# Question about super large number units in hubbles constant

• zeromodz
In summary, Hubble's Constant is a value that describes the rate at which the universe is expanding and is important in understanding the age and size of the universe. It is measured using various methods and can change over time due to factors such as matter and energy. The units of Hubble's Constant are kilometers per second per megaparsec and the current accepted value is around 70 km/s/Mpc, although there is ongoing debate and research for a potentially higher value.
zeromodz
This is hubbles constant from my source
74.2 ± 3.6 (km/s)/Mpc

What does the ± mean?

That means that the value of the Hubble constant lies somewhere in the range of 74.2 -3.6 and 74.2 + 3.6. Every measured quantity has errors due to method and instrumentation called the error bounds.

For example, when using a ruler we usually assume an error equal to 1/2 the smallest division mark. Let's say you use a standard meter stick for a measurement of 10cm. Your error bound would be specified by 10 +/- .05 cm

The ± symbol represents the margin of error or uncertainty in the value of Hubble's constant. In this case, the value is reported as 74.2 km/s/Mpc, but there is a possible range of 3.6 km/s/Mpc above or below this value. This margin of error is important to consider when making calculations or interpretations based on Hubble's constant.

## 1. What is Hubble's Constant and why is it important in astronomy?

Hubble's Constant is a value that describes the rate at which the universe is expanding. It is named after the American astronomer Edwin Hubble who first discovered this expansion in the 1920s. This constant is important because it helps us understand the age and size of the universe, as well as the rate at which galaxies and other celestial objects are moving away from each other.

## 2. How is Hubble's Constant measured?

Hubble's Constant is measured using a variety of methods, such as observing the redshift of galaxies, the brightness of supernovae, and the cosmic microwave background radiation. These measurements can then be used to calculate the expansion rate of the universe and determine the value of Hubble's Constant.

## 3. Can Hubble's Constant change over time?

Yes, there is evidence to suggest that Hubble's Constant has changed over the history of the universe. The expansion rate of the universe is affected by various factors, such as the amount of matter and energy present, which can cause fluctuations in the value of Hubble's Constant.

## 4. What are the units of Hubble's Constant?

Hubble's Constant is typically measured in units of kilometers per second per megaparsec (km/s/Mpc). This means that for every megaparsec (a unit of distance equal to about 3.26 million light-years), the universe is expanding at a rate of a certain number of kilometers per second.

## 5. What is the current accepted value of Hubble's Constant?

The exact value of Hubble's Constant is still a topic of debate among scientists, but the most commonly accepted value as of 2021 is around 70 km/s/Mpc. However, there have been recent studies that suggest a higher value of around 73-74 km/s/Mpc, which is still being studied and debated by the scientific community.

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