Lightspeed & observing explosions & GRB's - missing something.....

[Aenima]

Hi,

I dont usually worry myself with too much fact or fiction either side of what is actually observable with our limited eyesight alone.

I have a reasonable grasp of the way our brains act like filters and take bits of information from the external world to then reconstruct a workable 'reality' that we can physically interact with, that involves varying levels of energy and matter. Its all just different types of interconnected energy, and we are close to knowing how it works.

This partially understood incongruence between what we perceive and what is truly real serves many of us well as an 'ad hoc' explanation for a multitude of mysteries.

However, I am finding myself using the 'its just one of those things' line with increasing regularity and using it to fill in the gaps where real knowledge and real scientific investigation should be.

I use, quite lazily, the complexity of our surroundings and science's inability to fully comprehend it as an excuse for not mentally tackling many of these issues personally, even ignoring huge amounts of information if it happens to challenge my complacent and makeshift understanding of the physical world.

In this I am assuredly not alone.

So when I read about star explosions and gamma ray bursts being viewed by astronomical equipment in what sounds like real-time, I struggle to picture it and often wonder about the familiar remarks made that the sky being seen now by us is millions of years old and light reaches us from sources that are long dead and gone.

I always use the Speed Of light 'thing' as a band aid to explain why light from the stars is ancient but when one explodes we see it happen almost (ALMOST..) in real time terms. ?

I dont view this as a contradiction at all, it is just my failure to comfortably 'picture' it properly in my mind. Its something I need help to understand, to lessen the trouble my brain has when trying to visualise the movement of light over vast distances and near-impossible speeds relative to the passage of time as experienced here on earth.

Before anyone berates my lack of accurate knowledge here I want to point out that I have admitted above to using faulty logic in order to compensate for not figuring it out on my own.

(Its a terrible habit affecting many millions of people - probably more than smoking, nail biting and swearing combined - and I wish quitting was as easy..)

Hopefully someone who understands this subject can explain in a way that helps translate the math etc. into a more visual or intuitive means of imagining starlight and exploding stars.

I'd be grateful for any insight.

Regards

Aenima

[ArmyAirForce]

The light may be millions of years old, but we are still seeing it in real time. So an explosion in the distant universe, should to my logic, happen over the same time period as we see it here, there's just a long gap from the incident happening out there, and us seeing the flash here.

[George Jones]

I think this is the right idea, but the time period here is longer because of the expansion of the universe. Roughly, the light has to catch up with us. This same effect causes a redshift.

[nameunknown]

Like thunder and lightning... there is a flash as the light arrives and bang just after. The flash travels pretty fast, but the sound needs to catch up, and the further you are from the strike the longer the delay. Imagine some poor person on a distant mountain who gets hit by lightning (poof...vaporised), and you are sitting with your eyes screwed shut, by the time the "bang" arrives they are already fried. In the same way, by the time you read the news in the paper it is already history, especially if your are on holiday and you can only get yesterdays Times. News from far away takes time to arrive. Once it was the speed of a camel, now it might be the speed of light. Even sunlight is eight minutes old when you see it...

P

[nmoushon]

I know that its "real time" in the sense of we are seeing exactly how it happened millions of years ago and that we will see it unfold the same way as if someone only 1 light year away would. But I dont get why they call it "real time" if it happened millions of years ago? Real time refers to as it's happening or live. Well at least in my mind.

[nameunknown]

..and of course, when the signal from whenever starts on its way the space through which it travels will be stretching all the time, so the picture might get a little slowed down just like as if a strip of film was stretched while being sent through the post...

P

[101nut]

'Real time' simply infers what is happening now. Perception has a minimum time delay according to the speed of light and relativity so it may be surmised that, wherever an observer is in the universe, a particular event happens in real time to that and every other observer despite observers being in completely different time frames ...

The massive assumption here is that information cannot be transferred faster than the speed of light, otherwise one observer may be able to perceive an event, retransmit the information at faster-than-light speed and enable a second observer to 'see' an event before they perceive it in 'real time' ...

I think this is a massive can of relativistic worms ...

AndyG

[Aenima]

Did we just have a time based phenomena on this thread?

reading through I got a powerful sense of deja vu

But seriously, I have trouble matching the twinkling lights in the sky which is a snapshot of the ancient universe with an explosion that began peaked and faded in recent history - what am i missing?

Regards

Aenima

[Aenima]

'Real time' simply infers what is happening now. Perception has a minimum time delay according to the speed of light and relativity so it may be surmised that, wherever an observer is in the universe, a particular event happens in real time to that and every other observer despite observers being in completely different time frames ...

The massive assumption here is that information cannot be transferred faster than the speed of light, otherwise one observer may be able to perceive an event, retransmit the information at faster-than-light speed and enable a second observer to 'see' an event before they perceive it in 'real time' ...

I think this is a massive can of relativistic worms ...

AndyG

Definitely a can of worms. I wasn't sure if it should be opened but got curious (and slightly bored). Apologies in advance.

