A teacher is introducing the geologic time scale to third-grade students. She tells them that the entire history of Earth, from its formation to the present day, was 24 hours long, with 12:00 midnight representing the time of the formation of Earth and 12:00 midnight the following night representing the present day. About what time did humans appear in this 24-hour time scale?
- A. 11:58 PM
- B. 9:00 PM
- C. 6:00 PM
- D. 1:00 PM
Correct Answer & Rationale
Correct Answer: A
In this 24-hour analogy of Earth's history, humans appeared very recently, approximately 200,000 years ago, which is just a fraction of the total time. This corresponds to 11:58 PM, indicating that humans emerged just two minutes before the "midnight" representing the present day. Option B (9:00 PM) suggests a much earlier appearance, which does not align with the scientific timeline of human evolution. Option C (6:00 PM) is even earlier, placing humans in a time when dinosaurs were still prominent. Option D (1:00 PM) is far too early, as it would imply humans existed when early mammals were just beginning to evolve. Thus, only 11:58 PM accurately reflects the brief time humans have existed in the context of Earth's history.
In this 24-hour analogy of Earth's history, humans appeared very recently, approximately 200,000 years ago, which is just a fraction of the total time. This corresponds to 11:58 PM, indicating that humans emerged just two minutes before the "midnight" representing the present day. Option B (9:00 PM) suggests a much earlier appearance, which does not align with the scientific timeline of human evolution. Option C (6:00 PM) is even earlier, placing humans in a time when dinosaurs were still prominent. Option D (1:00 PM) is far too early, as it would imply humans existed when early mammals were just beginning to evolve. Thus, only 11:58 PM accurately reflects the brief time humans have existed in the context of Earth's history.
Other Related Questions
A reaction occurs between two liquid substances in a sealed container. Based on the law of conservation of mass, what will happen to the mass of the sealed container and its contents overall?
- A. If the reaction produces a gas, the mass will decrease.
- B. If the reaction produces a solid, the mass will increase.
- C. If the reaction produces a liquid, the mass will increase as well.
- D. No matter what the reaction produces, the mass will remain the same.
Correct Answer & Rationale
Correct Answer: D
The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. Therefore, regardless of whether a gas, solid, or liquid is produced, the total mass of the sealed container and its contents will remain constant. Option A is incorrect; while gas may escape in an open system, a sealed container retains all products, so mass does not decrease. Option B is misleading; while a solid may form, it does not increase the total mass, as the mass of reactants equals that of products. Option C also misinterprets mass conservation; producing a liquid does not add to the total mass. Thus, the overall mass remains unchanged throughout the reaction.
The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. Therefore, regardless of whether a gas, solid, or liquid is produced, the total mass of the sealed container and its contents will remain constant. Option A is incorrect; while gas may escape in an open system, a sealed container retains all products, so mass does not decrease. Option B is misleading; while a solid may form, it does not increase the total mass, as the mass of reactants equals that of products. Option C also misinterprets mass conservation; producing a liquid does not add to the total mass. Thus, the overall mass remains unchanged throughout the reaction.
Of the following, which has Earth completed when it makes one revolution around the Sun?
- A. One Earth year
- B. One Earth day
- C. One light year
- D. One lunar month
Correct Answer & Rationale
Correct Answer: A
When Earth completes one revolution around the Sun, it takes approximately 365.25 days, which defines one Earth year. Option B, one Earth day, represents the time it takes for Earth to rotate on its axis, not its orbit around the Sun. Option C, one light year, is a measure of distance that light travels in one year, not a measure of time related to Earth's orbit. Option D, one lunar month, refers to the time it takes for the Moon to orbit Earth, which is about 29.5 days, and is unrelated to Earth's revolution around the Sun.
When Earth completes one revolution around the Sun, it takes approximately 365.25 days, which defines one Earth year. Option B, one Earth day, represents the time it takes for Earth to rotate on its axis, not its orbit around the Sun. Option C, one light year, is a measure of distance that light travels in one year, not a measure of time related to Earth's orbit. Option D, one lunar month, refers to the time it takes for the Moon to orbit Earth, which is about 29.5 days, and is unrelated to Earth's revolution around the Sun.
Which of the following was the dependent variable in this investigation?
- A. The wingspan
- B. The flight distance
- C. The stopwatch
- D. The tape measure
Correct Answer & Rationale
Correct Answer: B
In this investigation, the dependent variable is the outcome that is measured in response to changes in the independent variable. Flight distance (B) reflects how far something travels, which depends on the conditions set by the experiment. Wingspan (A) is an independent variable if it is being manipulated to see its effect on flight distance. The stopwatch (C) is a tool used to measure time and does not represent a variable in the experiment. Similarly, the tape measure (D) is an instrument for measuring distance, not a variable being tested. Thus, flight distance is the key outcome that reflects the effects of the experiment.
In this investigation, the dependent variable is the outcome that is measured in response to changes in the independent variable. Flight distance (B) reflects how far something travels, which depends on the conditions set by the experiment. Wingspan (A) is an independent variable if it is being manipulated to see its effect on flight distance. The stopwatch (C) is a tool used to measure time and does not represent a variable in the experiment. Similarly, the tape measure (D) is an instrument for measuring distance, not a variable being tested. Thus, flight distance is the key outcome that reflects the effects of the experiment.
Which of the following best predicts what will happen when white light passes through a green object?
- A. The object will mostly reflect the green part of the light.
- B. The object will mostly absorb the green part of the light.
- C. The object will appear black.
- D. The object will appear white.
Correct Answer & Rationale
Correct Answer: A
When white light passes through a green object, the object primarily reflects green wavelengths while absorbing others. This reflection causes the object to appear green to our eyes. Option B is incorrect because if the object absorbed the green part of the light, it would not appear green. Option C is not valid, as a black appearance would result from the object absorbing all wavelengths of light, not reflecting any. Option D is also wrong; an object appears white when it reflects all wavelengths of light equally, which does not apply to a green object.
When white light passes through a green object, the object primarily reflects green wavelengths while absorbing others. This reflection causes the object to appear green to our eyes. Option B is incorrect because if the object absorbed the green part of the light, it would not appear green. Option C is not valid, as a black appearance would result from the object absorbing all wavelengths of light, not reflecting any. Option D is also wrong; an object appears white when it reflects all wavelengths of light equally, which does not apply to a green object.