Astronomy Mid Term – Flashcards

Unlock all answers in this set

Unlock answers
question
The number of degrees in a full circle is
answer
360
question
How many arcseconds are there in a full circle?
answer
360 x 3600
question
In angular measurements used in astronomy, how many right angles are there in a full circle?
answer
four
question
One arcsecond is equal to
answer
1/3600 degree
question
One arcminute is equal to
answer
1/60 degree.
question
On a particular night, Jupiter subtends an angle of 42 arcseconds as seen from Earth. This angle is
answer
roughly three-quarters of an arcminute.
question
Astronauts on the Moon look back at Earth, a distance of about 400,000 km away. If the cities of Washington, D.C., and New York are separated by about 300 km, what will be the angle between them when viewed from the Moon?
answer
2.5 arcminutes
question
Two very bright fireworks are exploded at the same time during the July 4 celebrations, one in New York, the other in Los Angeles (4000 km apart). How far apart in angle will these flashes appear to astronauts on the Moon, who are 400,000 km from Earth?
answer
34.4 arcminutes
question
At what distance would a friend have to hold a dime (about 1 cm diameter) for it to subtend an angle of 2 arcseconds?
answer
1 km
question
The number five hundred thousand is written in powers-of-ten notation as
answer
5 × 105.
question
10^5 × 10^8 =
answer
10^13
question
One billionth divided by one millionth is equal to
answer
10^-3
question
By what approximate factor in powers-of-ten notation is a human being (height about 2 m) larger than the nucleus of a hydrogen atom, or proton (diameter about 10^-15 m)?
answer
2 × 10^15
question
One astronomical unit, or one AU is defined as the
answer
mean distance between the Sun and Earth.
question
A light-year is a measure of
answer
distance.
question
If you were able to travel out into space until the angular distance between Earth and the Sun was 1 second of arc, how far would you be from the Sun? (Assume that Earth-Sun line is at right angles to your line of sight.)
answer
1 pc
question
The distance to the star τ Scorpii has been measured as 230 pc. Expressed in light-years, this is approximately
answer
750 ly.
question
The time taken for light to travel to Earth from a galaxy that is 10 Mpc away is
answer
3.26 × 10^7 years.
question
The following distance units, arranged in size from smallest to largest, are
answer
km, AU, ly, pc
question
A star rises at 8 P.M., moves across the sky (crossing high overhead), and then sets at
answer
8 A.M.
question
The phrase "diurnal motion" refers to the
answer
gradual motion of the constellations from east to west across the sky each night, resulting in different constellations being visible at 4 A.M. than at 10 P.M. on any given night.
question
What basic pattern do stars seem to trace out in our sky if you watch (or photograph) stars near the north celestial pole for a period of several hours?
answer
circles, with the north celestial pole at the center
question
With respect to the stars, the rotation of Earth carries you toward the
answer
east.
question
Which of the following lines or points is always directly over your head, no matter where on Earth you go?
answer
zenith
question
Diurnal motion of objects in the sky is caused by the
answer
rotation of Earth on its axis.
question
The nightly motion of objects across our the sky is caused by the
answer
rotation of Earth on its axis.
question
The ecliptic is defined as the
answer
line traced in our sky by the Sun over one year against the background stars.
question
The ecliptic crosses the celestial equator at
answer
two points, known as equinoxes.
question
Earth would not have seasons if
answer
its axis of rotation were perpendicular to its orbital plane.
question
Summertime in the northern hemisphere is when
answer
more direct sunlight shines on this hemisphere.
question
It is warmer in summer than winter because
answer
the Sun is higher in the sky and the days are longer.
question
One required condition for seasons to occur is that a planet's
answer
spin axis be tilted with respect to the perpendicular to its orbital plane.
question
The equinoxes are located at the intersections of the
answer
ecliptic and the celestial equator.
question
When the Sun is at one of the equinoxes,
answer
day and night are of equal length everywhere on Earth.
question
If you observe from a location north of the equator the Sun's position on the horizon as it rises each morning throughout the year you will find that
answer
the rising position moves progressively northward from December through June.
question
The Sun rises due east in the sky when viewed from any site
answer
on Earth only on the first day of spring and the first day of fall.
question
The Arctic Circle is at a latitude of
answer
66.5° N.
question
The Arctic Circle is defined as a line on Earth where the Sun
answer
can be seen for 24 hours on at least one day of the year.
