How was the presumed age of the Universe determined?

Question

Emilia Acosta · Accepted Answer

Using Hubble's law.

According to Hubble's law, a galaxy moves more quickly the further away it is from us: #v prop d# This law implies that everything in the universe was once concentrated at one point, supporting the theory of the big bang and allowing one to calculate the age of the universe's creation. This law can be applied backwards to determine how long ago everything was concentrated at one location. However, this is not using SI units, but rather the units for velocity is #kms^-1# and distance is measured in Mega-parsecs #MPc#. Since this equation is linear, Hubble's constant must exist: #H_o# Creating the formula: #v=H_od# The constant's value varies throughout the universe, but we can very roughly estimate what it is at this point: H o = 70 km/s^-1 MPc^-1 We can use the following equation to determine the age of the universe thanks to this constant: #1/H_o approx T# But in order for this to function, the Hubble constant needs to be converted into SI units. So let's find the value of the constant: #70 kms^-1=70 000 ms^-1# 1 parsec= 3.26 ly= #3.08 times 10^16 m# A mega-parsec, or one million parsecs, is equal to 3.08 times 10^16 times 10^6 meters. #H_o=70 kms^-1 MPc^-1=(70 times 10^3)/(10^6 times 3.08 times 10^16)= 2.27 times 10^-18# To determine Hubble time, inverse it: #1/(2.27 times 10^-18) approx T# #T approx 4.4 times 10^17 s# #T approx 1.4 times 10^10# years Which is almost 14 billion years, but scientists often say that the value is 13.8 with an uncertainty of #+-0.2# billion years, so we are within the acceptable range. And that's essentially the way one can estimate the age of the universe.

Parker Albertson · Answer

undefined By measuring the rate of cosmic expansion using techniques like Hubble's law and making observations of cosmic microwave background radiation, scientists have estimated the age of the universe.