Regards

Aenima

Ps, i used the term 'real time' very loosely, and since faster than lightspeed is only theoretical and the time discrepancies i'm talking of aren't the 'lost minutes' from a astronauts trip to the moon and back I figured there was something i was missing..

[Aenima]

Are they really saying that these explosions are so close to us that we can watch it happen or at least perceive the effects of it in recent history? But also that the starlight we see is so many millennia old?

I guess the explosions are travelling very very fast, lightspeed fast, so it only takes a couple hundred thousand years ? All light - regardless of its ferocity - travels that way so my head gives me trouble in that area of things. Otherwise, I'm usually quite a visual person with eidetic way of problem solving etc. but far too often it gives up in favour of declaring the issue un-thinkable or too complicated.

Oh well, if all else fails I might just resort to reading a damn book.

Regards

Aenima

[Tiki]

But seriously, I have trouble matching the twinkling lights in the sky which is a snapshot of the ancient universe with an explosion that began peaked and faded in recent history - what am i missing?

Regards

Aenima

Perhaps the time that it takes for light to travel the intervening distance.

[Aenima]

The time it would take me to work out the math, possibly?

If the difference was just the difference in time it might explain why its not all happening at a similar rate. All those lightyears each one going ultra fast but not quite Infinitely fast (if it exists) so the further distances having a slowing effect compared to smaller distances, making us - from earth - and closer to certain areas (as we see other areas are farther from us) - we see time scale in one place moving slightly differently to time in another.

Are we simply seeing a delayed effect, light hitting us is millions of years old but we - on earth - just receiving the light, believe it to be new, and when a star blowws up its said to be both ancient and recent? and the difference in the timing of things isnt any easier to figure out? Light from stars is ancient except for the ones that explode?

I'm hoping now that its the difference in distance because the alternative isnt easy to think about.

[gkec]

The time it would take me to work out the math, possibly?

If the difference was just the difference in time it might explain why its not all happening at a similar rate. All those lightyears each one going ultra fast but not quite Infinitely fast (if it exists) so the further distances having a slowing effect compared to smaller distances, making us - from earth - and closer to certain areas (as we see other areas are farther from us) - we see time scale in one place moving slightly differently to time in another.

Are we simply seeing a delayed effect, light hitting us is millions of years old but we - on earth - just receiving the light, believe it to be new, and when a star blowws up its said to be both ancient and recent? and the difference in the timing of things isnt any easier to figure out? Light from stars is ancient except for the ones that explode?

I'm hoping now that its the difference in distance because the alternative isnt easy to think about.

You are really over thinking it. The sequence and timing of event does not change however far away the object is. If an object flashes once a second it will flash once a second if you observe it from 1 light year or a billion light years away.

Explosions have no special properties.

Your statement about a star blowing up being ancient and recent makes no sense. If we observe a star 100 light years away and we see it blow up then it blew up 100 years ago. It is that simple.

[Aenima]

Thats actually a really good way to explain it and its the best way for me to think about it. Have to admit its a little over the usual brain payload, not used to trying to think too much these days.

The bit I struggle with is the differences, and those are small, between very very large time and distance. We see what happens pretty accurately in the solar system where the light is immediate and delay free. The person here can look up and see small dots of light that are far enough away to be both small and old. We can measure that by the speed of light and it holds for a long way outwards.

To continue looking in that direction you could see the point where time can be said to have for you stood still (or at least the extreme of what has meaning in the word infinity. - what would be in the opposite direction? a black hole?) Looking from the center of a spiral outwards would be to look away from the center - which would be close by. Light follows laws that are relevant to us and travels in time fast, hardly noticeable but the numbers are enough so that the measurement gets complicated.

When things involve distances that mean what your seeing is extremely old, and something explosive happens in deep space, by the time we get to see it happen, the physical energy behind the explosion is gone before we see it? Like the fireworks analogy, or thunder... the delay is the thing...we see photons hitting us, like a fast machine gun the individual bangs make it seem like one long noise, and if anything energetic like an explosion is coming - ! - would it already be too late? Can some forms of distance be more conducive to light travel?

This is the bit where I find the pure numbers and what we perceive hard to keep together.

Too many questions, not enough answers. (in my case at least:))

Like glass, the vacuum thing light travels through (but not air) warps close to gravity and it warps light along with it. Can anything in the universe make the speed of light change? (other than both relativity and expansion of he universe?)

If you're looking toward the black hole rather than away, does it mean you are seeing any difference in how light and time relate to each other?

Help. I knew I should have left it alone.

Regards

Aenima

[Aenima]

Ha.

Stupidly spent even more time thinking about it - the problem is definitely with me. Whenever I imagine anything that happens both near myself and millions of lightyears away my brain puts me at two different places. AndyG (among others) was right, its not bad maths just relativity. Its not helpful to try and place my observing self in two places when BEING in two places changes how I would see things.

My brain cant deal with the idea of infinity or relative time easily, (if at all) and to try and be both the astronaut AND the earthbound observer in that experiment (synchronised watches etc.) or be both here AND at the other end of time / space is causing my brain extra trouble, otherwise I could just accept the maths and imagine light as a straight line which travels constantly.