question
Precession is
answer
the slow coning motion of the spin axis of Earth, similar to that of a spinning top.
question
What is the significance of Polaris, the North Star?
answer
Polaris is almost on the curve traced out by the rotation axis as a result of the precession of the rotation direction.
question
The position in Earth's orbit around the Sun which presently corresponds to Winter Solstice will instead correspond to Summer Solstice in about
answer
13,000 years.
question
Precession of Earth's axis of rotation is caused by
answer
the gravitational pull of the Moon and the Sun on the equatorial bulge of Earth.
question
The reason for the slow movement of the vernal equinox through our sky against the background stars over long periods of time is the
answer
precession of the spin axis of Earth.
question
The precessional motion of the north celestial pole of Earth over a period of 26,000 years is a circle of 47° diameter in the northern sky. The equivalent motion of the south celestial pole is
answer
a circle of 47° diameter, covered in 26,000 years.
question
Which of the following is the correct sequence of appearances of Moon phases in the sky?
answer
waxing crescent, first quarter, waxing gibbous, full moon
question
Why do we see different phases of the Moon?
answer
The motion of the Moon in its orbit around Earth causes us to see different amounts of the sunlit side of the Moon
question
A full moon is always at its highest in our sky at
answer
midnight.
question
In its orbit around Earth, the Moon
answer
always keeps the same side toward Earth.
question
Earth's shadow falling on the Moon is the reason we see
answer
lunar eclipses.
question
What is the one major difference between the Sun and the Moon in our sky?
answer
The Sun emits light while the Moon merely reflects it.
question
At what approximate time does a full moon rise?
answer
sunset
question
A full moon always occurs
answer
when the Moon is farther from the Sun than is Earth.
question
The phase of the Moon when the Sun and Moon are separated by 6 hours of right ascension is always
answer
either first or third quarter.
question
When the Sun and Moon are separated by 12 hours of right ascension, the phase of the Moon is always
answer
full moon.
question
The correct order of "appearance" of the following "actors" on the "stage" of scientific discovery is
answer
Ptolemy, Copernicus, Kepler, Newton, Einstein.
question
The word planet is derived from a Greek term meaning
answer
wanderer.
question
When observing planetary motions from Earth, the phrase "retrograde motion" refers to
answer
a slow westward motion of the planet from night to night against the background stars.
question
Retrograde motion of a planet against the background stars is always
answer
movement from east to west.
question
The epicycle in the Greek planetary model is
answer
a small circle through which the planet moves as the center of this circle orbits Earth.
question
In the geocentric model for the solar system developed by Ptolemy, to what does the word "deferent" refer?
answer
the large circle around Earth through which the center of a smaller circle moves while the planet moves around the smaller circle
question
When Venus is at inferior conjunction,
answer
it is at its smallest distance from Earth.
question
When Venus is at superior conjunction,
answer
it is at its greatest distance from Earth.
question
n which direction is Venus moving when it is at greatest elongation?
answer
directly toward or away from Earth
question
When Saturn is at its farthest distance from Earth, it is at
answer
conjunction.
question
Galileo's early observations of the sky with his newly made telescope included the
answer
fact that Venus showed phases similar to those of the Moon.
question
How many moons of Jupiter were seen by Galileo?
answer
4
question
Which of the following statements correctly states the significance of Galileo's observation that Jupiter has satellites (moons)?
answer
It showed that bodies can orbit an object other than Earth.
question
As Venus orbits the Sun, by what factor, as viewed from Earth, does its angular size change from smallest to largest?
answer
5.8 ×
question
Which of the following statements correctly states the significance of Galileo's observation that Venus shows phases?
answer
The phases were correlated with angular size in a way that supported the heliocentric theory.
question
In the geocentric model of the solar system, which one of the following phases of Venus should be visible from Earth?
answer
new
question
A body whose velocity is constant
answer
has zero acceleration.
question
Which path would a planet (like Earth) take if the force of gravity from the Sun were to be suddenly removed?
answer
The planet would move in a straight line tangential to its present orbit.
question
Newton's law of universal gravitation is so named because it
answer
holds for all objects in the universe.
question
Suppose that an object is discovered moving around the Sun once every 120 years. Which of the following paths is a possible orbit for this object?
answer
ellipse
question
Spring tides occur
answer
twice a month, at full and new moon.
question
The highest of all tides on Earth's oceans occur at
answer
full or new moon, at times when Moon and Sun are closest to Earth.
