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Galloping galaxies – Pt II

November2

The universe doesn’t look right. It suddenly looks . . . out of whack.

The universe is unimaginably big, and it keeps getting bigger. But astronomers cannot agree on how quickly it is growing – and the more they study the problem, the more they disagree. Some scientists call this a “crisis” in cosmology. A less dramatic term in circulation is “the Hubble Constant tension.”

Nine decades ago, the astronomer Edwin Hubble showed that the universe is orders of magnitude vaster than previously imagined – and the whole kit and kaboodle is expanding. The rate of that expansion is a number called the Hubble Constant.

It’s a slippery number, however. Measurements using different techniques have produced different results, and the numbers show no sign of converging even as researchers refine their observations.

No one is panicking. To the contrary, the theorists are intrigued. They hope the Hubble Constant confusion is the harbinger of a potential major discovery – some “new physics.”

“Any time there’s a discrepancy, some kind of anomaly, we all get very excited,” said Katherine Mack, a physicist at North Carolina State University who co-wrote a recent paper examining the issue.

The Hubble Constant is a central feature of any theory about the evolution and ultimate fate of the universe. This number may have zero effect on daily human existence, but there’s a lot at stake cosmologically.

“Where’s it all going to go? How’s it all going to end? That’s a big question,” Mack said. One widely supported estimate of the cosmic expansion uses the background radiation that permeates space – light emitted when the universe was young.

That gives a Hubble Constant of about 67 kilometres per second per megaparsec. (A parsec is a distance of a bit more than three light-years. According to this estimate, a galaxy one million parsecs from Earth is receding at 67 kilometres per second, and a galaxy twice as distant is receding at 134 kilometres per second.) All these speeds are faster than H3’s Camry!

But another carefully calibrated measurement, based on light emitted from exploding stars – supernovae – has come up with a Hubble Constant of 73.

This isn’t horseshoes or hand grenades: Close doesn’t count. People want the actual, real, universe-expanding Hubble Constant, and no one is eager to round it up to the nearest 10.

This northern hemisphere summer, as leaders in the field assembled in Santa Barbara, California, to discuss the “tension,” physicist Wendy Freedman of the University of Chicago presented a new estimate of the constant that was based on examination of red giant stars.

Her number: 70. But the advocates for 67 and 73 held their ground. The tension remained. Freedman told The Washington Post, “There can’t be three different numbers.”

There are more than that, actually. On October 23, researchers at the University of California at Davis published a paper that looked at three gravitational lenses – in which massive galaxies function like magnifying glasses for things behind them in deeper space. Their number: 77.

It could be simply that some of the measurements are based on erroneous assumptions. Imagine two speed guns giving strikingly different measurements of a bowled fastball. One obvious, boring explanation is that one of the speed guns needs to be recalibrated.

It’s conceivable, for example, that astronomers haven’t fully factored in the way cosmic dust can interfere with observations, which wouldn’t be the first time that has happened.

But the more delicious possibility is that there’s something new to be discovered about the way the universe evolved.

One idea floating around is that there could have been something called Early Dark Energy that skewed the appearance of the background radiation.

“New physics might be that there’s some form of energy that acted in the earliest moments of the evolution of the universe. You’d get an injection of energy that’d then have to disappear,” Freedman said.

“If it’s new physics, it’s so exciting,” says Jo Dunkley, a professor of physics at Princeton. But, she added: “I’m just not willing yet to jump into the opinion that it’s new physics. I’m more sceptical of our ability to understand our measurement uncertainties.”

Meanwhile, estimates from the team behind the Planck space telescope, which studied the cosmic microwave background radiation, continue to centre on 67.

So the disparity persists. That leaves open the tantalising possibility that “No one’s wrong. Something else is going on in the universe.”

Article first posted in The Washington Post. See also Galloping Galaxies, Pt I

 

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NCEA Level 2 Algebra Problem. Using the information given, the shaded area = 9, that is:
y(y-8) = 9 –> y.y – 8y – 9 =0
–> (y-9)(y+1) = 0, therefore y = 9 (can’t have a distance of – 1 for the other solution for y)
Using the top and bottom of the rectangle,
x = (y-8)(y+2) = (9-8)(9+2) = 11
but, the left side = (x-4) = 11-4 = 7, but rhs = y+? = 9+?, which is greater than the value of the opp. side??
[I think that the left had side was a mistake and should have read (x+4)?]

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