Probably a stupid question...

[CarlosSainz100]

This is almost certainly a stupid question, but here goes....

So the new James Webb telescope can peer back through to almost the dawn of time because the light from the stars it can see has taken that long to travel to earth....right?

So how do we know that right now there isn't some massive interstellar alien taskforce on its way to destroy everything, it's just we haven't picked up the light from it yet? And if there is, when will we see them? And even if there is no invasion force on its way how do we know what's happening on these far away stars and galaxies right now? Are we really going to (with present tech) have to wait billions of years into the future to see what's happening on some star today?

This makes my head hurt....

[Mr E]

We don’t.
The sun could cease to exist right now and we’d know nothing about it for about 8 minutes.

[Simpo Two]

CarlosSainz100 said:

So the new James Webb telescope can peer back through to almost the dawn of time because the light from the stars it can see has taken that long to travel to earth....right?

So how do we know that right now there isn't some massive interstellar alien taskforce on its way to destroy everything, it's just we haven't picked up the light from it yet?

If we can see back to almost the dawn of time then an alien taskforce wouldn't have had time to evolve. The further back you can see, the more certain you can be that it won't happen.

[BorkBorkBork]

CarlosSainz100 said:

This is almost certainly a stupid question, but here goes....

So the new James Webb telescope can peer back through to almost the dawn of time because the light from the stars it can see has taken that long to travel to earth....right?

So how do we know that right now there isn't some massive interstellar alien taskforce on its way to destroy everything, it's just we haven't picked up the light from it yet? And if there is, when will we see them? And even if there is no invasion force on its way how do we know what's happening on these far away stars and galaxies right now? Are we really going to (with present tech) have to wait billions of years into the future to see what's happening on some star today?

This makes my head hurt....

The Alien force isn’t forced to emit any visible light. So, we might not detect them until they are entering our atmosphere.

If they were emitting EMR in the visible spectrum, presumably they’d be travelling at a decent % of the speed of light if they’ve mastered interstellar travel. Let’s say 50% for argument’s sake. In which case, if they set off from Proxima Centauri (4 light years away) 6 years ago, if we had an instrument sensitive enough, the light from them would have arrived here 2 years ago, and they’ll physically arrive in 2 years from now. However, you have to assume their craft would be relatively small, so detecting that would, I assume, would be impossible with our current technology.

[Simpo Two]

BorkBorkBork said:

The Alien force isn’t forced to emit any visible light. So, we might not detect them until they are entering our atmosphere.

Much more likely. The doomsday scenario is not related to the telescope.

[Turtle Shed]

It's so unlikely to happen that the chances of it actually doing so can be regarded as zero.

Just finding earth in a galaxy of unimaginable size would be a near impossibility, and that assumes they evolved on a planet in the Milky Way.

[vaud]

BorkBorkBork said:

However, you have to assume their craft would be relatively small, so detecting that would, I assume, would be impossible with our current technology.

Eventually of course, after their Galaxy had been decimated over a few thousand years, it was realized that the whole thing had been a ghastly mistake, and so the two opposing battle fleets settled their few remaining differences in order to launch a joint attack on our own Galaxy - now positively identified as the source of the offending remark.

For thousands more years the mighty ships tore across the empty wastes of space and finally dived screaming on to the first planet they came across - which happened to be the Earth - where due to a terrible miscalculation of scale the entire battle fleet was accidentally swallowed by a small dog.