question
Neap tides occur
answer
twice a month, at first and third quarter moon.
question
Does the Sun or the Moon have a greater effect in causing the tides on Earth?
answer
The Moon, because it has a larger difference between pulling on the near side and pulling on the far side of Earth
question
How many "tidal bulges" are there on Earth, due to the Moon's gravitational pull?
answer
two, one facing (almost) directly toward the Moon and one facing (almost) directly away from the Moon
question
What are spring tides?
answer
High tides that are significantly higher than the average high tide
question
The reason the Moon always keeps one face toward Earth is that
answer
gravitational forces from Earth act on the tidal bulge of the Moon.
question
In 1675, Rømer measured the speed of light by
answer
timing eclipses of Jupiter's satellites, which appeared to occur later when Earth was farther from Jupiter.
question
The average distance of Pluto from the Sun is 40 AU. How long does it take for light to travel across the solar system from one side of Pluto's orbit to the other?
answer
11 hrs
question
Radio waves travel through space at what speed?
answer
at the speed of light, 3 × 108 m/s
question
When light passes through a prism of glass, the
answer
different colors or wavelengths of light are separated in angle by the prism.
question
Around 1670, Isaac Newton performed a crucial experiment on the nature of light when he
answer
demonstrated that the colors that make up white light are intrinsic, not produced by the glass through which the light passes.
question
Visible light occupies which position in the whole electromagnetic spectrum?
answer
between infrared and ultraviolet
question
In terms of wavelengths, gamma rays are
answer
the shortest-wavelength electromagnetic waves.
question
What is the wavelength of electromagnetic radiation whose frequency is 106 cycles per second (106 Hz or 1000 kHz, the frequency of ordinary AM radio)?
answer
300 m
question
On the absolute scale of temperature (in kelvins), the zero of the scale corresponds to the
answer
temperature at which motions of atoms and molecules essentially cease.
question
A typical but very cool star might have a temperature of 3100°C. On the Kelvin scale, this is about
answer
3373 K.
question
Wien's law, relating the peak wavelength λmax of light emitted by a dense object to its temperature T , can be represented by
answer
λmax T = constant.
question
We plot the intensity of the radiation emitted from a solid object at a certain temperature versus its wavelength. As we increase the temperature, the wavelength at which the spectrum peaks becomes shorter and shorter. This is an illustration of
answer
Wien's Displacement Law.
question
We plot the intensity of the radiation emitted from a solid object at a certain temperature versus its wavelength. As we increase the temperature, the total amount of energy emitted all across the spectrum increases as the fourth power of the temperature. This is an illustration of
answer
the Stefan-Boltzmann Law.
question
Cepheid-variable stars pulsate regularly in size. During the contraction part of the cycle, when the star's temperature is increasing, the peak wavelength of the emitted radiation
answer
shifts from the visible to the UV part of the spectrum.
question
The total energy flux F of radiation emitted per unit area by a blackbody (e.g., star) is related to its temperature T and a constant σ by which equation?
answer
F = σT 4
question
A piece of iron is heated from 400 to 800 K (127 to 527°C). By what factor will the total energy per second emitted by this iron increase?
answer
16
question
Pieces of metal are heated by varying amounts in a flame. The hottest of these is the one that shows which color most prominently?
answer
blue
question
What changes would you expect to see in the resulting spectrum of emitted light from a piece of metal when it is heated slowly in an intense flame from 500 K to 1500 K?
answer
The intensity of radiation would increase and its color would change from red through white to blue.
question
The spectrum of sunlight, when spread out by a spectrograph, has what characteristic appearance?
answer
continuous band of color, crossed by innumerable dark absorption lines
question
The dark absorption lines in the solar spectrum are caused by absorption
answer
of sunlight in a cooler layer of gas overlying the hot solar surface.
question
The star Betelgeuse has a lower surface temperature than the Sun; therefore (with IR = infrared and UV = ultraviolet)
answer
Betelgeuse emits less IR and less UV flux than the Sun.
question
When a rod of metal is heated intensely, its predominant color
answer
changes from red, through orange to white, and then to blue.
question
The Sun's surface has a temperature of 5800 K. What will be the peak wavelength of the spectrum of a star that emits twice the Sun's flux of energy?
answer
2.5 × 10^-7 m
question
Atoms in a hot, low-density gas (e.g., in a laboratory-type spectral source) emit a spectrum that is
answer
a series of specific colors, unique to the type of atom in the tube, but fixed in position even when the gas temperature changes.
