Freestetter’s world of formulas: When the universe hunts cosmology
If the constant is not constant, you have a problem. If this constant is supposed to describe the entire universe, the problem is very big.
A massive galaxy cluster distorts the world’s distant islands into elongated arcs.
We have known that our universe is expanding since the 1920s. This behavior can of course also be described mathematically using the following equation:
Function free) It is a Hubble parameter that describes the expansion rate. You can do this using what is called a scaling factor in) Calculate how much space increases over time. As mentioned in the formula, the Hubble parameter depends on time. Are you betting on? R But enter the time that has passed since the Big Bang, and then you get a special value for the Hubble parameter: H0This is called the “Hubble constant”, that is, the current rate of cosmic expansion.
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So far it’s just been math, but of course we also want the tangible value of it H0 knowledge. You can measure it, for example, when you determine the speed and distance of different galaxies. Edwin Hubble, the discoverer of the expansion of the universe, calculated this to be 500 kilometers per second per megaparsec in 1929. Better measurements in the 1950s were about 250 kilometers per second per megaparsec and 180 kilometers per second per megaparsec. This is a very large range of fluctuations, but this can at least be attributed to the difficulties in determining the exact distance using telescope technology of the time.
Not only do we now have much better space telescopes, we also have fundamentally different identification methods H0. On the one hand, we can determine the distance and speed of distant galaxies by observing supernova explosions or special stars whose brightness changes can be used to calculate the distance to Earth. On the other hand, we are now also able to measure cosmic background radiation. Simply put, this is the first light that was able to spread across the universe about 400,000 years after the Big Bang. From the variations that can be measured today in the intensity of background radiation, one can also infer what value the current expansion rate must have.
Hubble problem
When we determine the distance and speed of galaxies, we use information that comes from the late universe; When measuring background radiation, we use data from the early universe. In the first case, you get a value for the Hubble constant of about 73 kilometers per second per megaparsec. In the second case you get a value of about 67 kilometers per second per megaparsec. There’s little difference, you might think. In fact, the measurements are so precise and precise that the difference in values cannot be explained solely by imprecision. Late universe data consistently provide lower values for H0 than those found in the early universe.
The discrepancy has grown over time: the better our data gets, the clearer it becomes that something is wrong. This condition is so alarming that it has been given its own name: “Hubble tension”. There are several ways to resolve stress. Of course, it is possible that in one way there is a methodological error that we have overlooked so far. But there could also be a fundamental problem in our understanding of the evolution of the universe.
In the end, only better data will help us. The James Webb Space Telescope will be used to determine more precise distances in the next few years; At the same time, more precise measurements of cosmic background radiation are being made. It remains to be seen whether we will then get a completely new picture of the universe or whether we will simply discover some previously overlooked errors. The main thing is that the Hubble constant finally received a reliable value.
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