Why can we see light from not long after the Big Bang?

ThomasCovenant

Hi

Please excuse my simple mindedness but could someone explain in simple laymans terms how light from the big bang is visible to us. Someone asked me this the other day and I couldn't answer.

If light from an explosion billions of years ago has travelled at the speed of light from point A then what I can't get my head around is how come it never shot past us so to speak before we were even here at point B.

I've tried to imagine an explosion shooting off in all directions. Billions of years later life develops on a point B (Earth) that is one of the billions of bits flying out in all directions. If someone on point B turns around and looks back at the centre of the explosion why wouldn't he see nothing?

I hope I've explained this enough for someone to get my drift.

Thanks

Thomas Covenant

Awakened07

Well - certainly an interesting question, and one in which we have to twist our brains a bit to understand. But it's also important to get the concepts right; not so much an explosion as an expansion of space, for instance.

As far as I have understood it, we won't actually be able to collect light from the big bang itself (that is to say, the few seconds after it all started - the big bang really isn't over yet, as we're still expanding), both because light sources weren't formed for some time afterwords, and because matter was much denser for quite some time, and light was absorbed and scattered by matter such that it wouldn't reach us today. Only after ~400.000 years after the big bang started do we see light clearly (from what I have read). Radiation can be measured though.

Here are a couple of explanations to the question:

http://www.physlink.com/Education/AskExperts/ae38.cfm

http://en.wikipedia.org/wiki/Big_bang#Horizons

I should add that I'm in no way an expert in this field (quite the contrary although cosmology and astronomy has always fascinated me), so this is interesting to me as well.

Paralipomenon

You think of an explosion as instantaneous. Think of times when they monitor a supernova. The supernova isn't instantaneous, they can monitor it for quite a while from the time that they notice it.

Simply put, the larger the explosion, the longer it takes.

Also factor in that we are relatively new to exploring deep space. What is thought to be the Big Bang, could very well be wishful thinking.

poppers

If someone on point B turns around and looks back at the centre of the explosion why wouldn't he see nothing?

Just where is the center of the explosion? Besides that, it seems to me that to look back in "time" you look outward, not inward.

Satanus

I don't know the answer, for sure. Everything that is, including our solar system is/was part of that 'explosion'. As somebody pointed out, the explosion is still ongoing, in the form of universal expansion. Perhaps light is/was slowed down by interference in the form of dust, gases, gravitation and electromagnetism. Those things would cause it to change direction, slow down and bounce around.

S

worldtraveller

If we were looking outward from an explosion we wouldn't be looking very long!!! No matter what people tell us, it's all speculation. Some makes sense, other stuff is pure hogwash. So don't make too much out of it all. Still speculation is very interesting with an OPEN MIND.

SacrificialLoon

Even when something is travelling away from us it's light still approaches us at 300000 km/s, and when stuff is travelling towards us its light is heading towards us at 300000 km/s. The speed of light (in a vacuum) is always constant, but one strange thing that does happen to light emitted from objects travelling at very high speeds is that it becomes compressed (blue shifted)if the object is headed towards the observer and elongated (red shifted) if the object is moving away from the observer. This is called the doppler effect and you can hear the same effect by listening to the pitch of a racecar engine has it heads towards you (or the camera) then away.

This is one of the reasons we can see light from objects from so far away that are also heading away from us at very high rates of speed.