• Question: What do you think is the value of Hubble's constant? Have you ever worked it out using your own data?

    Asked by freddie to Adam, Geoff, Rob, Sheila, Suzie on 21 Mar 2011 in Categories: .
    • Photo: Suzie Sheehy

      Suzie Sheehy answered on 18 Mar 2011:

      Hi freddie, actually I have worked out Hubble’s constant using my own data!!
      I did it as an undergraduate student as a practical laboratory experiment, and it came out to be about 70+/-5 which is (within error) about what people think it should be. I was so chuffed!
      We took images of galaxies in the night sky and calculated it from them!

    • Photo: Geoff McBride

      Geoff McBride answered on 18 Mar 2011:

      I’ve not used it but in a discussion with another scientist this week on dark matter we were expressing real concern about such constants. Things don’t add up.

    • Photo: Adam Tuff

      Adam Tuff answered on 18 Mar 2011:

      I think the generally accepted value is around 70km/s/MPc – a lot of work points at that value, but it still varies a lot depending on who you ask. I haven’t done any work calculating it however…

    • Photo: Sheila Kanani

      Sheila Kanani answered on 20 Mar 2011:

      Hehe 🙂 I’ve never worked it out using my own data but have worked it out using other peoples data, as we did it for a science experiment when I was at uni 😀
      I can’t remember what we got exactly, I think the value came out at about H0 = 75 (km/s)/Mpc!

    • Photo: Robert Simpson

      Robert Simpson answered on 21 Mar 2011:

      I just take a textbook value. I’m not cosmologist so I’ve never worked it out with my own data. During my degree we did work it out once – but that was a long time ago. They probably changed the standard value since 🙂

Comments

  • Photo: freddie

    freddie commented on :

    That’s amazing, Suzie! So you think the universe is between 13 and 15 billion years old. Did you have to work out the red shift and then use v = HR ? I can see how you would measure v using Δλ/λ = v/c but how do you measure R?

  • Photo: Suzie

    Suzie commented on :

    Hi freddie, glad you think it’s amazing.

    Honestly it was too long ago to remember how we did it! (It was only in 1 week!)… But if R is the distance from ourselves, there are stars in astronomy that they refer to as ‘standard candles’ which you can pick out and they have a known brightness I think, so you can tell from the brightness you observe how far away they are… (I may be totally wrong here) and from that you can measure R. The only reason I’m not sure if that’s the method we used is because I’m not sure we could have easily picked out individual stars like that in the galaxies we used… !?

    Ah, my memory is clearly getting worse as I get older! I’m only 26… you wouldn’t think it’d be so hard to remember something but it was about 6 years ago!