question
Why is the sky blue?
answer
The air molecules scatter blue light better than red light, so more blue light reaches our eyes.
question
The setting Sun appears red because
answer
its light is scattered by a thicker layer of air than during the day.
question
The physical structure of an atom is
answer
negatively charged electrons moving around a very small but massive, positively charged core.
question
In a simple atom the electrons making transitions between the outermost energy levels and the innermost energy levels give rise to photons with
answer
the highest energies.
question
Electrons in atoms
answer
occupy levels whose energies are fixed.
question
The spectrum of a star shows an equivalent set of dark absorption lines to those of the Sun, but with one exception: Every line appears at a slightly longer wavelength, shifted toward the red end of the spectrum. What conclusion can be drawn from this observation?
answer
The star is moving rapidly away from Earth.
question
When electromagnetic radiation (e.g., light) is Doppler-shifted by motion of the source away from the detector the
answer
detected wavelength is longer than the emitted wavelength.
question
When an object is moving toward you the visible radiation which it emits is Doppler shifted toward the
answer
ultraviolet
question
An astronomer photographs the spectrum of an object and finds a spectral line at 499 nm wavelength. In the laboratory, this spectral line occurs at 500 nm. According to the Doppler effect, this object is moving
answer
toward Earth at 1/500 the speed of light.
question
Compared to its speed in a vacuum (or in space), the speed of light in glass is
answer
less
question
As light passes from air into a dense but transparent material it
answer
slows down
question
Lenses are used in applications like microscopes and telescopes. What does a lens do in these applications?
answer
Light which would not otherwise form an image enters a lens and has its direction changed so that it focuses to form an image.
question
When light passes from air into glass it is refracted. This means that
answer
the wave slows down.
question
Refraction is the
answer
bending of light as it enters a transparent material.
question
Which type of telescope uses a lens as the main optical element?
answer
refracting telescope
question
The main reason for building large optical telescopes on Earth's surface is
answer
to collect more light from faint objects.
question
A refracting telescope has an objective lens of focal length 80 cm, a diameter of 10 cm, and an eyepiece of focal length 5 cm and diameter 1 cm. What is the magnifying power of this telescope?
answer
16x
question
A particular reflecting telescope has an objective mirror with a focal length of 1.2 m and an eyepiece lens of focal length 6 mm. What is the magnifying power of this telescope?
answer
200x
question
Chromatic aberration occurs in a refracting telescope when
answer
all colors of light do not come to the same focal point.
question
How can you increase the magnification of a refracting telescope without decreasing the light gathering power?
answer
decrease the focal length of the eyepiece
question
At the mirror of a reflecting telescope, the light reflects from a coated surface rather than refracting through a lens. This eliminates
answer
chromatic aberration.
question
It is difficult to improve the angular resolution of optical telescopes located on the surface of Earth beyond a certain limit because
answer
air turbulence distorts the star images more than does the telescope optics.
question
One major difference between radio waves and light is that
answer
radio waves have lower frequencies.
question
A radio telescope
answer
is very similar to a reflecting optical telescope.
question
The correct sequence of planets in our solar system from the Sun outward is
answer
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
question
In our solar system, which of the following planets is not a member of the terrestrial group?
answer
Jupiter
question
In our solar system, which of the following planets is not a member of the Jovian group?
answer
Mars
question
Orbital eccentricity is a number that describes the
answer
shape of the orbital ellipse.
question
The planet whose orbit is inclined at the greatest angle to the plane of the ecliptic is
answer
Mercury.
question
A perfect circle is an ellipse with an eccentricity of
answer
zero.
question
The best way to measure the mass of a planet is to measure the
answer
gravitational pull of the planet on an orbiting satellite or a nearby spacecraft.
question
A curious fact about the structure of the planet Jupiter, compared to that of Earth, is that it has
answer
much greater mass but much lower average density.
question
Viewed from a position above the north pole of the Sun, the directions of the motions of the planets in their orbits are
answer
all counterclockwise.
question
Determination of the chemical composition of the atmospheres of the planets is carried out most effectively by what type of study?
answer
spectroscopy—the measurement of absorption features in their spectra
question
Comets are typically
answer
chunks of ice that begin to vaporize if they pass close to the Sun.
question
In general, large bodies in the solar system show less evidence of cratering than do small bodies. Why should we expect this correlation?
