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Universe expansion is speeding up

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Proud Mary

Fri Mar 26 2010, 09:39AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Hubble telescope shows Universe expansion is speeding up and proves Einstein's theory

By Richard Alleyne, Science Correspondent, BBC News,
25 Mar 2010

In the biggest survey ever conducted using the Hubble Space telescope, 446,000 galaxies were studied to see how matter was distributed throughout the universe and how quickly it had expanded.

And the astronomers found that the universe was growing faster and faster with time, as predicted by Einstein in his theory of general relativity.

Scientists claim that the universe is made up of three different components â€“ normal matter, which is the physical objects in the universe such as the planets â€“ dark matter, which is invisible matter that creates the gravitational pull that causes galaxies to form â€“ and an unknown energy referred to as "dark energy", the force which causes the universe to expand.

Einstein's theory of general relativity claims that space and time are a geometrical structure which can be changed by the behaviour of the matter inside it.

So proof that the expansion of the universe is speeding up shows that the contents of the universe, such as the "dark energy" causing it to inflate, are influencing its structure.

Ludovic Van Waerbeke, of the Department of Physics and Astronomy at Leiden University in the Netherlands, said: "Our results confirmed that there is an unknown source of energy in the universe which is causing the cosmic expansion to speed up, stretching the dark matter further apart exactly as predicted by Einstein's theory.

"The data from our study are consistent with these predictions and show no deviation from Einstein's theories."

Mr Van Waerbeke pioneered a technique to measure the invisible web of dark matter which was used in the study.

In a method similar to taking an X-ray of the body to reveal the underlying skeleton, the technique, known as weak gravitational lensing, allows astronomers to see how light from distant galaxies is bent and distorted by the dark matter as it travels towards earth.

They can then map the dark matter structures, which make up 80 per cent of the universe.

The study leader Tim Schrabback said: "What we tested is how the structure of the universe grows with time. If the universe expands then the gravitational lensing changes because the distance between the objects has changed.

"I think from that perspective this is quite exciting because this is the first time this measurement has been done with weak gravitational lensing alone. Before it's always been done with other measurements because the lensing was not effective.

"The other thing that is really exciting is that in the next years there will be much larger surveys which will have more accurate measurements for dark energy and expansions, and we will see some very interesting results."

As well as this technique, astronomers in the study used the Cosmic Evolution Survey (COSMOS), a joint project by the European Space Agency and NASA involving over 100 scientists from a dozen countries.

For the survey, a camera aboard the Hubble telescope photographed 575 slightly overlapping views of the same part of the universe, which took nearly 1,000 hours of observation, during which the Hubble circled the earth nearly 600 hundred times.

Mr Schrabback said: "This is the largest survey ever done with the Hubble telescope. The images make up a large mosaic of the sky.

"The Hubble has a great advantage from images taken from earth because there is no blurring from the atmosphere."

Fraggle

Fri Mar 26 2010, 09:54AM

Registered Member #1526 Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216

I thought it was Hubble who thought the expansion was speeding up?

Dr. Slack

Fri Mar 26 2010, 12:13PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

No, Hubble thought it was expanding, so dx/dt > 0, d2x/dt2 = 0.

Ludovic Van Waerbeke is saying that the expansion is speeding up, d2x/dt2 > 0.

I'm not sure about the Einstein connection though, other than name everybody knows. He did invent the term "cosmological constant" as a fudge for a theological problem he had, then proclaimed that it was his biggest blunder when he realised that. The fact that now we have new observations which requires something of the same properties to fit doesn't to my mind warrant giving Einstein the credit, it's more like luck he hit on a reasonable idea.

IntraWinding

Fri Mar 26 2010, 02:33PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

My first reaction to the title was: "I thought we already knew the rate of expansion of the universe is increasing"?

In fact the quote from Ludovic Van Waerbeke says he is 'Confirming' the result, if you dig deep enough.

It's annoying when science gets spun by someone who doesn't appreciate it. This is an important finding which confirms the current mysterious state of things, but it's been beaten into the shape of a totally different story to try to make something the writer thinks will bore people seem interesting.

The bit about it confirming Einstein is misleading 'name dropping'. In fact the whole point is that the rate of expansion accelerating, rather than being steady or slowing down, is deeply mysterious.

Or am I wrong (I'm just a geeky enthusiast)?

The interesting thought to me is that we might be in the run up to some new genius coming up with something as mind boggling as Einstein to explain the whole 'Dark Energy' and 'Dark Matter' thing.

Bjørn

Fri Mar 26 2010, 04:02PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

The "proof" seems to come from this line in the abstract of the original paper: "We find that the weak lensing signal scales with redshift as expected from General Relativity for a concordance Î›CDM cosmology, including the full cross-correlations between different redshift bins."

So the shape of distant galaxies are distorted by gravitational lensing in a way that you would expect if general relativity was true. So either general relativity is true or they messed up some of their models. A nice confirmation but not a very powerful proof.

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