Galaxy and the Universe

Content and key concepts

The galaxies contain stars, gas, dust, and dark matter. The observed red shift of distant galaxies indicates an expansion of space.
GEF · Grade 9
PIF · Baseline
Interactive model
Galaxy
Extension of the Universe
red offset
Relict radiation
01
The physical picture
What happens and what boundaries the model has.
Main message
The galaxies contain stars, gas, dust, and dark matter. The observed red shift of distant galaxies indicates an expansion of space.
The further the galaxy goes, the faster it is removed on average.
Relict radiation is the cool light of the early hot universe.
Cosmological models are checked by observations, not by a single image or measurement.
How to reason
First, name the system and the interaction, then select the values, and only then write down the law. The formula works within the model's assumptions.
02
Laws and values
Symbols should be read as a relationship of values, not as a recipe for substitution.
v
=
H
0
r
v=H_0r
v
=
H
0
​
r
Hubble Act
z
=
Δ
λ
λ
=
λ
набл
−
λ
0
λ
0
z=\frac{\Delta\lambda}{\lambda}=\frac{\lambda_{\mathrm{набл}}-\lambda_0}{\lambda_0}
z
=
λ
Δ
λ
​
=
λ
0
​
λ
Subtotal
​
−
λ
0
​
​
red offset
Review of the situation
The light of the distant galaxy shows it in the past: the telescope is at the same time an observer time machine.
04
Links and application
In the real world
The light of the distant galaxy shows it in the past: the telescope is at the same time an observer time machine.
Model verification
Compare the prediction with observation, evaluate the units, the order of magnitude and the influence of the factors not taken into account. Disparity does not always mean an error of law: often idealization is no longer sufficient.
C
What needs to be understood
Outcome 1
Explain the physical meaning of the topic "Galaxy and the Universe" through a model, not just a formula.
Outcome 2
Distinguish and correctly use terms: galaxy, expansion of the universe, red shift.
Outcome 3
Indicate the conditions for the applicability of the law, verify units and limit cases.
T
Terms of the topic
The definition should indicate the physical meaning, not a substitute for a domestic synonym.
Galaxy
Gravity-based system of stars, gas, dust and dark matter.
Extension of the Universe
The increase over time in cosmological distances between unrelated structures, as described by a major factor.
red offset
Relative increase in observed wave length compared to laboratory.
Relict radiation
Space microwave background radiation, preserved from the hot early universe.
F
Origin and conclusion of the formulas
The fundamental law cannot be "proven" by algebras: for each record, it is stated whether it is a definition, an experimental law, or a model effect.
v
=
H
0
r
v=H_0r
v
=
H
0
​
r
empirical law
Hubble law.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
z
=
Δ
λ
λ
>
0
z=\frac{\Delta\lambda}{\lambda}>0
z
=
λ
Δ
λ
​
>
0
In the range of distant galaxies, the red shift of the lines is measured and the rate of removal is estimated.
v
∝
r
v\propto r
v
∝
r
Observations show an approximately linear increase in the removal rate from the galaxy.
v
=
H
0
r
v=H_0r
v
=
H
0
​
r
The H_0 coefficient is determined by astronomical data; Hubble's law is set by observations rather than by geometry alone.
Conditions:
Cosmological distances, where the total expansion flow prevails over the galaxy's own speeds; linear shape is applicable at low red displacement.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
z
=
Δ
λ
λ
=
λ
набл
−
λ
0
λ
0
z=\frac{\Delta\lambda}{\lambda}=\frac{\lambda_{\mathrm{набл}}-\lambda_0}{\lambda_0}
z
=
λ
Δ
λ
​
=
λ
0
​
λ
Subtotal
​
−
λ
0
​
​
definition
Red shift.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
Δ
λ
=
λ
набл
−
λ
0
\Delta\lambda=\lambda_{\mathrm{набл}}-\lambda_0
Δ
λ
=
λ
Subtotal
​
−
λ
0
​
The change of the spectrum line is found to be the difference between the observed and the laboratory wave length.
z
≡
сдвиг длины волны
исходная длина волны
z\equiv\frac{\text{сдвиг длины волны}}{\text{исходная длина волны}}
z
≡
Baseline
length
Wave
change
length
Wave
​
The red shift is introduced as relative, so a dimensionless change in the wave length.
z
=
Δ
λ
λ
0
z=\frac{\Delta\lambda}{\lambda_0}
z
=
λ
0
​
Δ
λ
​
The positive z corresponds to the displacement to the long wave lengths and the negative to the blue displacement.
Conditions:
The same validly identified spectral line in the source and laboratory is compared; the denominator refers to its reference length ._0.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
!
Model boundaries and typical errors
Error: Forget model condition
You can't put the formula on any situation just because it's a coincidence of letters. The key condition of this topic is that the further away from the galaxy, the faster on average it'll be removed.
How to Check the Mind
Relict radiation is the cold light of the early hot universe. Then check the units, vector direction, and behavior of the result at zero or very large parameter.
Σ
Conclusion on the topic
Galaxy and the Universe
The galaxies contain stars, gas, dust, and dark matter. The observed red shift of distant galaxies indicates an expansion of space.
The further the galaxy goes, the faster it is removed on average.
Relict radiation is the cool light of the early hot universe.
Any numerical result shall be accompanied by a unit, a sign and an explanation of its physical meaning.
The content is consistent with the FRP on Physics of the OS/OSS 2025 and the subject matter of the current lines of the PNP: I. M. Peryškin and co-authors (7–9), G. J. Mäkishev and coauthors (10–11), and with the lines "Engineers of the Future" and V. A. Kasyanov. The original texts are not reproduced, the text of the textbooks is not reproduced.