It involves two things. Never thinking about the formulas that involve infinite anything - and forget entirely about learning what happens inside black holes. I could probably live with that.

My brain would thank me.

[nameunknown]

This is all really quite simple. Replace all the photons with messenger-pigeons (these are standard pigeons that always fly at a constant speed). Sell the telescope and buy a large coop, with the best quality bird-seed you can afford. Place it at the north pole. Build an igloo next to it, and sit there reading the messages the pigeons have brought. When a pigeon arrives from the equator saying you have won the lottery in Sao Tome, Singapore, or Macapa (each just north of the equator) do you say "I've just won the lottery in ....." or do you say "wow, I was worrying about money all last week and now I find out that I;d already won the lottery in...."

OK, then while you are sitting pretty at the north pole, a US Government project to increase the number of days in the year (and get fewer holidays/more tax) goes horribly wrong and the earth starts to spin much faster. It does not bother you at "the still centre of the turning world" (perhaps a bit dizzy - but you have a volume of T. S. Eliot), however the equator starts to get a lot further away as the earth turns into a CD-shaped object. The pigeons have further to fly, and take longer. Ignorant of all the trouble the pigeons are having (you ran out of batteries for the radio) you still say the same when the knackered birds arrive.... (but the lottery offices near the equator are probably in no fit state to pay out)

In other words:

• we are each closest to our own future;
  
• our knowledge of others is only of their past;
  
• You cannot know what another thinks/says but only what they thought/said...
  

However, does this really matter in the big scheme of things when the "telescope assistant" says - "I know Sigma Draconis XXI went nova 39,675 years ago, but I put a just pizza dough in the oven, you can watch it later on i-player, there will be a repeat on Channel 4, and if it is important it will be on U-bend."

P

[Aenima]

Haha.

Apart from amusing and slightly painful if I read it on a school night, its also quite a good perspective reset button. I'm now more worried about the pigeons than the explosions.

Aenima

ps.

Gamma-ray bursts are typically short or long. Astronomers think that the latter type, which usually last no longer than a minute or so, herald the death of a supermassive star. The collapse of the star's core triggers jets of relativistic matter so powerful that they bore outward through the star and into the surrounding space. Interactions with shells of gas previously shed by the dying star creates dazzling outbursts of radiation — the most luminous explosions known.

It still sounds to me like there is light that can travel faster than other types of light. Or energy. Or something.

[Knight of Clear Skies]

It still sounds to me like there is light that can travel faster than other types of light. Or energy. Or something.

Observing a GRB is no different from observing any other event really. The observed duration of the burst occurs because it emits gamma rays over a period of time, not because some of the light is taking longer to reach the observer. Explosions aren't instantaneous events, they have a (relatively short) duration.

Does that help at all?

[spurius]

'Real time' simply infers what is happening now. Perception has a minimum time delay according to the speed of light and relativity so it may be surmised that, wherever an observer is in the universe, a particular event happens in real time to that and every other observer despite observers being in completely different time frames ...

The massive assumption here is that information cannot be transferred faster than the speed of light, otherwise one observer may be able to perceive an event, retransmit the information at faster-than-light speed and enable a second observer to 'see' an event before they perceive it in 'real time' ...

I think this is a massive can of relativistic worms ...

AndyG

If something happens a billion light years away, it will take a billion years for us to see it. What is actually happening a billion light years away right now is impossible to know. This I understand because its a very simple concept but what do you mean by time frames? I thought time frames had to do with how you set up your watch depending upon your location on earth.

[Aenima]

Observing a GRB is no different from observing any other event really. The observed duration of the burst occurs because it emits gamma rays over a period of time, not because some of the light is taking longer to reach the observer. Explosions aren't instantaneous events, they have a (relatively short) duration.

Does that help at all?

It does help, yes. I 'm really trying to keep my thinking to the 'set in stone' physics and numbers that say lightspeed is a constant and the laws that govern it are applicable everywhere, even billions of lightyears away. Looking up (outwards from earth) is a strange thing when you try to imagine what would be at the 'other end' -ie the point where space either stops or ..... what? becomes 'infinite'? The word 'infinite' is pretty much an assumption or guess as to a measurement we cant actually put a number to. When we reach the limit of our minds capability to perceive a distance we fill in the blanks by saying it 'goes on forever' but without knowing this for sure how can we call it infinite?

That aside, I do appreciate the comfort in knowing that when a GRB or Supernova is observed it isnt bending the laws of physics too much, and just involves large enough measurements that we find the event and its effects are separated by sufficient amounts of space to cause time delays as we look further and further away from us, upwards into deep space. But its explainable. When I pictured it originally I imagined an event that was separate from the 'backdrop' of ancient light and tried to figure some weird contraction of time-space that allowed some things to occur over slightly differing timelines, like lines on a optical illusion that appear to do things they shouldn't do.

It might just be that space is a linear thing and its just people's perceptions that cause 'curves' to appear....

Time for coffee break, my brain is wiping sweat from its forehead and putting down the shovel it was using to dig this hole with.

Regards

Aenima