answer
Large bodies cool more slowly and are more likely to retain internal heat and be geologically active, capable of resurfacing the planet and obliterating craters.
question
In general, small bodies in the solar system are less likely than large bodies to possess a planet-wide magnetic field. Why should we expect size and magnetism to be correlated?
answer
A small body cools more rapidly and is less likely to possess a molten, liquid interior — one requirement for planet-wide magnetism.
question
One distinct difference between Earth and its neighboring planets, Venus and Mars, is the presence of
answer
liquid water on its surface and water molecules chemically locked into rocks.
question
The albedo of a planet is the fraction of energy that is
answer
reflected by the whole planet, including atmosphere and surface.
question
The greenhouse effect is the
answer
absorption by atmospheric gases of infrared radiation emitted by a planet that has been heated by solar visible and ultraviolet radiation.
question
Earth has an average density of
answer
5.5 times that of water.
question
"Chemical differentiation" in planetary sciences refers to
answer
the sinking of heavier elements toward the center of a planet and the floating of lighter elements toward the surface.
question
The mantle of Earth is composed of
answer
rock.
question
What is the basic structure of Earth's interior?
answer
solid iron inner core, molten iron outer core, rocky mantle, lighter rocky crust
question
Earth's magnetic field is caused by
answer
electric currents flowing in the molten core.
question
The auroral display of northern and southern lights in the atmosphere is caused by
answer
solar wind electrons hitting the high atmosphere after being accelerated by the magnetosphere.
question
Photosynthesis is a chemical process which takes place in green plants. What is its effect on our atmosphere?
answer
Photosynthesis consumes carbon dioxide from our atmosphere and produces oxygen.
question
Which is the most abundant gas in Earth's atmosphere?
answer
nitrogen
question
Why did Earth's earliest atmosphere, composed primarily of hydrogen, not last long?
answer
Hydrogen is a very light gas, and it soon escaped into space.
question
The major layers of Earth's atmosphere from the surface upward in correct order are
answer
troposphere, stratosphere, mesosphere, thermosphere.
question
In which layer of Earth's atmosphere does all weather occur?
answer
troposphere
question
In which layer of Earth's atmosphere is the ozone layer located?
answer
stratosphere
question
In its orbit around Earth, the Moon
answer
always keeps the same side toward Earth.
question
How long is a "lunar day," or the time between two successive sunrises or sunsets on the Moon?
answer
about 1 month
question
Astronauts at a Moon base visible from Earth will NOT see
answer
Earthrise or Earthset.
question
The Moon has
answer
no measurable atmosphere or liquid water.
question
Maria on the Moon exist
answer
only on Earth-facing side of the Moon.
question
Why are the lunar maria concentrated almost entirely on the near side of the Moon?
answer
The crust is thicker on the far side of the Moon, restricting massive lava flows after asteroid impact.
question
The mountains on the Moon were mostly caused by
answer
impacts from meteoroids from outer space.
question
One effect of the ocean water's tidal drag on Earth is to
answer
slow down Earth's spin rate.
question
Because of the tides on Earth's oceans, the Moon is
answer
spiraling outward away from Earth.
question
Which of the following is believed to be the correct explanation for the origin of the Moon?
answer
Earth was struck by a large planetesima, which caused material to be ejected. This material coalesced to form the Moon.
question
The existence of stars composed almost entirely of neutrons was first predicted by
answer
Fritz Zwicky and Walter Baade, in 1933.
question
A pulsar is
answer
a rapidly rotating neutron star, emitting beams of radio radiation and in some cases X-rays and visible light
question
The pulsation periods of most pulsars are in the range
answer
of 1/1000 second and a few seconds.
question
The very strong magnetic field of a neutron star is created by
answer
the collapse of a star, which significantly intensifies the original weak magnetic field of the star.
question
The strength of the magnetic field around a typical neutron star is
answer
about a trillion (1012) gauss, or about a million times stronger than the strongest magnetic fields ever produced in laboratories on Earth.
question
The periods of most pulsars
answer
increase with time.
question
Synchrotron radiation is emitted whenever
answer
charged particles are forced to move along curved paths within a magnetic field.
question
Glitches are occasionally observed by astronomers studying pulsars. What are these glitches?
answer
sudden increases in rotation rate
question
Astronomers believe neutron stars may have atmospheres. What form of evidence do we have for this?
