Astronaut Piers Sellers on Danny Baker

British astronaut, Piers Sellers was on the Danny Baker podcast this week. It was a fascinating interview. This is one of the guys who assembled the ISS in orbit while spacewalking. It was fascinating to hear him talk about his experiences and I found it amazing how down to earth (pun intended) he was. There was no arrogance and the conversation flowed freely and easily between them. I recommend you listen to it while it’s still available. I’m going to listen to it again.

Gravitational Waves – Lecture, University of Birmingham- Tuesday 30 October 2012

Went to a lecture at the University of Birmingham this evening. It was part of their outreach programme. There are further events coming up.

The lecture was supposed to be about the Square Kilometre Array (SKA) but the visiting lecturer was ill, so Dr Andreas Freise from University of Birmingham stepped in and delivered a lecture on Gravitational Waves and a Proposed Einstein Telescope(ET).

Below are my scribbled notes pretty much as is, purely for my own purposes as a reminder.

Gravitational waves stretch and squash on different axes
LIGO – Laser Interferometer Gravitational wave Observatory
Gravitational waves are a prediction of general relativity
Ripples in space-time
Sources – binary systems, pulsars, accreting stars, supernovae
Everything actually generates them but needs to be really large to be measurable

Detected using an Interferometer
Was impressed to see Processing being used to demonstrate a Michelson interferometer
(aside – Sky at Night Magazine November 2012 has an article about Michelson and Morley and the theory of the aether as a medium for propagation of light.  They used an interferometer to attempt to prove the existence of the aether – the failure ended up disproving it)
The interferometer acts as a detector.  A laser is fired into it.   If output changes – then either the mirror moved or it’s a gravitational wave.  In the interferometer photon is not affected by the the GW but the mirror is.  A lot of the tech seems to be about ensuring the mirrors don’t move so therefore anything that get’s detected is a gravitational wave.
LIGO is a big version of The interferometer.
Mirrors are decoupled and hanging on wires so they don’t move. Have to invent stuff.
Need very clean glass to eliminate thermal lensing

It didn’t work though so now they upgrade to the advanced LIGO.
This will be ready in 2015.
If it doesn’t see Gravitational waves though – does that mean prediction is wrong or mean it didn’t work?Have developed more For the advanced LIGO they have developed a more complex interferometer.
More information in the LIGO magazine – PDF download available.

Ground vibration seems to be the biggest problem – keeping that mirror as still as possible is essential. – (I’d wondered about that) so the next stage would be to go underground.  Also suggested going into space.

Questions from the audience:
Graviton got mentioned – particle equivalent of gravity. There is a field for each particle – quantum physics. Can behave as a field. Can behave as a particle.  Cf photon and em field.

Practical implications?
Hope to see something different in the sky. Perhaps. Add to cosmological models.

My question:  Why go to space?
Ground vibrations. Gravitational pull to centre of earth distorts the geoometry of the mirrors and puts a limit on length of about 3m

There was an excellent question from one of the school students.   She asked if the ET telescope is intended to be underground and in a triangle so there are two sets of 3 detectors picking up from multiple directions, why not take it from a two dimensional arrangement, ie a triangle, to a 3 dimension one – a tetrahedron?
Brilliant question.  Lecturer seemed surprised by it.  Comes down to financing and that would be the 4th generation.  They need to fund the 3rd generation, the ET first.

More info about detection of gravitational waves at http://www.gwoptics.org/

A bit of further reading about Gravitational Waves from Wikipedia.  I see that the Astronomy Cast podcast has an episode about them.  I should take a listen.

A final thought, having read the article about Michelson and Morley’s experiments with interferometers to attempt to detect the aether and the subsequent failure of this that led to a move away from that model of understanding.   So far Gravitation Waves have not been detected, only predicted and inferred.  What if using similar methods to the Michelson-Morley experiment ultimately fails to detect them?

Podcast – Glipsing The Edge of the Universe: Results from the Hubble Space Telescope

I’m listening to a lot of astronomy podcasts at the moment. I find them to be a great way of unwinding on my evening commute home. My brain is usually still active from a days work and I need something that shifts my attention from the working day. I’ve found science podcasts, and in particular those with an astronomy bias to be really good for this. They’re educational and thought provoking.

There are a lot of good ones out there. I’ll feature some in upcoming posts.

My latest discovery is an archive of lectures from Foothill College’s Silicon Valley Astronomical Lectures. There are around 30 lectures available going back to 2005.

One particular lecture from 2007, given by Dr. Bruce Margon (University of California, Santa Cruz), that I found fascinating is entitled Glimpsing the Edge of the Universe: Results from the Hubble Space Telescope. It last about an hour and a half but is engaging throughout. Whilst it refers to slides that are shown during the lecture and I can’t find any show notes, many of the images referred to can be found in the Hubble gallery. I really wanted to see what he was talking about when he was talking about planetary formation in the Orion Nebula. Guess this is the images. It shows a disk of matter forming and silhouetted against the bright cloud of the nebula. At some stage the matter will likely collapse to cause a star to ignite.

Source: Hubblesite.org

If iTunes is your podcast software of choice the the link is http://itunes.apple.com/gb/podcast/silicon-valley-astronomy-lectures/id213308887
I prefer to use Downcast on my iPhone for my Podcasts so I use the feed at http://www.astrosociety.org/education/podcast/sval.xml