I’m thinking of setting my 3rd year cosmology students questions from the general public to see how well they’ve been listening, and to prepare them for unexpected cosmology questions at dinner parties. So I need all your questions about the universe!
Examples:
- What is the universe expanding into?
- Using powerful telescopes we can look ‘back’ at light from very early on in the universe. But how did we beat it ‘here’? It has been traveling at the speed of light and yet we are already here waiting for its arrival.
- If everything is expanding, how would we know about it, since all our rulers are twice as big as well?
- I heard an Australian guy won the Nobel prize for his work in cosmology. What did he actually do?
- Where did the big bang happen?
- What is redshift? How do we know what wavelength the light left the galaxy with?
Ask away!
My question would be: what is the difference between “it’s” and “its”? Is it reasonable to expect someone teaching a course at university to know the difference?
I corected the speling misteak 4 u. Bad grammer makes me [sic]!
(I copied and pasted from a questioner on Facebook. Its/It’s all his fault!)
Could the big bang have been caused by a quantum event?
Is the universe ever going to stop expanding? Will it then implode?
How could the universe expand faster than light at some point?
Is the universe finite in extent or infinite? If it is finite, what is outside it?
Explain inflation.
I’ve heard there are more than 3 spatial dimensions. So where are all the others we don’t experience?
What is the multiverse and why do we think it might be real?
Could all the universal constants which appear to be fine-tuned actually be determined by the underlying Physics?
Do we know that time passes at a constant rate? If it didn’t, could we extrapolate back to the big bang?
Could the universe be cyclic – big bang, implosion, big bang, etc?
I’d be interested in your answers to those questions, but I suppose that would be giving the game away to your students. : (
I’ll post some answers after the exam!
What’s redshift quantization, and why do some people say that it means we’re at the centre of the universe?
What caused the big bang is surely the most asked question in cosmology
True. Might be a bit much for the 3rd years. I’ll ask the honours students.
I think you are right for a detailed asnwer but i think a simple answer of : we need a quantum theory of gravity to answer that question, that our current physics is inaqeduate and leave it at that. How exciting is it to be in a field where the biggest question remains unolved? Maybe one of those studetns wil be inspired to solve it.
I was thinking of throwing in a few questions like:
For bonus marks (and possibly a Nobel prize)
* How can the cosmic neutrino background be detected?
* What is the solution to the cosmic lithium problem?
* Is the universe infinite or finite?
* What is the correct theory of quantum gravity and what does it tell us about the universe before the Planck time?
* What is the identity of dark matter?
* What is dark energy?
* What is the inflation field? How did inflation start? How did inflation end?
* Why is there more matter than antimatter in the universe?
Maybe not the exam.
The assignment, though …
I just want to say Bravo, these are exactly the sorts of questions students should be involved in. Of course we shouldnt expect anyone to be giving Nobel prizze winning answers but expsoing them to current frontiers of knoweldge is what generates excitment.
* Why is dark matter called “dark” instead of “transparent”? After all, glasses are called “dark” when they block light, not when they let it pass through.
* Is it legitimate to start the timeline of Big Bang directly with the inflationary epoch and then move on to the electroweak epoch and so on? After all, the Plank and GUT epochs are pure speculations which cannot be proved or falsified, whereas inflation could have been falsified if they hadn’t found anisotropy in the CMB.
* If the previous question is answered as “yes”, does then a closed universe start with a bang or with a yawn?
As yawns are associated with falling asleep rather than with waking up, I should have said “with a bang or smoothly from a state of rest?”
Critique this as a model of the universe:
Imagine a ball of water held under constant pressure and temperature such that it is a fraction above its freezing point.
In the centre of this ball is a sphere of vacuum.
The vacuum sphere collapses. This sends a negative pressure wave propagating out through the water. As the wave passes the pressure drop is sufficient to lower the freezing point and start ice crystals forming. These form inconsistently because the pressure wave and all other components in the system are not all perfect.
As the wave passes pressure returns to normal and crystalisation ceases. Ceasing also occurs because the ice takes up more space than the water it crystalised from, increasing pressure again in the local vicinity and further lowering the freezing point.
As these ice crystals have taken up more room than previously the total water sphere expands. As a result the crystals are all moving outwards with the expansion of the sphere. This expansion accelerates the further out in the sphere each crystal is, as more and more crystals are formed adding to the outward acceleration.
If the crystals are galaxies and the collapse of the vaccum sphere is the “Big Bang” event where does this model fail in describing our observations of the universe, and what insights might it provide?