Variables + Data
In an experiment, this is the variable the scientist changes on purpose.
What is the independent variable?
This is the number of waves that pass a point each second.
What is frequency?
Scientists estimate the universe is about this old.
What is 13.8 billion years?
Stars are born inside this giant cloud of gas and dust.
What is a nebula?
The strength of gravity between two objects depends on these two factors.
What are mass and distance?
This variable is measured because it responds to the change, and it goes on the y-axis of a graph.
What is the dependent variable?
Telescopes like Hubble orbit above Earth because this layer of gases around the planet absorbs X-rays and most ultraviolet radiation.
What is Earth's atmosphere?
When light from a galaxy is stretched to longer wavelengths because the galaxy is moving away, this is the name of the shift.
What is redshift?
This stage is a contracting ball of gas with a core of about 2 million K, still too cool for hydrogen fusion (which needs about 10 million K).
What is a protostar?
An astronaut with a mass of 80 kg travels from Earth to the Moon. His mass stays the same, but this quantity decreases.
What is weight?
Variables that are kept the same so a test is fair are called these.
What are controlled variables (constants)?
Put these in order from longest wavelength to shortest: visible light, gamma rays, radio waves, X-rays.
What is radio waves, visible light, X-rays, gamma rays?
A hydrogen line that is normally 656 nm is observed in a galaxy at 642 nm. The galaxy is moving this direction, and the shift has this name.
What is toward Earth, blueshift? (Shorter wavelength means blueshift.)
On the H-R diagram, a star that is cool (3,500 K) but extremely luminous (5,000 times the Sun) is this type of star, and its brightness comes from being very large.
What is a red giant?
Put these nebular theory events in order: planets form, the Sun forms at the center, a cloud collapses, a rotating disk forms.
What is: cloud collapses, disk forms, Sun forms at the center, planets form from the disk?
A scientist tests whether galaxies that are farther from Earth move away faster. Name the independent AND dependent variables.
What are distance (independent) and speed (dependent)?
True or false, and explain: "Gamma rays travel faster than radio waves because they have more energy."
What is false? All electromagnetic waves travel at the same speed in a vacuum; gamma rays have more energy because they have a higher frequency and shorter wavelength.
This leftover radiation from the hot, dense early universe has been stretched into microwaves and reaches us from every direction.
What is the cosmic microwave background (CMB)?
A star with 20 times the Sun's mass lives about 10 million years, while a star with half the Sun's mass lives about 50 billion years. Explain why.
What is: massive stars use up their fuel much faster because their gravity makes fusion happen at a higher rate?
Mercury orbits the Sun in 0.24 years at 47 km/s, while Saturn takes 29.5 years at 9.7 km/s. As distance from the Sun increases, what happens to orbital period and orbital speed?
What is: period increases and speed decreases?
A scientist records the mass of four stars (0.5, 1, 5, and 20 times the Sun) and how long each stays on the main sequence (50 billion, 10 billion, 100 million, and 10 million years). Name the independent variable, the dependent variable, and the pattern in the data.
What are mass (independent) and main-sequence lifetime (dependent), and as mass increases, lifetime decreases?
Hydrogen's lines are 410, 434, 486, 656 nm; sodium's is 589 nm; calcium's are 393, 397 nm. A star shows lines at 393, 397, 410, 434, 486, and 656 nm. These are the elements present.
What are hydrogen and calcium? (No 589 nm line, so no sodium.)
Galaxies at 100, 300, and 500 million light-years are moving away at 2,000, 6,000, and 10,000 km/s. State the pattern AND what it suggests about space.
What is: farther galaxies move away faster, which shows space itself is expanding (Hubble's law)?
A hot, blue star with 20 times the Sun's mass will swell into a red supergiant and then end in this explosion, not by quietly fading into a white dwarf.
What is a supernova?
Two objects have masses m₁ = 10 kg and m₂ = 20 kg and are r = 4 m apart. In this model, the gravitational force between them is 50 N. Now m₁ is doubled to 20 kg and the distance is halved to r = 2 m. The new force is this.
What is 100 N? Doubling m₁ makes the force 2 times as strong. Halving the distance makes it 4 times as strong (the distance is squared).