A galaxy at a distance of 25 Mpc has a recession velocity of 1,875 km / sec . What is Hubble's c

step 1 Hey, everybody. So we need to find A, the distance, and we have distance equals Blossie of the H

A galaxy at a distance of 25 Mpc has a recession velocity of...

A galaxy at a distance of 25 Mpc has a recession velocity of $1,875 \mathrm{km} / \mathrm{sec} .$ What is Hubble's constant based on this one galaxy? Why is this not a good way to determine Hubble's constant?

Key Concepts

Hubble's Law

Hubble's Law states that the recessional velocity of a galaxy is directly proportional to its distance from the observer. This fundamental relation, expressed as v = H0 × d, underpins our understanding of the expanding universe and provides a method to estimate the rate of cosmic expansion through observational data.

Hubble's Constant

Hubble's Constant is the proportionality factor in Hubble's Law that quantifies the rate of expansion of the universe. It is typically measured in kilometers per second per megaparsec and represents the velocity at which a galaxy recedes for each megaparsec of distance. Accurate estimation of this constant requires careful calibration and measurements across many galaxies.

Peculiar Velocities

Peculiar velocities are the individual motions of galaxies relative to the overall cosmic expansion. These motions, influenced by local gravitational interactions, can cause deviations from the smooth recessional velocity predicted by Hubble's Law. When determining the Hubble constant from a single galaxy, such peculiar velocities can introduce significant errors, making it an unreliable method for measuring the true cosmic expansion rate.

Statistical Sampling and Measurement Uncertainty

Using a single galaxy to determine Hubble's constant overlooks the benefits of large sample sizes that can average out random errors and peculiar velocity effects. A statistically significant data set of many galaxies is crucial for minimizing uncertainties and obtaining a reliable measurement of the universe's expansion rate. This approach leads to more robust conclusions than would be possible from an isolated example.

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