It makes sense the better we can measure something, the more we learn.
In fact, in the 1990s, the rate of expansion was found to beaccelerating.
The current expansion rate is described by something called Hubbles Constant a fundamental cosmological parameter.
Until recently, it seemed we were converging on an accepted value for Hubbles Constant.
But a mysterious discrepancy has emerged between values measured using different techniques.
Now a new study,published in Science, presents a method that may help to solve the mystery.
But in the last few years, new measurements have shown thatthis might not be a final answer.
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But this early universe measurement gives a lower value of around 67.
Astronomers euphemistically refer to this as tension in the exact value of Hubbles Constant.
The new paper presents a neat approach to this challenge.
Many estimates of the expansion rate rely on the accurate measurement of distances to objects.
But this is really hard to do: we cant just run a tape measure across the universe.
One common approach is to useType 1a supernovas(exploding stars).
These are incredibly bright, so we can see them at great distance.
NASA/HUbble
The team has studied two galaxies that are lensing the light from two other background galaxies.
This causes a delay in the arrival time of light across the lensed image.
If the background source has a fairly constant brightness, we dont notice that time delay.
But when the background sourceitselfvaries in brightness, we can measure the difference in light arrival time.
This work does exactly that.
The answer they got was just over 82 kilometers per second per megaparsec.
This is quite high compared to the numbers mentioned above.
Importantly, though, it is statistically consistent with the value measured from the local universe.
The uncertainty will be reduced by hunting for and measuring distances to other strongly lensedand time-varyinggalaxies.
The result provides another piece of the puzzle.
So the mystery remains, but hopefully not for too long.
