anaconda wrote:
Thanks for posting that Nick, (or should that be saint Nic this time of year?). Very informative, though I'll need to watch it again to get to grips with some of the more complex ideas.
Anyone who get to grips wityh Krauss's idea after watching that lecture just once or twice is doing pretty well. {This from a person who had to read 'A brief History of Time' four times.) Krause is a brilliant explainer, and an entertaining speaker, but the greatest talent people like him possess is the ability to clarify without simplifying. Those of us who don't get all of it at once can be grateful to the author for not misleading us.
One thing that puzzled me was the explanation relating to movement of matter/ objects/space from its single point of origin, ie following the big bang. He was suggesting that from the point of view of any single item that all other objects would appear to be moving away from each single item, so in effect in our case it makes the earth look like the centre of all things, as it would from the point of view of any of the other single items. He used a grid to illustrate this with rows of dots representing each object. This didnt make sense to me. In my simple mind I would expect the expansion of the universe to involve objects moving not in a uniform way but in different directions, or at least different directions away from the central point. Has this guy never seen Die Hard with a vengeance....stuff firing off all over the place, different angles, velocities etc ;-) . Would everything be moving away In such a roughly uniform way? Wouldn't we see at least some objects getting closer to earth rather than everything moving away from us at different rates, or was the bang so long ago that anything that was going to pass us by (and so have a trajectory at least for a time getting closer to earth) has already done so. Also there didnt seem to be any reference to items expanding at a slower rate than earth and so appearing to be getting further away due to their moving slower than our speedy planet. Im sure this is the case and is just assumed for othe sake of the talk. Maybe I needed to pay more attention in physics classes.
I'm not expecting an answer to any of this. Best regards.
Some objects are moving closer together, some are moving further apart, some may at some times be moving parallel to each other or in orbit. These are
movements of objects through space.
In the expansion of the universe, it is the space between the objects that is expanding. This space is expanding everywhere ast the same rate. Therefore, the further away something is from any observer, the more expanding space there is between observer and observed objects. Hope that helps?
Jolly midwinter festivities!