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Universe expansion rate mystery deepens

Posted on Thursday, 18 July, 2019 | Comment icon 38 comments

Why has it proven so difficult to calculate the expansion rate ? Image Credit: NASA/ESA
A new attempt to calculate how fast the universe is expanding has thrown up more questions than answers.
Known as the Hubble Constant, the expansion rate of the universe was originally estimated by physicist and astronomer Georges Lemaitre all the way back in 1927.

More recently, by using data from the Hubble Space Telescope, physicists calculated that the expansion rate was approximately 73 kilometers per second per megaparsec.

Then a separate team of researchers using data from the European Space Agency's Planck spacecraft came up with a completely different figure of around 67 kilometers per second per megaparsec.

Most recently, University of Chicago astronomer Wendy Freedman and colleagues attempted to prove that the rate of expansion was either one or the other by using a different method which involved calculating the brightness of red giant stars in distant galaxies.

As it turned out however, their efforts resulted in a figure of 69.8 kilometers per second per megaparsec - a completely new answer that doesn't match any of the previous findings.

In fact over the years there have been numerous attempts to calculate the Hubble Constant and none of them agree with one another. It seems that physicists must be missing something.

"Naturally, questions arise as to whether the discrepancy is coming from some aspect that astronomers don't yet understand about the stars we're measuring, or whether our cosmological model of the universe is still incomplete," said Freedman.

"Or maybe both need to be improved upon."

Source: Science Alert | Comments (38)

Tags: Hubble Constant, Universe

Recent comments on this story
Comment icon #29 Posted by lightly on 13 August, 2019, 19:13
So,   Space is getting less dense as it expands....?  What is "space" ? ...What exactly,  is getting less dence?  How do "they" measure the density of space? Am I getting more dence as space expands.  .. .?   
Comment icon #30 Posted by lightly on 15 August, 2019, 13:46
If space and time are linked....is time getting less dence as well?  ( that doesn't make sence to me ) ...and if space can be distorted...time as well? ...( I think that IS believed and shown ) ?
Comment icon #31 Posted by Desertrat56 on 15 August, 2019, 14:57
When I was a kid I remember old people saying "time goes faster the older you get" and it seems to.  But I think time is a concept we created to explain how we experience linearly.  Time isn't real, just a concept, but it does need to be considered in certain types of math.
Comment icon #32 Posted by lightly on 16 August, 2019, 13:18
Time.      Time.         When the heck is time?  Is it now?   Was it a second me ago? .  I'm starting to wonder if energy is all there is....   
Comment icon #33 Posted by SmartAZ on 18 August, 2019, 7:22
There is science and then there is science. The two resemble each other only slightly. One science is based on measurements and tests, the other is based on commands to believe pronouncements from people who claim to have that authority. That is the definition of religion. I have no problem trusting science. The religion that goes by the same name is teh suxorz.
Comment icon #34 Posted by Piney on 18 August, 2019, 10:58
It's called "spacetime" and gravity is a "dent" in it.  .....let that stew for a while then PM @Harte    
Comment icon #35 Posted by Grey Area on 18 August, 2019, 12:13
It’s easier to visualise time not as the classical flow of time, but instead visualise it as the speed of causality. If we observe an event in the universe and measure its distance from us we can agree on the amount of time it took for the light to reach us, but we need to understand that the light can be manipulated along the way and so a calculation based solely on the speed of light is not reliable, and so time is inextricably linked to space and it’s geometry. Thus Einstein introduced space time as a model that described classical 3D space and the 4th time dimension. Thats a really clunky ... [More]
Comment icon #36 Posted by lightly on 18 August, 2019, 14:47
Thanks Piney....yes, I recently heard gravity described as a distortion in space.  I haven't noticed a corresponding dent in time? Harte has been more than generous in explaining    things.
Comment icon #37 Posted by lightly on 18 August, 2019, 14:56
Distortions in space...always make me wonder what space is composed of which would be attracted by Mass/Matter.  ?  
Comment icon #38 Posted by Harte on 18 August, 2019, 22:54
Space and time are two aspects of the same thing, so a dent in space is actually also a dent in tim, which is why a gravity well slows time down. Harte

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