and disperse too much to pick up any transmitted signal more then a few hundred or so light years.

Oh my God. WE'RE STRANDED!

 

[Delphiki]

Inverse-square law - Wikipedia, the free encyclopedia

^ Why far away stars don't appear as bright as the sun.

 

[Cain Spencer]

Inverse-square law - Wikipedia, the free encyclopedia

^ Why far away stars don't appear as bright as the sun.

Let's hope it helps.

 

[JustMeSee]

Interesting thread.

 

[Nabobalis]

Light travels forever as long as it doesn't interact with any material along its path.