13: Equations Flashcards

1
Q

Ratio of Δλ to λ

A

Δλ/λ = v/c, if v &laquo_space;c

Δλ = difference between the observed wavelength and emitted wavelength
λ = emitted wavelength
v = velocity if the source
c = speed of light
the double less than means ‘much less than’
the velocity of something must be much less than the speed of light to avoid relativistic effects

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2
Q

Velocity = (Hubble’s constant)

A

v = H₀d
v = recessional velocity
H₀ = Hubble’s constant
d = distance

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3
Q

In the equation v = H₀d, what unit is velocity?

A

kms⁻¹

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4
Q

In the equation v = H₀d, what unit is Hubble’s constant?

A

kms⁻¹Mpc⁻¹

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5
Q

In the equation v = H₀d, what unit is distance?

A

Mpc, megaparsec

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6
Q

What is 1 Mpc in m

A

3.09 * 10²²

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7
Q

Relativity t =

A

t = λτ

where t = actual time (longer)
τ = expected time w/o relativity (shorter)
λ = relativistic factor (always greater than 1)

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8
Q

equation with radar for working out distance to object

A

2d = ct

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9
Q

break down realivistic factor t = (1)t0 / sqr(1 - v²/c²)

A

t = longer interval
t0 = proper time
v = constant velocity
t0 can also be 1

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10
Q

how to calculate age of universe in years if given a value for hubbles constant of 300km s^-1 mpc^-1
mpc^-1 = 3.1 * 10^22

A

first convert that velocity into ms^-1 and divide by value of megaparsec to get hubble’s constant in seconds
then do timescale = 1 / hubbles constant to get age of universe in seconds
then divide this timescale in seconds by 3.16 * 10^7 (seconds in year) to get timescale for age of universe in years

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