answer
dips in the X-ray spectrum emitted by the neutron star suggesting that these wavelength ranges are absorbed by an atmosphere
question
The Black Widow pulsar is unusual because it appears to
answer
be eating away at its companion star.
question
The age of the solar system has been dated rather precisely to 4.56 billion years. What method was used to determine this number?
answer
determining the age of meteorites by radioactive dating
question
The most common elements in the universe are
answer
hydrogen, smaller quantities of helium, and very small quantities of heavier elements.
question
Together, hydrogen and helium account for what percentage of the total mass of all matter in the universe?
answer
98%
question
What fraction of the mass of the universe is in the form of atoms other than hydrogen and helium?
answer
2%
question
Where in the universe are heavy elements with masses greater than that of helium being produced at this time?
answer
central cores of stars
question
What was the form of the material from which the solar system formed?
answer
a nebula made mostly of hydrogen and helium gas, but enriched in heavier elements from supernova explosions
question
The temperature began to rise at the center of the solar nebula because
answer
the nebula was contracting, increasing the speed of motion of the atoms.
question
Which of the following statements is an example of Kelvin-Helmholtz contraction?
answer
A contraction of a dense cloud of gas slowly gets hotter due to the release of gravitational energy.
question
Which one of the following is not an example of the conservation of angular momentum?
answer
The Moon always keeps one face pointed toward Earth.
question
The most probable time sequence for the solar system's formation was that the
answer
Sun contracted first as a gas ball, and the planets and moons formed shortly afterward by accretion and condensation.
question
The process of accretion in planetary formation is the
answer
slow accumulation of solid particles by gravity and collision into larger, solid objects.
question
The formation of terrestrial-type planets around a star is most likely to have occurred by what process?
answer
accretion, or slow accumulation of smaller particles by mutual gravitational attraction
question
What is the process of chemical differentiation?
answer
the sinking of heavy material to the center of a planet or other object and the rising of lighter material toward the surface
question
The reason most of the terrestrial planets have dense, iron cores is because
answer
terrestrial planets were initially molten or partially molten, and the iron sank to the center.
question
A Tauri wind is
answer
a rapid expulsion of the tenuous outer layers of a young star.
question
The Oort cloud is
answer
a spherical solar system halo of icy objects far beyond the orbit of Pluto.
question
Astrometry is the very precise measurement of
answer
a star's position in the sky (e.g., to measure its motion).
question
So far, what is the typical mass of the majority of extrasolar planets discovered?
answer
between the the mass of Saturn and a few times the mass of Jupiter
question
What is "special" about the special theory of relativity?
answer
It deals only with objects moving in a straight line at constant speed.
question
In order to use the theory of special relativity to describe an object's motion, the object must be moving
answer
at a constant speed in a straight line; how fast it is moving is not important.
question
Einstein's theory of special relativity contains some very strange ideas such as time dilation (moving clocks run slow), length contraction (moving lengths are shorter), and lack of absolute simultaneity. What are these ideas based upon?
answer
The speed of light is the same for all observers in all reference frames.
question
Suppose you are in a jet airliner traveling at a constant speed of 400 km/h in a constant direction. All windows are blocked so you cannot see outside, and there are no vibrations from the engines. What experiment can you do to determine that you are in fact moving?
answer
None. All experiments will give the same results as when you are at rest on the ground.
question
You are flying your spacecraft on a parallel course with another spacecraft and at the same speed. You are both moving past Earth at an appreciable fraction of the speed of light. Which one of the following statements correctly describes the relationship between your clock and the clock in the other spacecraft?
answer
You will see the clock in the other spacecraft running at the same rate as yours.
question
Two rocket ships are traveling past Earth at 90% of the speed of light in opposite directions (i.e., they are approaching each other). One turns on a searchlight beam, which is seen by scientists aboard the second spaceship. What speed do the scientists measure for this light? (c = speed of light in a vacuum)
answer
c
question
If you see an object moving past you at 90% of the speed of light, you will measure the length of this object to be
answer
shorter than if it were at rest.
question
Einstein's principle of equivalence in his general theory of relativity asserts that
answer
being at rest in a gravitational field is equivalent to being in an upwardly accelerated frame of reference in a gravity-free environment.
question
According to general relativity, why does Earth orbit the Sun?
answer
Space around the Sun is curved and Earth follows this curved space.
question
Black holes are so named because
answer
no light or any other electromagnetic radiation can escape from inside them.
Get an explanation on any task
Get unstuck with the help of our AI assistant in seconds
New