Recent content by photonkid

ok, thanks for answering.

If that's all there is to it then why is the CMB and radiation from distant stars red-shifted due to the expansion of space? Could you please try to answer the question that I asked - "Does the distance between y1, y2 increase at the same rate as between x1, x2? Also, is the light that we...

I have another related question. I've been reading articles on the internet like this one https://medium.com/starts-with-a-bang/ask-ethan-if-the-universe-is-expanding-why-arent-we-71b46b5e9974 but so far I'm unable to tell whether space between say, two stars in our galaxy, is actually...

ok, so it's fairly complex. Thanks for answering.

Thanks. I had never heard of the cosmological principle before. On wikipedia it says and I'm still not understanding how matter (mass) can affect the rate of expansion and do it uniformly. e.g. suppose in the future the universe has expanded to the point that all galaxies apart from our...

I've read that until 5 billion years ago the rate of expansion of space was decreasing. How do we know that it was slowing down? Does the uniformity of the CMB mean that the rate of expansion is identical throughout the entire universe - or does it just mean that the average rate of expansion...

If two galaxies are separated by a large distance such that radiation transmitted from the mid-point between the two galaxies never reaches either galaxy due to the expansion of space, how can the expansion of space at the mid-point ever affect the distance between the two galaxies. i.e. how...

I've read that the temperature of the CMBR is 2.7 degrees K or so and is much cooler than when it started out, due to the expansion of the universe making the wavelength longer. What is meant by the temperature of the CMBR? How do you measure it? Is it determines purely by the wavelength...

Yep, that was Optimus you said it to but I did take notice. I've had a goal of understanding special relativity for a long time but nothing makes any sense. Like, how did Einstein figure out the speed of light is the same for all observers - do you need a full understanding of Maxwell's...

For an observer not moving towards the black hole. I read it somewhere on the internet but I can't find where just at the moment. There's a kind of allusion to it here but this is not where I read it. http://www.einstein-online.info/spotlights/changing_places [Edit] Found it here...

Yes there is. If I have two identical clocks on top of a mountain and take one down to sea level for a while, then back to the top of the mountain, it will be behind the clock that stayed on top of the mountain.

ok, yeah, I pretty much gathered that that's what the rationale was but... ...there seems to be a problem with this. If I move towards a gravitational field, time runs progressively more slowly (relative to where I was) and I cannot tell that it's doing so. If time actually stopped or ran...

So I'm guessing that the time dilation factor approaches infinity as you approach the Schwarzschild radius - because on the relativity faq website it says <quote On my worldline as I fall into the black hole, it turns out that the Schwarzschild coordinate called t goes to infinity when I go...

But the person who goes to Alabama can tell when he has arrived at Alabama. The person who goes to visit an event horizon has no way to know when he has reached it. Is there some way to know when you've reached an event horizon? Does the absence of radiation tell you? Can you calculate size...

yikes, I'm not sure I caught on to that even though PeterDonis said it. I can't get my head round this. Well what about this then. If I drop a stone from my hand to the ground, I can calculate within some small error margin, what the time on my clock will be when the stone hits the ground...